# Programming with gtkmm 4

Murray
Cumming
Bernhard
Rieder
Chapter on "Timeouts".
Jonathon
Jongsma
Chapter on "Drawing with Cairo".
Chapter on "Working with gtkmm's Source Code".
Chapter on "Recent Files".
Ole
Laursen
Parts of chapter on "Internationalization".
Marko
Anastasov
Chapter on "Printing".
Parts of chapter on "Internationalization".
Daniel
Elstner
Section "Build Structure" of chapter on "Wrapping C Libraries with gmmproc".
Chris
Vine
Chapter on "Multi-threaded programs".
David
King
Section on Gtk::Grid.
Pedro
Ferreira
Chapter on "Keyboard Events".
Kjell
Ahlstedt
Update from gtkmm 3 to gtkmm 4.
Chapter on "Building applications".
Chapter on "The DropDown Widget".
Chapter on "ListView, GridView, ColumnView".
Daniel
Boles
Notes on need to remove widgets in non-managed wrappers from parents to dispose, other tweaks.

Tato kniha vysvětluje klíčové koncepty gtkmm, což je API C++ pro vytváření uživatelského rozhraní. Seznamuje také v hlavními prvky uživatelského rozhraní, tzv. widgety.

2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
Murray Cumming

Je povoleno kopírovat, šířit a/nebo upravovat tento dokument za podmínek GNU Free Documentation License (GFDL) ve verzi 1.2 nebo v jakékoli novější verzi vydané nadací Free Software Foundation; bez neměnných oddílů, bez textů předních desek a bez textů zadních desek. Znění licence GNU Free Documentation License můžete získat od organizace Free Software Foundation na jejích webových stránkách, nebo si o ni napište na adresu: Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

## Úvod

### O této knize

Tato kniha vysvětluje klíčové koncepty gtkmm, což je API C++ pro vytváření uživatelského rozhraní. Seznamuje také v hlavními prvky uživatelského rozhraní, tzv. widgety. I když jsou zmíněny třídy, konstruktory a metody, nezachází do přílišných podrobností. Je to proto, že úplné informace o API byste měli hledat v odkazované referenční dokumentaci.

Pro čtení této knihy se předpokládá dobrá znalost jazyka C++, včetně znalosti jak v C++ vytvořit program.

Rádi bychom se dozvěděli, když budete mít problém se studiem gtkmm podle tohoto dokumentu a odměnou za to vám bude jeho vylepšení. Na více informací se prosím podívejte do kapitoly Přispívání.

### gtkmm

gtkmm is a C++ wrapper for GTK, a library used to create graphical user interfaces. It is licensed using the LGPL license, so you can develop open software, free software, or even commercial non-free software using gtkmm without purchasing licenses.

gtkmm was originally named gtk-- because GTK was originally named GTK+ and had a + in the name. However, as -- is not easily indexed by search engines, the package generally went by the name gtkmm, and that's what we stuck with.

#### Why use gtkmm instead of GTK?

gtkmm allows you to write code using normal C++ techniques such as encapsulation, derivation, and polymorphism. As a C++ programmer you probably already realize that this leads to clearer and better organized code.

gtkmm je také typově bezpečnější, takže kompilátor může odhalit chyby, které by při použití C šli odhalit jen za běhu. Používání konkrétnějších typů také zpřehledňuje celé API, protože můžete zjistit, které typy by měly být použity, jednoduše pohledem do deklarace metody.

Inheritance can be used to derive new widgets. The derivation of new widgets in GTK C code is so complicated and error prone that almost no C coders do it. As a C++ developer you know that derivation is an essential Object Orientated technique.

Member instances can be used, simplifying memory management. All GTK C widgets are dealt with by use of pointers. As a C++ coder you know that pointers should be avoided where possible.

gtkmm involves less code compared to GTK, which uses prefixed function names and lots of cast macros.

#### gtkmm ve srovnání s Qt

Nejbližší konkurencí gtkmm je Qt od Trolltechu, takže se na něj pojďme podívat blíže.

gtkmm developers tend to prefer gtkmm to Qt because gtkmm does things in a more C++ way. Qt originates from a time when C++ and the standard library were not standardized or well supported by compilers. It therefore duplicates a lot of stuff that is now in the standard library, such as containers and type information. Most significantly, Trolltech modified the C++ language to provide signals, so that Qt classes cannot be used easily with non-Qt classes. gtkmm was able to use standard C++ to provide signals without changing the C++ language. See the FAQ for more detailed differences.

#### gtkmm jen obaluje GTK+

gtkmm is not a native C++ toolkit, but a C++ wrapper of a C toolkit. This separation of interface and implementation has advantages. The gtkmm developers spend most of their time talking about how gtkmm can present the clearest API, without awkward compromises due to obscure technical details. We contribute a little to the underlying GTK code base, but so do the C coders, and the Perl coders and the Python coders, etc. Therefore GTK benefits from a broader user base than language-specific toolkits - there are more implementers, more developers, more testers, and more users.

## Instalace

### Závislosti

Before attempting to install gtkmm-4.0, you might first need to install these other packages.

- sigc++-3.0

- gtk4

- glibmm-2.68

- cairomm-1.16

- pangomm-2.48

Tyto závislosti mají zase své vlastní závislosti, včetně následujících aplikací a knihoven:

- pkg-config

- glib-2.0

- pango

- cairo

- gdk-pixbuf-2.0

- graphene-1.0

### Unix a Linux

#### Předem sestavené balíčky

V současnosti jsou nejnovější verze gtkmm zabaleny v téměř všech hlavních linuxových distribucích. Takže pokud používáte Linux, začnete nejspíše s gtkmm instalací balíčku z oficiálního repozitáře své distribuce. Mezi distribuce, které gtkmm obsahují ve svých repozitářích, patří Debian, Ubuntu, Red Hat, Fedora, Mandriva, Suse a mnohé další.

The names of the gtkmm packages vary from distribution to distribution (e.g. libgtkmm-4.0-dev on Debian and Ubuntu or gtkmm4.0-devel on Red Hat and Fedora), so check with your distribution's package management program for the correct package name and install it like you would any other package.

The package names will not change when new API/ABI-compatible versions of gtkmm are released. Otherwise they would not be API/ABI-compatible. So don't be surprised, for instance, to find gtkmm 4.8 supplied by Debian's libgtkmm-4.0-dev package.

#### Instalace ze zdrojových kódů

If your distribution does not provide a pre-built gtkmm package, or if you want to install a different version than the one provided by your distribution, you can also install gtkmm from source. The source code for gtkmm can be downloaded from .

After you've installed all of the dependencies, download the gtkmm source code, unpack it, and change to the newly created directory. gtkmm can be built with Meson. See the `README` file in the gtkmm version you've downloaded.

Nezapomeňte, že v operačních systémech Unix a Linux budete k instalaci nejspíše potřebovat oprávnění uživatele `root`. Příkaz `su` nebo `sudo` vám umožní zadat heslo uživatele `root` a získat dočasně jeho status.

The `configure` script or `meson` will check to make sure all of the required dependencies are already installed. If you are missing any dependencies, it will exit and display an error.

By default, gtkmm if built with Meson or Autotools, will be installed under the `/usr/local` directory. On some systems you may need to install to a different location. For instance, on Red Hat Linux systems you might use the `--prefix` option with configure, like one of:

    # meson setup --prefix=/usr <builddir> <srcdir>
    # meson configure --prefix=/usr
    # ./configure --prefix=/usr

Měli byste být opatrní, když instalujete do standardních systémových složek, jako je `/usr`. Linuxové distribuce instalují do `/usr` softwarové balíčky, takže instalace ze zdrojových kódů do této cesty by mohla poškodit software nainstalovaný správou balíčků vaší distribuce, nebo s ním být v konfliktu. Nejlépe, když použijete oddělenou složku pro všechen software instalovaný ze zdrojových kódů.

Pokud chcete pomoci s vývojem gtkmm nebo experimentovat s novými funkcemi, můžete nainstalovat gtkmm také ze systému správy verzí Git. Většina uživatelů to nikdy nebude potřebovat, ale jestli máte zájem pomoci s vývojem gtkmm, podívejte se do dodatku Práce se zdrojovými kódy gtkmm.

### Microsoft Windows

GTK and gtkmm were designed to work well with Microsoft Windows, and the developers encourage its use on the win32 platform. However, Windows has no standard installation system for development libraries. Please see the Windows Installation page or the gtkmm and Win32 appendix for Windows-specific installation instructions and notes.

## Základy

Tato kapitola vám představí některé z nejdůležitějších aspektů programování s gtkmm. Budou předvedeny na jednoduchém funkčním ukázkovém kódu. Nicméně se jedná jen o takovou ochutnávku, na podstatné věci se budete muset podívat do dalších kapitol.

Vaše stávající znalosti C++ vám budou s gtkmm ku prospěchu, stejně jako u jakékoliv jiné knihovny. Pokud neuvedeme jinak, očekávejte od tříd gtkmm chování jako u jakékoliv jiné třídy C++ a můžete očekávat, že třídy gtkmm používají běžné techniky C++.

### Jednoduchý příklad

Abychom vás uvedli do gtkmm, začneme s nejjednodušším možným programem. Tento program vytvoří okno o rozměrech 200 × 200 pixelů.

Source Code

File: `base.cc` (For use with gtkmm 4)

    #include <gtkmm.h>

    class MyWindow : public Gtk::Window
    {
    public:
      MyWindow();
    };

    MyWindow::MyWindow()
    {
      set_title("Basic application");
      set_default_size(200, 200);
    }

    int main(int argc, char* argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.examples.base");

      return app->make_window_and_run<MyWindow>(argc, argv);
    }

We will now explain each part of the example

    #include <gtkmm.h>

Všechny programy používající gtkmm musí mít vložené určité hlavičkové soubory gtkmm. `gtkmm.h` vloží celou sadu gtkmm. To obvykle není dobrý nápad, protože to vloží megabajty hlaviček, ale pro tento jednoduchý program nás to nemusí trápit.

The next part of the program:

    class MyWindow : public Gtk::Window
    {
    public:
      MyWindow();
    };

    MyWindow::MyWindow()
    {
      set_title("Basic application");
      set_default_size(200, 200);
    }

defines the `MyWindow` class. Its default constructor sets the window's title and default (initial) size.

The `main()` function's first statement:

    auto app = Gtk::Application::create("org.gtkmm.examples.base");

creates a `Gtk::Application` object, stored in a `Glib::RefPtr` smartpointer. This is needed in all gtkmm applications. The `create()` method for this object initializes gtkmm.

The last line creates and shows a window and enters the gtkmm main processing loop, which will finish when the window is closed. Your `main()` function will then return with an appropriate success or error code. The `argc` and `argv` arguments, passed to your application on the command line, can be checked when `make_window_and_run()` is called, but this simple application does not use those arguments.

    return app->make_window_and_run<MyWindow>(argc, argv);

After putting the source code in `simple.cc` you can compile the above program with gcc using:

    g++ simple.cc -o simple `pkg-config --cflags --libs gtkmm-4.0` -std=c++17

Note that you must surround the `pkg-config` invocation with backquotes. Backquotes cause the shell to execute the command inside them, and to use the command's output as part of the command line. Note also that `simple.cc` must come before the `pkg-config` invocation on the command line. `-std=c++17` is necessary only if your compiler is not C++17 compliant by default.

### Hlavičkové soubory a linkování

Although we have shown the compilation command for the simple example, you really should use the Meson build system. The examples used in this book are included in the gtkmm-documentation package, with appropriate build files, so we won't show the build commands in future. The `README` file in gtkmm-documentation describes how to build the examples.

Pro zjednodušení kompilace používáme `pkg-config`, který najdete ve všech (správně nainstalovaných) instalacích gtkmm. Tento program „zná“ přepínače, které jsou zapotřebí ke kompilaci programu, který používá gtkmm. Přepínač `--cflags` způsobí, že `pkg-config` vypíše seznam složek, ve kterých kompilátor hledá hlavičkové soubory, a přepínač `--libs` zažádá o seznam knihoven, které má kompilátor přilinkovat, a o složky, ve kterých je má hledat. Zkuste si to spustit ručně v shellu, abyste viděli výsledky pro váš systém.

However, this is even simpler when using the `dependency()` function in a `meson.build` file with Meson. For instance:

    gtkmm_dep = dependency('gtkmm-4.0', version: '>= 4.6.0')

This checks for the presence of gtkmm and defines `gtkmm_dep` for use in your `meson.build` files. For instance:

    exe_file = executable('my_program', 'my_source1.cc', 'my_source2.cc',
      dependencies: gtkmm_dep,
      win_subsystem: 'windows',
    )

gtkmm-4.0 is the name of the current stable API. There are older APIs called gtkmm-2.4 and gtkmm-3.0 which install in parallel when they are available. There are several versions of gtkmm-2.4, such as gtkmm 2.10 and there are several versions of the gtkmm-3.0 API. Note that the API name does not change for every version because that would be an incompatible API and ABI break. There might be a future gtkmm-5.0 API which would install in parallel with gtkmm-4.0 without affecting existing applications.

If you start by experimenting with a small application that you plan to use just for yourself, it's easier to start with a `meson.build` similar to the `meson.build` files in the Building applications chapter.

If you use the older Autotools build system, see also the GNU site. It has more information about autoconf and automake. There are also some books describing Autotools: "GNU Autoconf, Automake, and Libtool" by Gary Vaughan et al. and "Autotools, A Practitioner's Guide to GNU Autoconf, Automake, and Libtool" by John Calcote.

### Widgety

Aplikace vytvoření pomocí gtkmm jsou tvořené okny obsahujícími widgety, jako jsou tlačítka nebo textová pole. V některých jiných systémech se widgety nazývají „ovládací prvky“. Ke každému widgetu v oknech aplikace existuje objekt C++ ve vašem aplikačním kódu. Pro dosažení vizuálních projevů widgetu vám stačí volat metody třídy widgetu.

Widgets are arranged inside container widgets such as frames and notebooks, in a hierarchy of widgets within widgets. Some of these container widgets, such as `Gtk::Grid`, are not visible - they exist only to arrange other widgets. Here is some example code that adds 2 `Gtk::Button` widgets to a `Gtk::Box` container widget:

    m_box.append(m_Button1);
    m_box.append(m_Button2);

and here is how to add the `Gtk::Box`, containing those buttons, to a `Gtk::Frame`, which has a visible frame and title:

    m_frame.set_child(m_box);

Většina kapitol v této knize se zabývá konkrétními widgety. Více informací o přidávání widgetů do kontejnerového widgetu najdete v kapitole Kontejnerové widgety.

Although you can specify the layout and appearance of windows and widgets with C++ code, you will probably find it more convenient to design your user interfaces with `.ui` XML files and load them at runtime with `Gtk::Builder`. See the Gtk::Builder chapter.

Although gtkmm widget instances have lifetimes and scopes just like those of other C++ classes, gtkmm has an optional time-saving feature that you will see in some of the examples. The `Gtk::make_managed()` allows you to create a new widget and state that it will become owned by the container into which you place it. This allows you to create the widget, add it to the container and not be concerned about deleting it, since that will occur when the parent container (which may itself be managed) is deleted. You can learn more about gtkmm memory management techniques in the Memory Management chapter.

### Signály

gtkmm je, obdobně jako jiné vývojářské sady GUI, řízené událostmi. Když se vyskytne událost, jako je zmáčknutí tlačítka myši, je widgetem, který byl zmáčknut, vyslán příslušný signál. Různé widgety mají různé sady signálů, které mohou vyslat. Aby se kliknutí tlačítkem projevilo nějakou činností, je třeba nastavit obsluhu signálu (signal handler), která signál „clicked“ od tlačítka zachytí.

gtkmm uses the libsigc++ library to implement signals. Here is an example line of code that connects a Gtk::Button's "clicked" signal with a signal handler called "on_button_clicked":

    m_button1.signal_clicked().connect( sigc::mem_fun(*this,
      &HelloWorld::on_button_clicked) );

Více informací o signálech najdete v dodatku.

Pokud byste raději implementovali své vlastní signály, místo napojení těch stávajících v gtkmm, podívejte se do tohoto dodatku.

### Glib::ustring

Možná budete překvapeni, že gtkmm nepoužívá ve svých rozhraních `std::string`. Místo toho používá `Glib::ustring`, který je ale natolik podobný a nenápadný, že klidně můžete předstírat, že `Glib::ustring` je `std::string` a zbytek kapitoly ignorovat. Přečtěte si ji ale, pokud chcete ve svých aplikacích používat jiné jazyky, než jen angličtinu.

std::string uses 8 bits per character, but 8 bits aren't enough to encode languages such as Arabic, Chinese, and Japanese. Although the encodings for these languages have been specified by the Unicode Consortium, the C and C++ languages do not yet provide any standardized Unicode support for UTF-8 encoding. GTK and GNOME chose to implement Unicode using UTF-8, and that's what is wrapped by Glib::ustring. It provides almost exactly the same interface as std::string, along with automatic conversions to and from std::string.

Jednou z východ UTF-8 je, že jej nemusíte používat, když jej nechcete, a nemusíte tak opravovat veškerý kód naráz. `std::string` bude stále fungovat pro řetězce se 7bitovým ASCII. Když se ale rozhodnete lokalizovat své aplikace do jazyků, jako je čeština nebo čínština, začnou se objevovat zvláštní chyby a případně i zhroucení. Potom vše, co musíte udělat, je začít používat místo něj `Glib::ustring`.

Mějte ale na paměti, že UTF-8 není kompatibilní s 8bitovými kódováními, jako je ISO-8859-2. Například ypsilon s čárkou není v ASCII a potřebuje proto v UTF-8 k zakódování víc než jeden bajt. Pokud váš kód obsahuje 8bitové řetězcové literály, musíte je převést do UTF-8 (např. český pozdrav „Dobrý den“ by byl „Dobr\xC3\xBD den“).

Měli byste se vyvarovat ukazatelové aritmetiky ve stylu C a funkcí jako je strlen(). V UTF-8 mohou znaky zabírat od 1 do 6 bajtů, takže se nedá automaticky předpokládat, že následující bajt je jiný znak. `Glib::ustring` se o tyto věci postará, takže můžete používat metody jako je Glib::ustring::substr() a přitom stále uvažovat v intencích znaků, ale ne bajtů.

Na rozdíl od řešení Unikódu v podobě UCS-2 ve Windows, nejsou zapotřebí žádné speciální volby kompilátoru pro zpracování řetězcových literálů a nevznikají tak spustitelné programy a knihovny s podporou Unikódu, které by byly nekompatibilní s ASCII.

Reference

Více informací o poskytování řetězcových literálů v UTF-8 viz kapitola Internacionalizace.

### Míchání API z C a C++

You can use C APIs which do not yet have convenient C++ interfaces. It is generally not a problem to use C APIs from C++, and gtkmm helps by providing access to the underlying C object, and providing an easy way to create a C++ wrapper object from a C object, provided that the C API is also based on the `GObject` system.

To use a gtkmm instance with a C function that requires a C `GObject` instance, use the C++ instance’s `gobj()` function to obtain a pointer to the underlying C instance. For example:

    Gtk::Button button("example");
    gtk_button_do_something_that_gtkmm_cannot(button.gobj());

To obtain a gtkmm instance from a C `GObject` instance, use one of the many overloaded `Glib::wrap()` functions. The C instance’s reference count is not incremented, unless you set the optional `take_copy` argument to `true`. For example:

    GtkButton* cbutton = get_a_button();
    Gtk::Button* button = Glib::wrap(cbutton);
    button->set_label("Now I speak C++ too!");

The C++ wrapper shall be explicitly deleted if

- it's a widget or other class that inherits from `Gtk::Object`, and

- the C instance has a floating reference when the wrapper is created, and

- `Gtk::manage()` has not been called on it (which includes if it was created with `Gtk::make_managed()`), or

- `Gtk::manage()` was called on it, but it was never added to a parent.

`Glib::wrap()` binds the C and C++ instances to each other. Don't delete the C++ instance before you want the C instance to die.

In all other cases the C++ instance is automatically deleted when the last reference to the C instance is dropped. This includes all `Glib::wrap()` overloads that return a `Glib::RefPtr`.

### „Ahoj Světe“ v gtkmm

Nyní už toho víme dost na to, abychom se mohli podívat na nějaký funkční příklad. A jak už je v programování tradicí, začneme aplikací „Ahoj Světe“ a lá gtkmm:

Source Code

File: `helloworld.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLE_HELLOWORLD_H
    #define GTKMM_EXAMPLE_HELLOWORLD_H

    #include <gtkmm/button.h>
    #include <gtkmm/window.h>

    class HelloWorld : public Gtk::Window
    {

    public:
      HelloWorld();
      ~HelloWorld() override;

    protected:
      //Signal handlers:
      void on_button_clicked();

      //Member widgets:
      Gtk::Button m_button;
    };

    #endif // GTKMM_EXAMPLE_HELLOWORLD_H

File: `helloworld.cc` (For use with gtkmm 4)

    #include "helloworld.h"
    #include <iostream>

    HelloWorld::HelloWorld()
    : m_button("Hello World")   // creates a new button with label "Hello World".
    {
      // Sets the margin around the button.
      m_button.set_margin(10);

      // When the button receives the "clicked" signal, it will call the
      // on_button_clicked() method defined below.
      m_button.signal_clicked().connect(sigc::mem_fun(*this,
                  &HelloWorld::on_button_clicked));

      // This packs the button into the Window (a container).
      set_child(m_button);
    }

    HelloWorld::~HelloWorld()
    {
    }

    void HelloWorld::on_button_clicked()
    {
      std::cout << "Hello World" << std::endl;
    }

File: `main.cc` (For use with gtkmm 4)

    #include "helloworld.h"
    #include <gtkmm/application.h>

    int main(int argc, char* argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<HelloWorld>(argc, argv);
    }

Než budeme pokračovat, zkuste si ji přeložit a spustit. Měli byste vidět něco takového:

#### Hello World

Pěkný výsledek, ne? Pojďme si kód vysvětlit. Nejprve třída `HelloWorld`:

    class HelloWorld : public Gtk::Window
    {
    public:
      HelloWorld();
      ~HelloWorld() override;

    protected:
      //Signal handlers:
      void on_button_clicked();

      //Member widgets:
      Gtk::Button m_button;
    };

This class implements the "Hello World" window. It's derived from `Gtk::Window`, and has a single `Gtk::Button` as a member. We've chosen to use the constructor to do all of the initialization work for the window, including setting up the signals. Here it is, with the comments omitted:

    HelloWorld::HelloWorld()
    : m_button("Hello World")
    {
      m_button.set_margin(10);
      m_button.signal_clicked().connect(sigc::mem_fun(*this,
        &HelloWorld::on_button_clicked));
      set_child(m_button);
    }

Notice that we've used an initializer statement to give the `m_button` object the label "Hello World".

Next we call the Button's `set_margin()` method. This sets the amount of space around the button.

Potom zaháčkujeme obsluhu signálu na signál `clicked` widgetu `m_button`. V ní vypisujeme přátelské uvítání do `stdout`.

Next, we use the Window's `set_child()` method to put `m_button` in the Window. The `set_child()` method places the Widget in the Window.

Nyní se pojďme podívat na funkci `main()` našeho programu. Zde je i s komentáři:

    int main(int argc, char* argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");
      return app->make_window_and_run<HelloWorld>(argc, argv);
    }

First we instantiate an object stored in a `Glib::RefPtr` smartpointer called `app`. This is of type `Gtk::Application`. Every gtkmm program must have one of these.

Next we call `make_window_and_run()` which creates an object of our `HelloWorld` class, shows that Window and starts the gtkmm event loop. During the event loop gtkmm idles, waiting for actions from the user, and responding appropriately. When the user closes the Window, `make_window_and_run()` will return, causing our `main()` function to return. The application will then finish.

Like the simple example we showed earlier, this Hello World program does not use the command-line parameters.

## Změny v gtkmm 3

gtkmm-3.0 is an old version of the gtkmm API that installs in parallel with the still older gtkmm-2.4 API and the new gtkmm-4.0 API. The last version of the gtkmm-2.4 API was gtkmm 2.24. gtkmm 3 has no major fundamental differences to gtkmm 2 but does make several small changes that were not possible while maintaining binary compatibility. If you never used the gtkmm-2.4 API then you can safely ignore this chapter.

Knihovna tvořící gtkmm 3.0 se nazývá `libgtkmm-3.0` místo `libgtkmm-2.4` a instaluje své hlavičkové soubory do obdobně verzované složky, takže se pkg-config může doptat na `gtkmm-3.0` i `gtkmm-2.4`.

gtkmm 3 přidává některé nové třídy:

1. `Gtk::AppChooser`, `Gtk::AppChooserButton` a `Gtk::AppChooserDialog` umožňují uživateli vybrat nainstalovanou aplikaci pro otevření konkrétního typu obsahu.

2. `Gtk::Grid` je nový kontejnerový widget, který může případně nahradit `Gtk::Box` a `Gtk::Table`. Své potomky uspořádává přednostně podle jejich vlastností, místo nějakého svého daného rozvržení.

3. `Gtk::Switch` displays On/Off states more explicitly than `Gtk::CheckButton`. It may be useful, for instance, when allowing users to activate hardware.

gtkmm 3 má také několik menších změn v API, na které pravděpodobně narazíte při portování kódu, který používá gtkmm 2.4. Zde je jejich krátký seznam:

1. `Gtk::CellLayout` používaná třídami `Gtk::IconView`, `Gtk::TreeView::Column` a `Gtk::ComboBox` má nyní `Gtk::CellArea`, kterou lze použít k přesnějšímu určení, jak jsou objekty `CellRenderer` uspořádané a zarovnané.

2. Gtk::ComboBox nyní odvozuje z CellLayout, díky čemuž je rozvržení a zarovnání jeho instancí `Gtk::CellRenderer` snazší.

3. `Gtk::Adjustment`, `IconSet` a `Gdk::Cursor` se teď používají přes `Glib::RefPtr`.

4. `Gtk::Box`, `Gtk::ButtonBox`, `Gtk::IconView`, `Gtk::Paned`, `Gtk::ProgressBar`, `Gtk::ScaleButton`, `Gtk::Scrollbar` a `Gtk::Separator` jsou nyní odovozené z `Gtk::Orientable`, což umožňuje jejich otočení (svislé nebo vodorovné) určit bez požadavku na použití odvozené třídy, jako je `Gtk::HBox`.

5. `Gtk::IconView`, `Gtk::TextView`, `Gtk::TreeView` a další widgety odvozují ze Scrollable, místo aby si definovali své vlastní metody, jako je `get_vadjustment()`, a místo aby měli svůj vlastní signál set_scroll_adjustments.

6. `Gtk::Style` a `Gtk::Rc` byla odstraněny a nahrazují je třída `Gtk::StyleContext` a třídy `Gtk::StyleProvider`, jako je `Gtk::CssProvider`.

7. Metoda Widget::on_expose_event() byla nahrazena pomocí Widget::on_draw(), která předpokládá, že pro kreslení je použita knihovna cairomm přes poskytovaný `Cairo::Context` a nevyžaduje volání `Cairo::Context::clip()`.

8. `Gdk::RGBA` nahrazuje `Color`, přičemž přidává komponentu alfa pro průhlednost. `Colormap` byla odstraněna, spolu s jejím nevhodným alokováním barev.

9. `Gdk::Pixmap` and `Gdk::Bitmap` were removed in favor of `Gdk::Pixbuf`.

10. Třída `Gdk::Drawable` byla odstraněn a jeho metody přesunuty do `Gdk::Window`.

11. Nyní v několika metodách používáme std::vector místo mezilehlého typu *Handle, aby bylo API čistší.

All deprecated API was removed in gtkmm 3.0, though there have been new deprecations in later gtkmm 3.x versions.

As a first step to porting your source code to gtkmm-3.0 you should probably ensure that your application builds with the deprecated gtkmm-2.4 API disabled, by defining macro such as GTKMM_DISABLE_DEPRECATED. There are some autotools macros that can help with this by defining them optionally at build time. See the gtkmm 3 porting wiki page for more details.

## Changes in gtkmm-4.0 and glibmm-2.68

gtkmm-4.0 is a new version of the gtkmm API that installs in parallel with the older gtkmm-2.4 and gtkmm-3.0 APIs. The last version of the gtkmm-3.0 API is gtkmm 3.24. gtkmm 4 has no major fundamental differences to gtkmm 3 but does make several changes (both small and large ones) that were not possible while maintaining binary compatibility. If you never used the gtkmm-3.0 API then you can safely ignore this chapter.

gtkmm 4's library is called `libgtkmm-4.0` rather than `libgtkmm-3.0` and installs its headers in a similarly-versioned directory, so your pkg-config check should ask for `gtkmm-4.0` rather than `gtkmm-3.0`.

gtkmm-4.0 is used in combination with glibmm-2.68, which sets the global locale for your program. The older glibmm-2.4 does not do that, and gtkmm-3.0 does it only to some extent. What this means is briefly that if your gtkmm-3.0 program contains a call to `std::locale::global(std::locale(""))`, you can probably remove it. If you don't want glibmm or gtkmm to set the global locale for you, you should add a call to `Glib::set_init_to_users_preferred_locale(false)` before any call to `Glib::init()` or `Gtk::Application::create()`. See the glibmm reference.

There are lots and lots of differences between gtkmm-3.0 and gtkmm-4.0. The following lists are not complete.

There are some important behavioural changes, to which you must adapt when migrating:

- Whereas in gtkmm-3.0, destruction of a non-managed C++ widget wrapper caused the wrapped GtkWidget to be destroyed, changes in GTK4 mean that in gtkmm-4.0 this canʼt always be the case. GTK4 has no uniform way to remove a widget from a parent, as GTK3 did with `Gtk::Container::remove()`, so gtkmm-4.0 canʼt do the removal for you as gtkmm-3.0 did. Hence, if a non-managed C++ widget instance is destructed while the widget is a child of another, gtkmm-4.0 wonʼt remove it from the parent, the parent retains a ref that stops the child being disposed, and the GtkWidget stays alive. The end result is that to destroy a non-managed widget with its C++ wrapper you must first remove it from its parent (however that parent allows) so the C++ wrapperʼs dtor can drop the final reference.

Some new classes were added in gtkmm 4 and glibmm 2.68:

1. `Glib::ExtraClassInit` and `Gtk::Snapshot`: These classes are needed only for writing custom widgets. See the Custom Widgets section.

2. `Gtk::EventControllerKey`, `Gtk::EventControllerMotion`, `Gtk::EventControllerScroll` and `Gtk::GestureStylus`

3. `Gdk::Paintable`, `Gdk::Texture`, `Gtk::Picture` and `Gtk::WidgetPaintable`

4. `Gdk::Window` has been renamed to `Gdk::Surface`. (`Gtk::Window` keeps its name.)

5. `Gdk::DrawContext` and `Gdk::CairoContext` are new. `Gdk::DrawingContext` has been removed.

6. `Gtk::Clipboard` has been replaced by the new `Gdk::Clipboard`.

7. `Gdk::DragContext` has been split into `Gdk::Drag` and `Gdk::Drop`.

There have also been several changes to the API, which you will probably encounter when porting code that used gtkmm-3.0 and glibmm-2.4. Here is a short list:

1. A C++17 compiler is required.

2. `Gtk::Button`, `Gtk::ToolButton`, `Gtk::MenuItem` and `Gtk::Switch` implement the `Gtk::Actionable` interface instead of the removed `Gtk::Activatable` interface.

3. `Gtk::FontButton` implements the `Gtk::FontChooser` interface.

4. `Gtk::Widget`: The `get_preferred_*_vfunc()`s have been replaced by `measure_vfunc()`. This change only affects custom widgets.

5. `sigc::slot`s use the `sigc::slot<R(Args...)>` syntax. Example: `sigc::slot<void(int, int)>` instead of `sigc::slot<void, int, int>`.

6. `Gtk::DrawingArea` uses a draw function instead of the draw signal.

7. `Glib::ArrayHandle`, `Glib::StringArrayHandle`, `Glib::ListHandle` and `Glib::SListHandle` have been removed. They were used in glibmm-2.4, but not used in gtkmm-3.0. If you've ever used these classes, replace them with a standard C++ container, such as `std::vector`.

8. `Gtk::Container` has been removed.

9. `Gtk::Widget::show_all()` has been removed. The default value of `Gtk::Widget::property_visible()` has been changed from `false` to `true`.

10. All event signals have been removed from `Gtk::Widget`. In most cases you can use one of the subclasses of `Gtk::EventController` as a replacement. For instance, use `Gtk::GestureMultiPress` instead of `signal_button_press_event()` and `signal_button_release_event()`, and `Gtk::EventControllerKey` instead of `signal_key_press_event()` and `signal_key_release_event()`.

11. `Glib::RefPtr` is an alias for `std::shared_ptr`. If you make your own `Glib::ObjectBase`-derived classes with `create()` methods that return a `Glib::RefPtr`, you must use `Glib::make_refptr_for_instance()` in your `create()` methods.

12. `Gtk::Box::pack_start()` and `Gtk::Box::pack_end()` have been removed. Use the new `Gtk::Box` methods `append()`, `prepend()`, `insert_child_after()` and `insert_child_at_start()`.

13. `Gtk::ButtonBox` has been removed.

14. `Gtk::RadioButton` and `Gtk::RadioButtonGroup` have been removed. Use `Gtk::CheckButton` or `Gtk::ToggleButton` with `set_group()`.

All deprecated API was removed in gtkmm 4.0 and glibmm 2.68, though there will be new deprecations in future versions.

As a first step to porting your source code to gtkmm-4.0 you should probably ensure that your application builds with the deprecated gtkmm-3.0 and glibmm-2.4 API disabled, by defining the macros GTKMM_DISABLE_DEPRECATED, GDKMM_DISABLE_DEPRECATED, GLIBMM_DISABLE_DEPRECATED and GIOMM_DISABLE_DEPRECATED. There are some autotools macros that can help with this by defining them optionally at build time. See the Porting from gtkmm-2.4 to gtkmm-3.0 wiki page for more details.

See also Migrating from GTK 3.x to GTK 4.

### Deprecations in gtkmm 4.10

Many classes are deprecated since gtkmm 4.10. They can still be used in gtkmm4 applications, provided GTKMM_DISABLE_DEPRECATED and GDKMM_DISABLE_DEPRECATED are not defined. There are also many new classes in gtkmm 4.10, which replace some of the deprecated classes. Some example programs in this tutorial use classes deprecated since gtkmm 4.10. Some other programs use classes available since gtkmm 4.10.

Deprecated classes: AppChooser, AppChooserButton, AppChooserDialog, AppChooserWidget, CellArea, CellAreaBox, CellAreaContext, CellLayout, CellRenderer, CellRendererAccel, CellRendererCombo, CellRendererPixbuf, CellRendererProgress, CellRendererSpin, CellRendererSpinner, CellRendererText, CellRendererToggle, CellView, ComboBox, ComboBoxText, EntryCompletion, IconView, ListStore, ListViewText, StyleContext, TreeDragDest, TreeDragSource, TreeIter and other classes in treeiter.h, TreeModel, TreeModelFilter, TreeModelSort, TreePath, TreeRowReference, TreeSelection, TreeSortable, TreeStore, TreeView, TreeViewColumn, namespace CellRenderer_Generation, namespace TreeView_Private, ColorButton, ColorChooser, ColorChooserDialog, FileChooser, FileChooserDialog, FileChooserNative, FileChooserWidget, FontButton, FontChooser, FontChooserDialog, FontChooserWidget, MessageDialog, TreeModelColumn, TreeModelColumnRecord, InfoBar, Assistant, AssistantPage, LockButton, Statusbar, VolumeButton.

New classes and enums: AlertDialog, ColorDialog, ColorDialogButton, ColumnViewSorter, FileDialog, FontDialog, FontDialogButton, FileLauncher, UriLauncher, ATContext, enums DialogError, FontLevel, Collation.

In most cases there are replacements for the deprecated classes. See the reference documentation.

## Tlačítka

gtkmm poskytuje čtyři základní typy tlačítek:

Push buttons

  `Gtk::Button`. Standard buttons, usually marked with a label or picture. Pushing one triggers an action. See the Button section.

Přepínací tlačítka (ToggleButton)

  `Gtk::ToggleButton`. Unlike a normal Button, which springs back up, a ToggleButton stays down until you press it again. It might be useful as an on/off switch. See the ToggleButton section.

Check buttons

  `Gtk::CheckButton`. These act like ToggleButtons, but show their state in small squares, with their label at the side. They should be used in most situations which require an on/off setting. See the CheckButton section.

Skupinové přepínače (RadioButton)

  Named after the station selectors on old car radios, these buttons are used in groups for options which are mutually exclusive. Pressing one causes all the others in its group to turn off. They are similar to ToggleButtons or CheckButtons (a small widget with a label at the side), but usually look different. There is no separate radio button class. Check buttons and toggle buttons can act as radio buttons. See the Radio Button section.

Note that, due to GTK's theming system, the appearance of these widgets will vary. In the case of check buttons and radio buttons, they may vary considerably.

### Tlačítko (Button)

Existují dva postupy, jak vytvořit tlačítko. Můžete určit textový popisek v konstruktoru `Gtk::Button` nebo jej nastavit později pomocí `set_label()`.

K definici horké klávesy pro ovládání z klávesnice umístěte před jeden ze znaků popisku podtržítko a volitelný parametr `mnemonic` nastavte na `true`. Například:

    Gtk::Button* pButton = new Gtk::Button("_Something", true);

`Gtk::Button` je také kontejner, takže do něj můžete vložit jiný widget, jako třeba `Gtk::Image`.

The `Gtk::Button` widget has the `clicked` signal which is emitted when the button is pressed and released.

Reference

#### Příklad

Tento příklad vytvoří tlačítko s obrázkem a popiskem.

##### Příklad tlačítka

Source Code

File: `buttons.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLE_BUTTONS_H
    #define GTKMM_EXAMPLE_BUTTONS_H

    #include <gtkmm/window.h>
    #include <gtkmm/button.h>

    class Buttons : public Gtk::Window
    {
    public:
      Buttons();
      virtual ~Buttons();

    protected:
      //Signal handlers:
      void on_button_clicked();

      //Child widgets:
      Gtk::Button m_button;
    };

    #endif //GTKMM_EXAMPLE_BUTTONS_H

File: `buttons.cc` (For use with gtkmm 4)

    #include "buttons.h"
    #include <gtkmm/box.h>
    #include <gtkmm/image.h>
    #include <gtkmm/label.h>
    #include <iostream>

    Buttons::Buttons()
    {
      // This corresponds to Gtk::Bin::add_pixlabel("info.xpm", "cool button") in gtkmm3.
      //Create Image and Label widgets:
      auto pmap = Gtk::make_managed<Gtk::Image>("info.xpm");
      auto label = Gtk::make_managed<Gtk::Label>("cool button");
      label->set_expand(true);

      //Put them in a Box:
      auto hbox = Gtk::make_managed<Gtk::Box>(Gtk::Orientation::HORIZONTAL, 5);
      hbox->append(*pmap);
      hbox->append(*label);

      //And put that Box in the button:
      m_button.set_child(*hbox);

      set_title("Pixmap'd buttons!");

      m_button.signal_clicked().connect( sigc::mem_fun(*this,
                  &Buttons::on_button_clicked) );

      m_button.set_margin(10);
      set_child(m_button);
    }

    Buttons::~Buttons()
    {
    }

    void Buttons::on_button_clicked()
    {
      std::cout << "The Button was clicked." << std::endl;
    }

File: `main.cc` (For use with gtkmm 4)

    #include "buttons.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<Buttons>(argc, argv);
    }

### Přepínací tlačítko (ToggleButton)

`ToggleButton` se podobá na normální `Button`, ale když je zmáčknuto, tak zůstane zmáčknuté, dokud na něj znovu nekliknete.

Pro získání stavu widgetu `ToggleButton` můžete použít metodu `get_active()`. Ta vrací `true`, když je tlačítko „dole“. Můžete také stav tlačítka nastavit pomocí `set_active()`. Všimněte si, že když to uděláte a aktuální stav se tím změní, způsobí to vyslání signálu „clicked“, což je přesně to, co obvykle chcete.

Můžete používat metodu `toggled()` k přepnutí tlačítka a určitě ji dejte přednost pro vynucením zmáčknutí nebo vyskočení: Přepne stav tlačítka a způsobí vyslání signálu `toggled`.

Reference

### Zaškrtávací políčko (CheckButton)

`Gtk::CheckButton` inherits directly from `Gtk::Widget`. It is similar to `Gtk::ToggleButton`. The only real difference between the two is `Gtk::CheckButton`'s appearance. You can check and set a check button using the same member methods as for `Gtk::ToggleButton`.

Reference

#### Příklad

##### Zaškrtávací políčko (CheckButton)

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLE_BUTTONS_H
    #define GTKMM_EXAMPLE_BUTTONS_H

    #include <gtkmm/window.h>
    #include <gtkmm/checkbutton.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_toggled();

      //Child widgets:
      Gtk::CheckButton m_button;
    };

    #endif //GTKMM_EXAMPLE_BUTTONS_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_button("something")
    {
      set_title("checkbutton example");

      m_button.signal_toggled().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_toggled) );

      m_button.set_margin(10);
      set_child(m_button);
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_toggled()
    {
      std::cout << "The Button was toggled: state="
          << (m_button.get_active() ? "true" : "false")
          << std::endl;
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

### Radio Button

There is no separate class for radio buttons. Check buttons and toggle buttons act as radio buttons when they form a group. Only one button in a group can be selected at any one time.

#### Skupiny

You create the buttons, and set up their group afterwards. In the following example, we put 3 radio buttons in a group:

    auto rb1 = Gtk::make_managed<Gtk::CheckButton>("button1");
    auto rb2 = Gtk::make_managed<Gtk::CheckButton>("button2");
    auto rb3 = Gtk::make_managed<Gtk::CheckButton>("button3");
    rb2->set_group(*rb1);
    rb3->set_group(*rb1);

We told gtkmm to put all three `CheckButton`s in the same group by using `set_group()` to tell the other `CheckButton`s to share group with the first `CheckButton`.

#### Metody

`CheckButton`s and `ToggleButton`s are "off" when created; this means that when you first make a group of them, they will all be off. Don't forget to turn one of them on using `set_active()`.

Reference

#### Příklad

The following example demonstrates the use of grouped `CheckButton`s:

##### Skupinový přepínač (RadioButton)

Source Code

File: `radiobuttons.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLE_RADIOBUTTONS_H
    #define GTKMM_EXAMPLE_RADIOBUTTONS_H

    #include <gtkmm/box.h>
    #include <gtkmm/window.h>
    #include <gtkmm/button.h>
    #include <gtkmm/checkbutton.h>
    #include <gtkmm/separator.h>

    class RadioButtons : public Gtk::Window
    {
    public:
      RadioButtons();
      virtual ~RadioButtons();

    protected:
      //Signal handlers:
      void on_button_clicked();

      //Child widgets:
      Gtk::Box m_Box_Top, m_Box1, m_Box2;
      Gtk::CheckButton m_RadioButton1, m_RadioButton2, m_RadioButton3;
      Gtk::Separator m_Separator;
      Gtk::Button m_Button_Close;
    };

    #endif //GTKMM_EXAMPLE_RADIOBUTTONS_H

File: `main.cc` (For use with gtkmm 4)

    #include "radiobuttons.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<RadioButtons>(argc, argv);
    }

File: `radiobuttons.cc` (For use with gtkmm 4)

    #include "radiobuttons.h"

    RadioButtons::RadioButtons() :
      m_Box_Top(Gtk::Orientation::VERTICAL),
      m_Box1(Gtk::Orientation::VERTICAL, 10),
      m_Box2(Gtk::Orientation::VERTICAL, 10),
      m_RadioButton1("button1"),
      m_RadioButton2("button2"),
      m_RadioButton3("button3"),
      m_Button_Close("close")
    {
      // Set title and border of the window
      set_title("radio buttons");

      // Gtk::CheckButton and Gtk::ToggleButton have set_group() methods.
      // They act as radio buttons, if they are included in a group.

      // Put radio buttons 2 and 3 in the same group as 1:
      m_RadioButton2.set_group(m_RadioButton1);
      m_RadioButton3.set_group(m_RadioButton1);

      // Add outer box to the window (because the window
      // can only contain a single widget)
      set_child(m_Box_Top);

      //Put the inner boxes and the separator in the outer box:
      m_Box_Top.append(m_Box1);
      m_Box_Top.append(m_Separator);
      m_Box_Top.append(m_Box2);
      m_Separator.set_expand();

      // Set the inner boxes' margins
      m_Box1.set_margin(10);
      m_Box2.set_margin(10);

      // Put the radio buttons in Box1:
      m_Box1.append(m_RadioButton1);
      m_Box1.append(m_RadioButton2);
      m_Box1.append(m_RadioButton3);
      m_RadioButton1.set_expand();
      m_RadioButton2.set_expand();
      m_RadioButton3.set_expand();

      // Set the second button active
      m_RadioButton2.set_active(true);

      // Put Close button in Box2:
      m_Box2.append(m_Button_Close);
      m_Button_Close.set_expand();

      // Make the button the default widget
      set_default_widget(m_Button_Close);

      // Connect the toggled signal of the button to
      // RadioButtons::on_button_toggled()
      m_Button_Close.signal_clicked().connect(sigc::mem_fun(*this,
                  &RadioButtons::on_button_clicked) );
    }

    RadioButtons::~RadioButtons()
    {
    }

    void RadioButtons::on_button_clicked()
    {
      set_visible(false); //to close the application.
    }

## Widgety odvozené z Range

`Gtk::Scale` inherits from `Gtk::Range`. `Gtk::Scrollbar` does not inherit from `Gtk::Range`, but it shares much functionality with `Gtk::Scale`. They both contain a "trough" and a "slider" (sometimes called a "thumbwheel" in other GUI environments). Dragging the slider with the pointer moves it within the trough, while clicking in the trough advances the slider towards the location of the click, either completely, or by a designated amount, depending on which mouse button is used. This should be familiar scrollbar behavior.

As will be explained in the Adjustments section, all range widgets are associated with an `Adjustment` object. To change the lower, upper, and current values used by the widget you need to use the methods of its `Adjustment`, which you can get with the `get_adjustment()` method. The range widgets' default constructors create an `Adjustment` automatically, or you can specify an existing `Adjustment`, maybe to share it with another widget. See the Adjustments section for further details.

Reference

### Posuvníkové widgety

These are standard scrollbars. They should be used only to scroll another widget, such as a `Gtk::Entry` or a `Gtk::Viewport`, though it's usually easier to use the `Gtk::ScrolledWindow` widget in most cases.

Orientace widgetu `Gtk::Scrollbar` může být vodorovná nebo svislá.

Reference

### Stupnicové widgety

Widgety `Gtk::Scale` (nebo „táhla“) umožňují uživateli vizuálně vybrat a měnit hodnotu v rámci určeného rozsahu. Můžete je použít například ke změně úrovně přiblížení náhledu obrázku, nebo k ovládání jasu barvy, nebo k určení počtu minut nečinnosti před zapnutím šetřiče obrazovky.

As with `Scrollbar`s, the orientation can be either horizontal or vertical. The default constructor creates an `Adjustment` with all of its values set to `0.0`. This isn't useful so you will need to set some `Adjustment` details to get meaningful behavior.

#### Užitečné metody

Widgety `Scale` umí zobrazit vedle stupnice aktuální číselnou hodnotu. Výchozí je zobrazení hodnoty, ale můžete to změnit pomocí metody `set_draw_value()`.

Hodnota zobrazená u stupnicových widgetů je ve výchozím stavu zaokrouhlovaná na jedno desetinné místo, stejně jako pole `value` v jejich objektu `Gtk::Adjustment`. Změnit to můžete pomocí metody `set_digits()`.

Také může, pomocí metody `set_value_pos()`, nastavit místo pro vykreslování hodnoty, relativně k vodicí dráze.

Reference

### Příklad

Tento příklad zobrazuje okno se třemi widgety pro určení rozmezí, které jsou všechny napojené na ten stejný widget přizpůsobení, spolu s párem ovládacích prvků pro přizpůsobení některých parametrů zmíněných výše a v kapitole o třídě `Adjustment`, takže nyní můžete vidět, jak ovlivňují fungování z pohledu uživatele.

#### Widgety odvozené z Range

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLE_RANGEWIDGETS_H
    #define GTKMM_EXAMPLE_RANGEWIDGETS_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      ~ExampleWindow() override;

    protected:
      //Signal handlers:
      void on_checkbutton_toggled();
      void on_dropdown_position();
      void on_adjustment1_value_changed();
      void on_adjustment2_value_changed();
      void on_button_quit();

      //Child widgets:
      Gtk::Box m_VBox_Top, m_VBox2, m_VBox_HScale;
      Gtk::Box m_HBox_Scales, m_HBox_DropDown, m_HBox_Digits, m_HBox_PageSize;

      Glib::RefPtr<Gtk::Adjustment> m_adjustment, m_adjustment_digits, m_adjustment_pagesize;

      Gtk::Scale m_VScale;
      Gtk::Scale m_HScale, m_Scale_Digits, m_Scale_PageSize;

      Gtk::Separator m_Separator;

      Gtk::CheckButton m_CheckButton;

      Gtk::Scrollbar m_Scrollbar;

      Gtk::DropDown m_DropDown_Position;
      Gtk::Button m_Button_Quit;
    };

    #endif //GTKMM_EXAMPLE_RANGEWIDGETS_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <array>
    #include <iostream>

    namespace
    {
    struct PositionTypeStruct
    {
      Gtk::PositionType position;
      Glib::ustring text;
    };

    const std::array<PositionTypeStruct, 4> positionTypes =
    {
      PositionTypeStruct{Gtk::PositionType::TOP,    "Top"},
      PositionTypeStruct{Gtk::PositionType::BOTTOM, "Bottom"},
      PositionTypeStruct{Gtk::PositionType::LEFT,   "Left"},
      PositionTypeStruct{Gtk::PositionType::RIGHT,  "Right"}
    };

    } // anonymous namespace

    ExampleWindow::ExampleWindow()
    :
      m_VBox_Top(Gtk::Orientation::VERTICAL, 0),
      m_VBox2(Gtk::Orientation::VERTICAL, 20),
      m_VBox_HScale(Gtk::Orientation::VERTICAL, 10),
      m_HBox_Scales(Gtk::Orientation::HORIZONTAL, 10),
      m_HBox_DropDown(Gtk::Orientation::HORIZONTAL, 10),
      m_HBox_Digits(Gtk::Orientation::HORIZONTAL, 10),
      m_HBox_PageSize(Gtk::Orientation::HORIZONTAL, 10),

      // Value, lower, upper, step_increment, page_increment, page_size:
      // Note that the page_size value only makes a difference for
      // scrollbar widgets, and the highest value you'll get is actually
      // (upper - page_size).
      m_adjustment( Gtk::Adjustment::create(0.0, 0.0, 101.0, 0.1, 1.0, 1.0) ),
      m_adjustment_digits( Gtk::Adjustment::create(1.0, 0.0, 5.0, 1.0, 2.0) ),
      m_adjustment_pagesize( Gtk::Adjustment::create(1.0, 1.0, 101.0) ),

      m_VScale(m_adjustment, Gtk::Orientation::VERTICAL),
      m_HScale(m_adjustment, Gtk::Orientation::HORIZONTAL),
      m_Scale_Digits(m_adjustment_digits),
      m_Scale_PageSize(m_adjustment_pagesize),

      // A checkbutton to control whether the value is displayed or not:
      m_CheckButton("Display value on scale widgets", 0),

      // Reuse the same adjustment again.
      // Notice how this causes the scales to always be updated
      // continuously when the scrollbar is moved.
      m_Scrollbar(m_adjustment),

      m_Button_Quit("Quit")
    {
      set_title("range controls");
      set_default_size(300, 350);

      //VScale:
      m_VScale.set_digits(1);
      m_VScale.set_value_pos(Gtk::PositionType::TOP);
      m_VScale.set_draw_value();
      m_VScale.set_inverted(); // highest value at top

      //HScale:
      m_HScale.set_digits(1);
      m_HScale.set_value_pos(Gtk::PositionType::TOP);
      m_HScale.set_draw_value();

      set_child(m_VBox_Top);
      m_VBox_Top.append(m_VBox2);
      m_VBox2.set_expand(true);
      m_VBox2.set_margin(10);
      m_VBox2.append(m_HBox_Scales);
      m_HBox_Scales.set_expand(true);

      //Put VScale and HScale (above scrollbar) side-by-side.
      m_HBox_Scales.append(m_VScale);
      m_VScale.set_expand(true);
      m_HBox_Scales.append(m_VBox_HScale);
      m_VBox_HScale.set_expand(true);

      m_VBox_HScale.append(m_HScale);
      m_HScale.set_expand(true);

      //Scrollbar:
      m_VBox_HScale.append(m_Scrollbar);
      m_Scrollbar.set_expand(true);

      //CheckButton:
      m_CheckButton.set_active();
      m_CheckButton.signal_toggled().connect( sigc::mem_fun(*this,
        &ExampleWindow::on_checkbutton_toggled) );
      m_VBox2.append(m_CheckButton);

      //Position DropDown:
      //Create the StringList:
      auto string_list = Gtk::StringList::create({});
      m_DropDown_Position.set_model(string_list);

      // Fill the DropDown's list model:
      for (const auto& positionType : positionTypes)
        string_list->append(positionType.text);

      m_VBox2.append(m_HBox_DropDown);
      m_HBox_DropDown.append(*Gtk::make_managed<Gtk::Label>("Scale Value Position:", 0));
      m_HBox_DropDown.append(m_DropDown_Position);
      m_DropDown_Position.property_selected().signal_changed().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_dropdown_position));
      m_DropDown_Position.set_selected(0); // Top
      m_DropDown_Position.set_expand(true);

      //Digits:
      m_HBox_Digits.append(*Gtk::make_managed<Gtk::Label>("Scale Digits:", 0));
      m_Scale_Digits.set_digits(0);
      m_Scale_Digits.set_expand(true);
      m_adjustment_digits->signal_value_changed().connect(sigc::mem_fun(*this,
        &ExampleWindow::on_adjustment1_value_changed));
      m_HBox_Digits.append(m_Scale_Digits);

      //Page Size:
      m_HBox_PageSize.append(*Gtk::make_managed<Gtk::Label>("Scrollbar Page Size:", 0));
      m_Scale_PageSize.set_digits(0);
      m_Scale_PageSize.set_expand(true);
      m_adjustment_pagesize->signal_value_changed().connect(sigc::mem_fun(*this,
        &ExampleWindow::on_adjustment2_value_changed));
      m_HBox_PageSize.append(m_Scale_PageSize);

      m_VBox2.append(m_HBox_Digits);
      m_VBox2.append(m_HBox_PageSize);
      m_VBox_Top.append(m_Separator);
      m_VBox_Top.append(m_Button_Quit);

      set_default_widget(m_Button_Quit);
      m_Button_Quit.signal_clicked().connect(sigc::mem_fun(*this,
        &ExampleWindow::on_button_quit));
      m_Button_Quit.set_margin(10);
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_checkbutton_toggled()
    {
      m_VScale.set_draw_value(m_CheckButton.get_active());
      m_HScale.set_draw_value(m_CheckButton.get_active());
    }

    void ExampleWindow::on_dropdown_position()
    {
      const auto selected = m_DropDown_Position.get_selected();
      if (selected == GTK_INVALID_LIST_POSITION)
        return;

      const auto postype = positionTypes[selected].position;
      m_VScale.set_value_pos(postype);
      m_HScale.set_value_pos(postype);
    }

    void ExampleWindow::on_adjustment1_value_changed()
    {
      const double val = m_adjustment_digits->get_value();
      m_VScale.set_digits((int)val);
      m_HScale.set_digits((int)val);
    }

    void ExampleWindow::on_adjustment2_value_changed()
    {
      const double val = m_adjustment_pagesize->get_value();
      m_adjustment->set_page_size(val);
      m_adjustment->set_page_increment(val);

      // Note that we don't have to emit the "changed" signal
      // because gtkmm does this for us.
    }

    void ExampleWindow::on_button_quit()
    {
      set_visible(false);
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

## Různé widgety

### Popisek (Label)

Labels are the main method of placing non-editable text in windows, for instance to place a title next to an `Entry` widget. You can specify the text in the constructor, or later with the `set_text()` or `set_markup()` methods.

Šířka popisku se přizpůsobuje automaticky. Můžete vytvářet i víceřádkové popisky vloženém zalomení ("\n") do textového řetězce popisku.

The label text can be justified using the `set_justify()` method. The widget is also capable of word-wrapping, which can be activated with `set_wrap()`.

Gtk::Label supports some simple formatting, for instance allowing you to make some text bold, colored, or larger. You can do this by providing a string to `set_markup()`, using the Pango Markup syntax. For instance, `<b>bold text</b> and <s>strikethrough text</s>` .

Reference

#### Příklad

Níže je krátký příklad, který ilustruje tyto funkce. Pro lepší ukázku stylů popisku vyžívá widget Frame. (Widget Frame je vysvětlen v kapitole Rám (Frame).) Podle nastavení systému je možné, že první znak v `m_Label_Normal` se zobrazí podtržený, jen když zmáčknete klávesu Alt.

##### Popisek (Label)

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:

      //Child widgets:
      Gtk::Box m_HBox;
      Gtk::Box m_VBox, m_VBox2;
      Gtk::Frame m_Frame_Normal, m_Frame_Multi, m_Frame_Left, m_Frame_Right,
        m_Frame_LineWrapped, m_Frame_FilledWrapped, m_Frame_Underlined;
      Gtk::Label m_Label_Normal, m_Label_Multi, m_Label_Left, m_Label_Right,
        m_Label_LineWrapped, m_Label_FilledWrapped, m_Label_Underlined;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    :
      m_HBox(Gtk::Orientation::HORIZONTAL, 5),
      m_VBox(Gtk::Orientation::VERTICAL, 5),
      m_VBox2(Gtk::Orientation::VERTICAL, 5),
      m_Frame_Normal("Normal Label"),
      m_Frame_Multi("Multi-line Label"),
      m_Frame_Left("Left Justified Label"),
      m_Frame_Right("Right Justified Label"),
      m_Frame_LineWrapped("Line wrapped label"),
      m_Frame_FilledWrapped("Filled, wrapped label"),
      m_Frame_Underlined("Underlined label"),
      m_Label_Normal("_This is a Normal label", true),
      m_Label_Multi("This is a Multi-line label.\nSecond line\nThird line"),
      m_Label_Left("This is a Left-Justified\nMulti-line label.\nThird line"),
      m_Label_Right("This is a Right-Justified\nMulti-line label.\nThird line"),
      m_Label_Underlined("<u>This label is underlined!</u>\n"
              "<u>T</u>h<u>is one is</u> <u>u</u>n<u>derlin</u>ed "
              "in<u> q</u>u<u>ite a f</u>u<u>nky</u> fashion")
    {
      set_title("Label");

      m_HBox.set_margin(5);
      set_child(m_HBox);

      m_HBox.append(m_VBox);

      m_Frame_Normal.set_child(m_Label_Normal);
      m_VBox.append(m_Frame_Normal);

      m_Frame_Multi.set_child(m_Label_Multi);
      m_VBox.append(m_Frame_Multi);

      m_Label_Left.set_justify(Gtk::Justification::LEFT);
      m_Frame_Left.set_child(m_Label_Left);
      m_VBox.append(m_Frame_Left);

      m_Label_Right.set_justify(Gtk::Justification::RIGHT);
      m_Frame_Right.set_child(m_Label_Right);
      m_VBox.append(m_Frame_Right);

      m_HBox.append(m_VBox2);

      m_Label_LineWrapped.set_text(
              "This is an example of a line-wrapped label.  It "
              /* add a big space to the next line to test spacing */
              "should not be taking up the entire             "
              "width allocated to it, but automatically "
              "wraps the words to fit.  "
              "The time has come, for all good men, to come to "
              "the aid of their party.  "
              "The sixth sheik's six sheep's sick.\n"
              "     It supports multiple paragraphs correctly, "
              "and  correctly   adds "
              "many          extra  spaces. ");
      m_Label_LineWrapped.set_wrap();
      m_Frame_LineWrapped.set_child(m_Label_LineWrapped);
      m_VBox2.append(m_Frame_LineWrapped);

      m_Label_FilledWrapped.set_text(
              "This is an example of a line-wrapped, filled label.  "
              "It should be taking "
              "up the entire              width allocated to it.  "
              "Here is a sentence to prove "
              "my point.  Here is another sentence. "
              "Here comes the sun, do de do de do.\n"
              "    This is a new paragraph.\n"
              "    This is another newer, longer, better "
              "paragraph.  It is coming to an end, "
              "unfortunately.");
      m_Label_FilledWrapped.set_justify(Gtk::Justification::FILL);
      m_Label_FilledWrapped.set_wrap();
      m_Frame_FilledWrapped.set_child(m_Label_FilledWrapped);
      m_VBox2.append(m_Frame_FilledWrapped);

      m_Label_Underlined.set_justify(Gtk::Justification::LEFT);
      m_Label_Underlined.set_use_markup(true);
      m_Frame_Underlined.set_child(m_Label_Underlined);
      m_VBox2.append(m_Frame_Underlined);
    }

    ExampleWindow::~ExampleWindow()
    {
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

### Vstupní pole (Entry)

#### Jednoduché použití

Vstupní pole umožňují uživateli zadat text. Obsah pole můžete měnit pomocí metody `set_text()` a aktuální obsah číst pomocí metody `get_text()`.

Příležitostně můžete potřebovat, aby byl widget `Entry` jen ke čtení. Toho se dá dosáhnout předáním `false` metodě `set_editable()`.

Pro zadávání hesel, heslových frází a jiných citlivých informací, u kterých nechcete, aby se při psaní zobrazovaly, zavolejte metodu `set_visibility()` s parametrem `false`, což způsobí skrytí textu.

You might want to be notified whenever the user types in a text entry widget. `Gtk::Entry` provides two signals, `activate` (since gtkmm 4.8) and `changed`, for this purpose. `activate` is emitted when the user presses the Enter key in a text-entry widget; `changed` is emitted when the text in the widget changes. You can use these, for instance, to validate or filter the text the user types. Moving the keyboard focus to another widget may also signal that the user has finished entering text. The `leave` signal in a `Gtk::EventControllerFocus` can notify you when that happens. The ComboBox with an Entry section contains example programs that use these signals.

If you pass `true` to the `set_activates_default()` method, pressing Enter in the `Gtk::Entry` will activate the default widget for the window containing the `Gtk::Entry`. This is especially useful in dialog boxes. The default widget is usually one of the dialog buttons, which e.g. will close the dialog box. To set a widget as the default widget, use `Gtk::Window::set_default_widget()`.

Reference

##### Příklad s jednoduchým vstupním polem

Tento příklad používá `Gtk::Entry`. Má také dvě zaškrtávací políčka `CheckButton`, kterými můžete přepínat příznaky editovatelnosti a viditelnosti.

###### Vstupní pole (Entry)

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_checkbox_editable_toggled();
      void on_checkbox_visibility_toggled();
      void on_button_close();

      //Child widgets:
      Gtk::Box m_HBox;
      Gtk::Box m_VBox;
      Gtk::Entry m_Entry;
      Gtk::Button m_Button_Close;
      Gtk::CheckButton m_CheckButton_Editable, m_CheckButton_Visible;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::Orientation::VERTICAL),
      m_Button_Close("Close"),
      m_CheckButton_Editable("Editable"),
      m_CheckButton_Visible("Visible")
    {
      set_size_request(200, 100);
      set_title("Gtk::Entry");

      set_child(m_VBox);

      m_Entry.set_max_length(50);
      m_Entry.set_text("hello");
      m_Entry.set_text(m_Entry.get_text() + " world");
      m_Entry.select_region(0, m_Entry.get_text_length());
      m_Entry.set_expand(true);
      m_VBox.append(m_Entry);

      m_VBox.append(m_HBox);

      m_HBox.append(m_CheckButton_Editable);
      m_CheckButton_Editable.set_expand(true);
      m_CheckButton_Editable.signal_toggled().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_checkbox_editable_toggled) );
      m_CheckButton_Editable.set_active(true);

      m_HBox.append(m_CheckButton_Visible);
      m_CheckButton_Visible.set_expand(true);
      m_CheckButton_Visible.signal_toggled().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_checkbox_visibility_toggled) );
      m_CheckButton_Visible.set_active(true);

      m_Button_Close.signal_clicked().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_button_close) );
      m_VBox.append(m_Button_Close);
      m_Button_Close.set_expand();
      set_default_widget(m_Button_Close);
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_checkbox_editable_toggled()
    {
      m_Entry.set_editable(m_CheckButton_Editable.get_active());
    }

    void ExampleWindow::on_checkbox_visibility_toggled()
    {
      m_Entry.set_visibility(m_CheckButton_Visible.get_active());
    }

    void ExampleWindow::on_button_close()
    {
      set_visible(false);
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

#### Doplňování vstupu

`Gtk::EntryCompletion` is deprecated since gtkmm 4.10. There is no replacement in gtkmm.

An `Entry` widget can offer a drop-down list of pre-existing choices based on the first few characters typed by the user. For instance, a search dialog could suggest text from previous searches.

To enable this functionality, you must create an `EntryCompletion` object, and provide it to the `Entry` widget via the `set_completion()` method.

Pomocí metody `set_model()` můžete pro `EntryCompletion` určit `TreeModel`, který bude obsahovat možné vstupy. Pak byste měli ještě zavolat `set_text_column()` k určení sloupce ve vašem modelu, který se má používat k porovnávání možných textových vstupů.

Případně, když by seznam možných vstupů byl příliš dlouhý, nebo je nevhodné jej přímo vygenerovat, můžete místo toho použít zpětné volání, které zadáte pomocí `set_match_func()`. Hodí se to také, když potřebujete porovnávat jinou část řetězce, než začátek.

Reference

##### Příklad doplňování vstupu

Tento příklad vytvoří `Gtk::EntryCompletion` a přidruží jej k widgetu `Gtk::Entry`. Doplňování využívá `Gtk::TreeModel` s možnými vstupy a některé doplňující činnosti.

###### Doplňování vstupu

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_close();

      //See the comment in the implementation:
      //bool on_completion_match(const Glib::ustring& key, const Gtk::TreeModel::const_iterator& iter);

      //Tree model columns, for the EntryCompletion's filter model:
      class ModelColumns : public Gtk::TreeModel::ColumnRecord
      {
      public:
        ModelColumns()
        { add(m_col_id); add(m_col_name); }

        Gtk::TreeModelColumn<unsigned int> m_col_id;
        Gtk::TreeModelColumn<Glib::ustring> m_col_name;
      };

      ModelColumns m_Columns;

      //Child widgets:
      Gtk::Box m_HBox;
      Gtk::Box m_VBox;
      Gtk::Entry m_Entry;
      Gtk::Label m_Label;
      Gtk::Button m_Button_Close;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::Orientation::VERTICAL),
      m_Label("Press a or b to see a list of possible completions."),
      m_Button_Close("Close")
    {
      //set_size_request(200, 100);
      set_title("Gtk::EntryCompletion");

      set_child(m_VBox);
      m_VBox.append(m_Entry);

      m_VBox.append(m_Label);
      m_Label.set_expand(true);

      m_Button_Close.signal_clicked().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_button_close) );
      m_VBox.append(m_Button_Close);
      set_default_widget(m_Button_Close);

      //Add an EntryCompletion:
      auto completion =
          Gtk::EntryCompletion::create();
      m_Entry.set_completion(completion);

      //Create and fill the completion's filter model
      auto refCompletionModel =
          Gtk::ListStore::create(m_Columns);
      completion->set_model(refCompletionModel);

      // For more complex comparisons, use a filter match callback, like this.
      // See the comment below for more details:
      //completion->set_match_func( sigc::mem_fun(*this,
                  //&ExampleWindow::on_completion_match) );

      //Fill the TreeView's model
      auto row = *(refCompletionModel->append());
      row[m_Columns.m_col_id] = 1;
      row[m_Columns.m_col_name] = "Alan Zebedee";

      row = *(refCompletionModel->append());
      row[m_Columns.m_col_id] = 2;
      row[m_Columns.m_col_name] = "Adrian Boo";

      row = *(refCompletionModel->append());
      row[m_Columns.m_col_id] = 3;
      row[m_Columns.m_col_name] = "Bob McRoberts";

      row = *(refCompletionModel->append());
      row[m_Columns.m_col_id] = 4;
      row[m_Columns.m_col_name] = "Bob McBob";

      //Tell the completion what model column to use to
      //- look for a match (when we use the default matching, instead of
      //  set_match_func().
      //- display text in the entry when a match is found.
      completion->set_text_column(m_Columns.m_col_name);
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_close()
    {
      set_visible(false);
    }

    /* You can do more complex matching with a handler like this.
     * For instance, you could check for substrings inside the string instead of the start,
     * or you could look for the key in extra model columns as well as the model column that will be displayed.
     * The code here is not actually more complex - it's a reimplementation of the default behaviour.
     *
    bool ExampleWindow::on_completion_match(const Glib::ustring& key, const
            Gtk::TreeModel::const_iterator& iter)
    {
      if(iter)
      {
        const auto row = *iter;

        const auto key_length = key.size();
        auto filter_string = row[m_Columns.m_col_name];

        auto filter_string_start = filter_string.substr(0, key_length);
        //The key is lower-case, even if the user input is not.
        filter_string_start = filter_string_start.lowercase();

        if(key == filter_string_start)
          return true; //A match was found.
      }

      return false; //No match.
    }
    */

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

#### Ikony ve vstupním poli

An `Entry` widget can show an icon at the start or end of the text area. The icon can be specified by methods such as `set_icon_from_paintable()` or `set_icon_from_icon_name()`. An application can respond to the user pressing the icon by handling the `signal_icon_press` signal.

##### Příklad vstupního pole s ikonami

Tento příklad ukazuje widget `Gtk::Entry` s pojmenovanou vyhledávací ikonou, při jejímž zmáčknutí vypíše text do terminálu.

###### Vstupní pole s ikonou

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_icon_pressed(Gtk::Entry::IconPosition icon_pos);
      void on_button_close();

      //Child widgets:
      Gtk::Box m_VBox;
      Gtk::Entry m_Entry;
      Gtk::Button m_Button_Close;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::Orientation::VERTICAL),
      m_Button_Close("Close")
    {
      set_title("Gtk::Entry");

      set_child(m_VBox);

      m_Entry.set_max_length(50);
      m_Entry.set_text("Hello world");
      m_VBox.append(m_Entry);

      m_Entry.set_icon_from_icon_name("edit-find");
      m_Entry.signal_icon_press().connect( sigc::mem_fun(*this, &ExampleWindow::on_icon_pressed) );

      m_Button_Close.signal_clicked().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_button_close) );
      m_VBox.append(m_Button_Close);
      set_default_widget(m_Button_Close);
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_icon_pressed(Gtk::Entry::IconPosition /* icon_pos */)
    {
      std::cout << "Icon pressed." << std::endl;
    }

    void ExampleWindow::on_button_close()
    {
      set_visible(false);
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

#### Vstupní pole s ukazatelem průběhu

Widget `Entry` umí zobrazovat ukazatel průběhu uvnitř textové oblasti, pod zadávaným textem. Ukazatel průběhu se zobrazí, když je zavolána metoda `set_progress_fraction()` nebo `set_progress_pulse_step()`.

##### Příklad ukazatele průběhu ve vstupním poli

Tento příklad ukazuje widget `Gtk::Entry` s ukazatelem průběhu.

###### Vstupní pole s ukazatelem průběhu

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      bool on_timeout();
      void on_button_close();

      //Child widgets:
      Gtk::Box m_VBox;
      Gtk::Entry m_Entry;
      Gtk::Button m_Button_Close;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::Orientation::VERTICAL),
      m_Button_Close("Close")
    {
      set_title("Gtk::Entry");

      set_child(m_VBox);

      m_Entry.set_max_length(50);
      m_Entry.set_text("Hello world");
      m_VBox.append(m_Entry);

      //Change the progress fraction every 0.1 second:
      Glib::signal_timeout().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_timeout),
        100
      );

      m_Button_Close.signal_clicked().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_button_close) );
      m_VBox.append(m_Button_Close);
      set_default_widget(m_Button_Close);
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    bool ExampleWindow::on_timeout()
    {
      static double fraction = 0;
      m_Entry.set_progress_fraction(fraction);

      fraction += 0.01;
      if(fraction > 1)
        fraction = 0;

      return true;
    }

    void ExampleWindow::on_button_close()
    {
      set_visible(false);
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

### Číselník (SpinButton)

`SpinButton` umožňuje uživateli vybrat hodnotu z nějakého rozsahu číselných hodnot. Jedná se o widget `Entry` po stranně s tlačítky pro zvyšování a snižování. Klikání na tlačítka způsobuje zvýšení nebo snížení hodnoty v číselníku v rámci povoleného rozsahu hodnot. Widget `Entry` můžete použít také k přímému zadání hodnoty.

Hodnota má přizpůsobitelný počet desetinných míst a velikost kroku je také nastavitelná. `SpinButton` má rovněž funkci „automatického opakování“: když držíte zmáčknuté tlačítko pro zvyšování nebo snižování hodnoty, může se volitelně hodnota začít měnit rychleji, v závislosti na tom, jak dlouho je tlačítko drženo.

`SpinButton`s use an Adjustment object to hold information about the range of values. These Adjustment attributes are used by the Spin Button like so:

- `value`: value for the Spin Button

- `lower`: lower range value

- `upper`: upper range value

- `step_increment`: value to increment/decrement when pressing mouse button 1

- `page_increment`: value to increment/decrement when pressing mouse button 2

- `page_size`: unused

Navíc se dá použít třetí tlačítko myši ke skokům přímo na hodnoty `upper` nebo `lower`.

`SpinButton` si umí vytvořit výchozí objekt `Adjustment`, ke kterému se můžete dostat přes metodu `get_adjustment()`, nebo můžete v konstruktoru určit nějaký již existující objekt `Adjustment`.

#### Metody

Počet desetinných míst můžete měnit pomocí metody `set_digits()`.

Hodnotu číselníku můžete nastavit pomocí metody `set_value()` a naopak ji získat pomocí `get_value()`.

Metoda `spin` „pootočí“ číselníkem `SpinButton` stejně, jako když uživatel klikne na tlačítko pro zvýšení nebo snížení. Potřebujete určit `Gtk::SpinType`, podle kterého se řídí směr nebo nová hodnota.

Abyste uživateli zabránili v psaní nečíselných znaků do vstupního pole, předejte metodě `set_numeric()` hodnotu `true`.

Aby číselník `SpinButton` cyklicky přecházel mezi horní a dolní hranicí, použijte metodu `set_wrap()`.

Když jej chcete přinutit, aby se automaticky dorovnával na nejbližší násobek `step_increment`, použijte `set_snap_to_ticks()`.

Reference

#### Příklad

Zde je ukázka widgetu `SpinButton` v akci:

##### Číselník (SpinButton)

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_checkbutton_snap();
      void on_checkbutton_numeric();
      void on_spinbutton_digits_changed();
      void on_button_close();

      enum enumValueFormats
      {
        VALUE_FORMAT_INT,
        VALUE_FORMAT_FLOAT
      };
      void on_button_getvalue(enumValueFormats display);

      //Child widgets:
      Gtk::Frame m_Frame_NotAccelerated, m_Frame_Accelerated;
      Gtk::Box m_HBox_NotAccelerated, m_HBox_Accelerated,
        m_HBox_Buttons;
      Gtk::Box m_VBox_Main, m_VBox, m_VBox_Day, m_VBox_Month, m_VBox_Year,
        m_VBox_Accelerated, m_VBox_Value, m_VBox_Digits;
      Gtk::Label m_Label_Day, m_Label_Month, m_Label_Year,
        m_Label_Value, m_Label_Digits,
        m_Label_ShowValue;
      Glib::RefPtr<Gtk::Adjustment> m_adjustment_day, m_adjustment_month, m_adjustment_year,
        m_adjustment_value, m_adjustment_digits;
      Gtk::SpinButton m_SpinButton_Day, m_SpinButton_Month, m_SpinButton_Year,
        m_SpinButton_Value, m_SpinButton_Digits;
      Gtk::CheckButton m_CheckButton_Snap, m_CheckButton_Numeric;
      Gtk::Button m_Button_Int, m_Button_Float, m_Button_Close;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <iostream>
    #include <cstdio>

    ExampleWindow::ExampleWindow()
    :
      m_Frame_NotAccelerated("Not accelerated"),
      m_Frame_Accelerated("Accelerated"),
      m_VBox_Main(Gtk::Orientation::VERTICAL, 5),
      m_VBox(Gtk::Orientation::VERTICAL),
      m_VBox_Day(Gtk::Orientation::VERTICAL),
      m_VBox_Month(Gtk::Orientation::VERTICAL),
      m_VBox_Year(Gtk::Orientation::VERTICAL),
      m_VBox_Accelerated(Gtk::Orientation::VERTICAL),
      m_VBox_Value(Gtk::Orientation::VERTICAL),
      m_VBox_Digits(Gtk::Orientation::VERTICAL),
      m_Label_Day("Day: ", Gtk::Align::START),
      m_Label_Month("Month: ", Gtk::Align::START),
      m_Label_Year("Year: ", Gtk::Align::START),
      m_Label_Value("Value: ", Gtk::Align::START),
      m_Label_Digits("Digits: ", Gtk::Align::START),
      m_adjustment_day( Gtk::Adjustment::create(1.0, 1.0, 31.0, 1.0, 5.0, 0.0) ),
      m_adjustment_month( Gtk::Adjustment::create(1.0, 1.0, 12.0, 1.0, 5.0, 0.0) ),
      m_adjustment_year( Gtk::Adjustment::create(2012.0, 1.0, 2200.0, 1.0, 100.0, 0.0) ),
      m_adjustment_value( Gtk::Adjustment::create(0.0, -10000.0, 10000.0, 0.5, 100.0, 0.0) ),
      m_adjustment_digits( Gtk::Adjustment::create(2.0, 1.0, 5.0, 1.0, 1.0, 0.0) ),
      m_SpinButton_Day(m_adjustment_day),
      m_SpinButton_Month(m_adjustment_month),
      m_SpinButton_Year(m_adjustment_year),
      m_SpinButton_Value(m_adjustment_value, 1.0, 2),
      m_SpinButton_Digits(m_adjustment_digits),
      m_CheckButton_Snap("Snap to 0.5-ticks"),
      m_CheckButton_Numeric("Numeric only input mode"),
      m_Button_Int("Value as Int"),
      m_Button_Float("Value as Float"),
      m_Button_Close("Close")
    {
      set_title("SpinButton");

      m_VBox_Main.set_margin(10);
      set_child(m_VBox_Main);

      m_VBox_Main.append(m_Frame_NotAccelerated);

      m_VBox.set_margin(5);
      m_Frame_NotAccelerated.set_child(m_VBox);

      /* Day, month, year spinners */

      m_VBox.set_spacing(5);
      m_VBox.append(m_HBox_NotAccelerated);

      m_Label_Day.set_expand();
      m_VBox_Day.append(m_Label_Day);

      m_SpinButton_Day.set_wrap();
      m_SpinButton_Day.set_expand();
      m_VBox_Day.append(m_SpinButton_Day);

      m_HBox_NotAccelerated.set_spacing(5);
      m_HBox_NotAccelerated.append(m_VBox_Day);

      m_Label_Month.set_expand();
      m_VBox_Month.append(m_Label_Month);

      m_SpinButton_Month.set_wrap();
      m_SpinButton_Month.set_expand();
      m_VBox_Month.append(m_SpinButton_Month);

      m_HBox_NotAccelerated.append(m_VBox_Month);

      m_Label_Year.set_expand();
      m_VBox_Year.append(m_Label_Year);

      m_SpinButton_Year.set_wrap();
      m_SpinButton_Year.set_expand();
      m_SpinButton_Year.set_size_request(55, -1);
      m_VBox_Year.append(m_SpinButton_Year);

      m_HBox_NotAccelerated.append(m_VBox_Year);

      //Accelerated:
      m_VBox_Main.append(m_Frame_Accelerated);

      m_VBox_Accelerated.set_margin(5);
      m_Frame_Accelerated.set_child(m_VBox_Accelerated);

      m_VBox_Accelerated.set_spacing(5);
      m_VBox_Accelerated.append(m_HBox_Accelerated);

      m_HBox_Accelerated.append(m_VBox_Value);

      m_Label_Value.set_expand();
      m_VBox_Value.append(m_Label_Value);

      m_SpinButton_Value.set_wrap();
      m_SpinButton_Value.set_expand();
      m_SpinButton_Value.set_size_request(100, -1);
      m_VBox_Value.append(m_SpinButton_Value);

      m_HBox_Accelerated.append(m_VBox_Digits);

      m_VBox_Digits.append(m_Label_Digits);
      m_Label_Digits.set_expand();

      m_SpinButton_Digits.set_wrap();
      m_adjustment_digits->signal_value_changed().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_spinbutton_digits_changed) );

      m_VBox_Digits.append(m_SpinButton_Digits);
      m_SpinButton_Digits.set_expand();

      //CheckButtons:
      m_VBox_Accelerated.append(m_CheckButton_Snap);
      m_CheckButton_Snap.set_expand();
      m_CheckButton_Snap.set_active();
      m_CheckButton_Snap.signal_toggled().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_checkbutton_snap) );

      m_VBox_Accelerated.append(m_CheckButton_Numeric);
      m_CheckButton_Numeric.set_expand();
      m_CheckButton_Numeric.set_active();
      m_CheckButton_Numeric.signal_toggled().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_checkbutton_numeric) );

      //Buttons:
      m_VBox_Accelerated.append(m_HBox_Buttons);

      m_Button_Int.signal_clicked().connect( sigc::bind( sigc::mem_fun(*this,
                      &ExampleWindow::on_button_getvalue), VALUE_FORMAT_INT) );
      m_HBox_Buttons.set_spacing(5);
      m_HBox_Buttons.append(m_Button_Int);
      m_Button_Int.set_expand();

      m_Button_Float.signal_clicked().connect( sigc::bind( sigc::mem_fun(*this,
                      &ExampleWindow::on_button_getvalue), VALUE_FORMAT_FLOAT) );
      m_HBox_Buttons.append(m_Button_Float);
      m_Button_Float.set_expand();

      m_VBox_Accelerated.append(m_Label_ShowValue);
      m_Label_ShowValue.set_expand();
      m_Label_ShowValue.set_text("0");

      //Close button:
      m_Button_Close.signal_clicked().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_button_close) );
      m_VBox_Main.append(m_Button_Close);
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_close()
    {
      set_visible(false);
    }

    void ExampleWindow::on_checkbutton_snap()
    {
      m_SpinButton_Value.set_snap_to_ticks( m_CheckButton_Snap.get_active() );
    }

    void ExampleWindow::on_checkbutton_numeric()
    {
      m_SpinButton_Value.set_numeric( m_CheckButton_Numeric.get_active() );
    }

    void ExampleWindow::on_spinbutton_digits_changed()
    {
      m_SpinButton_Value.set_digits( m_SpinButton_Digits.get_value_as_int() );
    }

    void ExampleWindow::on_button_getvalue(enumValueFormats display)
    {
      gchar buf[32];

      if (display == VALUE_FORMAT_INT)
        sprintf (buf, "%d", m_SpinButton_Value.get_value_as_int());
      else
        sprintf (buf, "%0.*f", m_SpinButton_Value.get_digits(),
                m_SpinButton_Value.get_value());

      m_Label_ShowValue.set_text(buf);
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

### Ukazatel průběhu (PrograssBar)

Ukazatel průběhu zobrazuje stav probíhající operace. Například může `ProgressBar` zobrazovat, jak velká část úlohy je dokončená.

To change the value shown, use the `set_fraction()` method, passing a double between 0.0 and 1.0 to provide the new fraction.

Výchozí podoba widgetu `ProgressBar` je vodorovně a zleva doprava, ale můžete to změnit na svislou zavoláním metody `set_orientation()`.

Reference

#### Režim aktivity

Besides indicating the amount of progress that has occurred, the progress bar can also be used to indicate that there is some activity; this is done by placing the progress bar in activity mode. In this mode, the progress bar displays a small rectangle which moves back and forth. Activity mode is useful in situations where the progress of an operation cannot be calculated as a value range (e.g., receiving a file of unknown length).

Abyste to mohli provést, musíte volat v pravidelných intervalech metodu `pulse()`. Můžete také pomocí metody `set_pulse_step()` zvolit velikost kroku.

The progress bar can also display a configurable text string next to the bar, using the `set_text()` method.

#### Příklad

##### Ukazatel průběhu (PrograssBar)

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_checkbutton_text();
      void on_checkbutton_activity();
      void on_checkbutton_inverted();

      bool on_timeout();
      void on_button_close();

      //Child widgets:
      Gtk::Box m_VBox;
      Gtk::Grid m_Grid;
      Gtk::ProgressBar m_ProgressBar;
      Gtk::Separator m_Separator;
      Gtk::CheckButton m_CheckButton_Text, m_CheckButton_Activity, m_CheckButton_Inverted;
      Gtk::Button m_Button_Close;

      sigc::connection m_connection_timeout;
      bool m_bActivityMode;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::Orientation::VERTICAL, 5),
      m_CheckButton_Text("Show text"),
      m_CheckButton_Activity("Activity mode"),
      m_CheckButton_Inverted("Right to Left"),
      m_Button_Close("Close"),
      m_bActivityMode(false)
    {
      set_resizable();
      set_title("Gtk::ProgressBar");

      m_VBox.set_margin(10);
      set_child(m_VBox);

      m_VBox.append(m_ProgressBar);
      m_ProgressBar.set_margin_end(5);
      m_ProgressBar.set_halign(Gtk::Align::CENTER);
      m_ProgressBar.set_valign(Gtk::Align::CENTER);
      m_ProgressBar.set_size_request(100, -1);
      m_ProgressBar.set_text("some text");
      m_ProgressBar.set_show_text(false);

      //Add a timer callback to update the value of the progress bar:
      m_connection_timeout = Glib::signal_timeout().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_timeout), 50 );

      m_VBox.append(m_Separator);
      m_VBox.append(m_Grid);
      m_Grid.set_expand(true);
      m_Grid.set_row_homogeneous(true);

      //Add a check button to select displaying of the trough text:
      m_Grid.attach(m_CheckButton_Text, 0, 0);
      m_CheckButton_Text.set_margin(5);
      m_CheckButton_Text.signal_toggled().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_checkbutton_text) );

      //Add a check button to toggle activity mode:
      m_Grid.attach(m_CheckButton_Activity, 0, 1);
      m_CheckButton_Activity.set_margin(5);
      m_CheckButton_Activity.signal_toggled().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_checkbutton_activity) );

      //Add a check button to select growth from left to right or from right to left:
      m_Grid.attach(m_CheckButton_Inverted, 0, 2);
      m_CheckButton_Inverted.set_margin(5);
      m_CheckButton_Inverted.signal_toggled().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_checkbutton_inverted) );

      //Add a button to exit the program.
      m_VBox.append(m_Button_Close);
      m_Button_Close.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_close) );
      set_default_widget(m_Button_Close);
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_checkbutton_text()
    {
      const bool show_text = m_CheckButton_Text.get_active();
      m_ProgressBar.set_show_text(show_text);
    }

    void ExampleWindow::on_checkbutton_activity()
    {
      m_bActivityMode = m_CheckButton_Activity.get_active();

      if(m_bActivityMode)
        m_ProgressBar.pulse();
      else
        m_ProgressBar.set_fraction(0.0);
    }

    void ExampleWindow::on_checkbutton_inverted()
    {
      const bool inverted = m_CheckButton_Inverted.get_active();
      m_ProgressBar.set_inverted(inverted);
    }

    void ExampleWindow::on_button_close()
    {
      set_visible(false);
    }

    /* Update the value of the progress bar so that we get
     * some movement */
    bool ExampleWindow::on_timeout()
    {
      if(m_bActivityMode)
        m_ProgressBar.pulse();
      else
      {
        double new_val = m_ProgressBar.get_fraction() + 0.01;

        if(new_val > 1.0)
          new_val = 0.0;

        //Set the new value:
        m_ProgressBar.set_fraction(new_val);
      }

      //As this is a timeout function, return true so that it
      //continues to get called
      return true;
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

### Informační lišta (InfoBar)

`InfoBar` může zobrazovat menší počet informací nebo stručné dotazy. Na rozdíl od dialogového okna `Dialog` neotevírá nové okno, ale objeví se v horní části aktuálního okna. Jeho API je velmi podobné API Gtk::Dialog.

Reference

#### Příklad

The `InfoBar` widget is deprecated since gtkmm 4.10. The example shows an info bar consisting of a `Box` with a `Label` and a `Button`.

##### Informační lišta (InfoBar)

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      ~ExampleWindow() override;

    protected:
      //Signal handlers:
      void on_infobar_ok();
      void on_button_quit();
      void on_button_clear();
      void on_textbuffer_changed();
      void on_parsing_error(const Glib::RefPtr<const Gtk::CssSection>& section,
        const Glib::Error& error);

      void set_infobar_background();

      //Child widgets:
      Gtk::Box m_VBox;

      Gtk::ScrolledWindow m_ScrolledWindow;
      Gtk::TextView m_TextView;

      Glib::RefPtr<Gtk::TextBuffer> m_refTextBuffer;

      Gtk::Box m_InfoBar;
      Gtk::Label m_Message_Label;
      Gtk::Button m_Button_OK;

      Gtk::Box m_ButtonBox;
      Gtk::Button m_Button_Quit;
      Gtk::Button m_Button_Clear;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <iostream>

    // The Gtk::InfoBar widget is deprecated since gtk/gtkmm 4.10.
    // A Box with a Label and Button is often a good replacement.
    // If you don't care about its background color, it's even easier
    // than the InfoBar replacement in this example program.

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::Orientation::VERTICAL, 6),
      m_InfoBar(Gtk::Orientation::HORIZONTAL, 6),
      m_Button_OK("_OK", true),
      m_ButtonBox(Gtk::Orientation::HORIZONTAL, 6),
      m_Button_Quit("_Quit", true),
      m_Button_Clear("_Clear", true)
    {
      set_title("Infobar example");
      set_default_size(400, 200);

      m_VBox.set_margin(6);
      set_child(m_VBox);

      // Add the message label to the InfoBar:
      m_InfoBar.append(m_Message_Label);
      m_Message_Label.set_margin_start(5);
      m_Message_Label.set_hexpand(true);
      m_Message_Label.set_halign(Gtk::Align::START);

      // Add an ok button to the InfoBar:
      m_InfoBar.append(m_Button_OK);
      m_Button_OK.set_margin(5);

      // Add the InfoBar to the vbox:
      m_VBox.append(m_InfoBar);

      // Create the buffer and set it for the TextView:
      m_refTextBuffer = Gtk::TextBuffer::create();
      m_TextView.set_buffer(m_refTextBuffer);

      // Add the TextView, inside a ScrolledWindow:
      m_ScrolledWindow.set_child(m_TextView);

      // Show the scrollbars only when they are necessary:
      m_ScrolledWindow.set_policy(Gtk::PolicyType::AUTOMATIC, Gtk::PolicyType::AUTOMATIC);
      m_ScrolledWindow.set_expand();

      m_VBox.append(m_ScrolledWindow);

      // Add button box:
      m_VBox.append(m_ButtonBox);

      m_ButtonBox.append(m_Button_Clear);
      m_ButtonBox.append(m_Button_Quit);
      m_Button_Clear.set_hexpand(true);
      m_Button_Clear.set_halign(Gtk::Align::END);

      // Connect signals:
      m_Button_OK.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_infobar_ok) );
      m_Button_Quit.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_quit) );
      m_Button_Clear.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_clear) );
      m_refTextBuffer->signal_changed().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_textbuffer_changed) );

      // Keep the InfoBar hidden until a message needs to be shown:
      m_InfoBar.set_visible(false);
      set_infobar_background();

      // Make the clear button insensitive until text is typed in the buffer.  When
      // the button is sensitive and it is pressed, the InfoBar is displayed with a
      // message.
      m_Button_Clear.set_sensitive(false);
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_infobar_ok()
    {
      // Clear the message and hide the info bar:
      m_Message_Label.set_text("");
      m_InfoBar.set_visible(false);
    }

    void ExampleWindow::on_button_quit()
    {
      set_visible(false);
    }

    void ExampleWindow::on_button_clear()
    {
      m_refTextBuffer->set_text("");
      m_Message_Label.set_text("Cleared the text.");
      m_InfoBar.set_visible(true);
    }

    void ExampleWindow::on_textbuffer_changed()
    {
      m_Button_Clear.set_sensitive(m_refTextBuffer->size() > 0);
    }

    void ExampleWindow::set_infobar_background()
    {
      // Concerning color in CSS files, see https://www.w3.org/TR/css-color-3.
      const std::string css = "#infobarbox { background-color: beige; }";

      m_InfoBar.set_name("infobarbox");
      auto css_provider = Gtk::CssProvider::create();
      Gtk::StyleProvider::add_provider_for_display(
        m_InfoBar.get_display(), css_provider, GTK_STYLE_PROVIDER_PRIORITY_APPLICATION);

      css_provider->load_from_data(css);
      css_provider->signal_parsing_error().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_parsing_error));
    }

    void ExampleWindow::on_parsing_error(const Glib::RefPtr<const Gtk::CssSection>& section,
      const Glib::Error& error)
    {
      std::cerr << "on_parsing_error(): " << error.what() << std::endl;
      if (section)
      {
        const auto file = section->get_file();
        if (file)
        {
          std::cerr << "  URI = " << file->get_uri() << std::endl;
        }

        auto start_location = section->get_start_location();
        auto end_location = section->get_end_location();
        std::cerr << "  start_line = " << start_location.get_lines()+1
                  << ", end_line = " << end_location.get_lines()+1 << std::endl;
        std::cerr << "  start_position = " << start_location.get_line_chars()
                  << ", end_position = " << end_location.get_line_chars() << std::endl;
      }
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

### Vysvětlivky

Tooltips are the little information windows that pop up when you leave your pointer over a widget for a few seconds. Use `set_tooltip_text()` to set a text string as a tooltip on any `Widget`. `Gtk::Tooltip` is used for more advanced tooltip usage, such as showing an image as well as text.

Widget Reference

Tooltip Reference

#### Příklad

##### Vysvětlivka (Tooltip)

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:

      ExampleWindow();
      virtual ~ExampleWindow();

    protected:

      //Methods:
      void prepare_textview();
      void connect_signals();

      //Signal handlers:
      void on_markup_checkbutton_toggled();
      bool on_textview_query_tooltip(int x, int y, bool keyboard_tooltip, const Glib::RefPtr<Gtk::Tooltip>& tooltip);
      bool on_button_query_tooltip(int x, int y, bool keyboard_tooltip, const Glib::RefPtr<Gtk::Tooltip>& tooltip);

      //Child widgets:
      Gtk::Box m_vbox;

      Gtk::CheckButton m_checkbutton;
      Gtk::Label m_label;

      Gtk::ScrolledWindow m_scrolled_window;
      Gtk::TextView m_text_view;
      Glib::RefPtr<Gtk::TextBuffer> m_ref_text_buffer;
      Glib::RefPtr<Gtk::TextTag> m_ref_bold_tag;

      Gtk::Button m_button;
      Gtk::Box m_button_tooltip_widget;
    };

    #endif // GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <vector>

    const Glib::ustring app_title = "gtkmm tooltips example";
    const Glib::ustring non_markedup_tip = "A tooltip without markup.";
    const Glib::ustring markedup_tip = "<i>Markup</i> in a tooltip.";

    ExampleWindow::ExampleWindow()
      :
      m_vbox(Gtk::Orientation::VERTICAL, 3),
      m_checkbutton("Click to alternate markup in tooltip"),
      m_label("A label"),
      m_button("Button with a custom tooltip widget")
    {
      //Set up window and the top-level container:
      set_title(app_title);

      m_vbox.set_margin(10);
      set_child(m_vbox);

      //Check button with markup in tooltip:
      m_checkbutton.set_tooltip_text(non_markedup_tip);
      m_vbox.append(m_checkbutton);

      //Label:
      m_label.set_tooltip_text("Another tooltip");
      m_vbox.append(m_label);

      //Textview:
      prepare_textview();

      //Button:
      //When only connecting to the query-tooltip signal, and not using any
      //of set_tooltip_text() or set_tooltip_markup(), we need to explicitly
      //tell GTK that the widget has a tooltip which we'll show.
      m_button.set_has_tooltip();
      m_vbox.append(m_button);

      //Button's custom tooltip widget:
      auto label = Gtk::make_managed<Gtk::Label>("A label in a custom tooltip widget");
      m_button_tooltip_widget.append(*label);

      connect_signals();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::prepare_textview()
    {
      Gtk::TextIter iter;
      std::vector<Glib::RefPtr<Gtk::TextTag>> tags;

      //Set up a scrolled window:
      m_scrolled_window.set_child(m_text_view);
      m_scrolled_window.set_policy(Gtk::PolicyType::AUTOMATIC, Gtk::PolicyType::AUTOMATIC);
      m_scrolled_window.set_expand();
      m_vbox.append(m_scrolled_window);

      //Create a text buffer with some text:
      m_ref_text_buffer = Gtk::TextBuffer::create();

      iter = m_ref_text_buffer->end();
      m_ref_text_buffer->insert(iter, "Hover over the text ");

      //Insert some text with a tag.
      //In the tooltip signal handler below, we will show a tooltip
      //when mouse pointer is above this tagged text.
      m_ref_bold_tag = m_ref_text_buffer->create_tag("bold");
      m_ref_bold_tag->set_property("weight", Pango::Weight::BOLD);

      tags.push_back(m_ref_bold_tag);

      iter = m_ref_text_buffer->end();
      m_ref_text_buffer->insert_with_tags(iter, "in bold", tags);

      iter = m_ref_text_buffer->end();
      m_ref_text_buffer->insert(iter, " to see its tooltip");

      m_text_view.set_buffer(m_ref_text_buffer);

      m_text_view.set_size_request(320, 50);

      //When only connecting to the query-tooltip signal, and not using any
      //of set_tooltip_text() or set_tooltip_markup(), we need to explicitly
      //tell GTK that the widget has a tooltip which we'll show.
      m_text_view.set_has_tooltip();
    }

    void ExampleWindow::connect_signals()
    {
      m_checkbutton.signal_toggled().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_markup_checkbutton_toggled));

      m_text_view.signal_query_tooltip().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_textview_query_tooltip), true);

      m_button.signal_query_tooltip().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_button_query_tooltip), true);
    }

    void ExampleWindow::on_markup_checkbutton_toggled()
    {
      if (m_checkbutton.get_active())
      {
        m_checkbutton.set_tooltip_markup(markedup_tip);
      }
      else
      {
        m_checkbutton.set_tooltip_markup(non_markedup_tip);
      }
    }

    bool ExampleWindow::on_textview_query_tooltip(int x, int y, bool keyboard_tooltip, const Glib::RefPtr<Gtk::Tooltip>& tooltip)
    {
      Gtk::TextIter iter;

      if (keyboard_tooltip)
      {
        int offset = m_ref_text_buffer->property_cursor_position().get_value();
        iter = m_ref_text_buffer->get_iter_at_offset(offset);
      }
      else
      {
        int mouse_x, mouse_y, trailing;
        m_text_view.window_to_buffer_coords(Gtk::TextWindowType::TEXT,
                                            x, y, mouse_x, mouse_y);
        m_text_view.get_iter_at_position(iter, trailing, mouse_x, mouse_y);
      }

      if (!iter.has_tag(m_ref_bold_tag))
        return false;

      //Show a tooltip if the cursor or mouse pointer is over the text
      //with the specific tag:
      tooltip->set_markup("<b>Information</b> attached to a text tag");
      tooltip->set_icon("dialog-information");
      return true;
    }

    bool ExampleWindow::on_button_query_tooltip(int, int, bool, const Glib::RefPtr<Gtk::Tooltip>& tooltip)
    {
      tooltip->set_custom(m_button_tooltip_widget);
      return true;
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

## Kontejnerové widgety

Container widgets, like other widgets, derive from `Gtk::Widget`. Some container widgets, such as `Gtk::Grid` can hold many child widgets, so these typically have more complex interfaces. Others, such as `Gtk::Frame` contain only one child widget.

### Jednopoložkové kontejnery

Most single-item container widgets have `set_child()` and `unset_child()` methods for the child widget. `Gtk::Button` and `Gtk::Window` are technically single-item containers, but we have discussed them already elsewhere.

Probírán je také widget `Gtk::Paned`, který umožňuje rozdělit okno do dvou oddělených „panelů“. Tento widget ve skutečnosti obsahuje dva synovské widgety, ale tento počet je pevně dán, takže je správné jej zařadit sem.

#### Rám (Frame)

Frames can enclose one or a group of widgets within a box, optionally with a title. For instance, you might place a group of `ToggleButton`s or `CheckButton`s in a `Frame`.

Reference

##### Příklad

###### Rám (Frame)

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:

      //Child widgets:
      Gtk::Frame m_Frame;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    {
     /* Set some window properties */
      set_title("Frame Example");
      set_size_request(300, 300);

      /* Sets the margin around the frame. */
      m_Frame.set_margin(10);

      set_child(m_Frame);

      /* Set the frames label */
      m_Frame.set_label("Gtk::Frame Widget");

      /* Align the label at the right of the frame */
      m_Frame.set_label_align(Gtk::Align::END);
    }

    ExampleWindow::~ExampleWindow()
    {
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

#### Dvojitý panel (Paned)

Dvojitý panel rozdělí widget na dvě části oddělené rozdělovací čárou. Oba panely mohou být orientované buďto vodorovně (vedle sebe) nebo svisle (nad sebou).

Unlike the other widgets in this section, pane widgets contain not one but two child widgets, one in each pane. Therefore, you should use `set_start_child()` and `set_end_child()` instead of a `set_child()` method.

Rozdělovací čáru můžete umístit pomocí metody `set_position()`, a nejspíše to budete potřebovat udělat.

Reference

##### Příklad

###### Dvojitý panel (Paned)

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include "messageslist.h"
    #include "messagetext.h"
    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:

      //Child widgets:
      Gtk::Paned m_VPaned;
      MessagesList m_MessagesList;
      MessageText m_MessageText;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `messageslist.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLE_MESSAGESLIST_H
    #define GTKMM_EXAMPLE_MESSAGESLIST_H

    #include <gtkmm.h>

    class MessagesList: public Gtk::ScrolledWindow
    {
    public:
      MessagesList();
      ~MessagesList() override;

    protected:
      // Signal handlers:
      void on_setup_message(const Glib::RefPtr<Gtk::ListItem>& list_item);
      void on_bind_message(const Glib::RefPtr<Gtk::ListItem>& list_item);

      Glib::RefPtr<Gtk::StringList> m_refStringList; // The List Model.
      Gtk::ListView m_ListView; // The List View.
    };
    #endif //GTKMM_EXAMPLE_MESSAGESLIST_H

File: `messagetext.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLE_MESSAGETEXT_H
    #define GTKMM_EXAMPLE_MESSAGETEXT_H

    #include <gtkmm.h>

    class MessageText : public Gtk::ScrolledWindow
    {
    public:
      MessageText();
      virtual ~MessageText();

      void insert_text();

    protected:
      Gtk::TextView m_TextView;
    };

    #endif //GTKMM_EXAMPLE_MESSAGETEXT_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_VPaned(Gtk::Orientation::VERTICAL)
    {
      set_title ("Paned Windows");
      set_default_size(450, 400);
      m_VPaned.set_margin(10);

      /* Add a vpaned widget to our toplevel window */
      set_child(m_VPaned);

      /* Now add the contents of the two halves of the window */
      m_VPaned.set_start_child(m_MessagesList);
      m_VPaned.set_end_child(m_MessageText);
    }

    ExampleWindow::~ExampleWindow()
    {
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

File: `messageslist.cc` (For use with gtkmm 4)

    #include "messageslist.h"

    MessagesList::MessagesList()
    {
      /* Create a new scrolled window, with scrollbars only if needed */
      set_policy(Gtk::PolicyType::AUTOMATIC, Gtk::PolicyType::AUTOMATIC);

      set_child(m_ListView);

      /* create list store */
      m_refStringList = Gtk::StringList::create({});
      auto selection_model = Gtk::SingleSelection::create(m_refStringList);
      m_ListView.set_model(selection_model);

      /* Add some messages to the window */
      for (int i = 1; i <= 10; ++i)
        m_refStringList->append(Glib::ustring::format("message #", i));

      // Create a ListItemFactory to use for populating list items.
      auto factory = Gtk::SignalListItemFactory::create();
      factory->signal_setup().connect(sigc::mem_fun(*this, &MessagesList::on_setup_message));
      factory->signal_bind().connect(sigc::mem_fun(*this, &MessagesList::on_bind_message));
      m_ListView.set_factory(factory);
    }

    MessagesList::~MessagesList()
    {
    }

    void MessagesList::on_setup_message(const Glib::RefPtr<Gtk::ListItem>& list_item)
    {
      auto label = Gtk::make_managed<Gtk::Label>();
      label->set_halign(Gtk::Align::START);
      list_item->set_child(*label);
    }

    void MessagesList::on_bind_message(const Glib::RefPtr<Gtk::ListItem>& list_item)
    {
      auto pos = list_item->get_position();
      if (pos == GTK_INVALID_LIST_POSITION)
        return;
      auto label = dynamic_cast<Gtk::Label*>(list_item->get_child());
      if (!label)
        return;
      label->set_text(m_refStringList->get_string(pos));
    }

File: `messagetext.cc` (For use with gtkmm 4)

    #include "messagetext.h"

    MessageText::MessageText()
    {
      set_policy(Gtk::PolicyType::AUTOMATIC, Gtk::PolicyType::AUTOMATIC);

      set_child(m_TextView);
      insert_text();
    }

    MessageText::~MessageText()
    {
    }

    void MessageText::insert_text()
    {
      auto refTextBuffer = m_TextView.get_buffer();

      auto iter = refTextBuffer->get_iter_at_offset(0);
      refTextBuffer->insert(iter,
        "From: pathfinder@nasa.gov\n"
        "To: mom@nasa.gov\n"
        "Subject: Made it!\n"
        "\n"
        "We just got in this morning. The weather has been\n"
        "great - clear but cold, and there are lots of fun sights.\n"
        "Sojourner says hi. See you soon.\n"
        " -Path\n");
    }

#### Okno s posuvníky (ScrolledWindow)

`ScrolledWindow` widgets create a scrollable area. You can insert any type of widget into a `ScrolledWindow`, and it will be accessible regardless of its size by using the scrollbars. Note that `ScrolledWindow` is not a `Gtk::Window` despite the slightly misleading name.

Scrolled windows have scrollbar policies which determine whether the `Scrollbar`s will be displayed. The policies can be set with the `set_policy()` method. The policy may be for instance `Gtk::PolicyType::AUTOMATIC` or `Gtk::PolicyType::ALWAYS`. `Gtk::PolicyType::AUTOMATIC` will cause the scrolled window to display the scrollbar only if the contained widget is larger than the visible area. `Gtk::PolicyType::ALWAYS` will cause the scrollbar to be displayed always.

Reference

##### Příklad

Zde je jednoduchý příklad, který sbalí 100 přepínacích tlačítek do okna s posuvníky. Zkuste měnit velikost okna, abyste viděli, jak posuvníky reagují.

###### Okno s posuvníky (ScrolledWindow)

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      ~ExampleWindow() override;

    protected:
      //Signal handlers:
      void on_button_close();

      //Child widgets:
      Gtk::Box m_VBox;
      Gtk::ScrolledWindow m_ScrolledWindow;
      Gtk::Grid m_Grid;
      Gtk::Button m_ButtonClose;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::Orientation::VERTICAL, 10),
      m_ButtonClose("_Close", true)
    {
      set_title("Gtk::ScrolledWindow example");
      set_size_request(300, 300);

      set_child(m_VBox);
      m_VBox.set_margin(10);

      /* The policy is one of Gtk::PolicyType::AUTOMATIC, or Gtk::PolicyType::ALWAYS.
       * Gtk::PolicyType::AUTOMATIC will automatically decide whether you need
       * scrollbars, whereas Gtk::PolicyType::ALWAYS will always leave the scrollbars
       * there. The first one is the horizontal scrollbar, the second, the vertical. */
      m_ScrolledWindow.set_policy(Gtk::PolicyType::AUTOMATIC, Gtk::PolicyType::ALWAYS);
      m_ScrolledWindow.set_expand();

      m_VBox.append(m_ScrolledWindow);

      /* set the spacing to 10 on x and 10 on y */
      m_Grid.set_row_spacing(10);
      m_Grid.set_column_spacing(10);

      /* pack the grid into the scrolled window */
      m_ScrolledWindow.set_child(m_Grid);

      /* this simply creates a grid of toggle buttons
       * to demonstrate the scrolled window. */
      for (int i = 0; i < 10; i++)
      {
        for (int j = 0; j < 10; j++)
        {
          auto s = Glib::ustring::compose("button (%1,%2)", i, j);
          auto pButton = Gtk::make_managed<Gtk::ToggleButton>(s);
          m_Grid.attach(*pButton, i, j);
        }
      }

      /* Add a "close" button to the bottom of the dialog */
      m_VBox.append(m_ButtonClose);
      m_ButtonClose.set_halign(Gtk::Align::END);
      m_ButtonClose.signal_clicked().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_button_close));

      /* Hitting the "Enter" key will cause this button to activate. */
      m_ButtonClose.grab_focus();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_close()
    {
      set_visible(false);
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

#### AspectFrame

Widget `AspectFrame` vypadá podobně jako widget `Frame`, ale navíc dodržuje poměr stran (poměr mezi šířkou a výškou) synovského widgetu. Využívá k tomu doplňování prázdného místa okolo widgetu v případě potřeby. Využít se dá například k zobrazení fotografie, aniž by ji uživatel při změně velikosti vodorovně nebo svisle deformoval.

Reference

##### Příklad

Následující program použív `Gtk::AspectFrame` k zobrazení kreslící oblasti, jejíž poměr stran bude vždy 2∶1, bez ohledu na to, jak uživatel mění velikost nadřazeného okna.

###### AspectFrame

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:

      //Child widgets:
      Gtk::AspectFrame m_AspectFrame;
      Gtk::Frame m_Frame;
      Gtk::DrawingArea m_DrawingArea;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_AspectFrame(
        Gtk::Align::CENTER, /* center x */
        Gtk::Align::CENTER, /* center y */
        2.0, /* xsize/ysize = 2 */
        false /* ignore child's aspect */),
      m_Frame("2x1" /* label */)
    {
      set_title("Aspect Frame");

      // Set a child widget to the aspect frame */
      // Ask for a 200x200 window, but the AspectFrame will give us a 200x100
      // window since we are forcing a 2x1 aspect ratio */
      m_DrawingArea.set_content_width(200);
      m_DrawingArea.set_content_height(200);
      m_Frame.set_child(m_DrawingArea);
      m_AspectFrame.set_child(m_Frame);
      m_AspectFrame.set_margin(10);

      // Add the aspect frame to our toplevel window:
      set_child(m_AspectFrame);
    }

    ExampleWindow::~ExampleWindow()
    {
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

#### Other Single-item Containers

There are other single-item containers. See the reference documentation for a complete list. Here are links to some example programs that show containers, which are not mentioned elsewhere in this tutorial.

Source Code, Expander

Source Code, Popover

### Multiple-item Containers

Multiple-item container widgets have other methods than `set_child()` and `unset_child()`. Different containers can have different methods for adding and removing child widgets. For instance, `Gtk::Box` has `append()` and `remove()` as well as other methods. The `remove()` method for multiple-item containers takes an argument, specifying which widget to remove.

#### Balení

Nejspíše jste si všimli, že okna gtkmm jsou „elastická“ – můžete je různě roztahovat a zase zmenšovat. Je to díky systému balení widgetů (packing).

Řada vývojářských nástrojů pro GUI vyžaduje přesné umístění widgetů v oknech s použitím přesných souřadnic a často je k tomu zapotřebí vizuální editor. To vede k několika problémům:

- Widgety nemohou samy měnit uspořádání, když se změní velikost okna. Když je okno příliš malé, tak některé widgety nejsou vidět, a naopak u příliš velkého okna vzniká spousta nevyužitého místa.

- Není možné odhadnou množství potřebného místa pro texty po jejich přeložení do jiných národních jazyků nebo jejich zobrazení jiným písmem. V Unixu také není možné předvídat, jak se projeví různé motivy a správce oken.

- Změna rozvržení okna „za běhu“, například kvůli přidání dalšího widgetu, je velmi komplikovaná. Vyžaduje to unavné přepočítání pozice všech widgetů.

gtkmm uses the packing system to solve these problems. Rather than specifying the position and size of each widget in the window, you can arrange your widgets in rows, columns, and/or grids. gtkmm can size your window automatically, based on the sizes of the widgets it contains. And the sizes of the widgets are, in turn, determined by the amount of text they contain, or the minimum and maximum sizes that you specify, and/or how you have requested that the available space should be shared between sets of widgets. You can perfect your layout by specifying margins and centering values for each of your widgets. gtkmm then uses all this information to resize and reposition everything sensibly and smoothly when the user manipulates the window.

gtkmm arranges widgets hierarchically, using containers. A container widget contains other widgets. Most gtkmm widgets are containers. Windows, Notebook tabs, and Buttons are all container widgets. There are two flavors of containers: single-child containers and multiple-child containers. Most container widgets in gtkmm are single-child containers, including `Gtk::Window`.

Ano, to je správně: Okno nemůže obsahovat více jak jeden widget. Jak jej pak ale můžeme využít nějakým použitelným způsobem? Umístěním kontejneru pro více potomku do okna. Nejpoužívanější kontejnery na widgety jsou `Gtk::Grid` a `Gtk::Box`.

- `Gtk::Grid` arranges its child widgets in rows and columns. Use `attach()` and `attach_next_to()` to insert child widgets.

- `Gtk::Box` arranges its child widgets vertically or horizontally. Use `append()` to insert child widgets.

Existuje ještě několik dalších kontejnerů, které také probereme.

Jestliže jste doposud nepoužívali žádnou vývojářskou sadu pro balení, může vám chvíli trvat, než si na to zvyknete. Nejspíše ale zjistíte, že nejste závislí na vizuální podobě v editoru, stejně jako byste nemuseli u kterékoliv jiné vývojářské sady.

#### Vylepšené „Hello World“

Pojďme se podívat, jak s tím, co jsme si ukázali, trochu vylepšit `helloworld`.

##### „Hello World“ 2

Source Code

File: `helloworld.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLE_HELLOWORLD_H
    #define GTKMM_EXAMPLE_HELLOWORLD_H

    #include <gtkmm/box.h>
    #include <gtkmm/button.h>
    #include <gtkmm/window.h>

    class HelloWorld : public Gtk::Window
    {
    public:
      HelloWorld();
      ~HelloWorld() override;

    protected:

      // Signal handlers:
      // Our new improved on_button_clicked().
      void on_button_clicked(const Glib::ustring& data);

      // Child widgets:
      Gtk::Box m_box1;
      Gtk::Button m_button1, m_button2;
    };

    #endif // GTKMM_EXAMPLE_HELLOWORLD_H

File: `helloworld.cc` (For use with gtkmm 4)

    #include "helloworld.h"
    #include <iostream>

    HelloWorld::HelloWorld()
    : m_button1("Button 1"),
      m_button2("Button 2")
    {
      // This just sets the title of our new window.
      set_title("Hello Buttons!");

      // Sets the margin around the box.
      m_box1.set_margin(10);

      // put the box into the main window.
      set_child(m_box1);

      // Now when the button is clicked, we call the on_button_clicked() function
      // with a pointer to "button 1" as its argument.
      m_button1.signal_clicked().connect(sigc::bind(
                  sigc::mem_fun(*this, &HelloWorld::on_button_clicked), "button 1"));

      // We use Gtk::Box::append() to pack this button into the box,
      // which has been packed into the window.
      // A widget's default behaviour is not to expand if extra space is available.
      // A container widget by default expands if any of the contained widgets
      // wants to expand.
      m_box1.append(m_button1);
      m_button1.set_expand();

      // call the same signal handler with a different argument,
      // passing a pointer to "button 2" instead.
      m_button2.signal_clicked().connect(sigc::bind(
                  sigc::mem_fun(*this, &HelloWorld::on_button_clicked), "button 2"));

      m_box1.append(m_button2);
      m_button2.set_expand();

      // Gtk::Widget::set_visible(true) is seldom needed. All widgets are visible by default.
    }

    HelloWorld::~HelloWorld()
    {
    }

    // Our new improved signal handler.  The data passed to this method is
    // printed to stdout.
    void HelloWorld::on_button_clicked(const Glib::ustring& data)
    {
      std::cout << "Hello World - " << data << " was pressed" << std::endl;
    }

File: `main.cc` (For use with gtkmm 4)

    #include "helloworld.h"
    #include <gtkmm/application.h>

    int main(int argc, char* argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<HelloWorld>(argc, argv);
    }

After building and running this program, try resizing the window to see the behavior. Also, try playing with `set_expand()`, `set_hexpand()`, `set_vexpand()`, `set_halign()` and `set_valign()` while reading the Boxes section.

#### Boxy

Most packing uses boxes as in the above example. These are invisible containers into which we can pack our widgets. When packing widgets into a horizontal box, the objects are inserted horizontally from left to right. In a vertical box, widgets are packed from top to bottom. You may use any combination of boxes inside or beside other boxes to create the desired effect.

##### Přidání widgetů

###### Volby balení pro potomky

The `append()` method places widgets inside these containers. It will start at the top and work its way down in a `Box` with vertical orientation, or pack left to right in a `Box` with horizontal orientation. If it's inconvenient to add widgets in this order, use `insert_child_after()` or `insert_child_at_start()`. We will use `append()` in our examples.

There are several options governing how widgets are to be packed, and this can be confusing at first. You can modify the packing by using `set_expand()`, `set_hexpand()`, `set_vexpand()`, `set_halign()`, `set_valign()` and/or `set_margin()` on the child widgets. If you have difficulties, then it is sometimes a good idea to play with the Cambalache GUI designer to see what is possible. You can then use the `Gtk::Builder` API to load your GUI at runtime.

V základu existuje pět rozdílných stylů, které můžete vidět na tomto obrázku:

###### Balení boxů 1

Each line contains one horizontal `Box` with several buttons. Each of the buttons on a line is packed into the `Box` with the same arguments to the `set_hexpand()`, `set_halign()`, `set_margin_start()` and `set_margin_end()` methods.

Reference

###### Volby balení pro kontejner

Here's the constructor for the `Box` widget, and methods that set per-container packing options:

    Gtk::Box(Gtk::Orientation orientation = Gtk::Orientation::HORIZONTAL, int spacing = 0);
    void set_orientation(Gtk::Orientation orientation);
    void set_spacing(int spacing);
    void set_homogeneous(bool homogeneous = true);

Passing `true` to `set_homogeneous()` will cause all of the contained widgets to be the same size. `spacing` is a (minimum) number of pixels to leave between each widget.

What's the difference between spacing (set when the box is created) and margins (set separately for each child widget)? Spacing is added between objects, and margins are added on one or more sides of a widget. The following figure should make it clearer. The shown margins are the left and right margins of each button in the row.

###### Balení boxů 2

##### Gtk::Application a přepínače příkazového řádku

Program v následujícím příkladu požaduje přepínače na příkazové řádce. Zdrojový kód ukazuje dva způsoby, jak zpracovat přepínače příkazové řádky ve spojení s `Gtk::Application`.

- Handle the options in `main()` and hide them from `Gtk::Application` by setting `argc = 1` in the call to `Gtk::Application::run()`.

- Give all command-line options to `Gtk::Application::run()` and add the flag `Gio::Application::Flags::HANDLES_COMMAND_LINE` to `Gtk::Application::create()`. Connect a signal handler to the `command_line` signal, and handle the command-line options in the signal handler.

  Při volání `signal_command_line().connect()` musíte nastavit volitelný parametr `after = false`, protože vaše obsluha signálu musí být zavolána před výchozí obsluhou signálu. Také musíte v obsluze signálu zavolat `Gio::Application::activate()`, pokud tedy nechcete, aby vaše aplikace skončila dříve, než zobrazí hlavní okno. (`Gio::Application` je základem pro třídu `Gtk::Application`.)

##### Příklad

Zde je zdrojový kód pro příklad, jehož výsledkem je to, co můžete vidět na snímku obrazovky výše. Když příklad spouštíte, zadejte jako volbu příkazového řádku číslo v rozmezí 1 až 3, a uvidíte, jak se použijí různé volby balení.

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow(int which);
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_quit_clicked();

      //Child widgets:
      Gtk::Button m_button;
      Gtk::Box m_box1;
      Gtk::Box m_boxQuit;
      Gtk::Button m_buttonQuit;

      Gtk::Label m_Label1, m_Label2;

      Gtk::Separator m_separator1, m_separator2;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `packbox.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLE_PACKBOX_H
    #define GTKMM_EXAMPLE_PACKBOX_H

    #include <gtkmm.h>

    class PackBox : public Gtk::Box
    {
    public:
      PackBox(bool homogeneous = false, int spacing = 0, bool expand = false,
        Gtk::Align align = Gtk::Align::FILL, int margin = 0);

    protected:
      Gtk::Button m_buttons[4];
    };

    #endif //GTKMM_EXAMPLE_PACKBOX_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include <iostream>
    #include "examplewindow.h"
    #include "packbox.h"

    ExampleWindow::ExampleWindow(int which)
    : m_box1(Gtk::Orientation::VERTICAL),
      m_buttonQuit("Quit")
    {
      set_title("Gtk::Box example");

      m_separator1.set_margin_top(5);
      m_separator1.set_margin_bottom(5);
      m_separator2.set_margin_top(5);
      m_separator2.set_margin_bottom(5);

      switch(which)
      {
        case 1:
        {
          m_Label1.set_text("Gtk::Box(Gtk::Orientation::HORIZONTAL, 0); set_homogeneous(false);");

          // Align the label to the left side.
          m_Label1.set_halign(Gtk::Align::START);
          m_Label1.set_valign(Gtk::Align::START);

          // Pack the label into the vertical box (vbox box1).  Remember that
          // widgets added to a vbox will be packed one on top of the other in
          // order.
          m_box1.append(m_Label1);

          // Create a PackBox - homogeneous = false, spacing = 0,
          // expand = false, Gtk::Align::FILL, margin = 0
          // These are the default values.
          auto pPackBox = Gtk::make_managed<PackBox>();
          m_box1.append(*pPackBox);

          // Create a PackBox - homogeneous = false, spacing = 0,
          // expand = true, Gtk::Align::CENTER, margin = 0
          pPackBox = Gtk::make_managed<PackBox>(false, 0, true, Gtk::Align::CENTER);
          m_box1.append(*pPackBox);

          // Create a PackBox - homogeneous = false, spacing = 0,
          // expand = true, Gtk::Align::FILL, margin = 0
          pPackBox = Gtk::make_managed<PackBox>(false, 0, true);
          m_box1.append(*pPackBox);

          // pack the separator into the vbox.  Remember each of these
          // widgets are being packed into a vbox, so they'll be stacked
          // vertically.
          m_box1.append(m_separator1);

          // create another new label, and show it.
          m_Label2.set_text("Gtk::Box(Gtk::Orientation::HORIZONTAL, 0); set_homogeneous(true);");
          m_Label2.set_halign(Gtk::Align::START);
          m_Label2.set_valign(Gtk::Align::START);
          m_box1.append(m_Label2);

          // Args are: homogeneous, spacing, expand, align, margin
          pPackBox = Gtk::make_managed<PackBox>(true, 0, true, Gtk::Align::CENTER);
          m_box1.append(*pPackBox);

          // Args are: homogeneous, spacing, expand, align, margin
          pPackBox = Gtk::make_managed<PackBox>(true, 0, true);
          m_box1.append(*pPackBox);

          m_box1.append(m_separator2);

          break;
        }

        case 2:
        {
          m_Label1.set_text("Gtk::Box(Gtk::Orientation::HORIZONTAL, 10); set_homogeneous(false);");
          m_Label1.set_halign(Gtk::Align::START);
          m_Label1.set_valign(Gtk::Align::START);
          m_box1.append(m_Label1);

          auto pPackBox = Gtk::make_managed<PackBox>(false, 10, true, Gtk::Align::CENTER);
          m_box1.append(*pPackBox);

          pPackBox = Gtk::make_managed<PackBox>(false, 10, true);
          m_box1.append(*pPackBox);

          m_box1.append(m_separator1);

          m_Label2.set_text("Gtk::Box(Gtk::Orientation::HORIZONTAL, 0); set_homogeneous(false);");
          m_Label2.set_halign(Gtk::Align::START);
          m_Label2.set_valign(Gtk::Align::START);
          m_box1.append(m_Label2);

          pPackBox = Gtk::make_managed<PackBox>(false, 0, false, Gtk::Align::FILL, 10);
          m_box1.append(*pPackBox);

          pPackBox = Gtk::make_managed<PackBox>(false, 0, true, Gtk::Align::FILL, 10);
          m_box1.append(*pPackBox);

          m_box1.append(m_separator2);

          break;
        }

        case 3:
        {
          // This demonstrates the ability to use Gtk::Align::END to
          // right justify widgets.  First, we create a new box as before.
          auto pPackBox = Gtk::make_managed<PackBox>();

          // create the label that will be put at the end.
          m_Label1.set_text("end");

          // pack it using Gtk::Align::END, so it is put on the right side
          // of the PackBox.
          m_Label1.set_halign(Gtk::Align::END);
          m_Label1.set_hexpand(true);
          pPackBox->append(m_Label1);

          m_box1.append(*pPackBox);

          // This explicitly sets the separator to 700 pixels wide by 5 pixels
          // high.  This is so the hbox we created will also be 700 pixels wide,
          // and the "end" label will be separated from the other labels in the
          // hbox.  Otherwise, all the widgets in the hbox would be packed as
          // close together as possible.
          m_separator1.set_size_request(700, 5);

          // pack the separator into the vbox.
          m_box1.append(m_separator1);

          break;
        }

        default:
        {
          std::cerr << "Unexpected command-line option." << std::endl;
          break;
        }
      }

      // Connect the signal to hide the window:
      m_buttonQuit.signal_clicked().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_button_quit_clicked) );

      // pack the button into the quitbox.
      m_boxQuit.append(m_buttonQuit);
      m_buttonQuit.set_hexpand(true);
      m_buttonQuit.set_halign(Gtk::Align::CENTER);
      m_box1.append(m_boxQuit);

      // pack the vbox (box1) which now contains all our widgets, into the
      // main window.
      set_child(m_box1);
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_quit_clicked()
    {
      set_visible(false);
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>
    #include <iostream>
    #include <cstdlib>

    #define GTK_APPLICATION_RECEIVES_COMMAND_LINE_ARGUMENTS 0

    #if GTK_APPLICATION_RECEIVES_COMMAND_LINE_ARGUMENTS
    namespace
    {
    int on_command_line(const Glib::RefPtr<Gio::ApplicationCommandLine>& command_line,
                        Glib::RefPtr<Gtk::Application>& app)
    {
      int argc = 0;
      char** argv = command_line->get_arguments(argc);

      for (int i = 0; i < argc; ++i)
        std::cout << "argv[" << i << "] = " << argv[i] << std::endl;

      app->activate(); // Without activate() the window won't be shown.
      return EXIT_SUCCESS;
    }
    } // anonymous namespace
    #endif

    int main(int argc, char *argv[])
    {
      if (argc != 2)
      {
        std::cerr << "Usage: example <num>, where <num> is 1, 2, or 3." << std::endl;
        return EXIT_FAILURE;
      }

      int argc1 = argc;

    #if GTK_APPLICATION_RECEIVES_COMMAND_LINE_ARGUMENTS
      // The Gio::Application::Flags::HANDLES_COMMAND_LINE flag and the
      // on_command_line() signal handler are not necessary. This program is simpler
      // without them, and with argc = 1 in the call to Gtk::Application::make_window_and_run().
      // They are included to show a program with Gio::Application::Flags::HANDLES_COMMAND_LINE.
      // Gio::Application::Flags::NON_UNIQUE makes it possible to run several instances of
      // this application simultaneously.
      auto app = Gtk::Application::create(
        "org.gtkmm.example", Gio::Application::Flags::HANDLES_COMMAND_LINE | Gio::Application::Flags::NON_UNIQUE);

      // Note after = false.
      // Only one signal handler is invoked. This signal handler must run before
      // the default signal handler, or else it won't run at all.
      app->signal_command_line().connect(
        [&app](const auto& command_line)
        { return on_command_line(command_line, app); }, false);
    #else
      // Gio::Application::Flags::NON_UNIQUE makes it possible to run several instances of
      // this application simultaneously.
      argc1 = 1; // Don't give the command line arguments to Gtk::Application.
      auto app = Gtk::Application::create("org.gtkmm.example", Gio::Application::Flags::NON_UNIQUE);
    #endif

      // Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc1, argv, std::atoi(argv[1]));
    }

File: `packbox.cc` (For use with gtkmm 4)

    #include "packbox.h"
    #include <map>

    namespace
    {
      const std::map<Gtk::Align, Glib::ustring> align_string = {
        {Gtk::Align::FILL, "Gtk::Align::FILL"},
        {Gtk::Align::START, "Gtk::Align::START"},
        {Gtk::Align::END, "Gtk::Align::END"},
        {Gtk::Align::CENTER, "Gtk::Align::CENTER"},
        {Gtk::Align::BASELINE, "Gtk::Align::BASELINE"},
      };
    }

    PackBox::PackBox(bool homogeneous, int spacing, bool expand, Gtk::Align align, int margin)
    : Gtk::Box(Gtk::Orientation::HORIZONTAL, spacing)
    {
      set_homogeneous(homogeneous);

      m_buttons[0].set_label("box.append(button);");
      m_buttons[1].set_label("expand=" + Glib::ustring(expand ? "true" : "false"));
      m_buttons[2].set_label(align_string.at(align));
      m_buttons[3].set_label("margin=" + Glib::ustring::format(margin));

      for (auto& button : m_buttons)
      {
        append(button);
        button.set_hexpand(expand);
        button.set_halign(align);
        button.set_margin_start(margin);
        button.set_margin_end(margin);
      }
    }

#### Mřížka (Grid)

Kontejner `Grid` widgety dynamicky uspořádává do řádků a sloupců. Rozměry mřížky není zapotřebí zadávat v konstruktoru.

Synovské widgety mohou zabrat více řádků nebo sloupců pomocí `attach()` nebo mohou být přidány vedle stávajícího widgetu uvnitř mřížky pomocí `attach_next_to()`. Jednotlivé řádky a sloupce mřížky mohou být nastaveny tak, aby měly jednotnou výšku nebo šířku pomocí `set_row_homogeneous()` a `set_column_homogeneous()`.

You can set the margin and expand properties of the child `Widget`s to control their spacing and their behavior when the Grid is resized.

Reference

##### Příklad

Tento příklad vytvoří okno se třemi tlačítky v mřížce. První dvě tlačítka jsou v horním řádku, zleva doprava. Třetí tlačítko je připojeno pod prvním, v novém nižším řádku a zabírá dva sloupce.

###### Mřížka (Grid)

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    private:
      // Signal handlers:
      void on_button_quit();
      void on_button_numbered(const Glib::ustring& data);

      // Child widgets:
      Gtk::Grid m_grid;
      Gtk::Button m_button_1, m_button_2, m_button_quit;
    };

    #endif /* GTKMM_EXAMPLEWINDOW_H */

File: `examplewindow.cc` (For use with gtkmm 4)

    #include <iostream>
    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_button_1("button 1"),
      m_button_2("button 2"),
      m_button_quit("Quit")
    {
      set_title("Gtk::Grid");

      m_grid.set_margin(12);
      set_child(m_grid);

      m_grid.attach(m_button_1, 0, 0);
      m_grid.attach(m_button_2, 1, 0);
      m_grid.attach_next_to(m_button_quit, m_button_1, Gtk::PositionType::BOTTOM, 2, 1);

      m_button_1.signal_clicked().connect(
        sigc::bind( sigc::mem_fun(*this, &ExampleWindow::on_button_numbered), "button 1") );
      m_button_2.signal_clicked().connect(
        sigc::bind( sigc::mem_fun(*this, &ExampleWindow::on_button_numbered), "button 2") );

      m_button_quit.signal_clicked().connect(sigc::mem_fun(*this,
        &ExampleWindow::on_button_quit) );
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_quit()
    {
      set_visible(false);
    }

    void
    ExampleWindow::on_button_numbered(const Glib::ustring& data)
    {
      std::cout << data << " was pressed" << std::endl;
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      // Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

#### Sešit (Notebook)

`Notebook` má sadu navrstvených `karet`, z nichž každá může obsahovat widgety. `Ouška` s popisky umožňují uživateli vybrat požadovanou kartu. Díky objektům `Notebook` můžete umístit několik sad widgetů na malý prostor a v jednu chvíli zobrazit vždy jednu kartu. Často se používají například v dialogových oknech s předvolbami.

Pro přidání karet do objektu `Notebook` použijte metody `append_page()`, `prepend_page()` a `insert_page()`, kterým poskytnete synovský widget a název karty.

Ke zjištění, která stránka je právě viditelná, použijte metodu `get_current_page()`. Vrátí vám číslo stránky a s tímto číslem zavolejte `get_nth_page()`, abyste získali ukazatel na aktuální synovský widget.

K programové změně vybrané stránky použijte metodu `set_current_page()`.

Reference

##### Příklad

###### Sešit (Notebook)

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_quit();
      void on_notebook_switch_page(Gtk::Widget* page, guint page_num);

      //Child widgets:
      Gtk::Box m_VBox;
      Gtk::Notebook m_Notebook;
      Gtk::Label m_Label1, m_Label2;

      Gtk::Box m_ButtonBox;
      Gtk::Button m_Button_Quit;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include <iostream>
    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::Orientation::VERTICAL),
      m_Label1("Contents of tab 1"),
      m_Label2("Contents of tab 2"),
      m_Button_Quit("Quit")
    {
      set_title("Gtk::Notebook example");
      set_default_size(400, 200);

      m_VBox.set_margin(10);
      set_child(m_VBox);

      //Add the Notebook, with the button underneath:
      m_Notebook.set_margin(10);
      m_Notebook.set_expand();
      m_VBox.append(m_Notebook);
      m_VBox.append(m_ButtonBox);

      m_ButtonBox.append(m_Button_Quit);
      m_Button_Quit.set_hexpand(true);
      m_Button_Quit.set_halign(Gtk::Align::CENTER);
      m_Button_Quit.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_quit) );

      //Add the Notebook pages:
      m_Notebook.append_page(m_Label1, "First");
      m_Notebook.append_page(m_Label2, "Second");

      m_Notebook.signal_switch_page().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_notebook_switch_page) );
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_quit()
    {
      set_visible(false);
    }

    void ExampleWindow::on_notebook_switch_page(Gtk::Widget* /* page */, guint page_num)
    {
      std::cout << "Switched to tab with index " << page_num << std::endl;

      //You can also use m_Notebook.get_current_page() to get this index.
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

#### Průvodce (Assistant)

`Gtk::Assistant` is deprecated since gtkmm 4.10. There is no replacement in gtkmm. libadwaita (a C library) has replacement parts (like AdwCarousel). In some cases, a `Gtk::Notebook` might be an acceptable replacement.

Widget `Assistant` rozděluje složité operace do několika jednodušších kroků. Každý krok je na zvláštní stránce, která obsahuje záhlaví, synovský widget a oblast s akcemi. Oblast akcí obsahuje navigační tlačítka, která se aktualizují automaticky podle typu stránky nastaveného pomocí `set_page_type()`.

K přidání stránek do widgetu `Assistant` použijte metody `append_page()`, `prepend_page` a `insert_page()`. Ke každé stránce poskytněte synovský widget.

K určení právě viditelné stránky použijte metodu `get_current_page()` a výsledek předejte metodě `get_nth_page()`, která vrátí ukazatel na aktuální widget. K programové změně aktuální stránky použijte metodu `set_current_page()`.

To set the title of a page, use the `set_page_title()` method.

Pro přidání widgetů do oblasti akcí použijte metodu `add_action_widget()`. Budou baleny vedle výchozích tlačítek. Naopak, k jejich odebrání použijte metodu `remove_action_widget()`.

Reference

##### Příklad

###### Průvodce (Assistant)

Source Code

File: `exampleassistant.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEASSISTANT_H
    #define GTKMM_EXAMPLEASSISTANT_H

    #include <gtkmm.h>

    class ExampleAssistant : public Gtk::Assistant
    {
    public:
      ExampleAssistant();
      virtual ~ExampleAssistant();

      void get_result(bool& check_state, Glib::ustring& entry_text);

    private:
      // Signal handlers:
      void on_assistant_apply();
      void on_assistant_cancel();
      void on_assistant_close();
      void on_assistant_prepare(Gtk::Widget* widget);
      void on_entry_changed();

      // Member functions:
      void print_status();

      // Child widgets:
      Gtk::Box m_box;
      Gtk::Label m_label1, m_label2;
      Gtk::CheckButton m_check;
      Gtk::Entry m_entry;
    };

    #endif /* GTKMM_EXAMPLEASSISTANT_H */

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include "exampleassistant.h"
    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    private:
      // Signal handlers:
      void on_button_clicked();
      void on_assistant_apply();

      // Child widgets:
      Gtk::Grid m_grid;
      Gtk::Button m_button;
      Gtk::Label m_label1, m_label2;
      Gtk::CheckButton m_check;
      Gtk::Entry m_entry;
      ExampleAssistant m_assistant;
    };

    #endif /* GTKMM_EXAMPLEWINDOW_H */

File: `exampleassistant.cc` (For use with gtkmm 4)

    #include <iostream>
    #include "exampleassistant.h"

    ExampleAssistant::ExampleAssistant()
    : m_box(Gtk::Orientation::HORIZONTAL, 12),
      m_label1("Type text to allow the assistant to continue:"),
      m_label2("Confirmation page"),
      m_check("Optional extra information")
    {
      set_title("Gtk::Assistant example");
      set_default_size(400, 200);

      m_box.append(m_label1);
      m_box.append(m_entry);
      m_label1.set_wrap();
      m_label1.set_valign(Gtk::Align::CENTER);
      m_entry.set_valign(Gtk::Align::CENTER);

      append_page(m_box);
      append_page(m_check);
      append_page(m_label2);

      set_page_title(*get_nth_page(0), "Page 1");
      set_page_title(*get_nth_page(1), "Page 2");
      set_page_title(*get_nth_page(2), "Confirmation");

      set_page_complete(m_check, true);
      set_page_complete(m_label2, true);

      set_page_type(m_box, Gtk::AssistantPage::Type::INTRO);
      set_page_type(m_label2, Gtk::AssistantPage::Type::CONFIRM);

      signal_apply().connect(sigc::mem_fun(*this,
        &ExampleAssistant::on_assistant_apply));
      signal_cancel().connect(sigc::mem_fun(*this,
        &ExampleAssistant::on_assistant_cancel));
      signal_close().connect(sigc::mem_fun(*this,
        &ExampleAssistant::on_assistant_close));
      signal_prepare().connect(sigc::mem_fun(*this,
        &ExampleAssistant::on_assistant_prepare));

      m_entry.signal_changed().connect(sigc::mem_fun(*this,
        &ExampleAssistant::on_entry_changed));
    }

    ExampleAssistant::~ExampleAssistant()
    {
    }

    void ExampleAssistant::get_result(bool& check_state, Glib::ustring& entry_text)
    {
      check_state = m_check.get_active();
      entry_text = m_entry.get_text();
    }

    void ExampleAssistant::on_assistant_apply()
    {
      std::cout << "Apply was clicked";
      print_status();
    }

    void ExampleAssistant::on_assistant_cancel()
    {
      std::cout << "Cancel was clicked";
      print_status();
      set_visible(false);
    }

    void ExampleAssistant::on_assistant_close()
    {
      std::cout << "Assistant was closed";
      print_status();
      set_visible(false);
    }

    void ExampleAssistant::on_assistant_prepare(Gtk::Widget* /* widget */)
    {
      set_title(Glib::ustring::compose("Gtk::Assistant example (Page %1 of %2)",
        get_current_page() + 1, get_n_pages()));
    }

    void ExampleAssistant::on_entry_changed()
    {
      // The page is only complete if the entry contains text.
      if(m_entry.get_text_length())
        set_page_complete(m_box, true);
      else
        set_page_complete(m_box, false);
    }

    void ExampleAssistant::print_status()
    {
      std::cout << ", entry contents: \"" << m_entry.get_text()
        << "\", checkbutton status: " << m_check.get_active() << std::endl;
    }

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include "exampleassistant.h"

    ExampleWindow::ExampleWindow()
    : m_button("Show the assistant"),
      m_label1("State of assistant checkbutton:", Gtk::Align::START, Gtk::Align::CENTER),
      m_label2("Contents of assistant entry:", Gtk::Align::START, Gtk::Align::CENTER)
    {
      set_title("Gtk::Assistant example");

      m_grid.set_row_homogeneous(true);
      m_grid.set_column_spacing(5);
      m_grid.set_margin(12);

      m_grid.attach(m_button, 0, 0, 2, 1);
      m_button.set_hexpand(true);
      m_button.set_valign(Gtk::Align::CENTER);

      m_grid.attach(m_label1, 0, 1, 1, 1);

      m_grid.attach(m_label2, 0, 2, 1, 1);

      m_grid.attach(m_check, 1, 1, 1, 1);
      m_check.set_halign(Gtk::Align::START);

      m_grid.attach(m_entry, 1, 2, 1, 1);
      m_entry.set_hexpand(true);

      set_child(m_grid);

      m_button.signal_clicked().connect(sigc::mem_fun(*this,
        &ExampleWindow::on_button_clicked));
      m_assistant.signal_apply().connect(sigc::mem_fun(*this,
        &ExampleWindow::on_assistant_apply));

      m_check.set_sensitive(false);
      m_entry.set_sensitive(false);
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_assistant_apply()
    {
      bool check_state;
      Glib::ustring entry_text;

      m_assistant.get_result(check_state, entry_text);
      m_check.set_active(check_state);
      m_entry.set_text(entry_text);
    }

    void ExampleWindow::on_button_clicked()
    {
      m_assistant.set_visible(true);
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      // Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

#### Other Multi-item Containers

There are other multi-item containers. See the reference documentation for a complete list. Here are links to some example programs that show containers, which are not mentioned elsewhere in this tutorial.

Source Code, ActionBar

Source Code, FlowBox

## ListView, GridView, ColumnView

Lists are intended to be used whenever developers want to display many objects in roughly the same way. They are perfectly fine to be used for very short lists of only 2 or 3 items, but generally scale fine to thousands of items.

Lists are meant to be used with changing data, both with the items themselves changing as well as the list adding and removing items. Of course, they work just as well with static data.

The List Widget Overview chapter in the GTK documentation contains more information about list widgets.

Some examples are shown in this chapter. There are more examples in the listmodelviews directory in gtkmm-documentation's examples.

### The Data Model

The data model is a class that implements the `Gio::ListModel` interface. Examples of such classes are `Gio::ListStore` (not to be confused with the deprecated `Gtk::ListStore`), `Gtk:StringList`, `Gtk:DirectoryList` and `Pango::FontMap`.

The elements in a model are called items. All items are instances of a subclass of `Glib::Object`. For instance, you might have a `ColumnView` with one integer and one text column, like so:

    class ModelColumns : public Glib::Object
    {
    public:
      int m_col_id;
      Glib::ustring m_col_name;

      static Glib::RefPtr<ModelColumns> create(
        int col_id, const Glib::ustring& col_name)
      {
        return Glib::make_refptr_for_instance<ModelColumns>(
          new ModelColumns(col_id, col_name));
      }

    protected:
      ModelColumns(int col_id, const Glib::ustring& col_name)
      : m_col_id(col_id), m_col_name(col_name)
      {}
    };

    Glib::RefPtr<Gio::ListStore<ModelColumns>> m_ListStore;

Every item in a model has a position which is the unsigned integer that describes where in the model the item is located. The first item in a model is at position 0. The position of an item can of course change as other items are added to or removed from the model.

Gio::ListStore Reference

StringList Reference

DirectoryList Reference

### The Selection Model

The selection model is a class that implements the `Gtk::SelectionModel` interface. You can choose between `NoSelection`, `SingleSelection` and `MultiSelection`.

NoSelection Reference

SingleSelection Reference

MultiSelection Reference

### The Factory

Data from the data model is added to the view by a factory, which is a subclass of `ListItemFactory`. There is only one such subclass in gtkmm, `SignalListItemFactory`. Data from the model is added to the view with signal handlers connected to a `SignalListItemFactory`.

SignalListItemFactory Reference

### Zobrazení (View)

The View is the widget that displays the model data and allows the user to interact with it. The View can show all of the model's columns, or just some, and it can show them in various ways.

An important requirement for views (especially views of long lists) is that they need to know which items are not visible so they can be recycled. Views achieve that by implementing the `Scrollable` interface and expecting to be placed directly into a `ScrolledWindow`.

There are different view widgets to choose from.

#### ListView

The `ListView` shows a 1-dimensional list with one column.

Reference

##### Příklad

###### ListView

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      ~ExampleWindow() override;

    protected:
      // Signal handlers:
      void on_button_quit();
      void on_setup_label(const Glib::RefPtr<Gtk::ListItem>& list_item);
      void on_bind_name(const Glib::RefPtr<Gtk::ListItem>& list_item);

      // Child widgets:
      Gtk::Box m_VBox;
      Gtk::Label m_Heading;
      Gtk::ScrolledWindow m_ScrolledWindow;
      Gtk::ListView m_ListView;
      Gtk::Box m_ButtonBox;
      Gtk::Button m_Button_Quit;

      Glib::RefPtr<Gtk::StringList> m_StringList;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::Orientation::VERTICAL),
      m_Heading("<b>Name</b>", Gtk::Align::START),
      m_Button_Quit("Quit")
    {
      set_title("Gtk::ListView (Gtk::StringList) example");
      set_default_size(300, 200);

      m_VBox.set_margin(5);
      set_child(m_VBox);

      // Add the ListView, inside a ScrolledWindow, with the heading above
      // and the button underneath.
      m_Heading.set_use_markup();
      m_VBox.append(m_Heading);
      m_ScrolledWindow.set_child(m_ListView);

      // Only show the scrollbars when they are necessary:
      m_ScrolledWindow.set_policy(Gtk::PolicyType::AUTOMATIC, Gtk::PolicyType::AUTOMATIC);
      m_ScrolledWindow.set_expand();

      m_VBox.append(m_ScrolledWindow);
      m_VBox.append(m_ButtonBox);

      m_ButtonBox.append(m_Button_Quit);
      m_ButtonBox.set_margin(5);
      m_Button_Quit.set_hexpand(true);
      m_Button_Quit.set_halign(Gtk::Align::END);
      m_Button_Quit.signal_clicked().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_button_quit));

      // Create the list model:
      m_StringList = Gtk::StringList::create({"Billy Bob", "Joey Jojo", "Rob McRoberts"});

      // Set list model and selection model.
      auto selection_model = Gtk::SingleSelection::create(m_StringList);
      selection_model->set_autoselect(false);
      selection_model->set_can_unselect(true);
      m_ListView.set_model(selection_model);
      m_ListView.add_css_class("data-table"); // high density table

      // Add the factory for the ListView's single column.
      auto factory = Gtk::SignalListItemFactory::create();
      factory->signal_setup().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_setup_label));
      factory->signal_bind().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_bind_name));
      m_ListView.set_factory(factory);
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_quit()
    {
      set_visible(false);
    }

    void ExampleWindow::on_setup_label(const Glib::RefPtr<Gtk::ListItem>& list_item)
    {
      list_item->set_child(*Gtk::make_managed<Gtk::Label>("", Gtk::Align::START));
    }

    void ExampleWindow::on_bind_name(const Glib::RefPtr<Gtk::ListItem>& list_item)
    {
      auto pos = list_item->get_position();
      if (pos == GTK_INVALID_LIST_POSITION)
        return;
      auto label = dynamic_cast<Gtk::Label*>(list_item->get_child());
      if (!label)
        return;
      label->set_text(m_StringList->get_string(pos));
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char* argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      // Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

#### GridView

The `GridView` shows a 2-dimensional grid.

Reference

##### Příklad

###### GridView

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>
    #include <gdkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      ~ExampleWindow() override;

    protected:
      class ModelColumns;
      // Signal handlers:
      void on_button_quit();
      void on_item_activated(unsigned int position);
      void on_selection_changed();
      void on_setup_listitem(const Glib::RefPtr<Gtk::ListItem>& list_item);
      void on_bind_listitem(const Glib::RefPtr<Gtk::ListItem>& list_item);
      int on_model_sort(const Glib::RefPtr<const ModelColumns>& a, const Glib::RefPtr<const ModelColumns>& b);

      void add_entry(const std::string& filename, const Glib::ustring& description);

      // A Gio::ListStore stores filename, description and texture.
      class ModelColumns : public Glib::Object
      {
      public:
        std::string m_filename;
        Glib::ustring  m_description;
        Glib::RefPtr<Gdk::Texture> m_texture;

        static Glib::RefPtr<ModelColumns> create(const std::string& filename,
          const Glib::ustring& description, const Glib::RefPtr<Gdk::Texture>& texture)
        {
          return Glib::make_refptr_for_instance<ModelColumns>(
            new ModelColumns(filename, description, texture));
        }

      protected:
        ModelColumns(const std::string& filename, const Glib::ustring& description,
          const Glib::RefPtr<Gdk::Texture>& texture)
        : m_filename(filename), m_description(description), m_texture(texture)
        { }
      }; // ModelColumns

      Glib::RefPtr<Gio::ListStore<ModelColumns>> m_data_model;
      Glib::RefPtr<Gtk::SingleSelection> m_selection_model;
      Glib::RefPtr<Gtk::SignalListItemFactory> m_factory;

      // Child widgets:
      Gtk::Box m_VBox;
      Gtk::ScrolledWindow m_ScrolledWindow;
      Gtk::GridView m_GridView;
      Gtk::Box m_ButtonBox;
      Gtk::Button m_Button_Quit;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <array>
    #include <iostream>

    namespace
    {
      struct GridEntry
      {
        std::string m_filename;
        Glib::ustring m_description;
      };

      std::array<GridEntry, 8> entries =
      {
        GridEntry{"mozilla-firefox.png", "<b>Mozilla Firefox</b> Logo"},
        GridEntry{"xmms.xpm",            "<b>XMMS</b> Logo"},
        GridEntry{"gnome-dice-1.svg",    "<b>Gnome Dice 1</b> Logo"},
        GridEntry{"gnome-dice-2.svg",    "<b>Gnome Dice 2</b> Logo"},
        GridEntry{"gnome-dice-3.svg",    "<b>Gnome Dice 3</b> Logo"},
        GridEntry{"gnome-dice-4.svg",    "<b>Gnome Dice 4</b> Logo"},
        GridEntry{"gnome-dice-5.svg",    "<b>Gnome Dice 5</b> Logo"},
        GridEntry{"gnome-dice-6.svg",    "<b>Gnome Dice 6</b> Logo"}
      };

    } // anonymous namespace

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::Orientation::VERTICAL),
      m_Button_Quit("Quit")
    {
      set_title("Gtk::GridView (Gio::ListStore) example");
      set_default_size(400, 400);

      m_VBox.set_margin(5);
      set_child(m_VBox);

      // Add the GridView inside a ScrolledWindow, with the button underneath:
      m_ScrolledWindow.set_child(m_GridView);

      // Only show the scrollbars when they are necessary:
      m_ScrolledWindow.set_policy(Gtk::PolicyType::AUTOMATIC, Gtk::PolicyType::AUTOMATIC);
      m_ScrolledWindow.set_expand();

      m_VBox.append(m_ScrolledWindow);
      m_VBox.append(m_ButtonBox);

      m_ButtonBox.append(m_Button_Quit);
      m_ButtonBox.set_margin(6);
      m_Button_Quit.set_hexpand(true);
      m_Button_Quit.set_halign(Gtk::Align::END);
      m_Button_Quit.signal_clicked().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_button_quit));

      // Create the data model:
      m_data_model = Gio::ListStore<ModelColumns>::create();
      m_selection_model = Gtk::SingleSelection::create(m_data_model);
      m_selection_model->set_autoselect(false);

      m_factory = Gtk::SignalListItemFactory::create();
      m_factory->signal_setup().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_setup_listitem));
      m_factory->signal_bind().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_bind_listitem));

      // Fill the Gio::ListStore's data model and sort it.
      for (const auto& entry : entries)
        add_entry(entry.m_filename, entry.m_description);
      m_data_model->sort(sigc::mem_fun(*this, &ExampleWindow::on_model_sort));

      m_GridView.set_model(m_selection_model);
      m_GridView.set_factory(m_factory);

      m_GridView.signal_activate().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_item_activated));
      m_selection_model->property_selected().signal_changed().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_selection_changed));
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_quit()
    {
      set_visible(false);
    }

    void ExampleWindow::on_setup_listitem(const Glib::RefPtr<Gtk::ListItem>& list_item)
    {
      // Each ListItem contains a vertical Box with an Image and a Label.
      auto vBox = Gtk::make_managed<Gtk::Box>(Gtk::Orientation::VERTICAL);
      auto picture = Gtk::make_managed<Gtk::Picture>();
      picture->set_can_shrink(false);
      picture->set_halign(Gtk::Align::CENTER);
      picture->set_valign(Gtk::Align::END);
      vBox->append(*picture);
      vBox->append(*Gtk::make_managed<Gtk::Label>());
      list_item->set_child(*vBox);
    }

    void ExampleWindow::on_bind_listitem(const Glib::RefPtr<Gtk::ListItem>& list_item)
    {
      auto col = std::dynamic_pointer_cast<ModelColumns>(list_item->get_item());
      if (!col)
        return;
      auto vBox = dynamic_cast<Gtk::Box*>(list_item->get_child());
      if (!vBox)
        return;
      auto picture = dynamic_cast<Gtk::Picture*>(vBox->get_first_child());
      if (!picture)
        return;
      auto label = dynamic_cast<Gtk::Label*>(picture->get_next_sibling());
      if (!label)
        return;
      picture->set_paintable(col->m_texture);
      label->set_markup(col->m_description);
    }

    void ExampleWindow::on_item_activated(unsigned int position)
    {
      auto col = m_data_model->get_item(position);
      if (!col)
        return;

      const std::string filename = col->m_filename;
      const Glib::ustring description = col->m_description;

      std::cout  << "Item activated: filename=" << filename
        << ", description=" << description << std::endl;
    }

    void ExampleWindow::on_selection_changed()
    {
      auto position = m_selection_model->get_selected();
      auto col = m_data_model->get_item(position);
      if (!col)
        return;

      const std::string filename = col->m_filename;
      const Glib::ustring description = col->m_description;

      std::cout  << "Selection Changed to: filename=" << filename
        << ", description=" << description << std::endl;
    }

    int ExampleWindow::on_model_sort(const Glib::RefPtr<const ModelColumns>& a,
      const Glib::RefPtr<const ModelColumns>& b)
    {
      return (a->m_description < b->m_description) ? -1 : ((a->m_description > b->m_description) ? 1 : 0);
    }

    void ExampleWindow::add_entry(const std::string& filename,
            const Glib::ustring& description )
    {
      try
      {
         auto pixbuf = Gdk::Pixbuf::create_from_file(filename);
         auto texture = Gdk::Texture::create_for_pixbuf(pixbuf);
         m_data_model->append(ModelColumns::create(filename, description, texture));
      }
      catch (const Gdk::PixbufError& ex)
      {
        std::cerr << "Gdk::PixbufError: " << ex.what() << std::endl;
      }
      catch (const Glib::FileError& ex)
      {
        std::cerr << "Glib::FileError: " << ex.what() << std::endl;
      }
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

#### ColumnView

The `ColumnView` shows a 1-dimensional list with one or more columns.

Reference

##### Příklad

###### ColumnView

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      ~ExampleWindow() override;

    protected:
      // Signal handlers:
      void on_button_quit();
      void on_setup_label(const Glib::RefPtr<Gtk::ListItem>& list_item, Gtk::Align halign);
      void on_setup_progressbar(const Glib::RefPtr<Gtk::ListItem>& list_item);
      void on_bind_id(const Glib::RefPtr<Gtk::ListItem>& list_item);
      void on_bind_name(const Glib::RefPtr<Gtk::ListItem>& list_item);
      void on_bind_number(const Glib::RefPtr<Gtk::ListItem>& list_item);
      void on_bind_percentage(const Glib::RefPtr<Gtk::ListItem>& list_item);

      // A Gio::ListStore item.
      class ModelColumns : public Glib::Object
      {
      public:
        unsigned int m_col_id;
        Glib::ustring m_col_name;
        short m_col_number;
        int m_col_percentage;

        static Glib::RefPtr<ModelColumns> create(unsigned int col_id,
          const Glib::ustring& col_name, short col_number, int col_percentage)
        {
          return Glib::make_refptr_for_instance<ModelColumns>(
            new ModelColumns(col_id, col_name, col_number, col_percentage));
        }

      protected:
        ModelColumns(unsigned int col_id, const Glib::ustring& col_name,
          short col_number, int col_percentage)
        : m_col_id(col_id), m_col_name(col_name), m_col_number(col_number),
          m_col_percentage(col_percentage)
        {}
      }; // ModelColumns

      // Child widgets:
      Gtk::Box m_VBox;
      Gtk::ScrolledWindow m_ScrolledWindow;
      Gtk::ColumnView m_ColumnView;
      Gtk::Box m_ButtonBox;
      Gtk::Button m_Button_Quit;

      Glib::RefPtr<Gio::ListStore<ModelColumns>> m_ListStore;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::Orientation::VERTICAL),
      m_Button_Quit("Quit")
    {
      set_title("Gtk::ColumnView (Gio::ListStore) example");
      set_default_size(500, 250);

      m_VBox.set_margin(5);
      set_child(m_VBox);

      // Add the ColumnView, inside a ScrolledWindow, with the button underneath:
      m_ScrolledWindow.set_child(m_ColumnView);

      // Only show the scrollbars when they are necessary:
      m_ScrolledWindow.set_policy(Gtk::PolicyType::AUTOMATIC, Gtk::PolicyType::AUTOMATIC);
      m_ScrolledWindow.set_expand();

      m_VBox.append(m_ScrolledWindow);
      m_VBox.append(m_ButtonBox);

      m_ButtonBox.append(m_Button_Quit);
      m_ButtonBox.set_margin(5);
      m_Button_Quit.set_hexpand(true);
      m_Button_Quit.set_halign(Gtk::Align::END);
      m_Button_Quit.signal_clicked().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_button_quit));

      // Create the List model:
      m_ListStore = Gio::ListStore<ModelColumns>::create();
      m_ListStore->append(ModelColumns::create(1, "Billy Bob", 10, 15));
      m_ListStore->append(ModelColumns::create(2, "Joey Jojo", 20, 40));
      m_ListStore->append(ModelColumns::create(3, "Rob McRoberts", 30, 70));

      // Set list model and selection model.
      auto selection_model = Gtk::SingleSelection::create(m_ListStore);
      selection_model->set_autoselect(false);
      selection_model->set_can_unselect(true);
      m_ColumnView.set_model(selection_model);
      m_ColumnView.add_css_class("data-table"); // high density table

      // Make the columns reorderable.
      // This is not necessary, but it's nice to show the feature.
      m_ColumnView.set_reorderable(true);

      // Add the ColumnView's columns:

      // Id column
      auto factory = Gtk::SignalListItemFactory::create();
      factory->signal_setup().connect(sigc::bind(sigc::mem_fun(*this,
        &ExampleWindow::on_setup_label), Gtk::Align::END));
      factory->signal_bind().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_bind_id));
      auto column = Gtk::ColumnViewColumn::create("ID", factory);
      m_ColumnView.append_column(column);

      // Name column
      factory = Gtk::SignalListItemFactory::create();
      factory->signal_setup().connect(sigc::bind(sigc::mem_fun(*this,
        &ExampleWindow::on_setup_label), Gtk::Align::START));
      factory->signal_bind().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_bind_name));
      column = Gtk::ColumnViewColumn::create("Name", factory);
      m_ColumnView.append_column(column);

      // Number column
      factory = Gtk::SignalListItemFactory::create();
      factory->signal_setup().connect(sigc::bind(sigc::mem_fun(*this,
        &ExampleWindow::on_setup_label), Gtk::Align::END));
      factory->signal_bind().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_bind_number));
      column = Gtk::ColumnViewColumn::create("Formatted number", factory);
      m_ColumnView.append_column(column);

      // Percentage column
      factory = Gtk::SignalListItemFactory::create();
      factory->signal_setup().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_setup_progressbar));
      factory->signal_bind().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_bind_percentage));
      column = Gtk::ColumnViewColumn::create("Some percentage", factory);
      m_ColumnView.append_column(column);
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_quit()
    {
      set_visible(false);
    }

    void ExampleWindow::on_setup_label(
      const Glib::RefPtr<Gtk::ListItem>& list_item, Gtk::Align halign)
    {
      list_item->set_child(*Gtk::make_managed<Gtk::Label>("", halign));
    }

    void ExampleWindow::on_setup_progressbar(
      const Glib::RefPtr<Gtk::ListItem>& list_item)
    {
      auto progressbar = Gtk::make_managed<Gtk::ProgressBar>();
      progressbar->set_show_text(true);
      list_item->set_child(*progressbar);
    }

    void ExampleWindow::on_bind_id(const Glib::RefPtr<Gtk::ListItem>& list_item)
    {
      auto col = std::dynamic_pointer_cast<ModelColumns>(list_item->get_item());
      if (!col)
        return;
      auto label = dynamic_cast<Gtk::Label*>(list_item->get_child());
      if (!label)
        return;
      label->set_text(Glib::ustring::format(col->m_col_id));
    }

    void ExampleWindow::on_bind_name(const Glib::RefPtr<Gtk::ListItem>& list_item)
    {
      auto col = std::dynamic_pointer_cast<ModelColumns>(list_item->get_item());
      if (!col)
        return;
      auto label = dynamic_cast<Gtk::Label*>(list_item->get_child());
      if (!label)
        return;
      label->set_text(col->m_col_name);
    }

    void ExampleWindow::on_bind_number(const Glib::RefPtr<Gtk::ListItem>& list_item)
    {
      auto col = std::dynamic_pointer_cast<ModelColumns>(list_item->get_item());
      if (!col)
        return;
      auto label = dynamic_cast<Gtk::Label*>(list_item->get_child());
      if (!label)
        return;
      // 10 digits, using leading zeroes.
      label->set_text(Glib::ustring::sprintf("%010d", col->m_col_number));
    }

    void ExampleWindow::on_bind_percentage(const Glib::RefPtr<Gtk::ListItem>& list_item)
    {
      auto col = std::dynamic_pointer_cast<ModelColumns>(list_item->get_item());
      if (!col)
        return;
      auto progressbar = dynamic_cast<Gtk::ProgressBar*>(list_item->get_child());
      if (!progressbar)
        return;
      progressbar->set_fraction(col->m_col_percentage * 0.01);
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char* argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      // Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

### Řazení

The list can be sorted by wrapping it in a `SortListModel`. There are two ways to do this.

- In a `ColumnView`, get the `ColumnViewSorter` from the `ColumnView` and set it to the `SortListModel`. Set a `Sorter` to each `ColumnViewColumn`. Then the user of your app can sort the items by clicking on a column heading.

- In any view, set a `Sorter` such as a `StringSorter` or a `NumericSorter` to the `SortListModel`.

SortListModel Reference

StringSorter Reference

NumericSorter Reference

#### Příklad

##### SortListModel

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      ~ExampleWindow() override;

    protected:
      // Signal handlers:
      void on_button_nosort();
      void on_button_sortheadings();
      void on_button_sortlength();
      void on_button_quit();
      void on_setup_label(const Glib::RefPtr<Gtk::ListItem>& list_item, Gtk::Align halign);
      void on_bind_id(const Glib::RefPtr<Gtk::ListItem>& list_item);
      void on_bind_name(const Glib::RefPtr<Gtk::ListItem>& list_item);

      // A Gio::ListStore item.
      class ModelColumns : public Glib::Object
      {
      public:
        unsigned int m_col_id;
        Glib::ustring m_col_name;

        static Glib::RefPtr<ModelColumns> create(int col_id, const Glib::ustring& col_name)
        {
          return Glib::make_refptr_for_instance<ModelColumns>(
            new ModelColumns(col_id, col_name));
        }

      protected:
        ModelColumns(int col_id, const Glib::ustring& col_name)
        : m_col_id(col_id), m_col_name(col_name)
        {}
      }; // ModelColumns

      // Child widgets:
      Gtk::Box m_VBox;
      Gtk::ScrolledWindow m_ScrolledWindow;
      Gtk::ColumnView m_ColumnView;
      Gtk::Box m_ButtonBox;
      Gtk::ToggleButton m_Button_NoSort;
      Gtk::ToggleButton m_Button_SortHeadings;
      Gtk::ToggleButton m_Button_SortLength;
      Gtk::Button m_Button_Quit;

      Glib::RefPtr<Gtk::SingleSelection> m_SelectionModel;
      Glib::RefPtr<Gio::ListStore<ModelColumns>> m_ListStore;
      Glib::RefPtr<Gtk::SortListModel> m_SortListModel;
      Glib::RefPtr<Gtk::ColumnViewColumn> m_IdColumn;
      Glib::RefPtr<Gtk::ColumnViewColumn> m_NameColumn;
      Glib::RefPtr<Gtk::NumericSorter<Glib::ustring::size_type>> m_LengthSorter;
      Glib::RefPtr<Gtk::NumericSorter<unsigned int>> m_IdSorter;
      Glib::RefPtr<Gtk::StringSorter> m_NameSorter;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::Orientation::VERTICAL),
      m_Button_NoSort("Don't Sort"),
      m_Button_SortHeadings("Sort Headings"),
      m_Button_SortLength("Sort Length"),
      m_Button_Quit("Quit")
    {
      set_title("Gtk::ColumnView (Gtk::SortListModel) example");
      set_default_size(400, 350);

      m_VBox.set_margin(5);
      set_child(m_VBox);

      // Add the ColumnView, inside a ScrolledWindow, with the buttons underneath:
      m_ScrolledWindow.set_child(m_ColumnView);

      // Only show the scrollbars when they are necessary:
      m_ScrolledWindow.set_policy(Gtk::PolicyType::AUTOMATIC, Gtk::PolicyType::AUTOMATIC);
      m_ScrolledWindow.set_expand();

      m_VBox.append(m_ScrolledWindow);
      m_VBox.append(m_ButtonBox);

      m_ButtonBox.set_margin(5);
      m_ButtonBox.set_spacing(10);
      m_ButtonBox.append(m_Button_NoSort);
      m_ButtonBox.append(m_Button_SortHeadings);
      m_ButtonBox.append(m_Button_SortLength);
      m_ButtonBox.append(m_Button_Quit);
      m_Button_NoSort.signal_toggled().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_button_nosort));
      m_Button_SortHeadings.signal_toggled().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_button_sortheadings));
      m_Button_SortLength.signal_toggled().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_button_sortlength));
      m_Button_Quit.set_hexpand(true);
      m_Button_Quit.set_halign(Gtk::Align::END);
      m_Button_Quit.signal_clicked().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_button_quit));

      // Gtk::CheckButton and Gtk::ToggleButton have set_group() methods.
      // They act as radio buttons, if they are included in a group.
      m_Button_SortHeadings.set_group(m_Button_NoSort);
      m_Button_SortLength.set_group(m_Button_NoSort);

      // Create the List model.
      m_ListStore = Gio::ListStore<ModelColumns>::create();
      m_ListStore->append(ModelColumns::create(1, "Billy Bob"));
      m_ListStore->append(ModelColumns::create(11, "Billy Bob Junior"));
      m_ListStore->append(ModelColumns::create(12, "Sue Bob"));
      m_ListStore->append(ModelColumns::create(2, "Joey Jojo"));
      m_ListStore->append(ModelColumns::create(3, "Rob McRoberts"));
      m_ListStore->append(ModelColumns::create(31, "Xavier McRoberts"));

      // Create the sort model.
      auto size_expression = Gtk::ClosureExpression<Glib::ustring::size_type>::create(
        [](const Glib::RefPtr<Glib::ObjectBase>& item)->Glib::ustring::size_type
        {
          const auto col = std::dynamic_pointer_cast<ModelColumns>(item);
          return col ? col->m_col_name.size() : 0;
        });
      m_LengthSorter = Gtk::NumericSorter<Glib::ustring::size_type>::create(size_expression);
      m_LengthSorter->set_sort_order(Gtk::SortType::ASCENDING);
      m_SortListModel = Gtk::SortListModel::create(m_ListStore, m_LengthSorter);

      // Set list model and selection model.
      m_SelectionModel = Gtk::SingleSelection::create(m_ListStore);
      m_SelectionModel->set_autoselect(false);
      m_SelectionModel->set_can_unselect(true);
      m_ColumnView.set_model(m_SelectionModel);
      m_ColumnView.add_css_class("data-table"); // high density table

      // Make the columns reorderable.
      // This is not necessary, but it's nice to show the feature.
      m_ColumnView.set_reorderable(true);

      // Add the ColumnView's columns:

      // Id column
      auto factory = Gtk::SignalListItemFactory::create();
      factory->signal_setup().connect(sigc::bind(sigc::mem_fun(*this,
        &ExampleWindow::on_setup_label), Gtk::Align::END));
      factory->signal_bind().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_bind_id));
      m_IdColumn = Gtk::ColumnViewColumn::create("ID", factory);
      m_ColumnView.append_column(m_IdColumn);
      auto uint_expression = Gtk::ClosureExpression<unsigned int>::create(
        [](const Glib::RefPtr<Glib::ObjectBase>& item)->unsigned int
        {
          const auto col = std::dynamic_pointer_cast<ModelColumns>(item);
          return col ? col->m_col_id : 0;
        });
      m_IdSorter = Gtk::NumericSorter<unsigned int>::create(uint_expression);

      // Name column
      factory = Gtk::SignalListItemFactory::create();
      factory->signal_setup().connect(sigc::bind(sigc::mem_fun(*this,
        &ExampleWindow::on_setup_label), Gtk::Align::START));
      factory->signal_bind().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_bind_name));
      m_NameColumn = Gtk::ColumnViewColumn::create("Name", factory);
      m_ColumnView.append_column(m_NameColumn);
      auto ustring_expression = Gtk::ClosureExpression<Glib::ustring>::create(
        [](const Glib::RefPtr<Glib::ObjectBase>& item)->Glib::ustring
        {
          const auto col = std::dynamic_pointer_cast<ModelColumns>(item);
          return col ? col->m_col_name : "";
        });
      m_NameSorter = Gtk::StringSorter::create(ustring_expression);

      // Show the list model without sorting.
      m_Button_NoSort.set_active(true);
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_nosort()
    {
      if (m_Button_NoSort.get_active())
      {
        m_SelectionModel->set_model(m_ListStore);
        m_IdColumn->set_sorter({});
        m_NameColumn->set_sorter({});
      }
    }

    void ExampleWindow::on_button_sortheadings()
    {
      if (m_Button_SortHeadings.get_active())
      {
        m_SortListModel->set_sorter(m_ColumnView.get_sorter());
        m_SelectionModel->set_model(m_SortListModel);
        m_IdColumn->set_sorter(m_IdSorter);
        m_NameColumn->set_sorter(m_NameSorter);
      }
    }

    void ExampleWindow::on_button_sortlength()
    {
      if (m_Button_SortLength.get_active())
      {
        m_SortListModel->set_sorter(m_LengthSorter);
        m_SelectionModel->set_model(m_SortListModel);
        m_IdColumn->set_sorter({});
        m_NameColumn->set_sorter({});
      }
    }

    void ExampleWindow::on_button_quit()
    {
      set_visible(false);
    }

    void ExampleWindow::on_setup_label(
      const Glib::RefPtr<Gtk::ListItem>& list_item, Gtk::Align halign)
    {
      list_item->set_child(*Gtk::make_managed<Gtk::Label>("", halign));
    }

    void ExampleWindow::on_bind_id(const Glib::RefPtr<Gtk::ListItem>& list_item)
    {
      auto col = std::dynamic_pointer_cast<ModelColumns>(list_item->get_item());
      if (!col)
        return;
      auto label = dynamic_cast<Gtk::Label*>(list_item->get_child());
      if (!label)
        return;
      label->set_text(Glib::ustring::format(col->m_col_id));
    }

    void ExampleWindow::on_bind_name(const Glib::RefPtr<Gtk::ListItem>& list_item)
    {
      auto col = std::dynamic_pointer_cast<ModelColumns>(list_item->get_item());
      if (!col)
        return;
      auto label = dynamic_cast<Gtk::Label*>(list_item->get_child());
      if (!label)
        return;
      label->set_text(col->m_col_name);
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char* argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      // Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

### Filtering

The list can be filtered by wrapping it in a `FilterListModel`. Set a `Filter` such as a `StringFilter` or a `BoolFilter` to the `FilterListModel`.

FilterListModel Reference

StringFilter Reference

BoolFilter Reference

#### Příklad

##### FilterListModel

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      ~ExampleWindow() override;

    protected:
      // Signal handlers:
      void on_button_showall();
      void on_button_showj();
      void on_button_showm();
      void on_button_quit();
      void on_setup_label(const Glib::RefPtr<Gtk::ListItem>& list_item, Gtk::Align halign);
      void on_bind_id(const Glib::RefPtr<Gtk::ListItem>& list_item);
      void on_bind_name(const Glib::RefPtr<Gtk::ListItem>& list_item);

      // A Gio::ListStore item.
      class ModelColumns : public Glib::Object
      {
      public:
        unsigned int m_col_id;
        Glib::ustring m_col_name;

        static Glib::RefPtr<ModelColumns> create(int col_id, const Glib::ustring& col_name)
        {
          return Glib::make_refptr_for_instance<ModelColumns>(
            new ModelColumns(col_id, col_name));
        }

      protected:
        ModelColumns(int col_id, const Glib::ustring& col_name)
        : m_col_id(col_id), m_col_name(col_name)
        {}
      }; // ModelColumns

      // Child widgets:
      Gtk::Box m_VBox;
      Gtk::ScrolledWindow m_ScrolledWindow;
      Gtk::ColumnView m_ColumnView;
      Gtk::Box m_ButtonBox;
      Gtk::ToggleButton m_Button_ShowAll;
      Gtk::ToggleButton m_Button_ShowJ;
      Gtk::ToggleButton m_Button_ShowM;
      Gtk::Button m_Button_Quit;

      Glib::RefPtr<Gtk::SingleSelection> m_SelectionModel;
      Glib::RefPtr<Gio::ListStore<ModelColumns>> m_ListStore;
      Glib::RefPtr<Gtk::FilterListModel> m_FilterListModel;
      Glib::RefPtr<Gtk::StringFilter> m_StringFilter;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::Orientation::VERTICAL),
      m_Button_ShowAll("Show All"),
      m_Button_ShowJ("Show J"),
      m_Button_ShowM("Show M"),
      m_Button_Quit("Quit")
    {
      set_title("Gtk::ColumnView (Gtk::FilterListModel) example");
      set_default_size(400, 350);

      m_VBox.set_margin(5);
      set_child(m_VBox);

      // Add the ColumnView, inside a ScrolledWindow, with the buttons underneath:
      m_ScrolledWindow.set_child(m_ColumnView);

      // Only show the scrollbars when they are necessary:
      m_ScrolledWindow.set_policy(Gtk::PolicyType::AUTOMATIC, Gtk::PolicyType::AUTOMATIC);
      m_ScrolledWindow.set_expand();

      m_VBox.append(m_ScrolledWindow);
      m_VBox.append(m_ButtonBox);

      m_ButtonBox.set_margin(5);
      m_ButtonBox.set_spacing(10);
      m_ButtonBox.append(m_Button_ShowAll);
      m_ButtonBox.append(m_Button_ShowJ);
      m_ButtonBox.append(m_Button_ShowM);
      m_ButtonBox.append(m_Button_Quit);
      m_Button_ShowAll.signal_toggled().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_button_showall));
      m_Button_ShowJ.signal_toggled().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_button_showj));
      m_Button_ShowM.signal_toggled().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_button_showm));
      m_Button_Quit.set_hexpand(true);
      m_Button_Quit.set_halign(Gtk::Align::END);
      m_Button_Quit.signal_clicked().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_button_quit));

      // Gtk::CheckButton and Gtk::ToggleButton have set_group() methods.
      // They act as radio buttons, if they are included in a group.
      m_Button_ShowJ.set_group(m_Button_ShowAll);
      m_Button_ShowM.set_group(m_Button_ShowAll);

      // Create the List model.
      m_ListStore = Gio::ListStore<ModelColumns>::create();
      m_ListStore->append(ModelColumns::create(1, "Billy Bob"));
      m_ListStore->append(ModelColumns::create(11, "Billy Bob Junior"));
      m_ListStore->append(ModelColumns::create(12, "Sue Bob"));
      m_ListStore->append(ModelColumns::create(2, "Joey Jojo"));
      m_ListStore->append(ModelColumns::create(3, "Rob McRoberts"));
      m_ListStore->append(ModelColumns::create(31, "Xavier McRoberts"));

      // Create the filter model.
      auto expression = Gtk::ClosureExpression<Glib::ustring>::create(
        [](const Glib::RefPtr<Glib::ObjectBase>& item)->Glib::ustring
        {
          const auto col = std::dynamic_pointer_cast<ModelColumns>(item);
          return col ? col->m_col_name : "";
        });
      m_StringFilter = Gtk::StringFilter::create(expression);
      m_StringFilter->set_ignore_case(false);
      m_StringFilter->set_match_mode(Gtk::StringFilter::MatchMode::SUBSTRING);
      m_FilterListModel = Gtk::FilterListModel::create(m_ListStore, m_StringFilter);

      // Set list model and selection model.
      m_SelectionModel = Gtk::SingleSelection::create(m_ListStore);
      m_SelectionModel->set_autoselect(false);
      m_SelectionModel->set_can_unselect(true);
      m_ColumnView.set_model(m_SelectionModel);
      m_ColumnView.add_css_class("data-table"); // high density table

      // Make the columns reorderable.
      // This is not necessary, but it's nice to show the feature.
      m_ColumnView.set_reorderable(true);

      // Add the ColumnView's columns:

      // Id column
      auto factory = Gtk::SignalListItemFactory::create();
      factory->signal_setup().connect(sigc::bind(sigc::mem_fun(*this,
        &ExampleWindow::on_setup_label), Gtk::Align::END));
      factory->signal_bind().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_bind_id));
      auto column = Gtk::ColumnViewColumn::create("ID", factory);
      m_ColumnView.append_column(column);

      // Name column
      factory = Gtk::SignalListItemFactory::create();
      factory->signal_setup().connect(sigc::bind(sigc::mem_fun(*this,
        &ExampleWindow::on_setup_label), Gtk::Align::START));
      factory->signal_bind().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_bind_name));
      column = Gtk::ColumnViewColumn::create("Name", factory);
      m_ColumnView.append_column(column);

      // Show the list model without filtering.
      m_Button_ShowAll.set_active(true);
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_showall()
    {
      if (m_Button_ShowAll.get_active())
        m_SelectionModel->set_model(m_ListStore);
    }

    void ExampleWindow::on_button_showj()
    {
      if (m_Button_ShowJ.get_active())
      {
       m_StringFilter->set_search("J");
        m_SelectionModel->set_model(m_FilterListModel);
      }
    }

    void ExampleWindow::on_button_showm()
    {
      if (m_Button_ShowM.get_active())
      {
       m_StringFilter->set_search("M");
        m_SelectionModel->set_model(m_FilterListModel);
      }
    }

    void ExampleWindow::on_button_quit()
    {
      set_visible(false);
    }

    void ExampleWindow::on_setup_label(
      const Glib::RefPtr<Gtk::ListItem>& list_item, Gtk::Align halign)
    {
      list_item->set_child(*Gtk::make_managed<Gtk::Label>("", halign));
    }

    void ExampleWindow::on_bind_id(const Glib::RefPtr<Gtk::ListItem>& list_item)
    {
      auto col = std::dynamic_pointer_cast<ModelColumns>(list_item->get_item());
      if (!col)
        return;
      auto label = dynamic_cast<Gtk::Label*>(list_item->get_child());
      if (!label)
        return;
      label->set_text(Glib::ustring::format(col->m_col_id));
    }

    void ExampleWindow::on_bind_name(const Glib::RefPtr<Gtk::ListItem>& list_item)
    {
      auto col = std::dynamic_pointer_cast<ModelColumns>(list_item->get_item());
      if (!col)
        return;
      auto label = dynamic_cast<Gtk::Label*>(list_item->get_child());
      if (!label)
        return;
      label->set_text(col->m_col_name);
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char* argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      // Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

### Displaying Trees

While the deprecated `TreeView` provided built-in support for trees, the list widgets, and in particular `Gio::ListModel`, do not. However, gtkmm provides functionality to make trees look and behave like lists for the people who still want to display lists. This is achieved by using the `TreeListModel` to flatten a tree into a list. The `TreeExpander` widget can then be used inside a listitem to allow users to expand and collapse rows.

TreeListModel Reference

TreeExpander Reference

#### Příklad

##### TreeListModel

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      ~ExampleWindow() override;

    protected:
      // Signal handlers:
      void on_button_quit();
      void on_setup_id(const Glib::RefPtr<Gtk::ListItem>& list_item);
      void on_setup_name(const Glib::RefPtr<Gtk::ListItem>& list_item);
      void on_bind_id(const Glib::RefPtr<Gtk::ListItem>& list_item);
      void on_bind_name(const Glib::RefPtr<Gtk::ListItem>& list_item);

      Glib::RefPtr<Gio::ListModel> create_model(
        const Glib::RefPtr<Glib::ObjectBase>& item = {});

      // A Gio::ListStore item.
      class ModelColumns : public Glib::Object
      {
      public:
        int m_col_id;
        Glib::ustring m_col_name;

        static Glib::RefPtr<ModelColumns> create(int col_id, const Glib::ustring& col_name)
        {
          return Glib::make_refptr_for_instance<ModelColumns>(
            new ModelColumns(col_id, col_name));
        }

      protected:
        ModelColumns(int col_id, const Glib::ustring& col_name)
        : m_col_id(col_id), m_col_name(col_name)
        {}
      }; // ModelColumns

      // Child widgets:
      Gtk::Box m_VBox;
      Gtk::ScrolledWindow m_ScrolledWindow;
      Gtk::ColumnView m_ColumnView;
      Gtk::Box m_ButtonBox;
      Gtk::Button m_Button_Quit;

      Glib::RefPtr<Gtk::TreeListModel> m_TreeListModel;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::Orientation::VERTICAL),
      m_Button_Quit("Quit")
    {
      set_title("Gtk::ColumnView (Gtk::TreeListModel) example");
      set_default_size(300, 350);

      m_VBox.set_margin(5);
      set_child(m_VBox);

      // Add the ColumnView, inside a ScrolledWindow, with the button underneath:
      m_ScrolledWindow.set_child(m_ColumnView);

      // Only show the scrollbars when they are necessary:
      m_ScrolledWindow.set_policy(Gtk::PolicyType::AUTOMATIC, Gtk::PolicyType::AUTOMATIC);
      m_ScrolledWindow.set_expand();

      m_VBox.append(m_ScrolledWindow);
      m_VBox.append(m_ButtonBox);

      m_ButtonBox.append(m_Button_Quit);
      m_ButtonBox.set_margin(5);
      m_Button_Quit.set_hexpand(true);
      m_Button_Quit.set_halign(Gtk::Align::END);
      m_Button_Quit.signal_clicked().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_button_quit));

      // Create the root model:
      auto root = create_model();

      // Set list model and selection model.
      // passthrough must be false when Gtk::TreeExpander is used in the view.
      m_TreeListModel = Gtk::TreeListModel::create(root,
        sigc::mem_fun(*this, &ExampleWindow::create_model),
        /* passthrough */ false, /* autoexpand */ false);
      auto selection_model = Gtk::MultiSelection::create(m_TreeListModel);
      m_ColumnView.set_model(selection_model);
      m_ColumnView.add_css_class("data-table"); // high density table

      // Make the columns reorderable.
      // This is not necessary, but it's nice to show the feature.
      m_ColumnView.set_reorderable(true);

      // Add the ColumnView's columns:

      // Id column
      auto factory = Gtk::SignalListItemFactory::create();
      factory->signal_setup().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_setup_id));
      factory->signal_bind().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_bind_id));
      auto column = Gtk::ColumnViewColumn::create("ID", factory);
      m_ColumnView.append_column(column);

      // Name column
      factory = Gtk::SignalListItemFactory::create();
      factory->signal_setup().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_setup_name));
      factory->signal_bind().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_bind_name));
      column = Gtk::ColumnViewColumn::create("Name", factory);
      m_ColumnView.append_column(column);
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_quit()
    {
      set_visible(false);
    }

    Glib::RefPtr<Gio::ListModel> ExampleWindow::create_model(
      const Glib::RefPtr<Glib::ObjectBase>& item)
    {
      auto col = std::dynamic_pointer_cast<ModelColumns>(item);
      auto result = Gio::ListStore<ModelColumns>::create();
      if (!col)
      {
        // Top names
        result->append(ModelColumns::create(1, "Billy Bob"));
        result->append(ModelColumns::create(2, "Joey Jojo"));
        result->append(ModelColumns::create(3, "Rob McRoberts"));
      }
      else
      {
        switch (col->m_col_id)
        {
        case 1:
          result->append(ModelColumns::create(11, "Billy Bob Junior"));
          result->append(ModelColumns::create(12, "Sue Bob"));
          break;
        case 3:
          result->append(ModelColumns::create(31, "Xavier McRoberts"));
          break;
        }
      }

      // If result is empty, it's a leaf in the tree, i.e. an item without children.
      // Returning an empty RefPtr (not a RefPtr with an empty Gio::ListModel)
      // signals that the item is not expandable.
      return (result->get_n_items() > 0) ? result : Glib::RefPtr<Gio::ListModel>();
    }

    void ExampleWindow::on_setup_id(
      const Glib::RefPtr<Gtk::ListItem>& list_item)
    {
      // Each ListItem contains a TreeExpander, which contains a Label.
      // The Label shows the ModelColumns::m_col_id. That's done in on_bind_id().
      auto expander = Gtk::make_managed<Gtk::TreeExpander>();
      auto label = Gtk::make_managed<Gtk::Label>();
      label->set_halign(Gtk::Align::END);
      expander->set_child(*label);
      list_item->set_child(*expander);
    }

    void ExampleWindow::on_setup_name(
      const Glib::RefPtr<Gtk::ListItem>& list_item)
    {
      list_item->set_child(*Gtk::make_managed<Gtk::Label>("", Gtk::Align::START));
    }

    void ExampleWindow::on_bind_id(const Glib::RefPtr<Gtk::ListItem>& list_item)
    {
      // When TreeListModel::property_passthrough() is false, ListItem::get_item()
      // is a TreeListRow. TreeExpander needs the TreeListRow.
      // The ModelColumns item is returned by TreeListRow::get_item().
      auto row = std::dynamic_pointer_cast<Gtk::TreeListRow>(list_item->get_item());
      if (!row)
        return;
      auto col = std::dynamic_pointer_cast<ModelColumns>(row->get_item());
      if (!col)
        return;
      auto expander = dynamic_cast<Gtk::TreeExpander*>(list_item->get_child());
      if (!expander)
        return;
      expander->set_list_row(row);
      auto label = dynamic_cast<Gtk::Label*>(expander->get_child());
      if (!label)
        return;
      label->set_text(Glib::ustring::format(col->m_col_id));
    }

    void ExampleWindow::on_bind_name(const Glib::RefPtr<Gtk::ListItem>& list_item)
    {
      auto row = std::dynamic_pointer_cast<Gtk::TreeListRow>(list_item->get_item());
      if (!row)
        return;
      auto col = std::dynamic_pointer_cast<ModelColumns>(row->get_item());
      if (!col)
        return;
      auto label = dynamic_cast<Gtk::Label*>(list_item->get_child());
      if (!label)
        return;
      label->set_text(col->m_col_name);
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char* argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      // Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

## Widget TreeView

`Gtk::TreeView` is deprecated since gtkmm 4.10. In new code, use `Gtk::ListView` for lists and `Gtk::ColumnView` for tabular lists.

Widget `Gtk::TreeView` může obsahovat seznam nebo strom s daty ve sloupcích.

### Model

Každý widget `Gtk::TreeView` má přiřazený `Gtk::TreeModel`, který obsahuje data zobrazená v `TreeView`. Každý `Gtk::TreeModel` může být použit i více než jedním `Gtk::TreeView`. Umožňuje to například stejná podkladová data zobrazit a upravovat dvěma různými způsoby naráz. Nebo dvě zobrazení mohou ukazovat různé sloupce ze stejného datového modelu, podobně jako dva dotazy SQL (nebo pohledy) mohou zobrazovat různá pole ze stejné databázové tabulky.

I když si teoreticky můžete implementovat svůj vlastní Model, normálně budete používat buď třídu `ListStore` nebo `TreeStore`.

Reference

#### ListStore (pro řádky)

`ListStore` obsahuje jen řádková data, řádky nemají žádné potomky.

##### TreeView – ListStore

Reference

#### TreeStore (pro hierarchii)

`TreeStore` obsahuje řádková data a každý z řádků může mít potomky v podobě dalších řádků.

##### TreeView – TreeStore

Reference

#### Sloupce modelu

The `TreeModelColumnRecord` class is used to keep track of the columns and their data types. You add `TreeModelColumn` instances to the `ColumnRecord` and then use those `TreeModelColumn`s when getting and setting the data in model rows. You will probably find it convenient to derive a new `TreeModelColumnRecord` which has your `TreeModelColumn` instances as member data.

    class ModelColumns : public Gtk::TreeModelColumnRecord
    {
    public:

      ModelColumns()
        { add(m_col_text); add(m_col_number); }

      Gtk::TreeModelColumn<Glib::ustring> m_col_text;
      Gtk::TreeModelColumn<int> m_col_number;
    };

    ModelColumns m_Columns;

Když vytváříte Model, určíte `ColumnRecord` takto:

    Glib::RefPtr<Gtk::ListStore> refListStore =
        Gtk::ListStore::create(m_Columns);

As a `TreeModelColumnRecord` describes structure, not data, it can be shared among multiple models, and this is preferable for efficiency. However, the instance (such as `m_Columns` here) should usually not be static, because it often needs to be instantiated after glibmm has been initialized. The best solution is to make it a lazily instantiated singleton, so that it will be constructed on-demand, whenever the first model accesses it.

#### Přidávání řádků

Řádky do modelu přidejte pomocí metod `append()`, `prepend()` nebo `insert()`.

    auto iter = m_refListStore->append();

Pro získání řádku `Row` můžete použít dereferenci iterátoru:

    auto row = *iter;

##### Přidávání synovský řádků

Model `Gtk::TreeStore` může mít dceřiné položky. Přidávají se pomocí metody `append()`, `prepend()` nebo `insert()` takto:

    auto iter_child =
        m_refTreeStore->append(row.children());

#### Nastavení hodnot

You can use the `operator[]` overload to set the data for a particular column in the row, specifying the `TreeModelColumn` used to create the model.

    row[m_Columns.m_col_text] = "sometext";

#### Získání hodnot

You can use the `operator[]` overload to get the data in a particular column in a row, specifying the `TreeModelColumn` used to create the model.

    auto strText = row[m_Columns.m_col_text];
    auto number = row[m_Columns.m_col_number];

Kompilátor vás upozorní, když použijete nesprávný typ. Například následující ukázka by měla způsobit chybu kompilace:

    //compiler error - no conversion from ustring to int.
    int number = row[m_Columns.m_col_text];

#### „Skryté“ sloupce

Můžete potřebovat mít v řádcích zadaná nějaká doplňující data. V takovém případě stačí, když je přidáte do Modelu jako další sloupec, ale ten nebudete přidávat do zobrazení View.

### Zobrazení (View)

`View` je skutečný widget (`Gtk::TreeView`), který zobrazuje data modelu (`Gtk::TreeModel`) a umožňuje uživateli s nimi komunikovat. Může zobrazovat všechny sloupce modelu, nebo jen vybrané, a umí je zobrazovat různými způsoby.

Reference

#### Použití modelu

`Gtk::TreeModel` můžete určit, když konstruhujete `Gtk::TreeView`, nebo můžete použít metodu `set_model()`, nějak takto:

    m_TreeView.set_model(m_refListStore);

#### Přidání sloupců do zobrazení

Můžete použít metodu `append_column()`, abyste řekli widgetu `View`, že má použít konkrétní sloupce objektu `Modelu`, v konkrétním pořadí, s konkrétními záhlavími sloupců.

    m_TreeView.append_column("Messages", m_Columns.m_col_text);

When using this simple `append_column()` overload, the `TreeView` will display the model data with an appropriate `CellRenderer`. For instance, strings and numbers are shown in a simple `Gtk::Entry` widget, and booleans are shown in a `Gtk::CheckButton`. This is usually what you need. For other column types you must either connect a callback that converts your type into a string representation, with `TreeViewColumn::set_cell_data_func()`, or derive a custom `CellRenderer`. Note that (unsigned) short is not supported by default - You could use (unsigned) int or (unsigned) long as the column type instead.

#### Více než jeden sloupec modelu ve sloupci zobrazení

Když chcete v jednom sloupci zobrazení vykreslit více než jeden sloupec z modelu, musíte vytvořit widget `TreeView::Column` ručně a k přidání sloupce modelu do něj použít `pack_start()`.

Then use `append_column()` to add the view Column to the View. Notice that `Gtk::TreeView::append_column()` is overloaded to accept either a prebuilt `Gtk::TreeView::Column` widget, or just the `TreeModelColumn` from which it generates an appropriate `Gtk::TreeView::Column` widget.

Here is some example code, which has a pixbuf icon and a text name in the same column:

    auto pColumn = Gtk::make_managed<Gtk::TreeView::Column>("Icon Name");

    // m_columns.icon and m_columns.iconname are columns in the model.
    // pColumn is the column in the TreeView:
    pColumn->pack_start(m_columns.icon, /* expand= */ false);
    pColumn->pack_start(m_columns.iconname);

    m_TreeView.append_column(*pColumn);

#### Určení údajů pro CellRenderer

The default `CellRenderer`s and their default behavior will normally suffice, but you might occasionally need finer control. For instance, this example code from `gtkmm/demos/gtk-demo/example_treeview_treestore.cc`, appends a `Gtk::CellRenderer` widget and instructs it to render the data from various model columns through various aspects of its appearance.

    auto cols_count = m_TreeView.append_column_editable("Alex", m_columns.alex);
    auto pColumn = m_TreeView.get_column(cols_count-1);
    if(pColumn)
    {
      auto pRenderer = static_cast<Gtk::CellRendererToggle*>(pColumn->get_first_cell());
      pColumn->add_attribute(pRenderer->property_visible(), m_columns.visible);
      pColumn->add_attribute(pRenderer->property_activatable(), m_columns.world);

Můžete také napojit signál `CellRenderer`, abyste odhalili uživatelské činnosti. Například:

    auto pRenderer = Gtk::make_managed<Gtk::CellRendererToggle>();
    pRenderer->signal_toggled().connect(
        sigc::bind( sigc::mem_fun(*this,
            &Example_TreeView_TreeStore::on_cell_toggled), m_columns.dave)
    );

#### Editovatelné buňky

##### Editovatelné buňky s automatickým ukládáním.

Cells in a `TreeView` can be edited in-place by the user. To allow this, use the `Gtk::TreeView` `insert_column_editable()` and `append_column_editable()` methods instead of `insert_column()` and `append_column()`. When these cells are edited the new values will be stored immediately in the Model. Note that these methods are templates which can only be instantiated for simple column types such as `Glib::ustring`, int, and long.

##### Implementace vlastní logiky pro editovatelné buňky.

Může se stát, že budete chtít, aby se nové hodnoty neukládaly okamžitě. Například můžete chtít omezit vstup na konkrétní znaky nebo rozsah hodnot.

To achieve this, you should use the normal `Gtk::TreeView` `insert_column()` and `append_column()` methods, then use `get_column_cell_renderer()` to get the `Gtk::CellRenderer` used by that column.

Měli byste pak `Gtk::CellRenderer*` přetypovat na konkrétní `CellRenderer`, který očekáváte, abyste mohli použít jeho API.

Například, pro `CellRendererText` byste mohli nastavit vlastnost buňky editable na `true` takto:

    cell->property_editable() = true;

U `CellRendererToggle` byste místo toho mohli nastavit vlastnost activatable.

You can then connect to the appropriate "edited" signal. For instance, connect to `Gtk::CellRendererText::signal_edited()`, or `Gtk::CellRendererToggle::signal_toggled()`. If the column contains more than one `CellRenderer` then you will need to use `Gtk::TreeView::get_column()` and then call `get_cells()` on that view Column.

Ve své obsluze signálu byste měli zkontrolovat novou hodnotu a uložit ji do objektu `Model`, pokud se to vaší aplikaci může hodit.

### Iterace přes řádky modelu

`Gtk::TreeModel` poskytuje přes metodu `children()` kontejner ve stylu standardní knihovny C++ s jeho potomky. Pro iteraci můžete použít dobře známé metody `begin()` a `end()`, nějak takto:

    auto children = refModel->children();
    for (auto iter = children.begin(), end = children.end(); iter != end; ++iter)
    {
      auto row = *iter;
      //Do something with the row - see above for set/get.
    }

If you always want to iterate across the entire range, much more succinct syntax is possible using C++'s range-based `for` loop:

    for (auto row: refModel->children())
    {
      //Do something with the row - see above for set/get.
    }

#### Potomci řádku

When using a `Gtk::TreeStore`, the rows can have child rows, which can have their own children in turn. Use `Gtk::TreeModel::Row::children()` to get the container of child `Row`s:

    Gtk::TreeModel::Children children = row.children();

### Výběr

Když potřebujete vědět, které řádky uživatel označil, získejte z `TreeView` objekt `Gtk::TreeView::Selection`, takto:

    auto refTreeSelection = m_TreeView.get_selection();

#### Jednoduchý nebo vícenásobný výběr

By default, only single rows can be selected, but you can allow multiple selection by setting the mode, like so:

    refTreeSelection->set_mode(Gtk::SelectionMode::MULTIPLE);

#### Vybrané řádky

Pro označení jednoho řádku stačí zavolat `get_selected()`, takto:

    auto iter = refTreeSelection->get_selected();
    if(iter) //If anything is selected
    {
      auto row = *iter;
      //Do something with the row.
    }

For multiple-selection, you need to call `get_selected_rows()` or define a callback, and give it to `selected_foreach()`, `selected_foreach_path()`, or `selected_foreach_iter()`, like so:

    refTreeSelection->selected_foreach_iter(
        sigc::mem_fun(*this, &TheClass::selected_row_callback) );

    void TheClass::selected_row_callback(
        const Gtk::TreeModel::const_iterator& iter)
    {
      auto row = *iter;
      //Do something with the row.
    }

#### Signál "changed"

Když chcete reagovat na uživatelovo kliknutí na řádek nebo rozsah řádků, připojte nějak takto signál:

    refTreeSelection->signal_changed().connect(
        sigc::mem_fun(*this, &Example_IconTheme::on_selection_changed)
    );

#### Jak zabárnit výběru řádku

Někdy může být zapotřebí, aby uživatel nemohl vybrat všechny položky v seznamu nebo stromu. Například v gtk-demo může vybírat jednotlivé ukázky, aby si prohlédl zdrojový kód, ale na výběr nereagují kategorie ukázek.

K řízení, které řádky mohou být vybrány, použijte metodu `set_select_function()` poskytující zpětné volání `sigc::slot`. Například:

    m_refTreeSelection->set_select_function( sigc::mem_fun(*this,
        &DemoWindow::select_function) );

a pak

    bool DemoWindow::select_function(
        const Glib::RefPtr<Gtk::TreeModel>& model,
        const Gtk::TreeModel::Path& path, bool)
    {
      const auto iter = model->get_iter(path);
      return iter->children().empty(); // only allow leaf nodes to be selected
    }

#### Změna výběru

Pro změnu výběru určete `Gtk::TreeModel::iterator` nebo `Gtk::TreeModel::Row`, takto:

    auto row = m_refModel->children()[5]; //The sixth row.
    if(row)
      refTreeSelection->select(row.get_iter());

nebo

    auto iter = m_refModel->children().begin()
    if(iter)
      refTreeSelection->select(iter);

### Řazení

Standardní stromové modely (`TreeStore` a `ListStore`) jsou odvozené z `TreeSortable`, takže nabízejí funkci řazení. Například zavoláním `set_sort_column()` seřadíte model podle určeného sloupce. Nebo, když chcete složitější algoritmus řazení, poskytněte funkci zpětného volání do `set_sort_func()`.

TreeSortable Reference

#### Řazení klikáním na sloupce

Aby uživatel mohl kliknutím na záhlaví sloupce v `TreeView` seřadit obsah `TreeView`, je potřeba zavolat metodu `Gtk::TreeView::Column::set_sort_column()`, které předáte sloupec modelu, na jehož modelu se má řadit, když uživatel na záhlaví klikne. Například:

    auto pColumn = treeview.get_column(0);
    if(pColumn)
      pColumn->set_sort_column(m_columns.m_col_id);

#### Nezávisle řazená zobrazení téhož modelu

The `TreeView` already allows you to show the same `TreeModel` in two `TreeView` widgets. If you need one of these TreeViews to sort the model differently than the other then you should use a `TreeModelSort` instead of just, for instance, `Gtk::TreeViewColumn::set_sort_column()`. `TreeModelSort` is a model that contains another model, presenting a sorted version of that model. For instance, you might add a sorted version of a model to a `TreeView` like so:

    auto sorted_model = Gtk::TreeModelSort::create(model);
    sorted_model->set_sort_column(columns.m_col_name, Gtk::SortType::ASCENDING);
    treeview.set_model(sorted_model);

Všimněte si, že `TreeView` bude poskytovat iterátory řazenému modelu. Abyste mohli provádět akce na daném modelu, musíte je převést na iterátory do podkladového podřízeného modelu. Například:

    void ExampleWindow::on_button_delete()
    {
      auto refTreeSelection = m_treeview.get_selection();
      if(refTreeSelection)
      {
        auto sorted_iter = m_refTreeSelection->get_selected();
        if(sorted_iter)
        {
          auto iter = m_refModelSort->convert_iter_to_child_iter(sorted_iter);
          m_refModel->erase(iter);
        }
      }
    }

TreeModelSort Reference

### Táhni a upusť

`Gtk::TreeView` already implements simple drag-and-drop when used with the `Gtk::ListStore` or `Gtk::TreeStore` models (since gtk 4.8). If necessary, it also allows you to implement more complex behavior when items are dragged and dropped, using the normal Drag and Drop API.

#### Seřaditelné řádky

Když zavoláte `Gtk::TreeView::set_reorderable()`, bude možné přesouvat položky v rámci stromového zobrazení. Ukázáno je to v příkladu `TreeStore`.

However, this does not allow you any control of which items can be dragged, and where they can be dropped. If you need that extra control then you might create a derived `Gtk::TreeModel` from `Gtk::TreeStore` or `Gtk::ListStore` and override the `Gtk::TreeDragSource::row_draggable_vfunc()` and `Gtk::TreeDragDest::row_drop_possible_vfunc()` virtual methods. You can examine the `Gtk::TreeModel::Path`s provided and allow or disallow dragging or dropping by returning `true` or `false`.

Ukázané to je v příkladu drag_and_drop.

### Vyskakovací kontextová nabídka

Lots of people need to implement right-click context menus for `TreeView`s so we will explain how to do that here to save you some time. It's much the same as a normal context menu, as described in the menus chapter. You use a `Gtk::GestureClick` to detect the mouse click.

This is demonstrated in the Popup Context Menu example. In that example a derived `TreeView` is used, but that's not necessary.

### Příklady

Some `TreeView` examples are shown here. There are more examples in the treeview directory in gtkmm-documentation's examples.

If neither `ListStore` nor `TreeStore` is suitable for your application, look at the custom TreeModel example. It shows how you can make your own implementation of the `TreeModel` interface.

#### ListStore

Tento příklad obsahuje widget `Gtk::TreeView` s modelem `Gtk::ListStore`.

##### TreeView – ListStore

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_quit();

      //Tree model columns:
      class ModelColumns : public Gtk::TreeModel::ColumnRecord
      {
      public:

        ModelColumns()
        { add(m_col_id); add(m_col_name); add(m_col_number); add(m_col_percentage);}

        Gtk::TreeModelColumn<unsigned int> m_col_id;
        Gtk::TreeModelColumn<Glib::ustring> m_col_name;
        Gtk::TreeModelColumn<short> m_col_number;
        Gtk::TreeModelColumn<int> m_col_percentage;
      };

      ModelColumns m_Columns;

      //Child widgets:
      Gtk::Box m_VBox;

      Gtk::ScrolledWindow m_ScrolledWindow;
      Gtk::TreeView m_TreeView;
      Glib::RefPtr<Gtk::ListStore> m_refTreeModel;

      Gtk::Box m_ButtonBox;
      Gtk::Button m_Button_Quit;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include <iostream>
    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::Orientation::VERTICAL),
      m_Button_Quit("Quit")
    {
      set_title("Gtk::TreeView (ListStore) example");
      set_default_size(400, 200);

      m_VBox.set_margin(5);
      set_child(m_VBox);

      //Add the TreeView, inside a ScrolledWindow, with the button underneath:
      m_ScrolledWindow.set_child(m_TreeView);

      //Only show the scrollbars when they are necessary:
      m_ScrolledWindow.set_policy(Gtk::PolicyType::AUTOMATIC, Gtk::PolicyType::AUTOMATIC);
      m_ScrolledWindow.set_expand();

      m_VBox.append(m_ScrolledWindow);
      m_VBox.append(m_ButtonBox);

      m_ButtonBox.append(m_Button_Quit);
      m_ButtonBox.set_margin(5);
      m_Button_Quit.set_hexpand(true);
      m_Button_Quit.set_halign(Gtk::Align::END);
      m_Button_Quit.signal_clicked().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_button_quit) );

      //Create the Tree model:
      m_refTreeModel = Gtk::ListStore::create(m_Columns);
      m_TreeView.set_model(m_refTreeModel);

      //Fill the TreeView's model
      auto row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = 1;
      row[m_Columns.m_col_name] = "Billy Bob";
      row[m_Columns.m_col_number] = 10;
      row[m_Columns.m_col_percentage] = 15;

      row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = 2;
      row[m_Columns.m_col_name] = "Joey Jojo";
      row[m_Columns.m_col_number] = 20;
      row[m_Columns.m_col_percentage] = 40;

      row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = 3;
      row[m_Columns.m_col_name] = "Rob McRoberts";
      row[m_Columns.m_col_number] = 30;
      row[m_Columns.m_col_percentage] = 70;

      //Add the TreeView's view columns:
      //This number will be shown with the default numeric formatting.
      m_TreeView.append_column("ID", m_Columns.m_col_id);
      m_TreeView.append_column("Name", m_Columns.m_col_name);

      m_TreeView.append_column_numeric("Formatted number", m_Columns.m_col_number,
              "%010d" /* 10 digits, using leading zeroes. */);

      //Display a progress bar instead of a decimal number:
      auto cell = Gtk::make_managed<Gtk::CellRendererProgress>();
      int cols_count = m_TreeView.append_column("Some percentage", *cell);
      auto pColumn = m_TreeView.get_column(cols_count - 1);
      if(pColumn)
      {
        pColumn->add_attribute(cell->property_value(), m_Columns.m_col_percentage);
      }

      //Make all the columns reorderable:
      //This is not necessary, but it's nice to show the feature.
      //You can use TreeView::set_column_drag_function() to more
      //finely control column drag and drop.
      for(guint i = 0; i < 2; i++)
      {
        auto column = m_TreeView.get_column(i);
        column->set_reorderable();
      }
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_quit()
    {
      set_visible(false);
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

#### TreeStore

Tento příklad je velmi podobný příkladu s `ListStore`, ale místo něj používá `Gtk::TreeStore` a přidává potomky do řádků.

##### TreeView – TreeStore

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_quit();
      void on_treeview_row_activated(const Gtk::TreeModel::Path& path, Gtk::TreeViewColumn* column);

      //Tree model columns:
      class ModelColumns : public Gtk::TreeModel::ColumnRecord
      {
      public:

        ModelColumns()
        { add(m_col_id); add(m_col_name); }

        Gtk::TreeModelColumn<int> m_col_id;
        Gtk::TreeModelColumn<Glib::ustring> m_col_name;
      };

      ModelColumns m_Columns;

      //Child widgets:
      Gtk::Box m_VBox;

      Gtk::ScrolledWindow m_ScrolledWindow;
      Gtk::TreeView m_TreeView;
      Glib::RefPtr<Gtk::TreeStore> m_refTreeModel;

      Gtk::Box m_ButtonBox;
      Gtk::Button m_Button_Quit;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include <iostream>
    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::Orientation::VERTICAL),
      m_Button_Quit("Quit")
    {
      set_title("Gtk::TreeView (TreeStore) example");
      set_default_size(400, 200);

      m_VBox.set_margin(5);
      set_child(m_VBox);

      //Add the TreeView, inside a ScrolledWindow, with the button underneath:
      m_ScrolledWindow.set_child(m_TreeView);

      //Only show the scrollbars when they are necessary:
      m_ScrolledWindow.set_policy(Gtk::PolicyType::AUTOMATIC, Gtk::PolicyType::AUTOMATIC);
      m_ScrolledWindow.set_expand();

      m_VBox.append(m_ScrolledWindow);
      m_VBox.append(m_ButtonBox);

      m_ButtonBox.append(m_Button_Quit);
      m_ButtonBox.set_margin(5);
      m_Button_Quit.set_hexpand(true);
      m_Button_Quit.set_halign(Gtk::Align::END);
      m_Button_Quit.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_quit) );

      //Create the Tree model:
      m_refTreeModel = Gtk::TreeStore::create(m_Columns);
      m_TreeView.set_model(m_refTreeModel);

      //All the items to be reordered with drag-and-drop:
      m_TreeView.set_reorderable();

      //Fill the TreeView's model
      auto row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = 1;
      row[m_Columns.m_col_name] = "Billy Bob";

      auto childrow = *(m_refTreeModel->append(row.children()));
      childrow[m_Columns.m_col_id] = 11;
      childrow[m_Columns.m_col_name] = "Billy Bob Junior";

      childrow = *(m_refTreeModel->append(row.children()));
      childrow[m_Columns.m_col_id] = 12;
      childrow[m_Columns.m_col_name] = "Sue Bob";

      row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = 2;
      row[m_Columns.m_col_name] = "Joey Jojo";

      row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = 3;
      row[m_Columns.m_col_name] = "Rob McRoberts";

      childrow = *(m_refTreeModel->append(row.children()));
      childrow[m_Columns.m_col_id] = 31;
      childrow[m_Columns.m_col_name] = "Xavier McRoberts";

      //Add the TreeView's view columns:
      m_TreeView.append_column("ID", m_Columns.m_col_id);
      m_TreeView.append_column("Name", m_Columns.m_col_name);

      //Connect signal:
      m_TreeView.signal_row_activated().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_treeview_row_activated) );
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_quit()
    {
      set_visible(false);
    }

    void ExampleWindow::on_treeview_row_activated(const Gtk::TreeModel::Path& path,
            Gtk::TreeViewColumn* /* column */)
    {
      const auto iter = m_refTreeModel->get_iter(path);
      if(iter)
      {
        const auto row = *iter;
        std::cout << "Row activated: ID=" << row[m_Columns.m_col_id] << ", Name="
            << row[m_Columns.m_col_name] << std::endl;
      }
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

#### Editovatelné buňky

Tento příklad je stejný jako příklad s `ListStore`, ale používá `TreeView::append_column_editable()` místo `TreeView::append_column()`.

##### TreeView – editovatelné buňky

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_quit();

      void treeviewcolumn_validated_on_cell_data(Gtk::CellRenderer* renderer, const Gtk::TreeModel::const_iterator& iter);
      void cellrenderer_validated_on_editing_started(Gtk::CellEditable* cell_editable, const Glib::ustring& path);
      void cellrenderer_validated_on_edited(const Glib::ustring& path_string, const Glib::ustring& new_text);
      void on_message_response(int response_id, Gtk::MessageDialog* dialog);

      //Tree model columns:
      class ModelColumns : public Gtk::TreeModel::ColumnRecord
      {
      public:

        ModelColumns()
        { add(m_col_id); add(m_col_name); add(m_col_foo); add(m_col_number); add(m_col_number_validated); }

        Gtk::TreeModelColumn<unsigned int> m_col_id;
        Gtk::TreeModelColumn<Glib::ustring> m_col_name;
        Gtk::TreeModelColumn<bool> m_col_foo;
        Gtk::TreeModelColumn<int> m_col_number;
        Gtk::TreeModelColumn<int> m_col_number_validated;
      };

      ModelColumns m_Columns;

      //Child widgets:
      Gtk::Box m_VBox;

      Gtk::ScrolledWindow m_ScrolledWindow;
      Gtk::TreeView m_TreeView;
      Glib::RefPtr<Gtk::ListStore> m_refTreeModel;

      Gtk::Box m_ButtonBox;
      Gtk::Button m_Button_Quit;

      //For the validated column:
      //You could also use a CellRendererSpin or a CellRendererProgress:
      Gtk::CellRendererText m_cellrenderer_validated;
      Gtk::TreeView::Column m_treeviewcolumn_validated;
      bool m_validate_retry;
      Glib::ustring m_invalid_text_for_retry;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include <iostream>
    #include <cstdio>
    #include <cstdlib>
    #include "examplewindow.h"

    using std::sprintf;
    using std::strtol;

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::Orientation::VERTICAL),
      m_Button_Quit("Quit"),
      m_validate_retry(false)
    {
      set_title("Gtk::TreeView Editable Cells example");
      set_default_size(400, 200);

      m_VBox.set_margin(5);
      set_child(m_VBox);

      //Add the TreeView, inside a ScrolledWindow, with the button underneath:
      m_ScrolledWindow.set_child(m_TreeView);

      //Only show the scrollbars when they are necessary:
      m_ScrolledWindow.set_policy(Gtk::PolicyType::AUTOMATIC, Gtk::PolicyType::AUTOMATIC);
      m_ScrolledWindow.set_expand();

      m_VBox.append(m_ScrolledWindow);
      m_VBox.append(m_ButtonBox);

      m_ButtonBox.append(m_Button_Quit);
      m_ButtonBox.set_margin(5);
      m_Button_Quit.set_hexpand(true);
      m_Button_Quit.set_halign(Gtk::Align::END);
      m_Button_Quit.signal_clicked().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_button_quit) );

      //Create the Tree model:
      m_refTreeModel = Gtk::ListStore::create(m_Columns);
      m_TreeView.set_model(m_refTreeModel);

      //Fill the TreeView's model
      auto row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = 1;
      row[m_Columns.m_col_name] = "Billy Bob";
      row[m_Columns.m_col_foo] = true;
      row[m_Columns.m_col_number] = 10;

      row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = 2;
      row[m_Columns.m_col_name] = "Joey Jojo";
      row[m_Columns.m_col_foo] = true;
      row[m_Columns.m_col_number] = 20;

      row = *(m_refTreeModel->append());

      row[m_Columns.m_col_id] = 3;
      row[m_Columns.m_col_name] = "Rob McRoberts";
      row[m_Columns.m_col_foo] = false;
      row[m_Columns.m_col_number] = 30;

      //Add the TreeView's view columns:
      //We use the *_editable convenience methods for most of these,
      //because the default functionality is enough:
      m_TreeView.append_column_editable("ID", m_Columns.m_col_id);
      m_TreeView.append_column_editable("Name", m_Columns.m_col_name);
      m_TreeView.append_column_editable("foo", m_Columns.m_col_foo);
      m_TreeView.append_column_numeric_editable("Number", m_Columns.m_col_number,
              "%010d");

      //For this column, we create the CellRenderer ourselves, and connect our own
      //signal handlers, so that we can validate the data that the user enters, and
      //control how it is displayed.
      m_treeviewcolumn_validated.set_title("validated (<10)");
      m_treeviewcolumn_validated.pack_start(m_cellrenderer_validated);
      m_TreeView.append_column(m_treeviewcolumn_validated);

      //Tell the view column how to render the model values:
      m_treeviewcolumn_validated.set_cell_data_func(m_cellrenderer_validated,
              sigc::mem_fun(*this,
                  &ExampleWindow::treeviewcolumn_validated_on_cell_data) );

      //Make the CellRenderer editable, and handle its editing signals:
      m_cellrenderer_validated.property_editable() = true;

      m_cellrenderer_validated.signal_editing_started().connect(
              sigc::mem_fun(*this,
            &ExampleWindow::cellrenderer_validated_on_editing_started) );

      m_cellrenderer_validated.signal_edited().connect( sigc::mem_fun(*this,
                  &ExampleWindow::cellrenderer_validated_on_edited) );

      //If this was a CellRendererSpin then you would have to set the adjustment:
      //m_cellrenderer_validated.property_adjustment() = m_spin_adjustment;
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_quit()
    {
      set_visible(false);
    }

    void ExampleWindow::treeviewcolumn_validated_on_cell_data(
            Gtk::CellRenderer* /* renderer */,
            const Gtk::TreeModel::const_iterator& iter)
    {
      //Get the value from the model and show it appropriately in the view:
      if(iter)
      {
        const auto row = *iter;
        int model_value = row[m_Columns.m_col_number_validated];

        //This is just an example.
        //In this case, it would be easier to use append_column_editable() or
        //append_column_numeric_editable()
        char buffer[32];
        sprintf(buffer, "%d", model_value);

        auto view_text = buffer;
        m_cellrenderer_validated.property_text() = view_text;
      }
    }

    void ExampleWindow::cellrenderer_validated_on_editing_started(
            Gtk::CellEditable* cell_editable, const Glib::ustring& /* path */)
    {
      //Start editing with previously-entered (but invalid) text,
      //if we are allowing the user to correct some invalid data.
      if(m_validate_retry)
      {
        //This is the CellEditable inside the CellRenderer.
        auto celleditable_validated = cell_editable;

        //It's usually an Entry, at least for a CellRendererText:
        auto pEntry = dynamic_cast<Gtk::Entry*>(celleditable_validated);
        if(pEntry)
        {
          pEntry->set_text(m_invalid_text_for_retry);
          m_validate_retry = false;
          m_invalid_text_for_retry.clear();
        }
      }
    }

    void ExampleWindow::cellrenderer_validated_on_edited(
            const Glib::ustring& path_string,
            const Glib::ustring& new_text)
    {
      Gtk::TreePath path(path_string);

      //Convert the inputed text to an integer, as needed by our model column:
      char* pchEnd = nullptr;
      int new_value = strtol(new_text.c_str(), &pchEnd, 10);

      if(new_value >= 10)
      {
        //Prevent entry of numbers higher than 10.

        //Tell the user:
        auto dialog = new Gtk::MessageDialog(*this,
                "The number must be less than 10. Please try again.",
                false, Gtk::MessageType::ERROR, Gtk::ButtonsType::OK, true /* modal */);
        dialog->signal_response().connect(sigc::bind(
          sigc::mem_fun(*this, &ExampleWindow::on_message_response), dialog));

        dialog->set_visible(true);

        //Start editing again, with the bad text, so that the user can correct it.
        //A real application should probably allow the user to revert to the
        //previous text.

        //Set the text to be used in the start_editing signal handler:
        m_invalid_text_for_retry = new_text;
        m_validate_retry = true;

        //Start editing again, when the message dialog has been closed:
        m_TreeView.set_cursor(path, m_treeviewcolumn_validated,
                m_cellrenderer_validated, true /* start_editing */);
      }
      else
      {
        //Get the row from the path:
        auto iter = m_refTreeModel->get_iter(path);
        if(iter)
        {
          auto row = *iter;

          //Put the new value in the model:
          row[m_Columns.m_col_number_validated] = new_value;
        }
      }
    }

    void ExampleWindow::on_message_response(int /* response_id */, Gtk::MessageDialog* dialog)
    {
      delete dialog;
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

#### Táhni a upusť

Tento příklad je hodně podobný příkladu pro `TreeStore`, ale má navíc dva sloupce, které ukazují, jestli se dá řádek přesunout a jestli může řádek přijmout jiný přetahovaný řádek. Příklad používá `Gtk::TreeStore`, ve které přepisuje virtuální funkce, jak bylo ukázáno v kapitole Táhni a upusť ve stromovém zobrazení.

##### TreeView – táhni a upusť

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>
    #include "treemodel_dnd.h"

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_quit();

      //Child widgets:
      Gtk::Box m_VBox;

      Gtk::ScrolledWindow m_ScrolledWindow;
      Gtk::TreeView m_TreeView;
      Glib::RefPtr<TreeModel_Dnd> m_refTreeModel;

      Gtk::Box m_ButtonBox;
      Gtk::Button m_Button_Quit;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `treemodel_dnd.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLE_TREEMODEL_DND_H
    #define GTKMM_EXAMPLE_TREEMODEL_DND_H

    #include <gtkmm.h>

    class TreeModel_Dnd : public Gtk::TreeStore
    {
    protected:
      TreeModel_Dnd();

    public:

      //Tree model columns:
      class ModelColumns : public Gtk::TreeModel::ColumnRecord
      {
      public:

        ModelColumns()
        { add(m_col_id); add(m_col_name); add(m_col_draggable); add(m_col_receivesdrags); }

        Gtk::TreeModelColumn<int> m_col_id;
        Gtk::TreeModelColumn<Glib::ustring> m_col_name;
        Gtk::TreeModelColumn<bool> m_col_draggable;
        Gtk::TreeModelColumn<bool> m_col_receivesdrags;
      };

      ModelColumns m_Columns;

      static Glib::RefPtr<TreeModel_Dnd> create();

    protected:
      //Overridden virtual functions:
      bool row_draggable_vfunc(const Gtk::TreeModel::Path& path) const override;
      bool row_drop_possible_vfunc(const Gtk::TreeModel::Path& dest, const Glib::ValueBase& value) const override;
    };

    #endif //GTKMM_EXAMPLE_TREEMODEL_DND_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include <iostream>
    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::Orientation::VERTICAL),
      m_Button_Quit("_Quit", true)
    {
      set_title("Gtk::TreeView (Drag and Drop) example");
      set_default_size(400, 200);

      m_VBox.set_margin(5);
      set_child(m_VBox);

      //Add the TreeView, inside a ScrolledWindow, with the button underneath:
      m_ScrolledWindow.set_child(m_TreeView);

      //Only show the scrollbars when they are necessary:
      m_ScrolledWindow.set_policy(Gtk::PolicyType::AUTOMATIC, Gtk::PolicyType::AUTOMATIC);
      m_ScrolledWindow.set_expand();

      m_VBox.append(m_ScrolledWindow);
      m_VBox.append(m_ButtonBox);

      m_ButtonBox.append(m_Button_Quit);
      m_ButtonBox.set_margin(5);
      m_Button_Quit.set_hexpand(true);
      m_Button_Quit.set_halign(Gtk::Align::END);
      m_Button_Quit.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_quit) );

      //Create the Tree model:
      //Use our derived model, which overrides some Gtk::TreeDragDest and
      //Gtk::TreeDragSource virtual functions:
      //The columns are declared in the overridden TreeModel.
      m_refTreeModel = TreeModel_Dnd::create();
      m_TreeView.set_model(m_refTreeModel);

      //Enable Drag-and-Drop of TreeView rows:
      //See also the derived TreeModel's *_vfunc overrides.
      m_TreeView.enable_model_drag_source();
      m_TreeView.enable_model_drag_dest();

      //Fill the TreeView's model
      auto row = *(m_refTreeModel->append());
      row[m_refTreeModel->m_Columns.m_col_id] = 1;
      row[m_refTreeModel->m_Columns.m_col_name] = "Billy Bob";
      row[m_refTreeModel->m_Columns.m_col_draggable] = true;
      row[m_refTreeModel->m_Columns.m_col_receivesdrags] = true;

      auto childrow = *(m_refTreeModel->append(row.children()));
      childrow[m_refTreeModel->m_Columns.m_col_id] = 11;
      childrow[m_refTreeModel->m_Columns.m_col_name] = "Billy Bob Junior";
      childrow[m_refTreeModel->m_Columns.m_col_draggable] = true;
      childrow[m_refTreeModel->m_Columns.m_col_receivesdrags] = true;

      childrow = *(m_refTreeModel->append(row.children()));
      childrow[m_refTreeModel->m_Columns.m_col_id] = 12;
      childrow[m_refTreeModel->m_Columns.m_col_name] = "Sue Bob";
      childrow[m_refTreeModel->m_Columns.m_col_draggable] = true;
      childrow[m_refTreeModel->m_Columns.m_col_receivesdrags] = true;

      row = *(m_refTreeModel->append());
      row[m_refTreeModel->m_Columns.m_col_id] = 2;
      row[m_refTreeModel->m_Columns.m_col_name] = "Joey Jojo";
      row[m_refTreeModel->m_Columns.m_col_draggable] = true;
      row[m_refTreeModel->m_Columns.m_col_receivesdrags] = true;

      row = *(m_refTreeModel->append());
      row[m_refTreeModel->m_Columns.m_col_id] = 3;
      row[m_refTreeModel->m_Columns.m_col_name] = "Rob McRoberts";
      row[m_refTreeModel->m_Columns.m_col_draggable] = true;
      row[m_refTreeModel->m_Columns.m_col_receivesdrags] = true;

      childrow = *(m_refTreeModel->append(row.children()));
      childrow[m_refTreeModel->m_Columns.m_col_id] = 31;
      childrow[m_refTreeModel->m_Columns.m_col_name] = "Xavier McRoberts";
      childrow[m_refTreeModel->m_Columns.m_col_draggable] = true;
      childrow[m_refTreeModel->m_Columns.m_col_receivesdrags] = true;

      //Add the TreeView's view columns:
      m_TreeView.append_column("ID", m_refTreeModel->m_Columns.m_col_id);
      m_TreeView.append_column("Name", m_refTreeModel->m_Columns.m_col_name);
      m_TreeView.append_column_editable("Draggable",
              m_refTreeModel->m_Columns.m_col_draggable);
      m_TreeView.append_column_editable("Receives Drags",
              m_refTreeModel->m_Columns.m_col_receivesdrags);
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_quit()
    {
      set_visible(false);
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

File: `treemodel_dnd.cc` (For use with gtkmm 4)

    #include "treemodel_dnd.h"
    #include <iostream>

    TreeModel_Dnd::TreeModel_Dnd()
    {
      //We can't just call Gtk::TreeModel(m_Columns) in the initializer list
      //because m_Columns does not exist when the base class constructor runs.
      //And we can't have a static m_Columns instance, because that would be
      //instantiated before the gtkmm type system.
      //So, we use this method, which should only be used just after creation:
      set_column_types(m_Columns);
    }

    Glib::RefPtr<TreeModel_Dnd> TreeModel_Dnd::create()
    {
      return Glib::make_refptr_for_instance<TreeModel_Dnd>( new TreeModel_Dnd() );
    }

    bool
    TreeModel_Dnd::row_draggable_vfunc(const Gtk::TreeModel::Path& path) const
    {
      // Make the value of the "draggable" column determine whether this row can
      // be dragged:

      const const_iterator iter = get_iter(path);
      if(iter)
      {
        ConstRow row = *iter;
        bool is_draggable = row[m_Columns.m_col_draggable];
        return is_draggable;
      }

      return Gtk::TreeStore::row_draggable_vfunc(path);
    }

    bool
    TreeModel_Dnd::row_drop_possible_vfunc(const Gtk::TreeModel::Path& dest,
            const Glib::ValueBase& value) const
    {
      //Make the value of the "receives drags" column determine whether a row can be
      //dragged into it:

      //dest is the path that the row would have after it has been dropped:
      //But in this case we are more interested in the parent row:
      auto dest_parent = dest;
      bool dest_is_not_top_level = dest_parent.up();
      if(!dest_is_not_top_level || dest_parent.empty())
      {
        //The user wants to move something to the top-level.
        //Let's always allow that.
      }
      else
      {
        //Get an iterator for the row at this path:
        const const_iterator iter_dest_parent = get_iter(dest_parent);
        if(iter_dest_parent)
        {
          ConstRow row = *iter_dest_parent;
          bool receives_drags = row[m_Columns.m_col_receivesdrags];
          return receives_drags;
        }
      }

      // You could also examine the row being dragged (via value)
      // if you must look at both rows to see whether a drop should be allowed.
      // You could use
      //   Glib::RefPtr<const Gtk::TreeModel> model_dragged_row;
      //   Gtk::TreeModel::Path path_dragged_row;
      //   Gtk::TreeModel::Path::get_row_drag_data(value,
      //     model_dragged_row, path_dragged_row);

      return Gtk::TreeStore::row_drop_possible_vfunc(dest, value);
    }

#### Vyskakovací kontextová nabídka

This example is much like the `ListStore` example, but derives a custom `TreeView` to encapsulate the tree model code and popup menu code in our derived class. See the TreeView Popup Context Menu section.

##### TreeView – vyskakovací kontextová nabídka

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>
    #include "treeview_withpopup.h"

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_quit();

      //Child widgets:
      Gtk::Box m_VBox;

      Gtk::ScrolledWindow m_ScrolledWindow;
      TreeView_WithPopup m_TreeView;

      Gtk::Box m_ButtonBox;
      Gtk::Button m_Button_Quit;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `treeview_withpopup.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLE_TREEVIEW_WITHPOPUP_H
    #define GTKMM_EXAMPLE_TREEVIEW_WITHPOPUP_H

    #include <gtkmm.h>

    class TreeView_WithPopup : public Gtk::TreeView
    {
    public:
      TreeView_WithPopup();
      virtual ~TreeView_WithPopup();

    protected:
      // Signal handler for showing popup menu:
      void on_popup_button_pressed(int n_press, double x, double y);

      //Signal handler for popup menu items:
      void on_menu_file_popup_generic();

      //Tree model columns:
      class ModelColumns : public Gtk::TreeModel::ColumnRecord
      {
      public:

        ModelColumns()
        { add(m_col_id); add(m_col_name); }

        Gtk::TreeModelColumn<unsigned int> m_col_id;
        Gtk::TreeModelColumn<Glib::ustring> m_col_name;
      };

      ModelColumns m_Columns;

      //The Tree model:
      Glib::RefPtr<Gtk::ListStore> m_refTreeModel;

      Gtk::PopoverMenu m_MenuPopup;
    };

    #endif //GTKMM_EXAMPLE_TREEVIEW_WITHPOPUP_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include <iostream>
    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::Orientation::VERTICAL),
      m_Button_Quit("Quit")
    {
      set_title("Gtk::TreeView (ListStore) example");
      set_default_size(400, 200);

      m_VBox.set_margin(5);
      set_child(m_VBox);

      //Add the TreeView, inside a ScrolledWindow, with the button underneath:
      m_ScrolledWindow.set_child(m_TreeView);

      //Only show the scrollbars when they are necessary:
      m_ScrolledWindow.set_policy(Gtk::PolicyType::AUTOMATIC, Gtk::PolicyType::AUTOMATIC);
      m_ScrolledWindow.set_expand();

      m_VBox.append(m_ScrolledWindow);
      m_VBox.append(m_ButtonBox);

      m_ButtonBox.append(m_Button_Quit);
      m_ButtonBox.set_margin(5);
      m_Button_Quit.set_hexpand(true);
      m_Button_Quit.set_halign(Gtk::Align::END);
      m_Button_Quit.signal_clicked().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_button_quit) );
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_quit()
    {
      set_visible(false);
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

File: `treeview_withpopup.cc` (For use with gtkmm 4)

    #include "treeview_withpopup.h"
    #include <iostream>

    TreeView_WithPopup::TreeView_WithPopup()
    {
      //Create the Tree model:
      m_refTreeModel = Gtk::ListStore::create(m_Columns);
      set_model(m_refTreeModel);

      //Fill the TreeView's model
      auto row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = 1;
      row[m_Columns.m_col_name] = "right-click on this";

      row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = 2;
      row[m_Columns.m_col_name] = "or this";

      row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = 3;
      row[m_Columns.m_col_name] = "or this, for a popup context menu";

      //Add the TreeView's view columns:
      append_column("ID", m_Columns.m_col_id);
      append_column("Name", m_Columns.m_col_name);

      // Catch button press events:
      auto refGesture = Gtk::GestureClick::create();
      refGesture->set_button(GDK_BUTTON_SECONDARY);
      refGesture->signal_pressed().connect(
        sigc::mem_fun(*this, &TreeView_WithPopup::on_popup_button_pressed));
      add_controller(refGesture);

      // Fill popup menu:
      auto gmenu = Gio::Menu::create();
      gmenu->append("_Edit", "popup.edit");
      gmenu->append("_Process", "popup.process");
      gmenu->append("_Remove", "popup.remove");

      m_MenuPopup.set_parent(*this);
      m_MenuPopup.set_menu_model(gmenu);
      m_MenuPopup.set_has_arrow(false);

      // Create actions:
      auto refActionGroup = Gio::SimpleActionGroup::create();

      refActionGroup->add_action("edit",
        sigc::mem_fun(*this, &TreeView_WithPopup::on_menu_file_popup_generic));
      refActionGroup->add_action("process",
        sigc::mem_fun(*this, &TreeView_WithPopup::on_menu_file_popup_generic));
      refActionGroup->add_action("remove",
        sigc::mem_fun(*this, &TreeView_WithPopup::on_menu_file_popup_generic));

      insert_action_group("popup", refActionGroup);
    }

    TreeView_WithPopup::~TreeView_WithPopup()
    {
    }

    void TreeView_WithPopup::on_popup_button_pressed(int /* n_press */, double x, double y)
    {
      const Gdk::Rectangle rect(x, y, 1, 1);
      m_MenuPopup.set_pointing_to(rect);
      m_MenuPopup.popup();
    }

    void TreeView_WithPopup::on_menu_file_popup_generic()
    {
      std::cout << "A popup menu item was selected." << std::endl;

      auto refSelection = get_selection();
      if(refSelection)
      {
        auto iter = refSelection->get_selected();
        if(iter)
        {
          int id = (*iter)[m_Columns.m_col_id];
          std::cout << "  Selected ID=" << id << std::endl;
        }
      }
    }

## The DropDown Widget

The `DropDown` widget is an alternative to the deprecated `ComboBox`. It uses list models instead of tree models, and the content is displayed using widgets instead of cell renderers.

The `DropDown` widget offers a list of choices in a dropdown menu. If appropriate, it can show extra information about each item, such as text, a picture, or a check button. The `DropDown` widget can optionally have an `Entry` in the dropdown menu, allowing the user to search in a long list.

The list is provided via a `Gio::ListModel`, and data from this model is added to the `DropDown`'s view with signal handlers connected to a `SignalListItemFactory`. This provides flexibility, but the `StringList` class provides a simpler text-based specialization in case that flexibility is not required.

Reference

### Model

The model for a `DropDown` can be defined and filled exactly as for a `ListView` or a `ColumnView`. It must be a subclass of `Glib::Object`. For instance, you might have a `DropDown` with one integer and one text column, like so:

    class ModelColumns : public Glib::Object
    {
    public:
      int m_col_id;
      Glib::ustring m_col_name;

      static Glib::RefPtr<ModelColumns> create(
        int col_id, const Glib::ustring& col_name)
      {
        return Glib::make_refptr_for_instance<ModelColumns>(
          new ModelColumns(col_id, col_name));
      }

    protected:
      ModelColumns(int col_id, const Glib::ustring& col_name)
      : m_col_id(col_id), m_col_name(col_name)
      {}
    };

    Glib::RefPtr<Gio::ListStore<ModelColumns>> m_ListStore;

After appending rows to this model, you should provide the model to the `DropDown` with the `set_model()` method. Unless you use the `StringList` model, you also need to set a `ListItemFactory` with `set_factory()`. If you want the items in the dropdown menu to look different from the item in the `DropDown` widget, you also need to set a separate `ListItemFactory` with `set_list_factory()`.

### The selected item

To discover what item, if any, the user has selected from the `DropDown`, call `DropDown::get_selected()`. This returns an unsigned int that you can use to get the selected data from the model. For instance, you might read an integer ID value from the model, even though you have chosen only to show the human-readable description in the `DropDown`. For instance:

    unsigned int sel = m_DropDown.get_selected();
    if (sel != GTK_INVALID_LIST_POSITION)
    {
      // Get the data for the selected row, using our knowledge of the list model:
      auto id = m_ListStore->get_item(sel).m_col_id;
      set_some_id_chosen(id); // Your own function.
    }
    else
      set_nothing_chosen(); // Your own function.

### Reagování na změny

You might need to react to every change of selection in the `DropDown`, for instance to update other widgets. To do so, you should connect to `property_selected().signal_changed()`. For instance:

    m_DropDown.property_selected().signal_changed().connect(
      sigc::mem_fun(*this, &ExampleWindow::on_dropdown_changed));

### Simple String Example

#### Simple DropDown

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm/window.h>
    #include <gtkmm/dropdown.h>
    #include <gtkmm/stringlist.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      ~ExampleWindow() override;

    protected:
      // Signal handler:
      void on_dropdown_changed();

      // Child widget:
      Gtk::DropDown m_DropDown;

      Glib::RefPtr<Gtk::StringList> m_StringList;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    {
      set_title("DropDown example");

      set_child(m_DropDown);

      // Fill the dropdown:
      const std::vector<Glib::ustring> strings{
        "1 minute", "2 minutes", "5 minutes", "20 minutes"
      };
      m_StringList = Gtk::StringList::create(strings);
      m_DropDown.set_model(m_StringList);
      m_DropDown.set_selected(0);

      // Connect signal handler:
      m_DropDown.property_selected().signal_changed().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_dropdown_changed));
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_dropdown_changed()
    {
      const auto selected = m_DropDown.get_selected();
      std::cout << "DropDown changed: Row=" << selected
        << ", String=" << m_StringList->get_string(selected) << std::endl;
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char* argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      // Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

### Examples with a Search Entry

The dropdown menu may contain an `Entry` that allows to search for items in the list. Call `set_enable_search()` and `set_expression()`. For instance:

    m_DropDown.set_enable_search(true);
    auto expression = Gtk::ClosureExpression<Glib::ustring>::create(
      sigc::mem_fun(*this, &ExampleWindow::get_col_name));
    m_DropDown.set_expression(expression);

    //-------
    Glib::ustring ExampleWindow::get_col_name(const Glib::RefPtr<Glib::ObjectBase>& item)
    {
      const auto col = std::dynamic_pointer_cast<ModelColumns>(item);
      return col ? col->m_col_name : "";
    }

#### String Example

##### Search String

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm/window.h>
    #include <gtkmm/dropdown.h>
    #include <gtkmm/stringlist.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      ~ExampleWindow() override;

    protected:
      // Signal handler:
      void on_dropdown_changed();

      // Child widget:
      Gtk::DropDown m_DropDown;

      Glib::RefPtr<Gtk::StringList> m_StringList;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/expression.h>
    #include <gtkmm/stringobject.h>
    #include <iostream>

    ExampleWindow::ExampleWindow()
    {
      set_title("Searchable DropDown example");

      set_child(m_DropDown);

      // Fill the dropdown:
      const std::vector<Glib::ustring> many_times{
        "1 minute", "2 minutes", "5 minutes", "10 minutes", "15 minutes", "20 minutes",
        "25 minutes", "30 minutes", "35 minutes", "40 minutes", "45 minutes", "50 minutes",
        "55 minutes", "1 hour", "2 hours", "3 hours", "5 hours", "6 hours", "7 hours",
        "8 hours", "9 hours", "10 hours", "11 hours", "12 hours"
      };
      m_StringList = Gtk::StringList::create(many_times);
      m_DropDown.set_model(m_StringList);
      m_DropDown.set_selected(0);

      // Show a search entry.
      m_DropDown.set_enable_search(true);
      auto expression = Gtk::ClosureExpression<Glib::ustring>::create(
        [](const Glib::RefPtr<Glib::ObjectBase>& item)->Glib::ustring
        {
          // An item in a StringList is a StringObject.
          const auto string_object = std::dynamic_pointer_cast<Gtk::StringObject>(item);
          return string_object ? string_object->get_string() : "";
        });
      m_DropDown.set_expression(expression);

      // Connect signal handler:
      m_DropDown.property_selected().signal_changed().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_dropdown_changed));
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_dropdown_changed()
    {
      const auto selected = m_DropDown.get_selected();
      std::cout << "DropDown changed: Row=" << selected
        << ", String=" << m_StringList->get_string(selected) << std::endl;
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char* argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      // Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

#### Font Example

This example uses a `Pango::FontMap` as its model. This is possible because `Pango::FontMap` implements the `Gio::ListModel` interface. Of course you can use a `FontDialogButton` instead.

##### Search Font

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      ~ExampleWindow() override;

    protected:
      // Signal handler:
      void on_dropdown_changed();

      Glib::ustring get_family_name(const Glib::RefPtr<Glib::ObjectBase>& item);

      // Child widget:
      Gtk::DropDown m_DropDown;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <pangomm/cairofontmap.h>
    #include <iostream>
    //#include <typeinfo>

    ExampleWindow::ExampleWindow()
    {
      set_title("Searchable DropDown example");

      // Add the DropDown to the window.
      set_child(m_DropDown);

      // Show a search entry.
      m_DropDown.set_enable_search(true);
      auto expression = Gtk::ClosureExpression<Glib::ustring>::create(
        sigc::mem_fun(*this, &ExampleWindow::get_family_name));
      m_DropDown.set_expression(expression);

      // Pango::FontMap is a Gio::ListModel.
      auto model = Pango::CairoFontMap::get_default();
      m_DropDown.set_model(model);
      m_DropDown.set_selected(0);

      // Connect signal handler.
      m_DropDown.property_selected().signal_changed().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_dropdown_changed));
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_dropdown_changed()
    {
      const auto selected = m_DropDown.get_selected();
      const auto item = m_DropDown.get_selected_item();
      std::cout << "DropDown changed: Row=" << selected
        << ", Font=" << get_family_name(item) << std::endl;

      // Pango::FontMap is often a list of items of type Pango::FontFamily.
      // From the description of Pango::CairoFontMap: "The actual type of the font map
      // will depend on the particular font technology Cairo was compiled to use."
      // If get_family_name() does not return a family name, you can add
      // #include <typeinfo> and query the type of the items with:
      //   std::cout << typeid(*item.get()).name() << std::endl;
    }

    Glib::ustring ExampleWindow::get_family_name(const Glib::RefPtr<Glib::ObjectBase>& item)
    {
      auto family = std::dynamic_pointer_cast<Pango::FontFamily>(item);
      return family ? family->get_name() : "";
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char* argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      // Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

### Complex Example

This is a more complex example with two `SignalListItemFactory` objects and their signal handlers. This example would be simpler without the checkmark in the dropdown menu.

#### Search Font

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      ~ExampleWindow() override;

    protected:
      // Signal handlers:
      void on_setup_selected_item(const Glib::RefPtr<Gtk::ListItem>& list_item);
      void on_bind_selected_item(const Glib::RefPtr<Gtk::ListItem>& list_item);
      void on_setup_list_item(const Glib::RefPtr<Gtk::ListItem>& list_item);
      void on_bind_list_item(const Glib::RefPtr<Gtk::ListItem>& list_item);
      void on_unbind_list_item(const Glib::RefPtr<Gtk::ListItem>& list_item);
      void on_selected_item_changed(const Glib::RefPtr<Gtk::ListItem>& list_item);
      void on_dropdown_changed();

      void create_model();
      void liststore_add_item(const Glib::ustring& title, const Glib::ustring& icon,
        const Glib::ustring& description);

      // A Gio::ListStore item.
      class ModelColumns : public Glib::Object
      {
      public:
        Glib::ustring m_title;
        Glib::ustring m_icon;
        Glib::ustring m_description;

        static Glib::RefPtr<ModelColumns> create(const Glib::ustring& title,
          const Glib::ustring& icon, const Glib::ustring& description)
        {
          return Glib::make_refptr_for_instance<ModelColumns>(
            new ModelColumns(title, icon, description));
        }

      protected:
        ModelColumns(const Glib::ustring& title, const Glib::ustring& icon,
          const Glib::ustring& description)
        : m_title(title), m_icon(icon), m_description(description)
        {}
      }; // ModelColumns

      // Child widget:
      Gtk::DropDown m_DropDown;

      Glib::RefPtr<Gio::ListStore<ModelColumns>> m_ListStore;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    {
      set_title("DropDown example");

      // Add the DropDown to the window.
      set_child(m_DropDown);

      // Factory for presenting the selected item.
      auto factory = Gtk::SignalListItemFactory::create();
      factory->signal_setup().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_setup_selected_item));
      factory->signal_bind().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_bind_selected_item));
      m_DropDown.set_factory(factory);

      // Factory for presenting the items in the dropdown list.
      factory = Gtk::SignalListItemFactory::create();
      factory->signal_setup().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_setup_list_item));
      factory->signal_bind().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_bind_list_item));
      m_DropDown.set_list_factory(factory);

      // Create the model and fill it.
      create_model();
      m_DropDown.set_model(m_ListStore);
      m_DropDown.set_selected(0);

      // Connect signal handler:
      m_DropDown.property_selected().signal_changed().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_dropdown_changed));
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_dropdown_changed()
    {
      const auto selected = m_DropDown.get_selected();
      std::cout << "DropDown changed: Row=" << selected
        << ", Title=" << m_ListStore->get_item(selected)->m_title << std::endl;
    }

    void ExampleWindow::create_model()
    {
      m_ListStore = Gio::ListStore<ModelColumns>::create();

      liststore_add_item("Digital Output", "audio-card-symbolic", "Built-in Audio");
      liststore_add_item("Headphones", "audio-headphones-symbolic", "Built-in Audio");
      liststore_add_item("Digital Output", "audio-card-symbolic", "Thinkpad Tunderbolt 3 Dock USB Audio");
      liststore_add_item("Analog Output", "audio-card-symbolic", "Thinkpad Tunderbolt 3 Dock USB Audio");
    }

    void ExampleWindow::liststore_add_item(const Glib::ustring& title,
      const Glib::ustring& icon, const Glib::ustring& description)
    {
      m_ListStore->append(ModelColumns::create(title, icon, description));
    }

    void ExampleWindow::on_setup_selected_item(const Glib::RefPtr<Gtk::ListItem>& list_item)
    {
      auto box = Gtk::make_managed<Gtk::Box>(Gtk::Orientation::HORIZONTAL, 10);
      box->append(*Gtk::make_managed<Gtk::Image>());
      box->append(*Gtk::make_managed<Gtk::Label>());
      list_item->set_child(*box);
    }

    void ExampleWindow::on_bind_selected_item(const Glib::RefPtr<Gtk::ListItem>& list_item)
    {
      auto col = std::dynamic_pointer_cast<ModelColumns>(list_item->get_item());
      if (!col)
        return;
      auto box = dynamic_cast<Gtk::Box*>(list_item->get_child());
      if (!box)
        return;
      auto image = dynamic_cast<Gtk::Image*>(box->get_first_child());
      if (!image)
        return;
      image->set_from_icon_name(col->m_icon);
      auto label = dynamic_cast<Gtk::Label*>(image->get_next_sibling());
      if (!label)
        return;
      label->set_text(col->m_title);
    }

    void ExampleWindow::on_setup_list_item(const Glib::RefPtr<Gtk::ListItem>& list_item)
    {
      auto hbox = Gtk::make_managed<Gtk::Box>(Gtk::Orientation::HORIZONTAL, 10);
      auto vbox = Gtk::make_managed<Gtk::Box>(Gtk::Orientation::VERTICAL, 2);

      hbox->append(*Gtk::make_managed<Gtk::Image>());
      hbox->append(*vbox);
      auto title = Gtk::make_managed<Gtk::Label>();
      title->set_xalign(0.0);
      vbox->append(*title);
      auto description = Gtk::make_managed<Gtk::Label>();
      description->set_xalign(0.0);
      description->add_css_class("dim-label");
      vbox->append(*description);
      auto checkmark = Gtk::make_managed<Gtk::Image>();
      checkmark->set_from_icon_name("object-select-symbolic");
      checkmark->set_visible(false);
      hbox->append(*checkmark);

      list_item->set_child(*hbox);
    }

    void ExampleWindow::on_bind_list_item(const Glib::RefPtr<Gtk::ListItem>& list_item)
    {
      auto col = std::dynamic_pointer_cast<ModelColumns>(list_item->get_item());
      if (!col)
        return;
      auto hbox = dynamic_cast<Gtk::Box*>(list_item->get_child());
      if (!hbox)
        return;
      auto image = dynamic_cast<Gtk::Image*>(hbox->get_first_child());
      if (!image)
        return;
      image->set_from_icon_name(col->m_icon);
      auto vbox = dynamic_cast<Gtk::Box*>(image->get_next_sibling());
      if (!vbox)
        return;
      auto title = dynamic_cast<Gtk::Label*>(vbox->get_first_child());
      if (!title)
        return;
      title->set_text(col->m_title);
      auto description = dynamic_cast<Gtk::Label*>(title->get_next_sibling());
      if (!description)
        return;
      description->set_text(col->m_description);

      auto connection = m_DropDown.property_selected_item().signal_changed().connect(
        sigc::bind(sigc::mem_fun(*this, &ExampleWindow::on_selected_item_changed),
        list_item));
      list_item->set_data("connection", new sigc::connection(connection),
        Glib::destroy_notify_delete<sigc::connection>);
      on_selected_item_changed(list_item);
    }

    void ExampleWindow::on_unbind_list_item(const Glib::RefPtr<Gtk::ListItem>& list_item)
    {
      if (auto connection = static_cast<sigc::connection*>(list_item->get_data("connection")))
      {
        connection->disconnect();
        list_item->set_data("connection", nullptr);
      }
    }

    void ExampleWindow::on_selected_item_changed(const Glib::RefPtr<Gtk::ListItem>& list_item)
    {
      auto hbox = dynamic_cast<Gtk::Box*>(list_item->get_child());
      if (!hbox)
        return;
      auto checkmark = dynamic_cast<Gtk::Image*>(hbox->get_last_child());
      if (!checkmark)
        return;
      checkmark->set_visible(m_DropDown.get_selected_item() == list_item->get_item());
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char* argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      // Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

## Rozbalovací seznamy (ComboBox)

`Gtk::ComboBox` and `Gtk::ComboBoxText` are deprecated since gtkmm 4.10. Use `Gtk::DropDown` in new code.

The `ComboBox` widget offers a list (or tree) of choices in a dropdown menu. If appropriate, it can show extra information about each item, such as text, a picture, a check button, or a progress bar. The `ComboBox` widget usually restricts the user to the available choices, but it can optionally have an `Entry`, allowing the user to enter arbitrary text if none of the available choices are suitable.

Seznam je poskytován přes objekt `TreeModel` a sloupce tohoto modelu se přidávají do objektu `ComboBox`, který provádí zobrazení, pomocí metody `ComboBox::pack_start()`. Poskytuje to pružnost a typovou bezpečnost při kompilaci. Pokud ale tyto vymoženosti nejsou zrovna zapotřebí, je k dispozici zjednodušená třída `ComboBoxText` specializovaná čistě na textové položky.

Reference

### Model

Model pro `ComboBox` se dá definovat a vyplnit úplně stejně, jako pro `TreeView`. Například můžete odvodit třídu `ComboBox` s jedním celočíselným a jedním textovým sloupce, nějak takto:

    class ModelColumns : public Gtk::TreeModel::ColumnRecord
    {
    public:
      ModelColumns()
      { add(m_col_id); add(m_col_name); }

      Gtk::TreeModelColumn<int> m_col_id;
      Gtk::TreeModelColumn<Glib::ustring> m_col_name;
    };

    ModelColumns m_columns;

Po přidání řádků do tohoto modelu byste jej měli pomocí metody `set_model()` předat do objektu `ComboBox`. Pak použijte metodu `pack_start()` nebo `pack_end()` k určení, které sloupce se budou v rozbalovacím seznamu zobrazovat. Stejně jako u `TreeView`, můžete buď nastavit výchozí vykreslování buněk předáním `TreeModelColumn` do balicí metody, nebo můžete vytvořit instanci konkrétní třídy `CellRenderer` a určit konkrétní mapování buď pomocí `add_attribute()` nebo `set_cell_data_func()`. Tyto metody pochází ze základní třídy `CellLayout`.

### Vybraná položka

Chcete-li zjistit, kterou položku uživatel v rozbalovacím seznamu zvolil, pokud vůbec nějakou, zavolejte metodu `ComboBox::get_active()`. Ta vrací `TreeModel::iterator`, který můžete použít jako zpětný odkaz na objekt `Row`, abyste mohli číst hodnoty ve vašich sloupcích. Třeba můžete číst celočíselnou hodnotu ID z modelu, zatímco uživateli jste v rozbalovacím seznamu zobrazili pouze pro člověka čitelný textový popis. Například:

    Gtk::TreeModel::iterator iter = m_Combo.get_active();
    if(iter)
    {
      auto row = *iter;

      //Get the data for the selected row, using our knowledge
      //of the tree model:
      auto id = row[m_Columns.m_col_id];
      set_something_id_chosen(id); //Your own function.
    }
    else
      set_nothing_chosen(); //Your own function.

### Reagování na změny

Můžete chtít reagovat na všechny změny výběru v rozbalovacím seznamu, například kvůli aktualizaci ostatních widgetů. K tomu byste měli obsluhovat signál `changed`. Například:

    m_combo.signal_changed().connect( sigc::mem_fun(*this,
          &ExampleWindow::on_combo_changed) );

### Úplný příklad

#### ComboBox

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm/window.h>
    #include <gtkmm/comboboxtext.h>
    #include <gtkmm/liststore.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      void on_cell_data_extra(const Gtk::TreeModel::const_iterator& iter);

      //Signal handlers:
      void on_combo_changed();

      //Tree model columns:
      class ModelColumns : public Gtk::TreeModel::ColumnRecord
      {
      public:

        ModelColumns()
        { add(m_col_id); add(m_col_name); add(m_col_extra);}

        Gtk::TreeModelColumn<int> m_col_id;
        Gtk::TreeModelColumn<Glib::ustring> m_col_name;
        Gtk::TreeModelColumn<Glib::ustring> m_col_extra;
      };

      ModelColumns m_Columns;

      //Child widgets:
      Gtk::ComboBox m_Combo;
      Gtk::CellRendererText m_cell;
      Glib::RefPtr<Gtk::ListStore> m_refTreeModel;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    {
      set_title("ComboBox example");

      //Create the Tree model:
      //m_refTreeModel = Gtk::TreeStore::create(m_Columns);
      m_refTreeModel = Gtk::ListStore::create(m_Columns);
      m_Combo.set_model(m_refTreeModel);

      //Fill the ComboBox's Tree Model:
      auto iter = m_refTreeModel->append();
      auto row = *iter;
      row[m_Columns.m_col_id] = 1;
      row[m_Columns.m_col_name] = "Billy Bob";
      row[m_Columns.m_col_extra] = "something";
      m_Combo.set_active(iter);
      /*
      auto childrow = *(m_refTreeModel->append(row.children()));
      childrow[m_Columns.m_col_id] = 11;
      childrow[m_Columns.m_col_name] = "Billy Bob Junior";

      childrow = *(m_refTreeModel->append(row.children()));
      childrow[m_Columns.m_col_id] = 12;
      childrow[m_Columns.m_col_name] = "Sue Bob";
      */

      row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = 2;
      row[m_Columns.m_col_name] = "Joey Jojo";
      row[m_Columns.m_col_extra] = "yadda";

      row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = 3;
      row[m_Columns.m_col_name] = "Rob McRoberts";
      row[m_Columns.m_col_extra] = "";

      /*
      childrow = *(m_refTreeModel->append(row.children()));
      childrow[m_Columns.m_col_id] = 31;
      childrow[m_Columns.m_col_name] = "Xavier McRoberts";
      */

      //Add the model columns to the Combo (which is a kind of view),
      //rendering them in the default way:
      m_Combo.pack_start(m_Columns.m_col_id);
      m_Combo.pack_start(m_Columns.m_col_name);

      //An example of adding a cell renderer manually,
      //instead of using pack_start(model_column, Gtk::PackOptions::EXPAND_WIDGET)
      //so we have more control:
      m_Combo.set_cell_data_func(m_cell,
        sigc::mem_fun(*this, &ExampleWindow::on_cell_data_extra));
      m_Combo.pack_start(m_cell);

      //Add the ComboBox to the window.
      set_child(m_Combo);

      //Connect signal handler:
      m_Combo.signal_changed().connect( sigc::mem_fun(*this, &ExampleWindow::on_combo_changed) );
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_cell_data_extra(const Gtk::TreeModel::const_iterator& iter)
    {
      auto row = *iter;
      const Glib::ustring extra = row[m_Columns.m_col_extra];

      //Some arbitrary logic just to show that this is where you can do such things:

      //Transform the value, deciding how to represent it as text:
      if(extra.empty())
        m_cell.property_text() = "(none)";
      else
        m_cell.property_text() = "-" + extra + "-";

      //Change other cell renderer properties too:
      m_cell.property_foreground() = (extra == "yadda" ? "red" : "green");
    }

    void ExampleWindow::on_combo_changed()
    {
      const auto iter = m_Combo.get_active();
      if(iter)
      {
        const auto row = *iter;
        if(row)
        {
          //Get the data for the selected row, using our knowledge of the tree
          //model:
          int id = row[m_Columns.m_col_id];
          Glib::ustring name = row[m_Columns.m_col_name];

          std::cout << " ID=" << id << ", name=" << name << std::endl;
        }
      }
      else
        std::cout << "invalid iter" << std::endl;
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

### Jednoduchý textový příklad

#### Kombinované vstupní pole (ComboBoxText)

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm/window.h>
    #include <gtkmm/comboboxtext.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_combo_changed();

      //Child widgets:
      Gtk::ComboBoxText m_Combo;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    {
      set_title("ComboBoxText example");

      //Fill the combo:
      m_Combo.append("something");
      m_Combo.append("something else");
      m_Combo.append("something or other");
      m_Combo.set_active(1);

      set_child(m_Combo);

      //Connect signal handler:
      m_Combo.signal_changed().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_combo_changed) );
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_combo_changed()
    {
      Glib::ustring text = m_Combo.get_active_text();
      if(!(text.empty()))
        std::cout << "Combo changed: " << text << std::endl;
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

### ComboBox se vstupním polem

`ComboBox` může obsahovat widget `Entry` pro zadávání libovolného textu. Stačí zadat `true` do parametru `has_entry` v konstruktoru.

#### Textový sloupec

So that the `Entry` can interact with the drop-down list of choices, you must specify which of your model columns is the text column, with `set_entry_text_column()`. For instance:

    m_combo.set_entry_text_column(m_columns.m_col_name);

Když vyberete položku z robalovací nabídky, umístí se hodnota z tohoto sloupce do `Entry`.

#### Vstupní pole

Protože uživatel může zadat libovolný text, aktivní model řádku není dostačující, abychom zjistili, jaký text uživatel zadal. Proto byste měli za tímto účelem získat widget `Entry` pomocí metody `ComboBox::get_entry()` a zavolat `get_text()`.

#### Reagování na změny

When the user enters arbitrary text, it may not be enough to connect to the `changed` signal, which is emitted for every typed character. It is not emitted when the user presses the Enter key. Pressing the Enter key or moving the keyboard focus to another widget may signal that the user has finished entering text. To be notified of these events, connect to the `Entry`'s `activate` signal (available since gtkmm 4.8), and add a `Gtk::EventControllerFocus` and connect to its `leave` signal, like so

    auto entry = m_Combo.get_entry();
    if (entry)
    {
      // Alternatively you can connect to m_Combo.signal_changed().
      entry->signal_changed().connect(sigc::mem_fun(*this,
        &ExampleWindow::on_entry_changed));
      entry->signal_activate().connect(sigc::mem_fun(*this,
        &ExampleWindow::on_entry_activate));
      // The Entry shall receive focus-leave events.
      auto controller = Gtk::EventControllerFocus::create();
      m_ConnectionFocusLeave = controller->signal_leave().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_entry_focus_leave));
      entry->add_controller(controller);
    }

The `changed` signals of `ComboBox` and `Entry` are both emitted for every change. It doesn't matter which one you connect to. But the `EventControllerFocus` must be added to the `Entry`.

#### Úplný příklad

##### Rozbalovací seznam (ComboBox) se vstupním polem (Entry)

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm/window.h>
    #include <gtkmm/combobox.h>
    #include <gtkmm/liststore.h>
    #include <gtkmm/version.h>

    #define HAS_SIGNAL_ACTIVATE GTKMM_CHECK_VERSION(4,7,1)

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      ~ExampleWindow() override;

    protected:
      //Signal handlers:
      void on_entry_changed();
    #if HAS_SIGNAL_ACTIVATE
      void on_entry_activate();
    #endif
      void on_entry_focus_leave();

      //Signal connection:
      sigc::connection m_ConnectionFocusLeave;

      //Tree model columns:
      class ModelColumns : public Gtk::TreeModel::ColumnRecord
      {
      public:

        ModelColumns()
        { add(m_col_id); add(m_col_name); }

        Gtk::TreeModelColumn<Glib::ustring> m_col_id; //The data to choose - this must be text.
        Gtk::TreeModelColumn<Glib::ustring> m_col_name;
      };

      ModelColumns m_Columns;

      //Child widgets:
      Gtk::ComboBox m_Combo;
      Glib::RefPtr<Gtk::ListStore> m_refTreeModel;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/eventcontrollerfocus.h>
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_Combo(true /* has_entry */)
    {
      set_title("ComboBox example");

      //Create the Tree model:
      //m_refTreeModel = Gtk::TreeStore::create(m_Columns);
      m_refTreeModel = Gtk::ListStore::create(m_Columns);
      m_Combo.set_model(m_refTreeModel);

      //Fill the ComboBox's Tree Model:
      auto row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = "1";
      row[m_Columns.m_col_name] = "Billy Bob";
      /*
      auto childrow = *(m_refTreeModel->append(row.children()));
      childrow[m_Columns.m_col_id] = 11;
      childrow[m_Columns.m_col_name] = "Billy Bob Junior";

      childrow = *(m_refTreeModel->append(row.children()));
      childrow[m_Columns.m_col_id] = 12;
      childrow[m_Columns.m_col_name] = "Sue Bob";
      */

      row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = "2";
      row[m_Columns.m_col_name] = "Joey Jojo";

      row = *(m_refTreeModel->append());
      row[m_Columns.m_col_id] = "3";
      row[m_Columns.m_col_name] = "Rob McRoberts";

      /*
      childrow = *(m_refTreeModel->append(row.children()));
      childrow[m_Columns.m_col_id] = 31;
      childrow[m_Columns.m_col_name] = "Xavier McRoberts";
      */

      //Add the model columns to the Combo (which is a kind of view),
      //rendering them in the default way:
      //This is automatically rendered when we use set_entry_text_column().
      //m_Combo.pack_start(m_Columns.m_col_id, Gtk::PackOptions::EXPAND_WIDGET);
      m_Combo.pack_start(m_Columns.m_col_name);

      m_Combo.set_entry_text_column(m_Columns.m_col_id);
      m_Combo.set_active(1);

      //Add the ComboBox to the window.
      set_child(m_Combo);

      //Connect signal handlers:
      auto entry = m_Combo.get_entry();
      if (entry)
      {
        // Alternatively you can connect to m_Combo.signal_changed().
        entry->signal_changed().connect(sigc::mem_fun(*this,
          &ExampleWindow::on_entry_changed));
    #if HAS_SIGNAL_ACTIVATE
        entry->signal_activate().connect(sigc::mem_fun(*this,
          &ExampleWindow::on_entry_activate));
    #endif
        // The Entry shall receive focus-leave events.
        auto controller = Gtk::EventControllerFocus::create();
        m_ConnectionFocusLeave = controller->signal_leave().connect(
          sigc::mem_fun(*this, &ExampleWindow::on_entry_focus_leave));
        entry->add_controller(controller);
      }
      else
        std::cout << "No Entry ???" << std::endl;
    }

    ExampleWindow::~ExampleWindow()
    {
      // The focus-leave signal may be emitted while m_Combo is being destructed.
      // The signal handler can generate critical messages, if it's called when
      // m_Combo has been partly destructed.
      m_ConnectionFocusLeave.disconnect();
    }

    void ExampleWindow::on_entry_changed()
    {
      auto entry = m_Combo.get_entry();
      if (entry)
      {
        std::cout << "on_entry_changed(): Row=" << m_Combo.get_active_row_number()
          << ", ID=" << entry->get_text() << std::endl;
      }
    }

    #if HAS_SIGNAL_ACTIVATE
    void ExampleWindow::on_entry_activate()
    {
      auto entry = m_Combo.get_entry();
      if (entry)
      {
        std::cout << "on_entry_activate(): Row=" << m_Combo.get_active_row_number()
          << ", ID=" << entry->get_text() << std::endl;
      }
    }
    #endif

    void ExampleWindow::on_entry_focus_leave()
    {
      auto entry = m_Combo.get_entry();
      if (entry)
      {
        std::cout << "on_entry_focus_leave(): Row=" << m_Combo.get_active_row_number()
          << ", ID=" << entry->get_text() << std::endl;
      }
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

#### Jednoduchý textový příklad

##### Textový rozbalovací seznam (ComboBoxText) se vstupním polem (Entry)

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm/window.h>
    #include <gtkmm/comboboxtext.h>
    #include <gtkmm/version.h>

    #define HAS_SIGNAL_ACTIVATE GTKMM_CHECK_VERSION(4,7,1)

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      ~ExampleWindow() override;

    protected:
      //Signal handlers:
      void on_combo_changed();
    #if HAS_SIGNAL_ACTIVATE
      void on_entry_activate();
    #endif
      void on_entry_focus_leave();

      //Signal connection:
      sigc::connection m_ConnectionFocusLeave;

      //Child widgets:
      Gtk::ComboBoxText m_Combo;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/eventcontrollerfocus.h>
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_Combo(true /* has_entry */)
    {
      set_title("ComboBoxText example");

      //Fill the combo:
      m_Combo.append("something");
      m_Combo.append("something else");
      m_Combo.append("something or other");
      m_Combo.set_active(0);

      set_child(m_Combo);

      //Connect signal handlers:
      auto entry = m_Combo.get_entry();
      // Alternatively you can connect to entry->signal_changed().
      m_Combo.signal_changed().connect(sigc::mem_fun(*this,
        &ExampleWindow::on_combo_changed) );

      if (entry)
      {
    #if HAS_SIGNAL_ACTIVATE
        entry->signal_activate().connect(sigc::mem_fun(*this,
          &ExampleWindow::on_entry_activate));
    #endif
        // The Entry shall receive focus-leave events.
        auto controller = Gtk::EventControllerFocus::create();
        m_ConnectionFocusLeave = controller->signal_leave().connect(
          sigc::mem_fun(*this, &ExampleWindow::on_entry_focus_leave));
        entry->add_controller(controller);
      }
      else
        std::cout << "No Entry ???" << std::endl;

      m_Combo.property_has_frame() = false;
    }

    ExampleWindow::~ExampleWindow()
    {
      // The focus-leave signal may be emitted while m_Combo is being destructed.
      // The signal handler can generate critical messages, if it's called when
      // m_Combo has been partly destructed.
      m_ConnectionFocusLeave.disconnect();
    }

    void ExampleWindow::on_combo_changed()
    {
      std::cout << "on_combo_changed(): Row=" << m_Combo.get_active_row_number()
        << ", Text=" << m_Combo.get_active_text() << std::endl;
    }

    #if HAS_SIGNAL_ACTIVATE
    void ExampleWindow::on_entry_activate()
    {
      std::cout << "on_entry_activate(): Row=" << m_Combo.get_active_row_number()
        << ", Text=" << m_Combo.get_active_text() << std::endl;
    }
    #endif

    void ExampleWindow::on_entry_focus_leave()
    {
      std::cout << "on_entry_focus_leave(): Row=" << m_Combo.get_active_row_number()
        << ", Text=" << m_Combo.get_active_text() << std::endl;
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

## Zobrazení textu (TextView)

Widget `TextView` se dá použít k zobrazení a úpravám velkého množství formátovaného textu. Podobně jako `TreeView`, má design model/zobrazení. Modelem je v tomto případě `TextBuffer`.

### Vyrovnávací paměť

`Gtk::TextBuffer` je model obsahující data pro `Gtk::TextView`, podobně jako je `Gtk::TreeModel` používán `Gtk::TreeView`. To umožňuje dvěma a více `Gtk::TextView` sdílet stejný `TextBuffer` a při tom to umožňuje zobrazit textový obsah vyrovnávací paměti trochu odlišně. Nebo byste mohli spravovat několik objektů `Gtk::TextBuffer` a v různou dobu volit vždy jeden z nich pro zobrazení ve widgetu `Gtk::TextView`.

`TextView` vytváří svůj vlastní výchozí `TextBuffer`, ke kterému se můžete dostat přes metodu `get_buffer()`.

Reference

#### Iterátory

A `Gtk::TextBuffer::iterator` and a `Gtk::TextBuffer::const_iterator` represent a position between two characters in the text buffer. Whenever the buffer is modified in a way that affects the number of characters in the buffer, all outstanding iterators become invalid. Because of this, iterators can't be used to preserve positions across buffer modifications. To preserve a position, use `Gtk::TextBuffer::Mark`.

Reference

#### Formátovací značky a formátování

##### Formátovací značky (Tag)

K určení, že nějaký text ve vyrovnávací paměti by měl být nějak naformátován, musíte definovat formátovací značku, která si drží informaci o formátování, a pak ji použít na část textu. Příklad definice formátovací značky a jejích vlastností:

    auto refTagMatch = Gtk::TextBuffer::Tag::create();
    refTagMatch->property_background() = "orange";

Při použití metody `create()` můžete určit pro objekt `Tag` název, ale není to nutné.

Třída `Tag` má mnoho dalších vlastností.

Reference

##### Tabulka formátovacích značek (TagTable)

Každý `Gtk::TextBuffer` používá `Gtk::TextBuffer::TagTable`, který obsahuje objekty `Tag` pro vyrovnávací paměť. Dva nebo více objektů `TextBuffer` může sdílet stejnou instanci `TagTable`. Když vytvoříte objekty `Tag`, měli byste je přidat do `TagTable`. Například:

    auto refTagTable = Gtk::TextBuffer::TagTable::create();
    refTagTable->add(refTagMatch);
    //Hopefully a future version of gtkmm will have a set_tag_table() method,
    //for use after creation of the buffer.
    auto refBuffer = Gtk::TextBuffer::create(refTagTable);

Můžete také použít `get_tag_table()` pro získání, a případné změny, výchozího objektu `TagTable` z objektu `TextBuffer`, místo abyste jej přímo vytvářeli.

Reference

##### Použití formátovacích značek

Když vytvoříte objekt `Tag` a přidáte jej do `TagTable`, můžete použít tuto formátovací značku na část textu v `TextBuffer`, takže tento text se zobrazí s formátováním. Začátek a konec rozsahu definujete pomocí `Gtk::TextBuffer::iterator`. Například:

    refBuffer->apply_tag(refTagMatch, iterRangeStart, iterRangeStop);

Or you could specify the tag when first inserting the text:

    refBuffer->insert_with_tag(iter, "Some text", refTagMatch);

Na ten samý text můžete použít i více formátovacích značek použitím metody `apply_tag()` vícekrát, nebo pomocí `insert_with_tags()`. Více objektů `Tag` může určit pro tu samou vlastnost různé hodnoty, ale tyto konflikty se dají řešit pomocí `Tag::set_priority()`.

#### Poziční značky (Mark)

Iterátory třídy `TextBuffer` jsou obecně zneplatněny, když dojde ke změně textu, ale v těchto situacích můžete použít `Gtk::TextBuffer::Mark` k zapamatování pozice. Například:

    auto refMark = refBuffer->create_mark(iter);

Později můžete použít metodu `get_iter()` k vytvoření iterátoru pro novou pozici v objektu `Mark`.

Existují dvě vestavěné poziční značky `Mark` – `insert` a `selection_bound`, ke kterým se můžete dostat přes metody `get_insert()` a `get_selection_bound()` třídy `TextBuffer`.

Reference

#### Zobrazení (View)

Jak bylo zmíněno výše, každý `TextView` má `TextBuffer` a jeden nebo více `TextView` může sdílet stejný `TextBuffer`.

Obdobně jako u `TreeView`, byste měli svůj `TextView` nejspíše vložit do `ScrolledWindow`, aby uživatelé mohli vidět i přesahující text a mohli se po celém textu pohybovat pomocí posuvníků.

Reference

##### Výchozí formátování

`TextView` má různé metody, které umožňují měnit prezentovanou podobu vyrovnávací paměti pro konkrétní zobrazení. Některé jde přepsat pomocí objektů `Gtk::TextTag` ve vyrovnávací paměti, pokud určují ty stejné věci. Například pomocí `set_left_margin()`, `set_right_margin()`, `set_indent()` atd.

##### Posouvání

`Gtk::TextView` has various `scroll_to()` methods. These allow you to ensure that a particular part of the text buffer is visible. For instance, your application's Find feature might use `Gtk::TextView::scroll_to()` to show the found text.

### Widgety a kotvy potomků (ChildAnchors)

You can embed widgets, such as `Gtk::Button`s, in the text. Each such child widget needs a `ChildAnchor`. ChildAnchors are associated with `iterator`s. For instance, to create a child anchor at a particular position, use `Gtk::TextBuffer::create_child_anchor()`:

    auto refAnchor = refBuffer->create_child_anchor(iter);

Pro přidání widgetu na tuto pozici použijte `Gtk::TextView::add_child_at_anchor()`:

    m_TextView.add_child_at_anchor(m_Button, refAnchor);

Reference

### Příklady

#### Jednoduchý příklad

##### Zobrazení textu (TextView)

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:

      void fill_buffers();

      //Signal handlers:
      void on_button_quit();
      void on_button_buffer1();
      void on_button_buffer2();

      //Child widgets:
      Gtk::Box m_VBox;

      Gtk::ScrolledWindow m_ScrolledWindow;
      Gtk::TextView m_TextView;

      Glib::RefPtr<Gtk::TextBuffer> m_refTextBuffer1, m_refTextBuffer2;

      Gtk::Box m_ButtonBox;
      Gtk::Button m_Button_Quit, m_Button_Buffer1, m_Button_Buffer2;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::Orientation::VERTICAL),
      m_Button_Quit("_Quit", true),
      m_Button_Buffer1("Use buffer 1"),
      m_Button_Buffer2("Use buffer 2")
    {
      set_title("Gtk::TextView example");
      set_default_size(400, 200);

      m_VBox.set_margin(5);
      set_child(m_VBox);

      //Add the TreeView, inside a ScrolledWindow, with the button underneath:
      m_ScrolledWindow.set_child(m_TextView);

      //Only show the scrollbars when they are necessary:
      m_ScrolledWindow.set_policy(Gtk::PolicyType::AUTOMATIC, Gtk::PolicyType::AUTOMATIC);
      m_ScrolledWindow.set_expand();

      m_VBox.append(m_ScrolledWindow);

      //append buttons:
      m_VBox.append(m_ButtonBox);

      m_Button_Buffer1.set_hexpand(true);
      m_Button_Buffer1.set_halign(Gtk::Align::END);
      m_ButtonBox.append(m_Button_Buffer1);
      m_ButtonBox.append(m_Button_Buffer2);
      m_ButtonBox.append(m_Button_Quit);
      m_ButtonBox.set_margin(5);
      m_ButtonBox.set_spacing(5);

      //Connect signals:
      m_Button_Quit.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_quit) );
      m_Button_Buffer1.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_buffer1) );
      m_Button_Buffer2.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_buffer2) );

      fill_buffers();
      on_button_buffer1();
    }

    void ExampleWindow::fill_buffers()
    {
      m_refTextBuffer1 = Gtk::TextBuffer::create();
      m_refTextBuffer1->set_text("This is the text from TextBuffer #1.");

      m_refTextBuffer2 = Gtk::TextBuffer::create();
      m_refTextBuffer2->set_text(
              "This is some alternative text, from TextBuffer #2.");

    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_quit()
    {
      set_visible(false);
    }

    void ExampleWindow::on_button_buffer1()
    {
      m_TextView.set_buffer(m_refTextBuffer1);
    }

    void ExampleWindow::on_button_buffer2()
    {
      m_TextView.set_buffer(m_refTextBuffer2);
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

## Nabídky a nástrojové lišty

There are specific APIs for menus and toolbars, but you should usually deal with them together, creating `Gio::SimpleAction`s that you can refer to in both menus and toolbars. In this way you can handle activation of the action instead of responding to the menu and toolbar items separately. And you can enable or disable both the menu and toolbar item via the action. `Gtk::Builder` can create menus and toolbars.

This involves the use of the `Gio::SimpleActionGroup`, `Gio::SimpleAction` and `Gtk::Builder` classes, all of which should be instantiated via their `create()` methods, which return `RefPtr`s.

### Akce

First create the `Gio::SimpleAction`s and add them to a `Gio::SimpleActionGroup`, with `Gio::ActionMap::add_action()`. (`Gio::ActionMap` is a base class of `Gio::SimpleActionGroup`.) Then add the action group to your window with `Gtk::Widget::insert_action_group()`.

The arguments to `add_action()` specify the action's name, which is used in the menu items and toolbar buttons. You can also specify a signal handler when calling `add_action()`. This signal handler will be called when the action is activated via either a menu item or a toolbar button.

Například:

    m_refActionGroup = Gio::SimpleActionGroup::create();

    m_refActionGroup->add_action("new", sigc::mem_fun(*this, &ExampleWindow::on_action_file_new));
    m_refActionGroup->add_action("open", sigc::mem_fun(*this, &ExampleWindow::on_action_file_open));
    m_refActionGroup->add_action("quit", sigc::mem_fun(*this, &ExampleWindow::on_action_file_quit));

    insert_action_group("example", m_refActionGroup);

If you use an `Gtk::ApplicationWindow`, you don't have to create your own action group. `Gio::ActionGroup` and `Gio::ActionMap` are base classes of `Gtk::ApplicationWindow`.

### Menubar and Toolbar

Next you should create a `Gtk::Builder`. At this point is also a good idea to tell the application to respond to keyboard shortcuts, by using `Gtk::Application::set_accel_for_action()`.

Například

    m_refBuilder = Gtk::Builder::create();

    app->set_accel_for_action("example.new", "<Primary>n");
    app->set_accel_for_action("example.quit", "<Primary>q");
    app->set_accel_for_action("example.copy", "<Primary>c");
    app->set_accel_for_action("example.paste", "<Primary>v");

Then, you can define the actual visible layout of the menus and toolbars, and add the UI layout to the `Builder`. This "ui string" uses an XML format, in which you should mention the names of the actions that you have already created. For instance:

    Glib::ustring ui_info =
      "<interface>"
      "  <menu id='menubar'>"
      "    <submenu>"
      "      <attribute name='label' translatable='yes'>_File</attribute>"
      "      <section>"
      "        <item>"
      "          <attribute name='label' translatable='yes'>_New</attribute>"
      "          <attribute name='action'>example.new</attribute>"
      "        </item>"
      "      </section>"
      "      <section>"
      "        <item>"
      "          <attribute name='label' translatable='yes'>_Quit</attribute>"
      "          <attribute name='action'>example.quit</attribute>"
      "        </item>"
      "      </section>"
      "    </submenu>"
      "    <submenu>"
      "      <attribute name='label' translatable='yes'>_Edit</attribute>"
      "      <item>"
      "        <attribute name='label' translatable='yes'>_Copy</attribute>"
      "        <attribute name='action'>example.copy</attribute>"
      "      </item>"
      "      <item>"
      "        <attribute name='label' translatable='yes'>_Paste</attribute>"
      "        <attribute name='action'>example.paste</attribute>"
      "      </item>"
      "    </submenu>"
      "  </menu>"
      "</interface>";

    m_refBuilder->add_from_string(ui_info);
    m_refBuilder->add_from_resource("/toolbar/toolbar.ui");

This is where we specify the names of the menu items as they will be seen by users in the menu. Therefore, this is where you should make strings translatable, by adding `translatable='yes'`.

To instantiate a `Gtk::PopoverMenuBar` and toolbar (a horizontal `Gtk::Box`) which you can actually show, you should use the `Builder::get_object()` and `Builder::get_widget()` methods, and then add the widgets to a container. For instance:

    auto gmenu = m_refBuilder->get_object<Gio::Menu>("menubar");
    auto pMenuBar = Gtk::make_managed<Gtk::PopoverMenuBar>(gmenu);
    m_Box.append(*pMenuBar);

    auto toolbar = m_refBuilder->get_widget<Gtk::Box>("toolbar");
    m_Box.append(*toolbar);

### Vyskakovací nabídky

`Menu`s are normally just added to a window, but they can also be displayed temporarily as the result of a mouse button click. For instance, a context menu might be displayed when the user clicks their right mouse button.

Například:

    Glib::ustring ui_info =
      "<interface>"
      "  <menu id='menu-examplepopup'>"
      "    <section>"
      "      <item>"
      "        <attribute name='label' translatable='yes'>Edit</attribute>"
      "        <attribute name='action'>examplepopup.edit</attribute>"
      "      </item>"
      "      <item>"
      "        <attribute name='label' translatable='yes'>Process</attribute>"
      "        <attribute name='action'>examplepopup.process</attribute>"
      "      </item>"
      "      <item>"
      "        <attribute name='label' translatable='yes'>Remove</attribute>"
      "        <attribute name='action'>examplepopup.remove</attribute>"
      "      </item>"
      "    </section>"
      "  </menu>"
      "</interface>";

    m_refBuilder->add_from_string(ui_info);

    auto gmenu = m_refBuilder->get_object<Gio::Menu>("menu-examplepopup");
    m_MenuPopup.set_menu_model(gmenu);

To show the popup menu, use a `Gtk::GestureClick` and connect to its `pressed` signal. In the signal handler, use `Gtk::PopoverMenu`'s `popup()` method. For instance:

    void ExampleWindow::on_label_pressed(int /* n_press */, double x, double y)
    {
      const Gdk::Rectangle rect(x, y, 1, 1);
      m_MenuPopup.set_pointing_to(rect);
      m_MenuPopup.popup();
    }

### Gio::Resource and glib-compile-resources

Applications and libraries often contain binary or textual data that is really part of the application, rather than user data. For instance `Gtk::Builder` `.ui` files, splashscreen images, `Gio::Menu` markup xml, CSS files, icons, etc. These are often shipped as files in `$datadir/appname`, or manually included as literal strings in the code.

The `Gio::Resource` API and the glib-compile-resources program provide a convenient and efficient alternative to this, which has some nice properties. You maintain the files as normal files, so it's easy to edit them, but during the build the files are combined into a binary bundle that is linked into the executable. This means that loading the resource files is efficient (as they are already in memory, shared with other instances) and simple (no need to check for things like I/O errors or locate the files in the filesystem). It also makes it easier to create relocatable applications.

Resource bundles are created by the glib-compile-resources program which takes an xml file that describes the bundle, and a set of files that the xml references. These are combined into a binary resource bundle.

Gio::Resource Reference

An example:

    <?xml version="1.0" encoding="UTF-8"?>
    <gresources>
      <gresource prefix="/toolbar">
        <file preprocess="xml-stripblanks">toolbar.ui</file>
        <file>rain.png</file>
      </gresource>
    </gresources>

This will create a resource bundle with the files

- `/toolbar/toolbar.ui`

- `/toolbar/rain.png`

You can then use glib-compile-resources to compile the xml to a binary bundle that you can load with `Gio::Resource::create_from_file()`. However, it's more common to use the `--generate-source` argument to create a C source file to link directly into your application. E.g.

    $ glib-compile-resources --target=resources.c --generate-source toolbar.gresource.xml

Once a `Gio::Resource` has been created and registered all the data in it can be accessed globally in the process by using API calls like `Gio::Resource::open_stream_from_global_resources()` to stream the data or `Gio::Resource::lookup_data_in_global_resources()` to get a direct pointer to the data. You can also use URIs like `resource:///toolbar/rain.png` with `Gio::File` to access the resource data.

Often you don't need a `Gio::Resource` instance, because resource data can be loaded with methods such as `Gdk::Pixbuf::create_from_resource()`, `Gtk::Builder::add_from_resource()` and `Gtk::Image::set_from_resource()`.

### Příklady

#### Application Menu and Main Menu example

This program contains an application menu, a menubar and a toolbar. Classes are derived from `Gtk::Application` and `Gtk::ApplicationWindow`.

##### App and Main Menu

Source Code

File: `exampleapplication.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEAPPLICATION_H
    #define GTKMM_EXAMPLEAPPLICATION_H

    #include <gtkmm.h>

    class ExampleApplication : public Gtk::Application
    {
    protected:
      ExampleApplication();

    public:
      static Glib::RefPtr<ExampleApplication> create();

    protected:
      //Overrides of default signal handlers:
      void on_startup() override;
      void on_activate() override;

    private:
      void create_window();

      void on_menu_file_new_generic();
      void on_menu_file_quit();
      void on_menu_help_about();

      Glib::RefPtr<Gtk::Builder> m_refBuilder;
    };

    #endif /* GTKMM_EXAMPLEAPPLICATION_H */

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::ApplicationWindow
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_menu_others();

      void on_menu_choices(const Glib::ustring& parameter);
      void on_menu_choices_other(int parameter);
      void on_menu_toggle();

      //Child widgets:
      Gtk::Box m_Box;

      Glib::RefPtr<Gtk::Builder> m_refBuilder;

      //Two sets of choices:
      Glib::RefPtr<Gio::SimpleAction> m_refChoice;
      Glib::RefPtr<Gio::SimpleAction> m_refChoiceOther;

      Glib::RefPtr<Gio::SimpleAction> m_refToggle;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `exampleapplication.cc` (For use with gtkmm 4)

    #include "exampleapplication.h"
    #include "examplewindow.h"
    #include <iostream>

    ExampleApplication::ExampleApplication()
    : Gtk::Application("org.gtkmm.example.main_menu")
    {
      Glib::set_application_name("Main Menu Example");
    }

    Glib::RefPtr<ExampleApplication> ExampleApplication::create()
    {
      return Glib::make_refptr_for_instance<ExampleApplication>(new ExampleApplication());
    }

    void ExampleApplication::on_startup()
    {
      //Call the base class's implementation:
      Gtk::Application::on_startup();

      //Create actions for menus and toolbars.
      //We can use add_action() because Gtk::Application derives from Gio::ActionMap.

      //File|New sub menu:
      add_action("newstandard",
        sigc::mem_fun(*this, &ExampleApplication::on_menu_file_new_generic));

      add_action("newfoo",
        sigc::mem_fun(*this, &ExampleApplication::on_menu_file_new_generic));

      add_action("newgoo",
        sigc::mem_fun(*this, &ExampleApplication::on_menu_file_new_generic));

      //File menu:
      add_action("quit", sigc::mem_fun(*this, &ExampleApplication::on_menu_file_quit));

      //Help menu:
      add_action("about", sigc::mem_fun(*this, &ExampleApplication::on_menu_help_about));

      // Set accelerator keys:
      set_accel_for_action("app.newstandard", "<Primary>n");
      set_accel_for_action("app.quit", "<Primary>q");
      set_accel_for_action("win.copy", "<Primary>c");
      set_accel_for_action("win.paste", "<Primary>v");

      m_refBuilder = Gtk::Builder::create();

      //Layout the actions in a menubar and a menu:
      Glib::ustring ui_info =
        "<interface>"
        "  <!-- menubar -->"
        "  <menu id='menu-example'>"
        "    <submenu>"
        "      <attribute name='label' translatable='yes'>_File</attribute>"
        "      <section>"
        "        <item>"
        "          <attribute name='label' translatable='yes'>New _Standard</attribute>"
        "          <attribute name='action'>app.newstandard</attribute>"
        "          <attribute name='accel'>&lt;Primary&gt;n</attribute>"
        "        </item>"
        "        <item>"
        "          <attribute name='label' translatable='yes'>New _Foo</attribute>"
        "          <attribute name='action'>app.newfoo</attribute>"
        "        </item>"
        "        <item>"
        "          <attribute name='label' translatable='yes'>New _Goo</attribute>"
        "          <attribute name='action'>app.newgoo</attribute>"
        "        </item>"
        "      </section>"
        "      <section>"
        "        <item>"
        "          <attribute name='label' translatable='yes'>_Quit</attribute>"
        "          <attribute name='action'>app.quit</attribute>"
        "          <attribute name='accel'>&lt;Primary&gt;q</attribute>"
        "        </item>"
        "      </section>"
        "    </submenu>"
        "    <submenu>"
        "      <attribute name='label' translatable='yes'>_Edit</attribute>"
        "      <section>"
        "        <item>"
        "          <attribute name='label' translatable='yes'>_Copy</attribute>"
        "          <attribute name='action'>win.copy</attribute>"
        "          <attribute name='accel'>&lt;Primary&gt;c</attribute>"
        "        </item>"
        "        <item>"
        "          <attribute name='label' translatable='yes'>_Paste</attribute>"
        "          <attribute name='action'>win.paste</attribute>"
        "          <attribute name='accel'>&lt;Primary&gt;v</attribute>"
        "        </item>"
        "        <item>"
        "          <attribute name='label' translatable='yes'>_Something</attribute>"
        "          <attribute name='action'>win.something</attribute>"
        "        </item>"
        "      </section>"
        "    </submenu>"
        "    <submenu>"
        "      <attribute name='label' translatable='yes'>_Choices</attribute>"
        "      <section>"
        "        <item>"
        "          <attribute name='label' translatable='yes'>Choice _A</attribute>"
        "          <attribute name='action'>win.choice</attribute>"
        "          <attribute name='target'>a</attribute>"
        "        </item>"
        "        <item>"
        "          <attribute name='label' translatable='yes'>Choice _B</attribute>"
        "          <attribute name='action'>win.choice</attribute>"
        "          <attribute name='target'>b</attribute>"
        "        </item>"
        "      </section>"
        "    </submenu>"
        "    <submenu>"
        "      <attribute name='label' translatable='yes'>_Other Choices</attribute>"
        "      <section>"
        "        <item>"
        "          <attribute name='label' translatable='yes'>Choice 1</attribute>"
        "          <attribute name='action'>win.choiceother</attribute>"
        "          <attribute name='target' type='i'>1</attribute>"
        "        </item>"
        "        <item>"
        "          <attribute name='label' translatable='yes'>Choice 2</attribute>"
        "          <attribute name='action'>win.choiceother</attribute>"
        "          <attribute name='target' type='i'>2</attribute>"
        "        </item>"
        "      </section>"
        "      <section>"
        "        <item>"
        "          <attribute name='label' translatable='yes'>Some Toggle</attribute>"
        "          <attribute name='action'>win.sometoggle</attribute>"
        "        </item>"
        "      </section>"
        "    </submenu>"
        "    <submenu>"
        "      <attribute name='label' translatable='yes'>_Help</attribute>"
        "      <section>"
        "        <item>"
        "          <attribute name='label' translatable='yes'>_About Window</attribute>"
        "          <attribute name='action'>win.about</attribute>"
        "        </item>"
        "        <item>"
        "          <attribute name='label' translatable='yes'>_About App</attribute>"
        "          <attribute name='action'>app.about</attribute>"
        "        </item>"
        "      </section>"
        "    </submenu>"
        "  </menu>"
        "</interface>";

      try
      {
        m_refBuilder->add_from_string(ui_info);
      }
      catch (const Glib::Error& ex)
      {
        std::cerr << "Building menus failed: " << ex.what();
      }

      //Get the menubar and the app menu, and add them to the application:
      auto gmenu = m_refBuilder->get_object<Gio::Menu>("menu-example");
      if (!gmenu)
      {
        g_warning("GMenu not found");
      }
      else
      {
        set_menubar(gmenu);
      }
    }

    void ExampleApplication::on_activate()
    {
      //std::cout << "debug1: " << G_STRFUNC << std::endl;
      // The application has been started, so let's show a window.
      // A real application might want to reuse this window in on_open(),
      // when asked to open a file, if no changes have been made yet.
      create_window();
    }

    void ExampleApplication::create_window()
    {
      auto win = new ExampleWindow();

      //Make sure that the application runs for as long this window is still open:
      add_window(*win);

      //Delete the window when it is hidden.
      //That's enough for this simple example.
      win->signal_hide().connect([win]() { delete win; });

      win->set_show_menubar();
      win->set_visible(true);
    }

    void ExampleApplication::on_menu_file_new_generic()
    {
      std::cout << "A File|New menu item was selected." << std::endl;
    }

    void ExampleApplication::on_menu_file_quit()
    {
      std::cout << G_STRFUNC << std::endl;
      quit(); // Not really necessary, when Gtk::Widget::set_visible(false) is called.

      // Gio::Application::quit() will make Gio::Application::run() return,
      // but it's a crude way of ending the program. The window is not removed
      // from the application. Neither the window's nor the application's
      // destructors will be called, because there will be remaining reference
      // counts in both of them. If we want the destructors to be called, we
      // must remove the window from the application. One way of doing this
      // is to hide the window.
      std::vector<Gtk::Window*> windows = get_windows();
      if (windows.size() > 0)
        windows[0]->set_visible(false); // In this simple case, we know there is only one window.
    }

    void ExampleApplication::on_menu_help_about()
    {
      std::cout << "Help|About App was selected." << std::endl;
    }

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : Gtk::ApplicationWindow(),
      m_Box(Gtk::Orientation::VERTICAL)
    {
      set_title("Main menu example");
      set_default_size(300, 100);

      // ExampleApplication displays the menubar. Other stuff, such as a toolbar,
      // is put into the box.
      set_child(m_Box);

      // Create actions for menus and toolbars.
      // We can use add_action() because Gtk::ApplicationWindow derives from Gio::ActionMap.
      // This Action Map uses a "win." prefix for the actions.
      // Therefore, for instance, "win.copy", is used in ExampleApplication::on_startup()
      // to layout the menu.

      //Edit menu:
      add_action("copy", sigc::mem_fun(*this, &ExampleWindow::on_menu_others));
      add_action("paste", sigc::mem_fun(*this, &ExampleWindow::on_menu_others));
      add_action("something", sigc::mem_fun(*this, &ExampleWindow::on_menu_others));

      //Choices menus, to demonstrate Radio items,
      //using our convenience methods for string and int radio values:
      m_refChoice = add_action_radio_string("choice",
        sigc::mem_fun(*this, &ExampleWindow::on_menu_choices), "a");

      m_refChoiceOther = add_action_radio_integer("choiceother",
        sigc::mem_fun(*this, &ExampleWindow::on_menu_choices_other), 1);

      m_refToggle = add_action_bool("sometoggle",
        sigc::mem_fun(*this, &ExampleWindow::on_menu_toggle), false);

      //Help menu:
      add_action("about", sigc::mem_fun(*this, &ExampleWindow::on_menu_others));

      //Create the toolbar and add it to a container widget:

      m_refBuilder = Gtk::Builder::create();

      Glib::ustring ui_info =
        "<!-- Generated with glade 3.18.3 and then changed manually -->"
        "<interface>"
        "  <object class='GtkBox' id='toolbar'>"
        "    <property name='can_focus'>False</property>"
        "    <child>"
        "      <object class='GtkButton' id='toolbutton_new'>"
        "        <property name='can_focus'>False</property>"
        "        <property name='tooltip_text' translatable='yes'>New Standard</property>"
        "        <property name='action_name'>app.newstandard</property>"
        "        <property name='icon_name'>document-new</property>"
        "        <property name='hexpand'>False</property>"
        "        <property name='vexpand'>False</property>"
        "      </object>"
        "    </child>"
        "    <child>"
        "      <object class='GtkButton' id='toolbutton_quit'>"
        "        <property name='can_focus'>False</property>"
        "        <property name='tooltip_text' translatable='yes'>Quit</property>"
        "        <property name='action_name'>app.quit</property>"
        "        <property name='icon_name'>application-exit</property>"
        "        <property name='hexpand'>False</property>"
        "        <property name='vexpand'>False</property>"
        "      </object>"
        "    </child>"
        "  </object>"
        "</interface>";

      try
      {
        m_refBuilder->add_from_string(ui_info);
      }
      catch (const Glib::Error& ex)
      {
        std::cerr << "Building toolbar failed: " <<  ex.what();
      }

      auto toolbar = m_refBuilder->get_widget<Gtk::Box>("toolbar");
      if (!toolbar)
        g_warning("toolbar not found");
      else
        m_Box.append(*toolbar);
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_menu_others()
    {
      std::cout << "A menu item was selected." << std::endl;
    }

    void ExampleWindow::on_menu_choices(const Glib::ustring& parameter)
    {
      //The radio action's state does not change automatically:
      m_refChoice->change_state(parameter);

      Glib::ustring message;
      if (parameter == "a")
        message = "Choice a was selected.";
      else
        message = "Choice b was selected.";

      std::cout << message << std::endl;
    }

    void ExampleWindow::on_menu_choices_other(int parameter)
    {
      //The radio action's state does not change automatically:
      m_refChoiceOther->change_state(parameter);

      Glib::ustring message;
      if (parameter == 1)
        message = "Choice 1 was selected.";
      else
        message = "Choice 2 was selected.";

      std::cout << message << std::endl;
    }

    void ExampleWindow::on_menu_toggle()
    {
      bool active = false;
      m_refToggle->get_state(active);

      //The toggle action's state does not change automatically:
      active = !active;
      m_refToggle->change_state(active);

      Glib::ustring message;
      if (active)
        message = "Toggle is active.";
      else
        message = "Toggle is not active.";

      std::cout << message << std::endl;
    }

File: `main.cc` (For use with gtkmm 4)

    #include "exampleapplication.h"

    int main(int argc, char* argv[])
    {
      auto application = ExampleApplication::create();

      // Start the application, showing the initial window,
      // and opening extra windows for any files that it is asked to open,
      // for instance as a command-line parameter.
      // run() will return when the last window has been closed by the user.
      const int status = application->run(argc, argv);
      return status;
    }

#### Příklad hlavní nabídky

This program contains a menubar and a toolbar. A class is derived from `Gtk::Window`.

##### Hlavní nabídka

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow(const Glib::RefPtr<Gtk::Application>& app);
      virtual ~ExampleWindow();

    private:
      //Signal handlers:
      //void on_action_file_new();
      void on_action_file_quit();
      void on_action_others();
      void on_action_toggle();

      //Child widgets:
      Gtk::Box m_Box;

      Glib::RefPtr<Gtk::Builder> m_refBuilder;
      Glib::RefPtr<Gio::SimpleActionGroup> m_refActionGroup;
      Glib::RefPtr<Gio::SimpleAction> m_refActionRain;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm.h>
    #include <iostream>

    ExampleWindow::ExampleWindow(const Glib::RefPtr<Gtk::Application>& app)
    : m_Box(Gtk::Orientation::VERTICAL)
    {
      set_title("main_menu example");
      set_default_size(200, 200);

      set_child(m_Box); //We can put a MenuBar at the top of the box and other stuff below it.

      //Define the actions:
      m_refActionGroup = Gio::SimpleActionGroup::create();

      // There are several ways of calling a function that takes a sigc::slot.
      // If the slot function is very short, it might be easy to skip the on_xxx()
      // method and put its contents directly in a lambda expression.
      m_refActionGroup->add_action("new",
        [] { std::cout << "A File|New menu item was selected.\n"; /* on_action_file_new() */});
      // With sigc::mem_fun() or (for non-member functions and static member functions)
      // sigc::ptr_fun(). The only way before C++11 introduced lambda expressions.
      m_refActionGroup->add_action("open",
        sigc::mem_fun(*this, &ExampleWindow::on_action_others) );

      // With a lambda expression. Does not disconnect automatically when ExampleWindow
      // is deleted, like sigc::mem_fun() does.
      m_refActionRain = m_refActionGroup->add_action_bool("rain",
        [this] { on_action_toggle(); }, false);

      m_refActionGroup->add_action("quit",
        sigc::mem_fun(*this, &ExampleWindow::on_action_file_quit) );

      // With a lambda expression and sigc::track_obj() or sigc::track_object().
      // Disconnects automatically like sigc::mem_fun().
    #if SIGCXX_MINOR_VERSION >= 4
      m_refActionGroup->add_action("cut",
        sigc::track_object([this] { on_action_others(); }, *this));
    #else
      m_refActionGroup->add_action("cut",
        sigc::track_obj([this] { on_action_others(); }, *this));
    #endif
      m_refActionGroup->add_action("copy",
        sigc::mem_fun(*this, &ExampleWindow::on_action_others) );
      m_refActionGroup->add_action("paste",
        sigc::mem_fun(*this, &ExampleWindow::on_action_others) );

      insert_action_group("example", m_refActionGroup);

      //Define how the actions are presented in the menus and toolbars:
      m_refBuilder = Gtk::Builder::create();

      //Layout the actions in a menubar and toolbar:
      const Glib::ustring ui_info =
        "<interface>"
        "  <menu id='menubar'>"
        "    <submenu>"
        "      <attribute name='label' translatable='yes'>_File</attribute>"
        "      <section>"
        "        <item>"
        "          <attribute name='label' translatable='yes'>_New</attribute>"
        "          <attribute name='action'>example.new</attribute>"
        "        </item>"
        "        <item>"
        "          <attribute name='label' translatable='yes'>_Open</attribute>"
        "          <attribute name='action'>example.open</attribute>"
        "        </item>"
        "      </section>"
        "      <section>"
        "        <item>"
        "          <attribute name='label' translatable='yes'>Rain</attribute>"
        "          <attribute name='action'>example.rain</attribute>"
        "        </item>"
        "      </section>"
        "      <section>"
        "        <item>"
        "          <attribute name='label' translatable='yes'>_Quit</attribute>"
        "          <attribute name='action'>example.quit</attribute>"
        "        </item>"
        "      </section>"
        "    </submenu>"
        "    <submenu>"
        "      <attribute name='label' translatable='yes'>_Edit</attribute>"
        "      <item>"
        "        <attribute name='label' translatable='yes'>_Cut</attribute>"
        "        <attribute name='action'>example.cut</attribute>"
        "      </item>"
        "      <item>"
        "        <attribute name='label' translatable='yes'>_Copy</attribute>"
        "        <attribute name='action'>example.copy</attribute>"
        "      </item>"
        "      <item>"
        "        <attribute name='label' translatable='yes'>_Paste</attribute>"
        "        <attribute name='action'>example.paste</attribute>"
        "      </item>"
        "    </submenu>"
        "  </menu>"
        "</interface>";

      // Set accelerator keys:
      app->set_accel_for_action("example.new", "<Primary>n");
      app->set_accel_for_action("example.open", "<Primary>o");
      app->set_accel_for_action("example.quit", "<Primary>q");
      app->set_accel_for_action("example.cut", "<Primary>x");
      app->set_accel_for_action("example.copy", "<Primary>c");
      app->set_accel_for_action("example.paste", "<Primary>v");

      try
      {
        m_refBuilder->add_from_string(ui_info);
        m_refBuilder->add_from_resource("/toolbar/toolbar.ui");
      }
      catch(const Glib::Error& ex)
      {
        std::cerr << "Building menus and toolbar failed: " <<  ex.what();
      }

      //Get the menubar:
      auto gmenu = m_refBuilder->get_object<Gio::Menu>("menubar");
      if (!gmenu)
        g_warning("GMenu not found");
      else
      {
        auto pMenuBar = Gtk::make_managed<Gtk::PopoverMenuBar>(gmenu);

        //Add the PopoverMenuBar to the window:
        m_Box.append(*pMenuBar);
      }

      //Get the toolbar and add it to a container widget:
      auto toolbar = m_refBuilder->get_widget<Gtk::Box>("toolbar");
      if (!toolbar)
        g_warning("toolbar not found");
      else
        m_Box.append(*toolbar);
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_action_file_quit()
    {
      set_visible(false); //Closes the main window to stop the app->make_window_and_run().
    }

    //void ExampleWindow::on_action_file_new()
    //{
    //   std::cout << "A File|New menu item was selected." << std::endl;
    //}

    void ExampleWindow::on_action_others()
    {
      std::cout << "A menu item was selected." << std::endl;
    }

    void ExampleWindow::on_action_toggle()
    {
      std::cout << "The toggle menu item was selected." << std::endl;

      bool active = false;
      m_refActionRain->get_state(active);

      //The toggle action's state does not change automatically:
      active = !active;
      m_refActionRain->change_state(active);

      Glib::ustring message;
      if(active)
        message = "Toggle is active.";
      else
        message = "Toggle is not active";

      std::cout << message << std::endl;
    }

File: `main.cc` (For use with gtkmm 4)

    #include <gtkmm.h>
    #include "examplewindow.h"

    int main(int argc, char* argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv, app);
    }

File: `toolbar.gresource.xml` (For use with gtkmm 4)

    <?xml version="1.0" encoding="UTF-8"?>
    <gresources>
      <gresource prefix="/toolbar">
        <file preprocess="xml-stripblanks">toolbar.ui</file>
        <file>rain.png</file>
      </gresource>
    </gresources>

#### Příklad vyskakovací nabídky

##### Vyskakovací nabídka

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    #include <memory>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow(const Glib::RefPtr<Gtk::Application>& app);
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_label_pressed(int n_press, double x, double y);

      void on_menu_file_popup_generic();

      //Child widgets:
      Gtk::Box m_Box;
      Gtk::Label m_Label;
      Gtk::PopoverMenu m_MenuPopup;

      Glib::RefPtr<Gtk::Builder> m_refBuilder;
      Glib::RefPtr<Gtk::GestureClick> m_refGesture;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow(const Glib::RefPtr<Gtk::Application>& app)
    : m_Box(Gtk::Orientation::VERTICAL),
      m_Label("Right-click to see the popup menu.")
    {
      set_title("popup example");
      set_default_size(200, 200);

      set_child(m_Box);

      // Catch button_press events:
      m_Box.append(m_Label);
      m_Label.set_expand();
      m_refGesture = Gtk::GestureClick::create();
      m_refGesture->set_button(GDK_BUTTON_SECONDARY);
      m_refGesture->signal_pressed().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_label_pressed));
      m_Label.add_controller(m_refGesture);

      //Create actions:
      auto refActionGroup = Gio::SimpleActionGroup::create();

      //File|New sub menu:
      //These menu actions would normally already exist for a main menu, because a
      //context menu should not normally contain menu items that are only available
      //via a context menu.

      refActionGroup->add_action("edit",
        sigc::mem_fun(*this, &ExampleWindow::on_menu_file_popup_generic));

      refActionGroup->add_action("process",
        sigc::mem_fun(*this, &ExampleWindow::on_menu_file_popup_generic));

      refActionGroup->add_action("remove",
        sigc::mem_fun(*this, &ExampleWindow::on_menu_file_popup_generic));

      insert_action_group("examplepopup", refActionGroup);

      // Set accelerator keys:
      app->set_accel_for_action("examplepopup.edit", "<Primary>e");
      app->set_accel_for_action("examplepopup.process", "<Primary>p");
      app->set_accel_for_action("examplepopup.remove", "<Primary>r");

      m_refBuilder = Gtk::Builder::create();

      //Layout the actions in a menubar and toolbar:
      Glib::ustring ui_info =
        "<interface>"
        "  <menu id='menu-examplepopup'>"
        "    <section>"
        "      <item>"
        "        <attribute name='label' translatable='yes'>Edit</attribute>"
        "        <attribute name='action'>examplepopup.edit</attribute>"
        "      </item>"
        "      <item>"
        "        <attribute name='label' translatable='yes'>Process</attribute>"
        "        <attribute name='action'>examplepopup.process</attribute>"
        "      </item>"
        "      <item>"
        "        <attribute name='label' translatable='yes'>Remove</attribute>"
        "        <attribute name='action'>examplepopup.remove</attribute>"
        "      </item>"
        "    </section>"
        "  </menu>"
        "</interface>";

      try
      {
        m_refBuilder->add_from_string(ui_info);
      }
      catch(const Glib::Error& ex)
      {
        std::cerr << "building menus failed: " <<  ex.what();
      }

      //Get the menu:
      auto gmenu = m_refBuilder->get_object<Gio::Menu>("menu-examplepopup");
      if(!gmenu)
        g_warning("GMenu not found");

      m_MenuPopup.set_parent(m_Label);
      m_MenuPopup.set_menu_model(gmenu);
      m_MenuPopup.set_has_arrow(false);
    }

    ExampleWindow::~ExampleWindow()
    {
      m_MenuPopup.unparent();
    }

    void ExampleWindow::on_menu_file_popup_generic()
    {
       std::cout << "A popup menu item was selected." << std::endl;
    }

    void ExampleWindow::on_label_pressed(int /* n_press */, double x, double y)
    {
      const Gdk::Rectangle rect(x, y, 1, 1);
      m_MenuPopup.set_pointing_to(rect);
      m_MenuPopup.popup();
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv, app);
    }

## Přizpůsobení (Adjustment)

gtkmm má řadu widgetů, které mohou vizuálně měnit nějakou hodnotu pomocí myši nebo kalávesnice, např. widgety `Range` (popsané v kapitole Widgety Range). Existuje také několik widgetů, které zobrazují z velké oblasti jen nějakou zvolenou část, např. widget `Viewport`. Tyto widgety mají objekty `Gtk::Adjustment`, které jsou vyjádřením této části jejich API.

Aby aplikace mohly reagovat na změny, například když uživatel posune posuvníkem, má `Gtk::Adjustment` signál `value_changed`. Vy pak můžete použít metodu `get_value()` ke zjištění nové hodnoty.

### Vytváření objektů Adjustment

`Gtk::Adjustment` se vytváří jeho metodou `create()`, která vypadá takto:

    Glib::RefPtr<Gtk::Adjustment> Gtk::Adjustment::create(
      double value,
      double lower,
      double upper,
      double step_increment = 1,
      double page_increment = 10,
      double page_size = 0);

Argument `value` je počáteční hodnota přizpůsobení, obvykle odpovídající nejvyšší nebo nejlevější pozici ve widgetu. Argumenty `lower` a `upper` určují možný rozsah hodnot, kterých se má přizpůsobení držet. Argument `step_increment` určuje menší ze dvou kroků, po kterých uživatel může hodnotu měnit, zatímco `page_increment` určuje tu větší. Argument `page_size` obvykle nějak koresponduje s viditelnou oblastí pohybovaného widgetu. Argument `upper` se používá k reprezentaci nejnižší nebo nejpravější souřadnice v pohybovaném widgetu.

### Snadné použití objektů Adjustment

Widgety přizpůsobení lze zhruba rozdělit na ty, které používají a vyžadují pro hodnoty konkrétní jednotky, a ty, které pracují s libovolnými čísly.

Skupina, která zachází s hodnotami jako s libovolnými čísly, zahrnuje widgety `Range` (`Scrollbar` a `Scale`), widget `ScaleButton` a widget `SpinButton`. Tyto widgety typicky „přizpůsobují“ přímo podle uživatelova ovládání myší nebo klávesnicí. S hodnotami přizpůsobení `lower` a `upper` zachází jako s rozmezími, v rámci kterých uživatel může měnit `value` v přizpůsobení. Standardně bude měnit jen údaj `value`.

Do druhé skupiny patří widget `Viewport` a widget `ScrolledWindow`. Všechny tyto widgety používají pro svá přizpůsobení údaje v pixelech. Typicky přizpůsobují nepřímo přes posuvníky. Zatímco všechny widgety, které používají přizpůsobení, mohou buď vytvořit svá vlastní přizpůsobení, nebo použít ta, která dodáte, u této konkrétní skupiny widgetů bude obecně chtít nechat widgety, ať si vytvoří svá vlastní přizpůsobení.

Pokud sdílíte objekt přizpůsobení mezi widgety `Scrollbar` a `TextView`, manipulace s posuvníkem bude automaticky ovlivňovat widget `TextView`. Natavit to můžete takto:

    // creates its own adjustments
    Gtk::TextView textview;
    // uses the newly-created adjustment for the scrollbar as well
    Gtk::Scrollbar vscrollbar(textview.get_vadjustment(), Gtk::Orientation::VERTICAL);

### Objekty Adjustment zevnitř

Bezva, řeknete že je to pěkné, ale co když si chcete vytvořit vlastní obsluhu, abyste reagovali na uživatelovy změny hodnoty ve widgetu `Range` nebo `SpinButton`. Pro přístup k hondote z `Gtk::Adjustment` můžete použít metody `get_value()` a `set_value()`:

Jak již byl zmíněno, `Gtk::Adjustment` může vysílat signály. To je samozřejmě ta finta, jak se automaticky dějí aktualizace, když sdílíte objekt `Adjustment` mezi widgetem `Scrollbar` a jiným přizpůsobitelným widgetem. Všechny přizpůsobitelné widgety mohou napojit obsluhy signálů na svůj signál `value_changed`, stejně jako to může váš program.

Takže, když například máte widget `Scale` a chcete změnit otočení obrázku, kdykoliv se změní jeho hodnota, vytvořili byste obsluhu signálu nějak takto:

    void cb_rotate_picture(MyPicture* picture)
    {
      picture->set_rotation(adj->get_value());
    ...

a napojili byste jej na přizpůsobení widgetu `Scale` nějak takto:

    adj->signal_value_changed().connect(sigc::bind<MyPicture*>(sigc::mem_fun(*this,
        &cb_rotate_picture), picture));

Co když widget změní nastavení polí `upper` nebo `lower` ve svém objektu `Adjustment`, třeba když uživatel přidá další text do textového widgetu? V tomto případě vyšle signál `changed`.

Widgety `Range` typicky napojují obsluhu na tento signál, který mění jejich vzhled s ohledem na změny – například velikost táhla v posuvníku roste, nebo se zmenšuje, v opačném poměru k rozdílu mezi hodnotami `lower` a `upper` jeho objektu `Adjustment`.

Pravděpodobně nebudete muset pokaždé napojit obsluhu k tomuto signálu, vyjma případů, kdy používáte nový typ widgetu `Range`.

    adjustment->signal_changed();

## Dialogová okna

`Gtk::Dialog` and the classes derived from it, are deprecated since gtkmm 4.10. They can still be used in gtkmm4 applications, provided GTKMM_DISABLE_DEPRECATED and GDKMM_DISABLE_DEPRECATED are not defined. Some of the dialog classes are replaced by classes that are available since gtkmm 4.10.

The examples in this chapter use classes that are available since gtkmm 4.10. Similar examples with the deprecated classes are available in the gtkmm-4-0 branch in the git repository.

Dialogs are used as secondary windows, to provide specific information or to ask questions. `Gtk::Dialog` windows contain a few pre-packed widgets to ensure consistency, and a `response` signal which is emitted when the user dismisses the dialog.

Od třídy `Dialog` je odvozeno několik dalších tříd, které by se vám mohly hodit. `Gtk::MessageDialog` se používá pro úplně nejjednodušší oznámení. Časem ale můžete potřebovat odvodit svá vlastní dialogová okna, abyste mohli poskytnout ucelenější funkcionalitu.

Když chcete do vlastního dialogového okna zabalit widgety, měli byste je balit do instance `Gtk::Box` dostupné přes `get_content_area()`. Když chcete jen přidat tlačítko do dolní části dialogového okna, můžete použít metodu `add_button()`.

The `response` signal handler receives an `int`. This may be a value from the Gtk::ResponseType if the user closed the dialog by clicking a standard button, or it could be the custom response value that you specified when using `add_button()`.

To show the dialog, call `set_visible(true)`. If the same dialog instance will be shown several times, you must also call `set_hide_on_close()`, or else the dialog will be destroyed when it's closed. Connect to the `response` signal, if you want to know which button was pressed. The `response` signal handler is also where you should hide the dialog.

Reference

### AlertDialog and MessageDialog

`MessageDialog` (deprecated since gtkmm 4.10) and `AlertDialog` (available since gtkmm 4.10) are convenience classes, used to create simple, standard message dialogs, with a message and buttons for user response.

AlertDialog Reference

MessageDialog Reference

#### Příklad

##### AlertDialog

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      ~ExampleWindow() override;

    protected:
      //Signal handlers:
      void on_button_info_clicked();
      void on_button_question_clicked();
      void on_question_dialog_finish(const Glib::RefPtr<Gio::AsyncResult>& result);

      //Child widgets:
      Gtk::Box m_ButtonBox;
      Gtk::Button m_Button_Info;
      Gtk::Button m_Button_Question;

      Glib::RefPtr<Gtk::AlertDialog> m_pDialog;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/messagedialog.h>
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_ButtonBox(Gtk::Orientation::VERTICAL),
      m_Button_Info("Show Info AlertDialog"),
      m_Button_Question("Show Question AlertDialog")
    {
      set_title("Gtk::AlertDialog example");

      set_child(m_ButtonBox);

      m_ButtonBox.append(m_Button_Info);
      m_Button_Info.set_expand(true);
      m_Button_Info.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_info_clicked) );

      m_ButtonBox.append(m_Button_Question);
      m_Button_Question.set_expand(true);
      m_Button_Question.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_question_clicked) );
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_info_clicked()
    {
      if (!m_pDialog)
        m_pDialog = Gtk::AlertDialog::create();
      else
      {
        // Reset values that may have been set by on_button_question_clicked().
        m_pDialog->set_buttons({});
        m_pDialog->set_default_button(-1);
        m_pDialog->set_cancel_button(-1);
      }

      m_pDialog->set_message("This is an INFO AlertDialog.");
      m_pDialog->set_detail("And this is the secondary text that explains things.");
      m_pDialog->show(*this);
    }

    void ExampleWindow::on_button_question_clicked()
    {
      if (!m_pDialog)
        m_pDialog = Gtk::AlertDialog::create();
      m_pDialog->set_message("This is a QUESTION AlertDialog.");
      m_pDialog->set_detail("And this is the secondary text that explains things.");
      m_pDialog->set_buttons({"Cancel", "Retry", "OK"});
      m_pDialog->set_default_button(2); // OK button or Return key
      m_pDialog->set_cancel_button(0); // Cancel button or Escape key
      m_pDialog->choose(*this,
        sigc::mem_fun(*this, &ExampleWindow::on_question_dialog_finish));
    }

    void ExampleWindow::on_question_dialog_finish(const Glib::RefPtr<Gio::AsyncResult>& result)
    {
      try
      {
        const int response_id = m_pDialog->choose_finish(result);
        switch (response_id)
        {
        case 0:
          std::cout << "Cancel clicked." << std::endl;
          break;
        case 1:
          std::cout << "Retry clicked." << std::endl;
          break;
        case 2:
          std::cout << "OK clicked." << std::endl;
          break;
        default:
          std::cout << "Unexpected response: " << response_id << std::endl;
          break;
        }
      }
      catch (const Gtk::DialogError& err)
      {
        // Can be thrown by m_pDialog->choose_finish(result).
        std::cout << "DialogError, " << err.what() << std::endl;
      }
      catch (const Glib::Error& err)
      {
        std::cout << "Unexpected exception. " << err.what() << std::endl;
      }
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

### FileDialog and FileChooserDialog

The `FileChooserDialog` (deprecated since gtkmm 4.10) and `FileDialog` (available since gtkmm 4.10) are suitable for use with "Open" or "Save" menu items.

Most of the useful member methods for `FileChooserDialog` are actually in the `Gtk::FileChooser` base class.

FileDialog Reference

FileChooserDialog Reference

#### Příklad

##### FileDialog

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      ~ExampleWindow() override;

    protected:
      //Signal handlers:
      void on_button_file_clicked();
      void on_button_folder_clicked();
      void on_file_dialog_finish(const Glib::RefPtr<Gio::AsyncResult>& result,
        const Glib::RefPtr<Gtk::FileDialog>& dialog);
      void on_folder_dialog_finish(const Glib::RefPtr<Gio::AsyncResult>& result,
        const Glib::RefPtr<Gtk::FileDialog>& dialog);

      //Child widgets:
      Gtk::Box m_ButtonBox;
      Gtk::Button m_Button_File;
      Gtk::Button m_Button_Folder;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_ButtonBox(Gtk::Orientation::VERTICAL),
      m_Button_File("Choose File"),
      m_Button_Folder("Choose Folder")
    {
      set_title("Gtk::FileDialog example");

      set_child(m_ButtonBox);

      m_ButtonBox.append(m_Button_File);
      m_Button_File.set_expand(true);
      m_Button_File.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_file_clicked) );

      m_ButtonBox.append(m_Button_Folder);
      m_Button_Folder.set_expand(true);
      m_Button_Folder.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_folder_clicked) );
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_file_clicked()
    {
      auto dialog = Gtk::FileDialog::create();

      // Add filters, so that only certain file types can be selected:
      auto filters = Gio::ListStore<Gtk::FileFilter>::create();

      auto filter_text = Gtk::FileFilter::create();
      filter_text->set_name("Text files");
      filter_text->add_mime_type("text/plain");
      filters->append(filter_text);

      auto filter_cpp = Gtk::FileFilter::create();
      filter_cpp->set_name("C/C++ files");
      filter_cpp->add_mime_type("text/x-c");
      filter_cpp->add_mime_type("text/x-c++");
      filter_cpp->add_mime_type("text/x-c-header");
      filters->append(filter_cpp);

      auto filter_any = Gtk::FileFilter::create();
      filter_any->set_name("Any files");
      filter_any->add_pattern("*");
      filters->append(filter_any);

      dialog->set_filters(filters);

      // Show the dialog and wait for a user response:
      dialog->open(sigc::bind(sigc::mem_fun(
        *this, &ExampleWindow::on_file_dialog_finish), dialog));
    }

    void ExampleWindow::on_file_dialog_finish(const Glib::RefPtr<Gio::AsyncResult>& result,
      const Glib::RefPtr<Gtk::FileDialog>& dialog)
    {
      // Handle the response:
      try
      {
        auto file = dialog->open_finish(result);

        // Notice that this is a std::string, not a Glib::ustring.
        auto filename = file->get_path();
        std::cout << "File selected: " <<  filename << std::endl;
      }
      catch (const Gtk::DialogError& err)
      {
        // Can be thrown by dialog->open_finish(result).
        std::cout << "No file selected. " << err.what() << std::endl;
      }
      catch (const Glib::Error& err)
      {
        std::cout << "Unexpected exception. " << err.what() << std::endl;
      }
    }

    void ExampleWindow::on_button_folder_clicked()
    {
      auto dialog = Gtk::FileDialog::create();

      // Show the dialog and wait for a user response:
      dialog->select_folder(sigc::bind(sigc::mem_fun(
        *this, &ExampleWindow::on_folder_dialog_finish), dialog));
    }

    void ExampleWindow::on_folder_dialog_finish(const Glib::RefPtr<Gio::AsyncResult>& result,
      const Glib::RefPtr<Gtk::FileDialog>& dialog)
    {
      // Handle the response:
      try
      {
        auto folder = dialog->select_folder_finish(result);
        std::cout << "Folder selected: " << folder->get_path() << std::endl;
      }
      catch (const Gtk::DialogError& err)
      {
        // Can be thrown by dialog->select_folder_finish(result).
        std::cout << "No folder selected. " << err.what() << std::endl;
      }
      catch (const Glib::Error& err)
      {
        std::cout << "Unexpected exception. " << err.what() << std::endl;
      }
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

### ColorDialog and ColorChooserDialog

The `ColorChooserDialog` (deprecated since gtkmm 4.10) and `ColorDialog` (available since gtkmm 4.10) allow the user to choose a color. The `ColorButton` (deprecated since gtkmm 4.10) and `ColorDialogButton` (available since gtkmm 4.10) open a color selection dialog when it is clicked.

ColorDialog Reference

ColorChooserDialog Reference

#### Příklad

##### ColorDialog

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      ~ExampleWindow() override;

    protected:
      //Signal handlers:
      void on_color_button_color_set();
      void on_button_dialog_clicked();
      void on_dialog_finish(const Glib::RefPtr<Gio::AsyncResult>& result);

      //Draw function:
      void on_drawing_area_draw(const Cairo::RefPtr<Cairo::Context>& cr, int width, int height);

      //Child widgets:
      Gtk::Box m_VBox;
      Gtk::ColorDialogButton m_ColorDialogButton;
      Gtk::Button m_Button_Dialog;
      Gtk::DrawingArea m_DrawingArea; //To show the color.

      Glib::RefPtr<Gtk::ColorDialog> m_pDialog;
      Gdk::RGBA m_Color;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::Orientation::VERTICAL, 5),
      m_Button_Dialog("Choose Color")
    {
      set_title("Gtk::ColorDialog example");
      set_default_size(200, 200);

      m_pDialog = Gtk::ColorDialog::create();
      m_ColorDialogButton.set_dialog(m_pDialog);

      set_child(m_VBox);

      m_VBox.append(m_ColorDialogButton);
      m_ColorDialogButton.property_rgba().signal_changed().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_color_button_color_set));

      m_VBox.append(m_Button_Dialog);
      m_Button_Dialog.signal_clicked().connect(sigc::mem_fun(*this,
        &ExampleWindow::on_button_dialog_clicked) );

      //Set start color:
      m_Color.set_red(0.0);
      m_Color.set_green(0.0);
      m_Color.set_blue(1.0);
      m_Color.set_alpha(1.0); //opaque
      m_ColorDialogButton.set_rgba(m_Color);

      m_VBox.append(m_DrawingArea);
      m_DrawingArea.set_expand(true);
      m_DrawingArea.set_draw_func(sigc::mem_fun(*this, &ExampleWindow::on_drawing_area_draw));
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_color_button_color_set()
    {
      //Store the chosen color:
      m_Color = m_ColorDialogButton.get_rgba();
      m_DrawingArea.queue_draw();
    }

    void ExampleWindow::on_button_dialog_clicked()
    {
      m_pDialog->choose_rgba(*this, m_Color,
        sigc::mem_fun(*this, &ExampleWindow::on_dialog_finish));
    }

    void ExampleWindow::on_dialog_finish(const Glib::RefPtr<Gio::AsyncResult>& result)
    {
      try
      {
        // If this call changes the color, it will trigger a call to
        // on_color_button_color_set().
        m_ColorDialogButton.set_rgba(m_pDialog->choose_rgba_finish(result));

        // This is what you should do if m_ColorDialogButton and
        // on_color_button_color_set() did not exist:
        //m_Color = m_pDialog->choose_rgba_finish(result);
        //m_DrawingArea.queue_draw();
      }
      catch (const Gtk::DialogError& err)
      {
        // Can be thrown by m_pDialog->choose_rgba_finish(result).
        std::cout << "No color selected. " << err.what() << std::endl;
      }
      catch (const Glib::Error& err)
      {
        std::cout << "Unexpected exception. " << err.what() << std::endl;
      }
    }

    void ExampleWindow::on_drawing_area_draw(const Cairo::RefPtr<Cairo::Context>& cr, int, int)
    {
      Gdk::Cairo::set_source_rgba(cr, m_Color);
      cr->paint();
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

### FontDialog and FontChooserDialog

The `FontChooserDialog` (deprecated since gtkmm 4.10) and `FontDialog` (available since gtkmm 4.10) allow the user to choose a font. The `FontButton` (deprecated since gtkmm 4.10) and `FontDialogButton` (available since gtkmm 4.10) open a font chooser dialog when it is clicked.

FontDialog Reference

FontChooserDialog Reference

#### Příklad

##### FontDialog

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      ~ExampleWindow() override;

    protected:
      //Signal handlers:
      void on_font_button_font_set();
      void on_button_dialog_clicked();
      void on_dialog_finish(const Glib::RefPtr<Gio::AsyncResult>& result);

      //Child widgets:
      Gtk::Box m_ButtonBox;
      Gtk::FontDialogButton m_FontDialogButton;
      Gtk::Button m_Button_Dialog;

      Glib::RefPtr<Gtk::FontDialog> m_pDialog;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_ButtonBox(Gtk::Orientation::VERTICAL),
      m_Button_Dialog("Choose Font")
    {
      set_title("Gtk::FontDialog example");

      set_child(m_ButtonBox);

      m_pDialog = Gtk::FontDialog::create();

      m_ButtonBox.append(m_FontDialogButton);
      m_FontDialogButton.set_dialog(m_pDialog);
      m_FontDialogButton.set_font_desc(Pango::FontDescription("Sans 10"));
      m_FontDialogButton.set_expand(true);
      m_FontDialogButton.set_use_font(true);
      m_FontDialogButton.set_use_size(true);
      m_FontDialogButton.property_font_desc().signal_changed().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_font_button_font_set));

      m_ButtonBox.append(m_Button_Dialog);
      m_Button_Dialog.set_expand(true);
      m_Button_Dialog.signal_clicked().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_button_dialog_clicked));
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_font_button_font_set()
    {
      auto font_name = m_FontDialogButton.get_font_desc().to_string();
      std::cout << "Font chosen: " << font_name << std::endl;
    }

    void ExampleWindow::on_button_dialog_clicked()
    {
      // Get the previously selected font description from the FontDialogButton.
      m_pDialog->choose_font(*this,
        sigc::mem_fun(*this, &ExampleWindow::on_dialog_finish),
        m_FontDialogButton.get_font_desc());
    }

    void ExampleWindow::on_dialog_finish(const Glib::RefPtr<Gio::AsyncResult>& result)
    {
      try
      {
        // If this call changes the font, it will trigger a call to
        // on_font_button_font_set().
        m_FontDialogButton.set_font_desc(m_pDialog->choose_font_finish(result));
      }
      catch (const Gtk::DialogError& err)
      {
        // Can be thrown by m_pDialog->choose_font_finish(result).
        std::cout << "No font selected. " << err.what() << std::endl;
      }
      catch (const Glib::Error& err)
      {
        std::cout << "Unexpected exception. " << err.what() << std::endl;
      }
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

### Nemodální dialogové okno s informacemi o aplikaci (AboutDialog)

`AboutDialog` nabízí jednoduchý způsob pro zobrazení informací o programu, jako je jeho logo, název, copyright, webové stránky a licence.

Většina dialogových oken v této kapitole je modálních, což znamená, že po dobu co jsou zobrazená, zmrazí zbytek aplikace. Je možné vytvářet i nemodální dialogová okna, která ostatní okna v aplikaci nezmrazí. Následující příklad ukazuje nemodální `AboutDialog`. Není to ale druh dialogového okna, které byste běžně dělali jako nemodální, ale nemodální dialogová okna se hodí v různých jiných situacích. Např. dialogové okno pro hledání a nahrazování v aplikaci gedit je nemodální.

Reference

#### Příklad

##### Dialogové okno s informacemi o aplikaci (AboutDialog)

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_clicked();

      //Child widgets:
      Gtk::Box m_VBox;
      Gtk::Label m_Label;
      Gtk::Box m_ButtonBox;
      Gtk::Button m_Button;
      Gtk::AboutDialog m_Dialog;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::Orientation::VERTICAL),
      m_Label("The AboutDialog is non-modal. "
        "You can select parts of this text while the AboutDialog is shown."),
      m_ButtonBox(Gtk::Orientation::VERTICAL),
      m_Button("Show AboutDialog")
    {
      set_title("Gtk::AboutDialog example");
      set_default_size(400, 150);

      set_child(m_VBox);

      m_VBox.append(m_Label);
      m_Label.set_expand(true);
      m_Label.set_wrap(true);
      m_Label.set_selectable(true);

      m_VBox.append(m_ButtonBox);
      m_ButtonBox.append(m_Button);
      m_Button.set_expand(true);
      m_Button.set_halign(Gtk::Align::CENTER);
      m_Button.set_valign(Gtk::Align::CENTER);
      m_Button.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_clicked) );

      m_Dialog.set_transient_for(*this);
      m_Dialog.set_hide_on_close();

      m_Dialog.set_logo(Gdk::Texture::create_from_resource("/about/gtkmm_logo.gif"));
      m_Dialog.set_program_name("Example application");
      m_Dialog.set_version("1.0.0");
      m_Dialog.set_copyright("Murray Cumming");
      m_Dialog.set_comments("This is just an example application.");
      m_Dialog.set_license("LGPL");

      m_Dialog.set_website("http://www.gtkmm.org");
      m_Dialog.set_website_label("gtkmm website");

      std::vector<Glib::ustring> list_authors;
      list_authors.push_back("Murray Cumming");
      list_authors.push_back("Somebody Else");
      list_authors.push_back("AN Other");
      m_Dialog.set_authors(list_authors);

      m_Button.grab_focus();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_clicked()
    {
      m_Dialog.set_visible(true);

      //Bring it to the front, in case it was already shown:
      m_Dialog.present();
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

File: `aboutdialog.gresource.xml` (For use with gtkmm 4)

    <?xml version="1.0" encoding="UTF-8"?>
    <gresources>
      <gresource prefix="/about">
        <file>gtkmm_logo.gif</file>
      </gresource>
    </gresources>

### Custom Dialog

When none of the predefined dialog classes suit your needs, you can make your own dialog by deriving a class from `Window` and fill it with the widgets you need.

Window Reference

#### Příklad

##### Window Dialog

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>
    #include "namedialog.h"

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      ~ExampleWindow() override;

    protected:
      //Signal handlers:
      void on_button_clicked();
      void on_dialog_response(const Glib::ustring& response);
      void on_dialog_hidden();

      //Child widgets:
      Gtk::Button m_Button;

      NameDialog m_Dialog;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `namedialog.h` (For use with gtkmm 4)

    #ifndef GTKMM_NAME_DIALOG_H_
    #define GTKMM_NAME_DIALOG_H_

    #include <gtkmm.h>

    class NameDialog : public Gtk::Window
    {
    public:
      NameDialog();
      ~NameDialog() override;

      void buttons_clicked_connect(const sigc::slot<void(const Glib::ustring&)>& slot);
      Glib::ustring get_entry1() const;
      Glib::ustring get_entry2() const;

    protected:
      //Member widgets:
      Gtk::Grid m_Grid;
      Gtk::Image m_Image;
      Gtk::Label m_Label1;
      Gtk::Label m_Label2;
      Gtk::Entry m_Entry1;
      Gtk::Entry m_Entry2;
      Gtk::Box m_ButtonBox;
      Gtk::Button m_Button_OK;
      Gtk::Button m_Button_Cancel;
    };

    #endif /* GTKMM_NAME_DIALOG_H_ */

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_Button("Show Dialog"),
      m_Dialog()
    {
      set_title("Custom Dialog example");

      set_child(m_Button);
      m_Button.signal_clicked().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_button_clicked));

      m_Dialog.set_default_size(250, 100);
      m_Dialog.set_transient_for(*this);
      m_Dialog.set_modal();
      m_Dialog.set_hide_on_close();
      m_Dialog.buttons_clicked_connect(
        sigc::mem_fun(*this, &ExampleWindow::on_dialog_response));
      m_Dialog.signal_hide().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_dialog_hidden));
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_clicked()
    {
      m_Dialog.set_visible(true);
    }

    void ExampleWindow::on_dialog_response(const Glib::ustring& response)
    {
      m_Dialog.set_visible(false);

      if (response == "OK")
        std::cout << "Name: " << m_Dialog.get_entry1() << " "
          << m_Dialog.get_entry2() << std::endl;
      else
        std::cout << response << " button clicked" << std::endl;
    }

    void ExampleWindow::on_dialog_hidden()
    {
      std::cout << "Dialog hidden" << std::endl;
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

File: `namedialog.cc` (For use with gtkmm 4)

    NameDialog::NameDialog()
    : m_Label1("_First name", true),
      m_Label2("_Second name", true),
      m_ButtonBox(Gtk::Orientation::HORIZONTAL, 5),
      m_Button_OK("_OK", true),
      m_Button_Cancel("_Cancel", true)
    {
      set_destroy_with_parent(true);

      set_title("Name Dialog");
      set_child(m_Grid);

      m_Grid.set_row_spacing(4);
      m_Grid.set_column_spacing(4);
      m_Grid.set_expand(true);

      m_Image.set_from_icon_name("dialog-question");
      m_Image.set_icon_size(Gtk::IconSize::LARGE);
      m_Grid.attach(m_Image, 0, 0, 1, 2);

      m_Grid.attach(m_Label1, 1, 0);
      m_Grid.attach(m_Entry1, 2, 0);
      m_Label1.set_mnemonic_widget(m_Entry1);

      m_Grid.attach(m_Label2, 1, 1);
      m_Grid.attach(m_Entry2, 2, 1);
      m_Label2.set_mnemonic_widget(m_Entry2);

      m_Grid.attach(m_ButtonBox, 0, 2, 3, 1);
      m_ButtonBox.set_halign(Gtk::Align::END);
      m_ButtonBox.append(m_Button_OK);
      m_ButtonBox.append(m_Button_Cancel);
    }

    void NameDialog::buttons_clicked_connect(
      const sigc::slot<void(const Glib::ustring&)>& slot)
    {
      m_Button_OK.signal_clicked().connect(sigc::bind(slot, "OK"));
      m_Button_Cancel.signal_clicked().connect(sigc::bind(slot, "Cancel"));
    }

    Glib::ustring NameDialog::get_entry1() const
    {
      return m_Entry1.get_text();
    }

    Glib::ustring NameDialog::get_entry2() const
    {
      return m_Entry2.get_text();
    }

    NameDialog::~NameDialog()
    {
    }

## The DrawingArea Widget

The `DrawingArea` widget is a blank window that gives you the freedom to create any graphic you desire. Along with that freedom comes the responsibility to draw on the widget. When a widget is first shown, or when it is covered and then uncovered again it needs to redraw itself. Most widgets have code to do this, but the `DrawingArea` does not, allowing you to write your own draw function to determine how the contents of the widget will be drawn. This is done by setting a draw function with a call to the `set_draw_func()` member function.

GTK uses the Cairo drawing API. With gtkmm, you may use the cairomm C++ API for cairo.

Pomocí Cairo můžete kreslit i velmi složité tvary, ale metody k tomu používané jsou vcelku základní. Cairo poskytuje metody pro kreslení rovných čar, křivek a oblouků (včetně celých kružnic). Tyto základní tvary můžete kombinovat, abyste vytvořili složitější tvary a cesty, které můžete vyplnit plnou barvou, přechody, vzory a dalšími věcmi. Navíc Cairo zvládá komplexní transformace, skládání obrázků a vykreslování vyhlazeného textu.

### Cairo a Pango

Ačkoliv Cairo umí vykreslit text, neznamená to, že by mohlo nahradit Pango. Pango je lepší volbou, když potřebujete provádět pokročilejší vykreslování textu, jako je zalamování nebo vypouštění textu. Kreslení textu pomocí Cairo by se mělo dělat je v případě, že je text součástí grafiky.

V této části výukového textu pokryjeme základní kreslicí model Cairo, popíšeme podrobně jednotlivé základní kreslicí prvky (včetně příkladů) a ukážeme si jednoduchou aplikaci, která používá Cairo ke kreslení widgetu s hodinami.

### Kreslicí model Cairo

Základní koncept kreslení v Cairo obnáší definici „neviditelných“ cest a jejich následné obtažení a vyplnění, aby byly viditelné.

To do any drawing in gtkmm with Cairo, you must first get a `Cairo::Context` object. This class holds all of the graphics state parameters that describe how drawing is to be done. This includes information such as line width, color, the surface to draw to, and many other things. This allows the actual drawing functions to take fewer arguments to simplify the interface. Usually, you use the `Cairo::Context` that you get as input data to the draw function that you set with the call to `set_draw_func()`. It's also possible to create a `Cairo::Context` by calling the `Gdk::Surface::create_cairo_context()` and `Gdk::CairoContext::cairo_create()` functions. Since Cairo contexts are reference-counted objects, `cairo_create()` returns a `Cairo::RefPtr<Cairo::Context>` object. (Note the difference between `Gdk::CairoContext` and `Cairo::Context`.)

Následující příklad ukazuje, jak nastavit kontext Cairo s červenou barvou pozadí a tloušťkou 2. Kterákoliv kreslicí funkce, která použije tento kontext, použije toto nastavení.

    Gtk::DrawingArea myArea;
    auto gdkCairoContext = myArea.get_surface()->create_cairo_context();
    auto myContext = gdkCairoContext->cairo_create();
    myContext->set_source_rgb(1.0, 0.0, 0.0);
    myContext->set_line_width(2.0);

Each `Cairo::Context` is associated with a particular `Gdk::Surface`, so the first line of the above example creates a `Gtk::DrawingArea` widget and the next two lines use its associated `Gdk::Surface` to create a `Cairo::Context` object. The final two lines change the graphics state of the context.

There are a number of graphics state variables that can be set for a Cairo context. The most common context attributes are color (using `set_source_rgb()` or `set_source_rgba()` for translucent colors), line width (using `set_line_width()`), line dash pattern (using `set_dash()`), line cap style (using `set_line_cap()`), and line join style (using `set_line_join()`), and font styles (using `set_font_size()`, `set_font_face()` and others). There are many other settings as well, such as transformation matrices, fill rules, whether to perform antialiasing, and others. For further information, see the cairomm API documentation.

The current state of a `Cairo::Context` can be saved to an internal stack of saved states and later be restored to the state it was in when you saved it. To do this, use the `save()` method and the `restore()` method. This can be useful if you need to temporarily change the line width and color (or any other graphics setting) in order to draw something and then return to the previous settings. In this situation, you could call `Cairo::Context::save()`, change the graphics settings, draw the lines, and then call `Cairo::Context::restore()` to restore the original graphics state. Multiple calls to `save()` and `restore()` can be nested; each call to `restore()` restores the state from the matching paired `save()`.

It is good practice to put all modifications to the graphics state between `save()`/`restore()` function calls. For example, if you have a function that takes a `Cairo::Context` reference as an argument, you might implement it as follows:

    void doSomething(const Cairo::RefPtr<Cairo::Context>& context, int x)
    {
        context->save();
        // change graphics state
        // perform drawing operations
        context->restore();
    }

The draw function that you set with a call to `set_draw_func()` is called with a Cairo context that you shall use for drawing in the `Gtk::DrawingArea` widget. It is not necessary to save and restore this Cairo context in the draw function.

### Kreslení rovných čar

Now that we understand the basics of the Cairo graphics library, we're almost ready to start drawing. We'll start with the simplest of drawing elements: the straight line. But first you need to know a little bit about Cairo's coordinate system. The origin of the Cairo coordinate system is located in the upper-left corner of the window with positive x values to the right and positive y values going down.

Since the Cairo graphics library was written with support for multiple output targets (the X window system, PNG images, OpenGL, etc), there is a distinction between user-space and device-space coordinates. The mapping between these two coordinate systems defaults to one-to-one so that integer values map roughly to pixels on the screen, but this setting can be adjusted if desired. Sometimes it may be useful to scale the coordinates so that the full width and height of a window both range from 0 to 1 (the 'unit square') or some other mapping that works for your application. This can be done with the `Cairo::Context::scale()` function.

#### Příklad

V tomto příkladu sestavíme malý, ale plně funkční program používající gtkmm a nakreslíme do okna pár čar. Čáry se kreslí vytvořením cesty a jejím obtažením. Cesta se vytváří pomocí funkcí `Cairo::Context::move_to()` a `Cairo::Context::line_to()`. Funkce `move_to()` funguje podobně, jako když zvednete pero nad papír a posunete ruku jinam a znovu jej přiložíte – během přesunu ruky pero nic nekreslilo. Pro kreslení čáry mezi dvěma body se používá funkce `line_to()`.

Po dokončení tvorby cesty pořád nemáte nakreslené nic viditelného. Aby se cesta zviditelnila, musíte použít funkci `stroke()`, která obtáhne cestu čarou s tloušťkou a stylem definovanými v objektu `Cairo::Context`. Po obtažení se aktuální cesta smaže a můžete začít s novou cestou.

Mnoho kreslicích funkcí Cairo má variantu `_preserve()`. Normální kreslicí funkce, jako jsou `clip()`, `fill()` nebo `stroke()`, mažou aktuální cestu. Když použijete variantu `_preserve()`, bude aktuální cesta ponechána, takže ji můžete použít v následující kreslicí funkci.

##### Kreslicí oblast – čáry

Source Code

File: `myarea.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLE_MYAREA_H
    #define GTKMM_EXAMPLE_MYAREA_H

    #include <gtkmm/drawingarea.h>

    class MyArea : public Gtk::DrawingArea
    {
    public:
      MyArea();
      virtual ~MyArea();

    protected:
      void on_draw(const Cairo::RefPtr<Cairo::Context>& cr, int width, int height);
    };

    #endif // GTKMM_EXAMPLE_MYAREA_H

File: `main.cc` (For use with gtkmm 4)

    #include "myarea.h"
    #include <gtkmm/application.h>
    #include <gtkmm/window.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();

    protected:
      MyArea m_area;
    };

    ExampleWindow::ExampleWindow()
    {
      set_title("DrawingArea");
      set_child(m_area);
    }

    int main(int argc, char** argv)
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

File: `myarea.cc` (For use with gtkmm 4)

    #include "myarea.h"
    #include <cairomm/context.h>

    MyArea::MyArea()
    {
      set_draw_func(sigc::mem_fun(*this, &MyArea::on_draw));
    }

    MyArea::~MyArea()
    {
    }

    void MyArea::on_draw(const Cairo::RefPtr<Cairo::Context>& cr, int width, int height)
    {
      // coordinates for the center of the window
      int xc, yc;
      xc = width / 2;
      yc = height / 2;

      cr->set_line_width(10.0);

      // draw red lines out from the center of the window
      cr->set_source_rgb(0.8, 0.0, 0.0);
      cr->move_to(0, 0);
      cr->line_to(xc, yc);
      cr->line_to(0, height);
      cr->move_to(xc, yc);
      cr->line_to(width, yc);
      cr->stroke();
    }

This program contains a single class, `MyArea`, which is a subclass of `Gtk::DrawingArea` and contains an `on_draw()` member function. This function becomes the draw function by a call to `set_draw_func()` in `MyArea`'s constructor. `on_draw()` is then called whenever the image in the drawing area needs to be redrawn. It is passed a `Cairo::RefPtr` pointer to a `Cairo::Context` that we use for the drawing. The actual drawing code sets the color we want to use for drawing by using `set_source_rgb()` which takes arguments defining the Red, Green, and Blue components of the desired color (valid values are between 0 and 1). After setting the color, we created a new path using the functions `move_to()` and `line_to()`, and then stroked this path with `stroke()`.

##### Kreslení s relativními souřadnicemi

V příkladu výše jsme všechno nakreslili pomocí absolutních souřadnic. Můžeme kreslit také pomocí relativních souřadnic. Pro přímé čáry se to dělá pomocí funkce `Cairo::Context::rel_line_to()`.

#### Styly čar

Mimo kreslení základních rovných čar, existuje řada věcí, které si u čar můžete přizpůsobit. Již jste viděli příklad nastavení barvy a tloušťky čáry, ale jsou tu i další.

Když kreslíte posloupnost čar ve formě cesty, můžete je chtít spojovat dohromady konkrétním způsobem. Cairo nabízí tři různé způsoby, jak čáry spojit: hranatý spoj – Miter, zkosený spoj – Bevel a zaoblený spoj – Round. Zde jsou ukázané ve zmíněném pořadí:

##### Různé typy spojů v Cairo

Styl spojování čar se nastavuje pomocí funkce `Cairo::Context::set_line_join()`.

Stejně tak mohou mít různé styly konce čar. Výchozí styl pro čáru je začínat a končit přesně v koncových bodech čáry. To se nazývá rovný konec – Butt. Dalšími volbami jsou zaoblení – Round (zaoblení má střed v koncovém bodu) a čtvercový konec – Square (rovněž čtverec má střed v koncovém bodu). Tyto volby se nastavují pomocí funkce `Cairo::Context::set_line_cap()`.

Existují i další věci, které si můžete přizpůsobit, včetně vytváření přerušovaných čar a jiného. Více informací najdete v dokumentaci k API Cairo.

#### Kreslení tenkých čar

Když zkusíte kreslit čáru tlustou jeden pixel, můžete být překvapeni, že místy bude čára rozmazaná a širší, než by měla. To se děje, protože Cairo se snaží kreslit z vybraných souřadnic obě strany (polovinu tloušťky na každou stranu), takže když zadáte umístění přesně mezi pixely a chcete jeden pixel tlustou čáru, pokouší se Cairo použí polovinu z každého pixelu, což není možní (pixel je nejmenší možná jednotka). Děje se to pokaždé, když je tloušťka čáry lichý počet pixelů (ne jen pro jeden pixel).

The trick is to position in the middle of the pixel where you want the line to be drawn, and thus guaranteeing you get the desired results. See Cairo FAQ.

##### Kreslicí oblast – tenké čáry

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm/window.h>
    #include <gtkmm/box.h>
    #include <gtkmm/checkbutton.h>
    #include "myarea.h"

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_toggled();

    private:
      Gtk::Box m_HBox;
      MyArea m_Area_Lines;
      Gtk::CheckButton m_Button_FixLines;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `myarea.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLE_MYAREA_H
    #define GTKMM_EXAMPLE_MYAREA_H

    #include <gtkmm/drawingarea.h>

    class MyArea : public Gtk::DrawingArea
    {
    public:
      MyArea();
      virtual ~MyArea();

      void fix_lines(bool fix = true);

    protected:
      void on_draw(const Cairo::RefPtr<Cairo::Context>& cr, int width, int height);

    private:
      double m_fix;
    };

    #endif // GTKMM_EXAMPLE_MYAREA_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_HBox(Gtk::Orientation::HORIZONTAL),
      m_Button_FixLines("Fix lines")
    {
      set_title("Thin lines example");

      m_HBox.append(m_Area_Lines);
      m_HBox.append(m_Button_FixLines);

      set_child(m_HBox);

      m_Button_FixLines.signal_toggled().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_button_toggled));

      // Synchonize the drawing in m_Area_Lines with the state of the toggle button.
      on_button_toggled();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_toggled()
    {
      m_Area_Lines.fix_lines(m_Button_FixLines.get_active());
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char* argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

File: `myarea.cc` (For use with gtkmm 4)

    #include "myarea.h"

    MyArea::MyArea()
    : m_fix (0)
    {
      set_content_width(200);
      set_content_height(100);
      set_draw_func(sigc::mem_fun(*this, &MyArea::on_draw));
    }

    MyArea::~MyArea()
    {
    }

    void MyArea::on_draw(const Cairo::RefPtr<Cairo::Context>& cr, int width, int height)
    {
      cr->set_line_width(1.0);

      // draw one line, every two pixels
      // without the 'fix', you won't notice any space between the lines,
      // since each one will occupy two pixels (width)
      for (int i = 0; i < width; i += 2)
      {
        cr->move_to(i + m_fix, 0);
        cr->line_to(i + m_fix, height);
      }

      cr->stroke();
    }

    // Toogle between both values (0 or 0.5)
    void MyArea::fix_lines(bool fix)
    {
      // to get the width right, we have to draw in the middle of the pixel
      m_fix = fix ? 0.5 : 0.0;

      // force the redraw of the image
      queue_draw();
    }

### Kreslení křivek

Mimo rovných čar umožňuje Cairo kreslit jednoduše i křivky (přesný technický termín je kubické Bézierovy splajny) pomocí funkcí `Cairo::Context::curve_to()` a `Cairo::Context::rel_curve_to()`. Tyto funkce přebírají souřadnice pro cílový bod a souřadnice dvou „řídících“ bodů. Nejlépe to bude vysvětlit na příkladu, tak pojďme na to.

#### Příklad

Tato jednoduchá aplikace kreslí pomocí Cairo křivku a zobrazuje řídící body pro její jednotlivé konce.

##### Kreslicí oblast – čáry

Source Code

File: `myarea.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLE_MYAREA_H
    #define GTKMM_EXAMPLE_MYAREA_H

    #include <gtkmm/drawingarea.h>

    class MyArea : public Gtk::DrawingArea
    {
    public:
      MyArea();
      virtual ~MyArea();

    protected:
      void on_draw(const Cairo::RefPtr<Cairo::Context>& cr, int width, int height);
    };

    #endif // GTKMM_EXAMPLE_MYAREA_H

File: `main.cc` (For use with gtkmm 4)

    #include "myarea.h"
    #include <gtkmm/application.h>
    #include <gtkmm/window.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();

    protected:
      MyArea m_area;
    };

    ExampleWindow::ExampleWindow()
    {
      set_title("DrawingArea");
      set_child(m_area);
    }

    int main(int argc, char** argv)
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

File: `myarea.cc` (For use with gtkmm 4)

    #include "myarea.h"
    #include <cairomm/context.h>

    MyArea::MyArea()
    {
      set_draw_func(sigc::mem_fun(*this, &MyArea::on_draw));
    }

    MyArea::~MyArea()
    {
    }

    void MyArea::on_draw(const Cairo::RefPtr<Cairo::Context>& cr, int width, int height)
    {
      double x0=0.1, y0=0.5, // start point
             x1=0.4, y1=0.9,  // control point #1
             x2=0.6, y2=0.1,  // control point #2
             x3=0.9, y3=0.5;  // end point

      // scale to unit square (0 to 1 width and height)
      cr->scale(width, height);

      cr->set_line_width(0.05);
      // draw curve
      cr->move_to(x0, y0);
      cr->curve_to(x1, y1, x2, y2, x3, y3);
      cr->stroke();
      // show control points
      cr->set_source_rgba(1, 0.2, 0.2, 0.6);
      cr->move_to(x0, y0);
      cr->line_to (x1, y1);
      cr->move_to(x2, y2);
      cr->line_to (x3, y3);
      cr->stroke();
    }

Jediný rozdíl mezi tímto příkladem a příkladem s rovnými čárami je ve funkci `on_draw()`, ale je zde uvedeno pár nových konceptů a funkcí, tak si je pojďme ve stručnosti vysvětlit.

Voláme metodu `Cairo::Context::scale()` a předáváme jí šířku a výšku kreslicí oblasti. Tím se přepočítá systém souřadnic v uživatelském prostoru, jako by tato šířka a výška widgetu byly obojí rovny 1,0 „jednotek“. K tomuto systému přepočítání není žádný konkrétní důvod, ale občas to může kreslení zjednodušit.

Volání metody `Cairo::Context::curve_to()` by mělo být pochopitelné na pohled. První pár souřadnic definuje řídící bod pro začátek křivky. Druhá sada souřadnic definuje řídící bod pro konec křivky a poslední sada souřadnic definuje cílový bod. Abyste si dokázali koncept řídících bodů snáze vizuálně představit, nakreslí se čára z obou řídících bodů do příslušných koncových bodů křivky. Tyto pomocné čáry jsou průsvitné, čehož se dosáhne zavoláním metody `set_source_rgba()`, která je jen rozšířenou variantou `set_source_rgb()`. Přebírá navíc čtvrtý argument určující alfakanál barvy (platné hodnoty jsou mezi 0 a 1).

### Kreslení oblouků a kružnic

Ke kreslení oblouků, kružnic a elips se v Cairo používá ta samá funkce: `Cairo::Context::arc()`. Tato funkce má pět argumentů. První dva jsou souřadnice středu oblouku, třetí je poloměr oblouku a konečně poslední dva argumenty definují počáteční a koncový úhel oblouku. Všechny úhly se určují v radiánech, takže nakreslení kružnice je to stejné, jako nakreslení oblouku od 0 do 2 * M_PI radiánů. Úhel 0 leží na kladné ose X (v uživatelském prostoru). Úhel M_PI/2 radiánů (90 stupňů) je v kladném směru osy Y (v uživatelském prostoru). Úhel se zvyšuje ve směru z kladné osy X ke kladné ose Y. Takže s výchozí transformační maticí se úhel zvyšuje po směru hodinových ručiček. (Vzpomeňte, že kladná osa Y jde směrem dolů.)

To draw an ellipse, you can scale the current transformation matrix by different amounts in the X and Y directions. For example, to draw an ellipse with center at `x`, `y` and size `width`, `height`:

    context->save();
    context->translate(x, y);
    context->scale(width / 2.0, height / 2.0);
    context->arc(0.0, 0.0, 1.0, 0.0, 2 * M_PI);
    context->restore();

#### Příklad

Zde je příklad jednoduchého programu, který kreslí do kreslicí oblasti oblouk, kružnici a elipsu.

##### Kreslicí oblast – oblouky

Source Code

File: `myarea.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLE_MYAREA_H
    #define GTKMM_EXAMPLE_MYAREA_H

    #include <gtkmm/drawingarea.h>

    class MyArea : public Gtk::DrawingArea
    {
    public:
      MyArea();
      virtual ~MyArea();

    protected:
      void on_draw(const Cairo::RefPtr<Cairo::Context>& cr, int width, int height);
    };

    #endif // GTKMM_EXAMPLE_MYAREA_H

File: `main.cc` (For use with gtkmm 4)

    #include "myarea.h"
    #include <gtkmm/application.h>
    #include <gtkmm/window.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();

    protected:
      MyArea m_area;
    };

    ExampleWindow::ExampleWindow()
    {
      set_title("DrawingArea");
      set_child(m_area);
    }

    int main(int argc, char** argv)
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

File: `myarea.cc` (For use with gtkmm 4)

    #include "myarea.h"
    #include <cairomm/context.h>
    #include <cmath>

    MyArea::MyArea()
    {
      set_draw_func(sigc::mem_fun(*this, &MyArea::on_draw));
    }

    MyArea::~MyArea()
    {
    }

    void MyArea::on_draw(const Cairo::RefPtr<Cairo::Context>& cr, int width, int height)
    {
      const int lesser = std::min(width, height);

      // coordinates for the center of the window
      const int xc = width / 2;
      const int yc = height / 2;

      cr->set_line_width(lesser * 0.02);  // outline thickness changes
                                          // with window size

      // first draw a simple unclosed arc
      cr->save();
      cr->arc(width / 3.0, height / 4.0, lesser / 4.0, -(M_PI / 5.0), M_PI);
      cr->close_path();   // line back to start point
      cr->set_source_rgb(0.0, 0.8, 0.0);
      cr->fill_preserve();
      cr->restore();  // back to opaque black
      cr->stroke();   // outline it

      // now draw a circle
      cr->save();
      cr->arc(xc, yc, lesser / 4.0, 0.0, 2.0 * M_PI); // full circle
      cr->set_source_rgba(0.0, 0.0, 0.8, 0.6);    // partially translucent
      cr->fill_preserve();
      cr->restore();  // back to opaque black
      cr->stroke();

      // and finally an ellipse
      double ex, ey, ew, eh;
      // center of ellipse
      ex = xc;
      ey = 3.0 * height / 4.0;
      // ellipse dimensions
      ew = 3.0 * width / 4.0;
      eh = height / 3.0;

      cr->save();

      cr->translate(ex, ey);  // make (ex, ey) == (0, 0)
      cr->scale(ew / 2.0, eh / 2.0);  // for width: ew / 2.0 == 1.0
                                      // for height: eh / 2.0 == 1.0

      cr->arc(0.0, 0.0, 1.0, 0.0, 2 * M_PI);  // 'circle' centered at (0, 0)
                                              // with 'radius' of 1.0

      cr->set_source_rgba(0.8, 0.0, 0.0, 0.7);
      cr->fill_preserve();
      cr->restore();  // back to opaque black
      cr->stroke();
    }

Je tu pár věcí, které v tomto příkladu stojí za zmínku. Ještě jednou, jediný skutečný rozdíl mezi tímto příkladem a předchozím je ve funkci `on_draw()`, takže se zaměříme jen na ni. Navíc, první část této funkce je hodně podobná předchozímu příkladu, takže ji přeskočíme.

Všimněte si, že v tomto případě jsme téměř vše vyjádřili v pojmech výšky a šířky okna, včetně tloušťky čar. Díky tomu vše při změně velikosti okna správně změní měřítko. Navíc si všimněte, že jsou ve funkci tři samostatné celky kreslení, které jsou obalené v páru funkcí `save()` a `restore()`, takže po každém kreslení se vrátíme zpět do známého stavu.

V části kreslící oblouk můžete potkat novou funkci `close_path()`. Tato funkce se projevuje nakreslením rovné čáry z aktuálního do prvního bodu cesty. Je ale podstatný rozdíl mezi zavoláním `close_path()` a ručním nakreslením čáry zpět k počátečnímu bodu. Když použijete `close_path()`, budou čáry spolu pěkně spojené. Když místo toho použijete `line_to()`, budou čáry sice končit ve stejném bodě, ale Cairo je nijak speciálně nespojí.

##### Kreslení po směru hodinových ručiček

Funkce `Cairo::Context::arc_negative()` je úplně stejná, jako `Cairo::Context::arc()`, jen úhly se počítají v opačném směru.

### Kreslení textu

#### Kreslení textu pomocí knihovny Pango

Text se kreslí pomocí `Layout` z knihovny Pango. Nejjednodušším způsobem, jak vytvořit `Pango::Layout`, je použít `Gtk::Widget::create_pango_layout()`. Když je vytvořený, dá se s ním pracovat několika způsoby, včetně změny textu, fontu apod. Nakonec jej můžete vykreslit pomocí metody `Pango::Layout::show_in_cairo_context()`.

#### Příklad

Here is an example of a program that draws some text, some of it upside-down. The Printing chapter contains another example of drawing text.

##### Kreslicí oblast – text

Source Code

File: `myarea.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLE_MYAREA_H
    #define GTKMM_EXAMPLE_MYAREA_H

    #include <gtkmm/drawingarea.h>

    class MyArea : public Gtk::DrawingArea
    {
    public:
      MyArea();
      virtual ~MyArea();

    protected:
      void on_draw(const Cairo::RefPtr<Cairo::Context>& cr, int width, int height);

    private:
      void draw_rectangle(const Cairo::RefPtr<Cairo::Context>& cr, int width, int height);
      void draw_text(const Cairo::RefPtr<Cairo::Context>& cr, int rectangle_width, int rectangle_height);

    };

    #endif // GTKMM_EXAMPLE_MYAREA_H

File: `main.cc` (For use with gtkmm 4)

    #include "myarea.h"
    #include <gtkmm/application.h>
    #include <gtkmm/window.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();

    protected:
      MyArea m_area;
    };

    ExampleWindow::ExampleWindow()
    {
      set_title("Drawing text example");
      set_child(m_area);
    }

    int main(int argc, char* argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

File: `myarea.cc` (For use with gtkmm 4)

    #include "myarea.h"

    MyArea::MyArea()
    {
      set_draw_func(sigc::mem_fun(*this, &MyArea::on_draw));
    }

    MyArea::~MyArea()
    {
    }

    void MyArea::on_draw(const Cairo::RefPtr<Cairo::Context>& cr, int width, int height)
    {
      const int rectangle_width = width;
      const int rectangle_height = height / 2;

      // Draw a black rectangle
      cr->set_source_rgb(0.0, 0.0, 0.0);
      draw_rectangle(cr, rectangle_width, rectangle_height);

      // and some white text
      cr->set_source_rgb(1.0, 1.0, 1.0);
      draw_text(cr, rectangle_width, rectangle_height);

      // flip the image vertically
      // see http://www.cairographics.org/documentation/cairomm/reference/classCairo_1_1Matrix.html
      // the -1 corresponds to the yy part (the flipping part)
      // the height part is a translation (we could have just called cr->translate(0, height) instead)
      // it's height and not height / 2, since we want this to be on the second part of our drawing
      // (otherwise, it would draw over the previous part)
      Cairo::Matrix matrix(1.0, 0.0, 0.0, -1.0, 0.0, height);

      // apply the matrix
      cr->transform(matrix);

      // white rectangle
      cr->set_source_rgb(1.0, 1.0, 1.0);
      draw_rectangle(cr, rectangle_width, rectangle_height);

      // black text
      cr->set_source_rgb(0.0, 0.0, 0.0);
      draw_text(cr, rectangle_width, rectangle_height);
    }

    void MyArea::draw_rectangle(const Cairo::RefPtr<Cairo::Context>& cr,
                                int width, int height)
    {
      cr->rectangle(0, 0, width, height);
      cr->fill();
    }

    void MyArea::draw_text(const Cairo::RefPtr<Cairo::Context>& cr,
                           int rectangle_width, int rectangle_height)
    {
      // http://developer.gnome.org/pangomm/unstable/classPango_1_1FontDescription.html
      Pango::FontDescription font;

      font.set_family("Monospace");
      font.set_weight(Pango::Weight::BOLD);

      // http://developer.gnome.org/pangomm/unstable/classPango_1_1Layout.html
      auto layout = create_pango_layout("Hi there!");

      layout->set_font_description(font);

      int text_width;
      int text_height;

      //get the text dimensions (it updates the variables -- by reference)
      layout->get_pixel_size(text_width, text_height);

      // Position the text in the middle
      cr->move_to((rectangle_width-text_width)/2, (rectangle_height-text_height)/2);

      layout->show_in_cairo_context(cr);
    }

### Kreslení obrázků

Existuje metoda pro kreslení z `Gdk::Pixbuf` do `Cairo::Context`. Vyrovnávací paměť `Gdk::Pixbuf` je užitečná jako obal okolo množiny pixelů tvořících obrázek, které můžete načíst ze souboru a pak s nimi různým způsobem pracovat.

Probably the most common way of creating `Gdk::Pixbuf`s is to use `Gdk::Pixbuf::create_from_file()` or `Gdk::Pixbuf::create_from_resource()`, which can read an image file, such as a png file into a pixbuf ready for rendering.

`Gdk::Pixbuf` lze vykreslit jeho nastavením jako zdrojového vzorku v kontextu Cairo pomocí `Gdk::Cairo::set_source_pixbuf()`. Pak obrázek nakreslíte pomocí `Cairo::Context::paint()` (nakreslí celý obrázek), nebo pomocí `Cairo::Context::rectangle()` a `Cairo::Context::fill()` (vyplní určený obdélník). `set_source_pixbuf()` není členská metoda z `Cairo::Context`. Jako první parametr je vyžadován `Cairo::Context`.

Zde je malý kousek kódu, který dává vše dohromady: (Samozřejmě, že obvykle byste obrázek v obsluze kreslicího signálu nenačítali pokaždé! Zde je to jen proto, aby bylo ukázané vše pohromadě.)

    void MyArea::on_draw(const Cairo::RefPtr<Cairo::Context>& cr, int width, int height)
    {
      auto image = Gdk::Pixbuf::create_from_file("myimage.png");
      // Draw the image at 110, 90, except for the outermost 10 pixels.
      Gdk::Cairo::set_source_pixbuf(cr, image, 100, 80);
      cr->rectangle(110, 90, image->get_width()-20, image->get_height()-20);
      cr->fill();
    }

#### Příklad

Here is an example of a simple program that draws an image. The program loads the image from a resource file. See the Gio::Resource and glib-compile-resources section. Use glib-compile-resources to compile the resources into a C source file that can be compiled and linked with the C++ code. E.g.

    $ glib-compile-resources --target=resources.c --generate-source image.gresource.xml

##### Kreslicí oblast – obrázek

Source Code

File: `myarea.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLE_MYAREA_H
    #define GTKMM_EXAMPLE_MYAREA_H

    #include <gtkmm/drawingarea.h>
    #include <gdkmm/pixbuf.h>

    class MyArea : public Gtk::DrawingArea
    {
    public:
      MyArea();
      virtual ~MyArea();

    protected:
      void on_draw(const Cairo::RefPtr<Cairo::Context>& cr, int width, int height);

      Glib::RefPtr<Gdk::Pixbuf> m_image;
    };

    #endif // GTKMM_EXAMPLE_MYAREA_H

File: `main.cc` (For use with gtkmm 4)

    #include "myarea.h"
    #include <gtkmm/application.h>
    #include <gtkmm/window.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();

    protected:
      MyArea m_area;
    };

    ExampleWindow::ExampleWindow()
    {
      set_title("DrawingArea");
      set_default_size(300, 200);
      set_child(m_area);
    }

    int main(int argc, char** argv)
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

File: `myarea.cc` (For use with gtkmm 4)

    #include "myarea.h"
    #include <cairomm/context.h>
    #include <giomm/resource.h>
    #include <gdkmm/general.h> // set_source_pixbuf()
    #include <glibmm/fileutils.h>
    #include <iostream>

    MyArea::MyArea()
    {
      try
      {
        // The fractal image has been created by the XaoS program.
        // http://xaos.sourceforge.net
        m_image = Gdk::Pixbuf::create_from_resource("/image/fractal_image.png");
      }
      catch(const Gio::ResourceError& ex)
      {
        std::cerr << "ResourceError: " << ex.what() << std::endl;
      }
      catch(const Gdk::PixbufError& ex)
      {
        std::cerr << "PixbufError: " << ex.what() << std::endl;
      }

      // Show at least a quarter of the image.
      if (m_image)
      {
        set_content_width(m_image->get_width()/2);
        set_content_height(m_image->get_height()/2);
      }

      // Set the draw function.
      set_draw_func(sigc::mem_fun(*this, &MyArea::on_draw));
    }

    MyArea::~MyArea()
    {
    }

    void MyArea::on_draw(const Cairo::RefPtr<Cairo::Context>& cr, int width, int height)
    {
      if (!m_image)
        return;

      // Draw the image in the middle of the drawing area, or (if the image is
      // larger than the drawing area) draw the middle part of the image.
      Gdk::Cairo::set_source_pixbuf(cr, m_image,
        (width - m_image->get_width())/2, (height - m_image->get_height())/2);
      cr->paint();
    }

File: `image.gresource.xml` (For use with gtkmm 4)

    <?xml version="1.0" encoding="UTF-8"?>
    <gresources>
      <gresource prefix="/image">
        <file>fractal_image.png</file>
      </gresource>
    </gresources>

### Ukázková aplikace: Kreslení hodin pomocí knihovny Cairo

Tímto jsme pokryli všechny základy o kreslení pomocí Cairo. Takže to zkusme dát vše dohromady a vytvořit jednoduchou aplikaci, která bude dělat něco reálného. Následující příklad používá Cairo k vytvoření vlastního widgetu s hodinami `Clock`. Hodiny mají sekundovou, minutovou a hodinovou ručičku a aktualizují se po sekundě.

Source Code

File: `clock.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLE_CLOCK_H
    #define GTKMM_EXAMPLE_CLOCK_H

    #include <gtkmm/drawingarea.h>

    class Clock : public Gtk::DrawingArea
    {
    public:
      Clock();
      virtual ~Clock();

    protected:
      void on_draw(const Cairo::RefPtr<Cairo::Context>& cr, int width, int height);

      bool on_timeout();

      double m_radius;
      double m_line_width;
    };

    #endif // GTKMM_EXAMPLE_CLOCK_H

File: `clock.cc` (For use with gtkmm 4)

    #include <ctime>
    #include <cmath>
    #include <cairomm/context.h>
    #include <glibmm/main.h>
    #include "clock.h"

    Clock::Clock()
    : m_radius(0.42), m_line_width(0.05)
    {
      Glib::signal_timeout().connect( sigc::mem_fun(*this, &Clock::on_timeout), 1000 );
      set_draw_func(sigc::mem_fun(*this, &Clock::on_draw));
    }

    Clock::~Clock()
    {
    }

    void Clock::on_draw(const Cairo::RefPtr<Cairo::Context>& cr, int width, int height)
    {
      // scale to unit square and translate (0, 0) to be (0.5, 0.5), i.e.
      // the center of the window
      cr->scale(width, height);
      cr->translate(0.5, 0.5);
      cr->set_line_width(m_line_width);

      cr->save();
      cr->set_source_rgba(0.337, 0.612, 0.117, 0.9);   // green
      cr->paint();
      cr->restore();
      cr->arc(0, 0, m_radius, 0, 2 * M_PI);
      cr->save();
      cr->set_source_rgba(1.0, 1.0, 1.0, 0.8);
      cr->fill_preserve();
      cr->restore();
      cr->stroke_preserve();
      cr->clip();

      //clock ticks
      for (int i = 0; i < 12; i++)
      {
        double inset = 0.05;

        cr->save();
        cr->set_line_cap(Cairo::Context::LineCap::ROUND);

        if(i % 3 != 0)
        {
          inset *= 0.8;
          cr->set_line_width(0.03);
        }

        cr->move_to(
          (m_radius - inset) * cos (i * M_PI / 6),
          (m_radius - inset) * sin (i * M_PI / 6));
        cr->line_to (
          m_radius * cos (i * M_PI / 6),
          m_radius * sin (i * M_PI / 6));
        cr->stroke();
        cr->restore(); /* stack-pen-size */
      }

      // store the current time
      time_t rawtime;
      time(&rawtime);
      struct tm * timeinfo = localtime (&rawtime);

      // compute the angles of the indicators of our clock
      double minutes = timeinfo->tm_min * M_PI / 30;
      double hours = timeinfo->tm_hour * M_PI / 6;
      double seconds= timeinfo->tm_sec * M_PI / 30;

      cr->save();
      cr->set_line_cap(Cairo::Context::LineCap::ROUND);

      // draw the seconds hand
      cr->save();
      cr->set_line_width(m_line_width / 3);
      cr->set_source_rgba(0.7, 0.7, 0.7, 0.8); // gray
      cr->move_to(0, 0);
      cr->line_to(sin(seconds) * (m_radius * 0.9),
        -cos(seconds) * (m_radius * 0.9));
      cr->stroke();
      cr->restore();

      // draw the minutes hand
      cr->set_source_rgba(0.117, 0.337, 0.612, 0.9);   // blue
      cr->move_to(0, 0);
      cr->line_to(sin(minutes + seconds / 60) * (m_radius * 0.8),
        -cos(minutes + seconds / 60) * (m_radius * 0.8));
      cr->stroke();

      // draw the hours hand
      cr->set_source_rgba(0.337, 0.612, 0.117, 0.9);   // green
      cr->move_to(0, 0);
      cr->line_to(sin(hours + minutes / 12.0) * (m_radius * 0.5),
        -cos(hours + minutes / 12.0) * (m_radius * 0.5));
      cr->stroke();
      cr->restore();

      // draw a little dot in the middle
      cr->arc(0, 0, m_line_width / 3.0, 0, 2 * M_PI);
      cr->fill();
    }

    bool Clock::on_timeout()
    {
      // force our program to redraw the entire clock.
      queue_draw();
      return true;
    }

File: `main.cc` (For use with gtkmm 4)

    #include "clock.h"
    #include <gtkmm/application.h>
    #include <gtkmm/window.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();

    protected:
      Clock m_clock;
    };

    ExampleWindow::ExampleWindow()
    {
      set_title("Cairomm Clock");
      set_child(m_clock);
    }

    int main(int argc, char** argv)
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

As before, almost all of the interesting stuff is done in the draw function `on_draw()`. Before we dig into the draw function, notice that the constructor for the `Clock` widget connects a handler function `on_timeout()` to a timer with a timeout period of 1000 milliseconds (1 second). This means that `on_timeout()` will get called once per second. The sole responsibility of this function is to invalidate the window so that gtkmm will be forced to redraw it.

Nyní se zaměřme na kód, který provádí skutečné vykreslení. První část funkce `on_draw()` by vám měla být dobře známá. Tento příklad znovu mění měřítko systému souřadnic na čtvercovou jednotku, takže bude jednodušší vykreslit hodiny jako procentní část velikosti okna a při změně velikosti okna dojde k automatickému přizpůsobení velikosti hodin. Navíc je systém souřadnic posunut vpřed a dolů, takže souřadnice (0, 0) je přímo uprostřed okna.

Funkce `Cairo::Context::paint()` je zde použita k nastavení barvy pozadí okna. Tato funkce nepřebírá žádný argument a vyplní aktuální povrch (nebo oříznutou část povrchu) právě aktivní zdrojovou barvou. Po nastavení barvy pozadí okna nakreslíme kružnici tvořící obrys hodin a následně tu stejnou cestu ořízneme, abychom si zajistili, že naše následující čáry nepůjdou mimo hodiny.

Po nakreslení obrysu projdeme po ciferníku a nakreslíme značky pro každou hodinu, s výraznějšími značkami pro 3, 6, 9 a 12 hodin. Nyní máme vše připravené k implementaci funkcionality udržování času na hodinách, což představuje získání aktuální hodnoty pro hodiny, minuty a sekundy a vykreslení ručiček v příslušném úhlu.

## Táhni a upusť

The `Gtk::DragSource` and `Gtk::DropTarget` event controllers have methods and signals which are used for Drag and Drop.

### Sources and Targets

Things are dragged from `sources` to be dropped on `targets`. Each source and target has information about the data formats that it can send or receive, provided by `Gdk::ContentFormats`. A drop target will only accept a dragged item if they both share a compatible format. Appropriate signals will then be emitted, telling the signal handlers which format was used.

`Gdk::ContentFormats` objects contain information about available GTypes and mime types (media types).

### Metody

`Widget`s can be identified as sources or targets using `Gtk::DragSource` and `Gtk::DropTarget` event controllers.

    auto source = Gtk::DragSource::create();
    m_source_widget.add_controller(source);

Some `DragSource` methods:

- `void set_content(const Glib::RefPtr<Gdk::ContentProvider>& content)`: Sets a content provider on the drag source.

- `void set_actions(Gdk::DragAction actions)`: Sets the actions on the drag source. For instance `Gdk::DragAction::COPY | Gdk::DragAction::MOVE`.

- `void set_icon(const Glib::RefPtr<const Gdk::Paintable>& paintable, int hot_x, int hot_y)`: Sets a paintable to use as icon during DND operations.

    auto target = Gtk::DropTarget::create(gtype, actions);
    m_target_widget.add_controller(target);

Some `DropTarget` methods:

- `void set_gtypes(const std::vector<GType>& types)`: Sets the supported types for this drop target.

- `void set_actions(Gdk::DragAction actions)`: Sets the actions that this drop target supports.

- `Glib::ValueBase get_value() const`: Gets the current drop data, as a `Glib::Value`.

- `void reject()`: Rejects the ongoing drop operation. This function should be used when delaying the decision on whether to accept a drag or not until after reading the data.

### Signály

When a drop target has accepted a dragged item, certain signals will be emitted, depending on what action has been selected. For instance, the user might have held down the Shift key to specify a `move` rather than a `copy`. Remember that the user can only select the actions which you have specified in your calls to `Gtk::DragSource::set_actions()` and `Gtk::DropTarget::set_actions()`.

The source widget will emit these `DragSource` signals:

- `drag_begin`: Provides a `Gdk::Drag`.

- `prepare`: Shall return a `Gdk::ContentProvider`, with the data to use for the drag that is about to start.

- `drag_end`: Provides a `Gdk::Drag`, and a bool that tells if the drag was performing a `move` and the data should be deleted.

- `drag_cancel`: Emitted on the drag source when a drag has failed.

The target widget will emit these `DropTarget` signals:

- `enter`: Provides coordinates. Shall return the preferred Gdk::DragAction.

- `motion`: Provides coordinates. Shall return the preferred Gdk::DragAction.

- `leave`: Emitted on the drop site when the pointer leaves the widget.

- `accept`: Provides a `Gdk::Drop`. You can call the `status()` method of the `Gdk::Drop` to indicate which actions will be accepted.

- `drop`: Provides the data being dropped and coordinates. Shall return a bool indicating whether the drop was accepted.

The following signals call only one signal handler when emitted. When you connect a handler to such a signal, your signal handler must be called before (instead of) the default handler, otherwise it won't be called. Set the `after` parameter in `connect()` to `false`.

- `Gtk::DragSource::signal_prepare()`

- `Gtk::DropTarget::signal_enter()`

- `Gtk::DropTarget::signal_motion()`

- `Gtk::DropTarget::signal_accept()`

- `Gtk::DropTarget::signal_drop()`

### Příklad

Zde je velmi jednoduchý příklad předvádějící operaci `kopírování` pomocí tažení a upuštění:

#### Táhni a upusť

Source Code

File: `dndwindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLE_DNDWINDOW_H
    #define GTKMM_EXAMPLE_DNDWINDOW_H

    #include <gdkmm/drop.h>
    #include <gtkmm/box.h>
    #include <gtkmm/label.h>
    #include <gtkmm/window.h>
    #include <gtkmm/button.h>

    class DnDWindow : public Gtk::Window
    {

    public:
      DnDWindow();
      virtual ~DnDWindow();

    protected:
      //Signal handlers:
      Glib::RefPtr<Gdk::ContentProvider> on_label_drag_prepare_data(double x, double y);
      bool on_button_drop_drop_data(const Glib::ValueBase& value, double x, double y);

      //Member widgets:
      Gtk::Box m_HBox;
      Gtk::Label m_Label_Drag;
      Gtk::Button m_Button_Drop;
    };

    #endif // GTKMM_EXAMPLE_DNDWINDOW_H

File: `dndwindow.cc` (For use with gtkmm 4)

    #include "dndwindow.h"
    #include <gdkmm/contentprovider.h>
    #include <gtkmm/dragsource.h>
    #include <gtkmm/droptarget.h>
    #include <iostream>

    DnDWindow::DnDWindow()
    : m_Label_Drag("Drag Here\n"),
      m_Button_Drop("Drop here\n")
    {
      set_title("DnD example");

      set_child(m_HBox);

      //Drag site:

      //Make m_Label_Drag a DnD drag source:
      auto source = Gtk::DragSource::create();
      source->set_actions(Gdk::DragAction::COPY);
      source->signal_prepare().connect(
        sigc::mem_fun(*this, &DnDWindow::on_label_drag_prepare_data), false);
      m_Label_Drag.add_controller(source);

      m_HBox.append(m_Label_Drag);
      m_Label_Drag.set_expand(true);

      //Drop site:

      //Make m_Button_Drop a DnD drop destination:
      const GType ustring_type = Glib::Value<Glib::ustring>::value_type();
      auto target = Gtk::DropTarget::create(ustring_type, Gdk::DragAction::COPY);
      target->signal_drop().connect(
        sigc::mem_fun(*this, &DnDWindow::on_button_drop_drop_data), false);
      m_Button_Drop.add_controller(target);

      m_HBox.append(m_Button_Drop);
      m_Button_Drop.set_expand(true);
    }

    DnDWindow::~DnDWindow()
    {
    }

    // In this simple example where just a small amount of data is copied,
    // it would be reasonable to store the ContentProvider in the DragSource.
    // Then this signal handler would be unnecessary.
    Glib::RefPtr<Gdk::ContentProvider> DnDWindow::on_label_drag_prepare_data(double, double)
    {
      Glib::Value<Glib::ustring> ustring_value;
      ustring_value.init(ustring_value.value_type());
      ustring_value.set("I'm Data!");
      return Gdk::ContentProvider::create(ustring_value);
    }

    bool DnDWindow::on_button_drop_drop_data(const Glib::ValueBase& value, double, double)
    {
      if (G_VALUE_HOLDS(value.gobj(), Glib::Value<Glib::ustring>::value_type()))
      {
        // We got the value type that we expected.
        Glib::Value<Glib::ustring> ustring_value;
        ustring_value.init(value.gobj());
        const Glib::ustring dropped_string = ustring_value.get();

        std::cout << "Received \"" << dropped_string << "\" in button " << std::endl;
        return true;
      }
      else
      {
        std::cout << "Received unexpected data type \""
          << G_VALUE_TYPE_NAME(value.gobj()) << "\" in button " << std::endl;
        return false;
      }
    }

File: `main.cc` (For use with gtkmm 4)

    #include "dndwindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char* argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<DnDWindow>(argc, argv);
    }

V `examples/others/dnd` najdete ucelenější příklad.

## Schránka

Jednoduchá funkcionalita kopírování/vložení textu je volně poskytována widgety, jako jsou `Gtk::Entry` a `Gtk::TextView`. Pro zacházení se svým vlastním datovým formátem ale budete potřebovat speciální kód. Například kreslicí program by potřeboval speciální kód, který by zprovoznil kopírování a vkládání v rámci zobrazení, nebo mezi dokumenty.

You can get a clipboard instance with `Gtk::Widget::get_clipboard()` or `Gdk::Display::get_clipboard()`.

Your application doesn't need to wait for clipboard operations, particularly between the time when the user chooses Copy and then later chooses Paste. Many `Gdk::Clipboard` methods take `sigc::slot`s which specify callback methods. When `Gdk::Clipboard` is ready, it will call these methods, providing the requested data.

Reference

### Formats

Different applications contain different types of data, and they might make that data available in a variety of formats. gtkmm calls these data types `format`s.

For instance, gedit can supply and receive the `text/plain` mime type, so you can paste data into gedit from any application that supplies that format. Or two different image editing applications might supply and receive a variety of image formats. As long as one application can receive one of the formats that the other supplies then you will be able to copy data from one to the other.

Clipboard data can be in a variety of binary formats. This chapter, and the examples, assume that the data is 8-bit text. This would allow us to use an XML format for the clipboard data. However this would probably not be appropriate for binary data such as images.

The Drag and Drop API uses the same mechanism. You should probably use the same data formats for both Clipboard and Drag and Drop operations.

### Kopírování

When the user asks to copy some data, you should copy the data to the `Clipboard`. For instance,

    void ExampleWindow::on_button_copy()
    {
      get_clipboard()->set_text("example_custom_target");
    }

### Vložení

Když uživatel požádá o vložení dat ze schránky, tj. z objektu `Clipboard`, měli byste si požádat o konkrétní formát a poskytnout metodu zpětného volání, která bude zavolána na skutečná data. Například:

    void ExampleWindow::on_button_paste()
    {
      get_clipboard()->read_text_async(sigc::mem_fun(*this,
                  &ExampleWindow::on_clipboard_received));
    }

Zde je příklad metody zpětného volání:

    void ExampleWindow::on_clipboard_received(Glib::RefPtr<Gio::AsyncResult>& result)
    {
      auto text = get_clipboard()->read_text_finish(result);
      //Do something with the pasted data.
    }

#### Discovering the available formats

To find out what formats are currently available on the `Clipboard` for pasting, call the `get_formats()` method. Then call a `Gdk::ContentFormats` method to find out if a format that your application supports is available.

### Příklady

#### Jednoduchý

This example allows copy and pasting of application-specific data, using the standard text format. Although this is simple, it's not ideal because it does not identify the `Clipboard` data as being of a particular type.

##### Schránka – jednoduchý příklad

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_copy();
      void on_button_paste();

      void on_clipboard_text_received(Glib::RefPtr<Gio::AsyncResult>& result);

      Glib::ustring m_strData;

      //Child widgets:
      Gtk::Box m_VBox;

      Gtk::Label m_Label;

      Gtk::Grid m_Grid;
      Gtk::ToggleButton m_ButtonA1, m_ButtonA2, m_ButtonB1, m_ButtonB2;

      Gtk::Box m_ButtonBox;
      Gtk::Button m_Button_Copy, m_Button_Paste;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::Orientation::VERTICAL),
      m_Label("Select cells in the grid, click Copy, then open a second "
            "instance of this example to try pasting the copied data."),
      m_ButtonA1("A1"), m_ButtonA2("A2"), m_ButtonB1("B1"), m_ButtonB2("B2"),
      m_Button_Copy("_Copy", /* mnemonic= */ true), m_Button_Paste("_Paste", true)
    {
      set_title("Gtk::Clipboard example");

      m_VBox.set_margin(12);
      set_child(m_VBox);

      m_VBox.append(m_Label);

      //Fill Grid:
      m_VBox.append(m_Grid);
      m_Grid.set_expand(true);
      m_Grid.set_row_homogeneous(true);
      m_Grid.set_column_homogeneous(true);
      m_Grid.attach(m_ButtonA1, 0, 0);
      m_Grid.attach(m_ButtonA2, 1, 0);
      m_Grid.attach(m_ButtonB1, 0, 1);
      m_Grid.attach(m_ButtonB2, 1, 1);

      //Add ButtonBox to bottom:
      m_VBox.append(m_ButtonBox);
      m_VBox.set_spacing(6);

      //Fill ButtonBox:
      m_ButtonBox.append(m_Button_Copy);
      m_Button_Copy.set_hexpand(true);
      m_Button_Copy.set_halign(Gtk::Align::END);
      m_Button_Copy.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_copy) );
      m_ButtonBox.append(m_Button_Paste);
      m_Button_Paste.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_paste) );
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_copy()
    {
      //Build a string representation of the stuff to be copied:
      //Ideally you would use XML, with an XML parser here:
      m_strData = m_ButtonA1.get_active() ? "1" : "0";
      m_strData += m_ButtonA2.get_active() ? "1" : "0";
      m_strData += m_ButtonB1.get_active() ? "1" : "0";
      m_strData += m_ButtonB2.get_active() ? "1" : "0";

      // Gdk::Clipboard::set_text() does not take a copy of the text.
      // The text can only be pasted (in this program or in some other program)
      // for as long as it exists.
      get_clipboard()->set_text(m_strData);
    }

    void ExampleWindow::on_button_paste()
    {
      //Tell the clipboard to call our method when it is ready:
      get_clipboard()->read_text_async(sigc::mem_fun(*this,
                  &ExampleWindow::on_clipboard_text_received));
    }

    void ExampleWindow::on_clipboard_text_received(Glib::RefPtr<Gio::AsyncResult>& result)
    {
      Glib::ustring text;
      try
      {
        text = get_clipboard()->read_text_finish(result);
      }
      catch (const Glib::Error& err)
      {
        // Print an error about why pasting failed.
        // Usually you probably want to ignore such failures,
        // but for demonstration purposes, we show the error.
        std::cout << "Pasting failed: " << err.what() << std::endl;
      }

      //See comment in on_button_copy() about this silly clipboard format.
      if(text.size() >= 4)
      {
        m_ButtonA1.set_active( text[0] == '1' );
        m_ButtonA2.set_active( text[1] == '1' );
        m_ButtonB1.set_active( text[2] == '1' );
        m_ButtonB2.set_active( text[3] == '1' );
      }
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      // Gio::Application::Flags::NON_UNIQUE because it shall be possible to run
      // several instances of this application simultaneously.
      auto app = Gtk::Application::create(
        "org.gtkmm.example", Gio::Application::Flags::NON_UNIQUE);

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

#### Ideální

This is like the simple example, but it

1. Defines a custom clipboard target, though the format is still text.

2. It uses the `Gdk::ContentFormats::signal_changed()` signal and disables the Paste button if it can't use anything on the clipboard.

##### Schránka – ideální příklad

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_copy();
      void on_button_paste();

      void on_clipboard_content_changed();

      void on_clipboard_received(Glib::RefPtr<Gio::AsyncResult>& result);
      void on_clipboard_received_status(Glib::RefPtr<Gio::AsyncResult>& result);

      void update_paste_status(); //Disable the paste button if there is nothing to paste.

      Glib::ustring m_strData;

      //Child widgets:
      Gtk::Box m_VBox;

      Gtk::Label m_Label;

      Gtk::Grid m_Grid;
      Gtk::ToggleButton m_ButtonA1, m_ButtonA2, m_ButtonB1, m_ButtonB2;

      Gtk::Box m_ButtonBox;
      Gtk::Button m_Button_Copy, m_Button_Paste;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <iostream>
    #include <string>

    namespace
    {

    const char example_format_custom[] = "gtkmmclipboardexample";

    } // anonymous namespace

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::Orientation::VERTICAL),
      m_Label("Select cells in the grid, click Copy, then open a second instance "
              "of this example to try pasting the copied data.\nOr try pasting the "
              "text representation into gedit."),
      m_ButtonA1("A1"), m_ButtonA2("A2"), m_ButtonB1("B1"), m_ButtonB2("B2"),
      m_Button_Copy("_Copy", /* mnemonic= */ true), m_Button_Paste("_Paste", true)
    {
      set_title("Gtk::Clipboard example");

      m_VBox.set_margin(12);
      set_child(m_VBox);

      m_VBox.append(m_Label);

      //Fill Grid:
      m_VBox.append(m_Grid);
      m_Grid.set_expand(true);
      m_Grid.set_row_homogeneous(true);
      m_Grid.set_column_homogeneous(true);
      m_Grid.attach(m_ButtonA1, 0, 0);
      m_Grid.attach(m_ButtonA2, 1, 0);
      m_Grid.attach(m_ButtonB1, 0, 1);
      m_Grid.attach(m_ButtonB2, 1, 1);

      //Add ButtonBox to bottom:
      m_VBox.append(m_ButtonBox);
      m_VBox.set_spacing(6);

      //Fill ButtonBox:
      m_ButtonBox.append(m_Button_Copy);
      m_Button_Copy.set_hexpand(true);
      m_Button_Copy.set_halign(Gtk::Align::END);
      m_Button_Copy.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_copy) );
      m_ButtonBox.append(m_Button_Paste);
      m_Button_Paste.signal_clicked().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_button_paste) );

      //Connect a signal handler that will be called when the contents of
      //the clipboard change.
      get_clipboard()->signal_changed().connect(sigc::mem_fun(*this,
                  &ExampleWindow::on_clipboard_content_changed));

      update_paste_status();
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_copy()
    {
      //Build a string representation of the stuff to be copied:
      //Ideally you would use XML, with an XML parser here:
      m_strData = example_format_custom;
      m_strData += m_ButtonA1.get_active() ? " A1" : "";
      m_strData += m_ButtonA2.get_active() ? " A2" : "";
      m_strData += m_ButtonB1.get_active() ? " B1" : "";
      m_strData += m_ButtonB2.get_active() ? " B2" : "";

      // Gdk::Clipboard::set_text() does not take a copy of the text.
      // The text can only be pasted (in this program or in some other program)
      // for as long as it exists.
      get_clipboard()->set_text(m_strData);
    }

    void ExampleWindow::on_button_paste()
    {
      //Tell the clipboard to call our method when it is ready:
      get_clipboard()->read_text_async(sigc::mem_fun(*this,
                  &ExampleWindow::on_clipboard_received));
    }

    void ExampleWindow::on_clipboard_content_changed()
    {
      update_paste_status();
    }

    void ExampleWindow::on_clipboard_received(Glib::RefPtr<Gio::AsyncResult>& result)
    {
      Glib::ustring text;
      try
      {
        text = get_clipboard()->read_text_finish(result);
      }
      catch (const Glib::Error& err)
      {
        // Print an error about why pasting failed.
        // Usually you probably want to ignore such failures,
        // but for demonstration purposes, we show the error.
        std::cout << "Pasting failed: " << err.what() << std::endl;
      }

      if (text.find(example_format_custom) == 0)
      {
        // It's the expected format.
        m_ButtonA1.set_active(text.find("A1") != std::string::npos);
        m_ButtonA2.set_active(text.find("A2") != std::string::npos);
        m_ButtonB1.set_active(text.find("B1") != std::string::npos);
        m_ButtonB2.set_active(text.find("B2") != std::string::npos);
      }
      else
      {
        // Unexpected format. Disable the Paste button.
        std::cout << "Unexpected pasted text: \"" << text << "\"" << std::endl;
        m_Button_Paste.set_sensitive(false);
      }
    }

    void ExampleWindow::update_paste_status()
    {
      // Disable the paste button if there is nothing to paste.
      get_clipboard()->read_text_async(sigc::mem_fun(*this,
                  &ExampleWindow::on_clipboard_received_status));
    }

    void ExampleWindow::on_clipboard_received_status(Glib::RefPtr<Gio::AsyncResult>& result)
    {
      Glib::ustring text;
      try
      {
        text = get_clipboard()->read_text_finish(result);
      }
      catch (const Glib::Error&)
      {
      }

      const bool bPasteIsPossible = text.find(example_format_custom) == 0;

      // Enable/Disable the Paste button appropriately:
      m_Button_Paste.set_sensitive(bPasteIsPossible);
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      // Gio::Application::Flags::NON_UNIQUE because it shall be possible to run
      // several instances of this application simultaneously.
      auto app = Gtk::Application::create(
        "org.gtkmm.example", Gio::Application::Flags::NON_UNIQUE);

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

## Tisk

Z hlediska vývoje aplikací, poskytuje tiskové API v gtkmm dialogová okna, která jsou jednotná napříč aplikacemi a umožňují používat běžné kreslicí API Cairo, spolu s vykreslováním textu pomocí knihovny Pango. V implementaci tohoto společného API se používají výkonné části specifické pro platformu a ovladače specifické pro tiskárnu.

### Tisková operace (PrintOperation)

Hlavním objektem je `Gtk::PrintOperation`, který se alokuje zvlášť pro jednotlivé tiskové operace. Abyste mohli obsluhovat kreslení stránky, musíte se napojit na jeho signály, nebo jej zdědit a přepsat jeho výchozí virtuální obsluhy signálů. `PrintOperation` automaticky obsluhuje všechna nastavení ovlivňující tiskovou smyčku.

#### Signály

The `PrintOperation::run()` method starts the print loop, during which various signals are emitted:

- `begin_print`: You must handle this signal, because this is where you create and set up a `Pango::Layout` using the provided `Gtk::PrintContext`, and break up your printing output into pages.

- `paginate`: Pagination is potentially slow so if you need to monitor it you can call the `PrintOperation::set_show_progress()` method and handle this signal.

- For each page that needs to be rendered, the following signals are emitted:

  - `request_page_setup`: Provides a `PrintContext`, page number and `Gtk::PageSetup`. Handle this signal if you need to modify page setup on a per-page basis.

  - `draw_page`: You must handle this signal, which provides a `PrintContext` and a page number. The `PrintContext` should be used to create a `Cairo::Context` into which the provided page should be drawn. To render text, iterate over the `Pango::Layout` you created in the `begin_print` handler.

- `end_print`: A handler for it is a safe place to free any resources related to a `PrintOperation`. If you have your custom class that inherits from `PrintOperation`, it is naturally simpler to do it in the destructor.

- `done`: This signal is emitted when printing is finished, meaning when the print data is spooled. Note that the provided `Gtk::PrintOperation::Result` may indicate that an error occurred. In any case you probably want to notify the user about the final status.

- `status_changed`: Emitted whenever a print job's status changes, until it is finished. Call the `PrintOperation::set_track_print_status()` method to monitor the job status after spooling. To see the status, use `get_status()` or `get_status_string()`.

Reference

### Nastavení stránky

Třída `PrintOperation` má metodu nazvanou `set_default_page_setup()`, která vybírá výchozí velikost papíru, jeho otočení a okraje. K zobrazení dialogového okna s nastavením stránky pro svoji aplikaci použijte metodu `Gtk::run_page_setup_dialog()`, která vrací objekt `Gtk::PageSetup` se zvolený nastavením. Tento objek použijte k aktualizaci `PrintOperation` a k přístupu k vybrané velikosti papíru `Gtk::PaperSize`, otočení papíru `Gtk::PageOrientation` a okrajům, které se liší podle tiskárny.

Zvolený `Gtk::PageSetup` byste si měli uložit, abyste jej mohli opětovně použít, když se znovu zobrazí dialogové okno nastavení stránky.

Například

    // Within a class that inherits from Gtk::Window and keeps m_refPageSetup
    // and m_refSettings as members...
    auto new_page_setup = Gtk::run_page_setup_dialog(*this, m_refPageSetup, m_refSettings);
    m_refPageSetup = new_page_setup;

Reference

Systém souřadnic v Cairo, v obsluze `draw_page`, je automaticky otočen podle aktuálního otočení stránky. Normálně je v rozmezí tiskových okrajů, ale to můžete změnit pomocí metody `PrintOperation::set_use_full_page()`. Výchozí měrnou jednotkou jsou pixely zařízení. K výběru jiných jednotek použijte metodu `PrintOperation::set_unit()`.

### Vykreslování textu

Vykreslování textu se provádí pomocí knihovny Pango. Objekt `Pango::Layout` pro tisk by se měl vytvořit zavoláním metody `PrintContext::create_pango_layout()`. Objekt `PrintContext` poskytuje také metriku stránky, přes `get_width()` a `get_height()`. Počet stránek můžete nastavit pomocí `PrintOperation::set_n_pages()`. Abyste mohli v `on_draw_page` provést skutečné vykreslení textu Pango, získejte `Cairo::Context` pomocí `PrintContext::get_cairo_context()` a zobrazte objekty `Pango::LayoutLine`, které se tím objeví na příslušné stránce.

See an example of exactly how this can be done.

### Asynchronní operace

Standardně se `PrintOperation::run()` vrací po té, co je tisková operace dokončená. Pokud potřebujete spustit neblokující tiskovou operaci, zavolejte `PrintOperation::set_allow_async()`. Pamatujte ale, že `set_allow_async()` není podporováno na všech platformách, ale signál `done` bude i tak vyslán.

`run()` may return `PrintOperation::Result::IN_PROGRESS`. To track status and handle the result or error you need to implement signal handlers for the `done` and `status_changed` signals:

Například

    // in class ExampleWindow's method...
    auto op = PrintOperation::create();
    // ...set up op...
    op->signal_done().connect(sigc::bind(sigc::mem_fun(
      *this, &ExampleWindow::on_printoperation_done), op));
    // run the op

Second, check for an error and connect to the `status_changed` signal. For instance:

    void ExampleWindow::on_printoperation_done(Gtk::PrintOperation::Result result,
      const Glib::RefPtr<PrintOperation>& op)
    {
      if (result == Gtk::PrintOperation::Result::ERROR)
        //notify user
      else if (result == Gtk::PrintOperation::Result::APPLY)
        //Update PrintSettings with the ones used in this PrintOperation

      if (! op->is_finished())
        op->signal_status_changed().connect(sigc::bind(sigc::mem_fun(
          *this, &ExampleWindow::on_printoperation_status_changed), op));
    }

Finally, check the status. For instance,

    void ExampleWindow::on_printoperation_status_changed(const Glib::RefPtr<PrintOperation>& op)
    {
      if (op->is_finished())
        //the print job is finished
      else
        //get the status with get_status() or get_status_string()

      //update UI
    }

### Export do PDF

The 'Print to file' option is available in the print dialog, without the need for extra implementation. However, it is sometimes useful to generate a pdf file directly from code. For instance,

    auto op = Gtk::PrintOperation::create();
    // ...set up op...
    op->set_export_filename("test.pdf");
    auto res = op->run(Gtk::PrintOperation::Action::EXPORT);

### Rozšířené dialogové okno tisku

You may add a custom tab to the print dialog:

- Set the title of the tab via `PrintOperation::set_custom_tab_label()`, create a new widget and return it from the `create_custom_widget` signal handler. You'll probably want this to be a container widget, packed with some others.

- Get the data from the widgets in the `custom_widget_apply` signal handler.

Although the `custom_widget_apply` signal provides the widget you previously created, to simplify things you can keep the widgets you expect to contain some user input as class members. For example, let's say you have a `Gtk::Entry` called `m_Entry` as a member of your `CustomPrintOperation` class:

    Gtk::Widget* CustomPrintOperation::on_create_custom_widget()
    {
      set_custom_tab_label("My custom tab");

      auto hbox = new Gtk::Box(Gtk::Orientation::HORIZONTAL, 8);
      hbox->set_margin(6);

      auto label = Gtk::make_managed<Gtk::Label>("Enter some text: ");
      hbox->append(*label);

      hbox->append(m_Entry);

      return hbox;
    }

    void CustomPrintOperation::on_custom_widget_apply(Gtk::Widget* /* widget */)
    {
      auto user_input = m_Entry.get_text();
      //...
    }

Prakticky to předvádí příklad v examples/book/printing/advanced.

### Náhled

The native GTK print dialog has a preview button, but you may also start a preview directly from an application:

    // in a class that inherits from Gtk::Window...
    auto op = PrintOperation::create();
    // ...set up op...
    op->run(Gtk::PrintOperation::Action::PREVIEW, *this);

On Unix, the default preview handler uses an external viewer program. On Windows, the native preview dialog will be shown. If necessary you may override this behavior and provide a custom preview dialog. See the example located in /examples/book/printing/advanced.

### PrintDialog

Since gtkmm 4.14 `Gtk::PrintDialog` is an alternative to `Gtk::PrintOperation`. `PrintDialog` uses the same `PageSetup` and `PrintSettings` classes as `PrintOperation`. The rendering with Cairo and Pango is also similar.

### Příklady

#### Jednoduchý

The following example demonstrates how to print some input from a user interface using `PrintOperation`. It shows how to implement `on_begin_print` and `on_draw_page`, as well as how to track print status and update the print settings.

##### Tisk – jednoduchý příklad

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    // This file is part of the printing/simple and printing/advanced examples

    #include <gtkmm.h>

    class PrintFormOperation;

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow(const Glib::RefPtr<Gtk::Application>& app);
      virtual ~ExampleWindow();

    protected:

      void build_main_menu(const Glib::RefPtr<Gtk::Application>& app);

      void print_or_preview(Gtk::PrintOperation::Action print_action);

      //PrintOperation signal handlers.
      //We handle these so can get necessary information to update the UI or print settings.
      //Our derived PrintOperation class also overrides some default signal handlers.
      void on_printoperation_status_changed();
      void on_printoperation_done(Gtk::PrintOperation::Result result);

      //Action signal handlers:
      void on_menu_file_new();
      void on_menu_file_page_setup();
      void on_menu_file_print_preview();
      void on_menu_file_print();
      void on_menu_file_quit();

      //Printing-related objects:
      Glib::RefPtr<Gtk::PageSetup> m_refPageSetup;
      Glib::RefPtr<Gtk::PrintSettings> m_refSettings;
      Glib::RefPtr<PrintFormOperation> m_refPrintFormOperation;

      //Child widgets:
      Gtk::Box m_VBox;
      Gtk::Grid m_Grid;

      Gtk::Label m_NameLabel;
      Gtk::Entry m_NameEntry;

      Gtk::Label m_SurnameLabel;
      Gtk::Entry m_SurnameEntry;

      Gtk::Label m_CommentsLabel;
      Gtk::ScrolledWindow m_ScrolledWindow;
      Gtk::TextView m_TextView;

      Glib::RefPtr<Gtk::TextBuffer> m_refTextBuffer;

      Gtk::Label m_Statusbar;

      Glib::RefPtr<Gtk::Builder> m_refBuilder;

      Glib::RefPtr<Gtk::AlertDialog> m_refDialog;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `printformoperation.h` (For use with gtkmm 4)

    #ifndef GTKMM_PRINT_FORM_OPERATION_H
    #define GTKMM_PRINT_FORM_OPERATION_H

    #include <gtkmm.h>
    #include <pangomm.h>
    #include <vector>

    //We derive our own class from PrintOperation,
    //so we can put the actual print implementation here.
    class PrintFormOperation : public Gtk::PrintOperation
    {
     public:
      static Glib::RefPtr<PrintFormOperation> create();
      virtual ~PrintFormOperation();

      void set_name(const Glib::ustring& name) { m_Name = name; }
      void set_comments(const Glib::ustring& comments) { m_Comments = comments; }

     protected:
      PrintFormOperation();

      //PrintOperation default signal handler overrides:
      void on_begin_print(const Glib::RefPtr<Gtk::PrintContext>& context) override;
      void on_draw_page(const Glib::RefPtr<Gtk::PrintContext>& context, int page_nr) override;

      Glib::ustring m_Name;
      Glib::ustring m_Comments;
      Glib::RefPtr<Pango::Layout> m_refLayout;
      std::vector<int> m_PageBreaks; // line numbers where a page break occurs
    };

    #endif // GTKMM_PRINT_FORM_OPERATION_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include "printformoperation.h"
    #include <iostream>

    ExampleWindow::ExampleWindow(const Glib::RefPtr<Gtk::Application>& app)
    : m_VBox(Gtk::Orientation::VERTICAL),
      m_NameLabel("Name"),
      m_SurnameLabel("Surname"),
      m_CommentsLabel("Comments")
    {
      m_refPageSetup = Gtk::PageSetup::create();
      m_refSettings = Gtk::PrintSettings::create();

      set_title("gtkmm Printing Example");
      set_default_size(400, 300);

      set_child(m_VBox);

      build_main_menu(app);

      m_VBox.append(m_Grid);

      //Arrange the widgets inside the grid:
      m_Grid.set_expand(true);
      m_Grid.set_row_spacing(5);
      m_Grid.set_column_spacing(5);
      m_Grid.attach(m_NameLabel, 0, 0);
      m_Grid.attach(m_NameEntry, 1, 0);

      m_Grid.attach(m_SurnameLabel, 0, 1);
      m_Grid.attach(m_SurnameEntry, 1, 1);

      //Add the TextView, inside a ScrolledWindow:
      m_ScrolledWindow.set_child(m_TextView);

      //Only show the scrollbars when they are necessary:
      m_ScrolledWindow.set_policy(Gtk::PolicyType::AUTOMATIC, Gtk::PolicyType::AUTOMATIC);

      m_Grid.attach(m_CommentsLabel, 0, 2);
      m_Grid.attach(m_ScrolledWindow, 1, 2);
      m_ScrolledWindow.set_expand(true);

      m_refTextBuffer = Gtk::TextBuffer::create();
      m_TextView.set_buffer(m_refTextBuffer);

      m_Statusbar.set_hexpand(true);
      m_VBox.append(m_Statusbar);
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::build_main_menu(const Glib::RefPtr<Gtk::Application>& app)
    {
      //Create actions for menus and toolbars:
      auto refActionGroup = Gio::SimpleActionGroup::create();

      //File menu:
      refActionGroup->add_action("new",
        sigc::mem_fun(*this, &ExampleWindow::on_menu_file_new));

      refActionGroup->add_action("pagesetup",
        sigc::mem_fun(*this, &ExampleWindow::on_menu_file_page_setup));

      refActionGroup->add_action("printpreview",
        sigc::mem_fun(*this, &ExampleWindow::on_menu_file_print_preview));

      refActionGroup->add_action("print",
        sigc::mem_fun(*this, &ExampleWindow::on_menu_file_print));

      refActionGroup->add_action("quit",
        sigc::mem_fun(*this, &ExampleWindow::on_menu_file_quit));

      insert_action_group("example", refActionGroup);

      // When the menubar is a child of a Gtk::Window, keyboard accelerators are not
      // automatically fetched from the Gio::Menu.
      // See the examples/book/menus/main_menu example for an alternative way of
      // adding the menubar when using Gtk::ApplicationWindow.
      app->set_accel_for_action("example.new", "<Primary>n");
      app->set_accel_for_action("example.print", "<Primary>p");
      app->set_accel_for_action("example.quit", "<Primary>q");

      m_refBuilder = Gtk::Builder::create();

      // Layout the actions in a menubar:
      Glib::ustring ui_menu_info =
        "<interface>"
        "  <menu id='menu-example'>"
        "    <submenu>"
        "      <attribute name='label' translatable='yes'>_File</attribute>"
        "      <section>"
        "        <item>"
        "          <attribute name='label' translatable='yes'>_New</attribute>"
        "          <attribute name='action'>example.new</attribute>"
        "        </item>"
        "      </section>"
        "      <section>"
        "        <item>"
        "          <attribute name='label' translatable='yes'>Page _Setup...</attribute>"
        "          <attribute name='action'>example.pagesetup</attribute>"
        "        </item>"
        "        <item>"
        "          <attribute name='label' translatable='yes'>Print Preview</attribute>"
        "          <attribute name='action'>example.printpreview</attribute>"
        "        </item>"
        "        <item>"
        "          <attribute name='label' translatable='yes'>_Print...</attribute>"
        "          <attribute name='action'>example.print</attribute>"
        "        </item>"
        "      </section>"
        "      <section>"
        "        <item>"
        "          <attribute name='label' translatable='yes'>_Quit</attribute>"
        "          <attribute name='action'>example.quit</attribute>"
        "        </item>"
        "      </section>"
        "    </submenu>"
        "  </menu>"
        "</interface>";

      try
      {
        m_refBuilder->add_from_string(ui_menu_info);
      }
      catch(const Glib::Error& ex)
      {
        std::cerr << "building menus failed: " << ex.what();
      }

      // Layout the actions in a toolbar:
      Glib::ustring ui_toolbar_info =
        "<!-- Generated with glade 3.18.3 and then changed manually -->"
        "<interface>"
          "<object class='GtkBox' id='toolbar'>"
            "<property name='can_focus'>False</property>"
            "<property name='spacing'>3</property>"
            "<child>"
              "<object class='GtkButton' id='toolbutton_new'>"
                "<property name='can_focus'>False</property>"
                "<property name='tooltip_text' translatable='yes'>New</property>"
                "<property name='action_name'>example.new</property>"
                "<property name='icon_name'>document-new</property>"
                "<property name='hexpand'>False</property>"
                "<property name='vexpand'>False</property>"
              "</object>"
            "</child>"
            "<child>"
              "<object class='GtkButton' id='toolbutton_print'>"
                "<property name='can_focus'>False</property>"
                "<property name='tooltip_text' translatable='yes'>Print</property>"
                "<property name='action_name'>example.print</property>"
                "<property name='icon_name'>document-print</property>"
                "<property name='hexpand'>False</property>"
                "<property name='vexpand'>False</property>"
              "</object>"
            "</child>"
            "<child>"
              "<object class='GtkSeparator' id='separator1'>"
                "<property name='can_focus'>False</property>"
                "<property name='hexpand'>False</property>"
                "<property name='vexpand'>False</property>"
              "</object>"
            "</child>"
            "<child>"
              "<object class='GtkButton' id='toolbutton_quit'>"
                "<property name='can_focus'>False</property>"
                "<property name='tooltip_text' translatable='yes'>Quit</property>"
                "<property name='action_name'>example.quit</property>"
                "<property name='icon_name'>application-exit</property>"
                "<property name='hexpand'>False</property>"
                "<property name='vexpand'>False</property>"
              "</object>"
            "</child>"
          "</object>"
        "</interface>";

      try
      {
        m_refBuilder->add_from_string(ui_toolbar_info);
      }
      catch(const Glib::Error& ex)
      {
        std::cerr << "building toolbar failed: " << ex.what();
      }

      // Get the menubar and add it to a container widget:
      auto object = m_refBuilder->get_object("menu-example");
      auto gmenu = std::dynamic_pointer_cast<Gio::Menu>(object);
      if (!gmenu)
        g_warning("GMenu not found");
      else
      {
        auto pMenuBar = Gtk::make_managed<Gtk::PopoverMenuBar>(gmenu);

        // Add the PopoverMenuBar to the window:
        m_VBox.append(*pMenuBar);
      }

      // Get the toolbar and add it to a container widget:
      auto toolbar = m_refBuilder->get_widget<Gtk::Box>("toolbar");
      if (!toolbar)
        g_warning("toolbar not found");
      else
        m_VBox.append(*toolbar);
    }

    void ExampleWindow::on_printoperation_status_changed()
    {
      Glib::ustring status_msg;

      if (m_refPrintFormOperation->is_finished())
      {
        status_msg = "Print job completed.";
      }
      else
      {
        //You could also use get_status().
        status_msg = m_refPrintFormOperation->get_status_string();
      }

      m_Statusbar.set_text(status_msg);
    }

    void ExampleWindow::on_printoperation_done(Gtk::PrintOperation::Result result)
    {
      //Printing is "done" when the print data is spooled.

      if (result == Gtk::PrintOperation::Result::ERROR)
      {
        if (!m_refDialog)
          m_refDialog = Gtk::AlertDialog::create("Error printing form");
        m_refDialog->show(*this);
      }
      else if (result == Gtk::PrintOperation::Result::APPLY)
      {
        //Update PrintSettings with the ones used in this PrintOperation:
        m_refSettings = m_refPrintFormOperation->get_print_settings();
      }

      if (!m_refPrintFormOperation->is_finished())
      {
        //We will connect to the status-changed signal to track status
        //and update a status bar. In addition, you can, for example,
        //keep a list of active print operations, or provide a progress dialog.
        m_refPrintFormOperation->signal_status_changed().connect(sigc::mem_fun(*this,
                        &ExampleWindow::on_printoperation_status_changed));
      }
    }

    void ExampleWindow::print_or_preview(Gtk::PrintOperation::Action print_action)
    {
      //Create a new PrintOperation with our PageSetup and PrintSettings:
      //(We use our derived PrintOperation class)
      m_refPrintFormOperation = PrintFormOperation::create();

      m_refPrintFormOperation->set_name(m_NameEntry.get_text() + " " + m_SurnameEntry.get_text());
      m_refPrintFormOperation->set_comments(m_refTextBuffer->get_text(false /*Don't include hidden*/));
      // In the printing/advanced example, the font will be set through a custom tab
      // in the print dialog.

      m_refPrintFormOperation->set_track_print_status();
      m_refPrintFormOperation->set_default_page_setup(m_refPageSetup);
      m_refPrintFormOperation->set_print_settings(m_refSettings);

      m_refPrintFormOperation->signal_done().connect(sigc::mem_fun(*this,
                      &ExampleWindow::on_printoperation_done));
      try
      {
        m_refPrintFormOperation->run(print_action /* print or preview */, *this);
      }
      catch (const Gtk::PrintError& ex)
      {
        //See documentation for exact Gtk::PrintError error codes.
        std::cerr << "An error occurred while trying to run a print operation:"
            << ex.what() << std::endl;
      }
    }

    void ExampleWindow::on_menu_file_new()
    {
      //Clear entries and textview:
      m_NameEntry.set_text("");
      m_SurnameEntry.set_text("");
      m_refTextBuffer->set_text("");
      m_TextView.set_buffer(m_refTextBuffer);
    }

    void ExampleWindow::on_menu_file_page_setup()
    {
      //Show the page setup dialog, asking it to start with the existing settings:
      auto new_page_setup =
          Gtk::run_page_setup_dialog(*this, m_refPageSetup, m_refSettings);

      //Save the chosen page setup dialog for use when printing, previewing, or
      //showing the page setup dialog again:
      m_refPageSetup = new_page_setup;
    }

    void ExampleWindow::on_menu_file_print_preview()
    {
      print_or_preview(Gtk::PrintOperation::Action::PREVIEW);
    }

    void ExampleWindow::on_menu_file_print()
    {
      print_or_preview(Gtk::PrintOperation::Action::PRINT_DIALOG);
    }

    void ExampleWindow::on_menu_file_quit()
    {
      set_visible(false);
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char* argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      // Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv, app);
    }

File: `printformoperation.cc` (For use with gtkmm 4)

    #include "printformoperation.h"

    PrintFormOperation::PrintFormOperation()
    {
    }

    PrintFormOperation::~PrintFormOperation()
    {
    }

    Glib::RefPtr<PrintFormOperation> PrintFormOperation::create()
    {
      return Glib::make_refptr_for_instance<PrintFormOperation>(new PrintFormOperation());
    }

    void PrintFormOperation::on_begin_print(
            const Glib::RefPtr<Gtk::PrintContext>& print_context)
    {
      //Create and set up a Pango layout for PrintData based on the passed
      //PrintContext: We then use this to calculate the number of pages needed, and
      //the lines that are on each page.
      m_refLayout = print_context->create_pango_layout();

      Pango::FontDescription font_desc("sans 12");
      m_refLayout->set_font_description(font_desc);

      const double width = print_context->get_width();
      const double height = print_context->get_height();

      m_refLayout->set_width(static_cast<int>(width * Pango::SCALE));

      //Set and mark up the text to print:
      Glib::ustring marked_up_form_text;
      marked_up_form_text += "<b>Name</b>: " + m_Name + "\n\n";
      marked_up_form_text += "<b>Comments</b>: " + m_Comments;

      m_refLayout->set_markup(marked_up_form_text);

      //Set the number of pages to print by determining the line numbers
      //where page breaks occur:
      const int line_count = m_refLayout->get_line_count();

      Glib::RefPtr<Pango::LayoutLine> layout_line;
      double page_height = 0;

      for (int line = 0; line < line_count; ++line)
      {
        Pango::Rectangle ink_rect, logical_rect;

        layout_line = m_refLayout->get_line(line);
        layout_line->get_extents(ink_rect, logical_rect);

        const double line_height = logical_rect.get_height() / 1024.0;

        if (page_height + line_height > height)
        {
          m_PageBreaks.push_back(line);
          page_height = 0;
        }

        page_height += line_height;
      }

      set_n_pages(m_PageBreaks.size() + 1);
    }

    void PrintFormOperation::on_draw_page(
            const Glib::RefPtr<Gtk::PrintContext>& print_context, int page_nr)
    {
      //Decide which lines we need to print in order to print the specified page:
      int start_page_line = 0;
      int end_page_line = 0;

      if(page_nr == 0)
      {
        start_page_line = 0;
      }
      else
      {
        start_page_line = m_PageBreaks[page_nr - 1];
      }

      if(page_nr < static_cast<int>(m_PageBreaks.size()))
      {
        end_page_line = m_PageBreaks[page_nr];
      }
      else
      {
        end_page_line = m_refLayout->get_line_count();
      }

      //Get a Cairo Context, which is used as a drawing board:
      Cairo::RefPtr<Cairo::Context> cairo_ctx = print_context->get_cairo_context();

      //We'll use black letters:
      cairo_ctx->set_source_rgb(0, 0, 0);

      //Render Pango LayoutLines over the Cairo context:
      auto iter = m_refLayout->get_iter();

      double start_pos = 0;
      int line_index = 0;

      do
      {
        if(line_index >= start_page_line)
        {
          auto layout_line = iter.get_line();
          auto logical_rect = iter.get_line_logical_extents();
          int baseline = iter.get_baseline();

          if (line_index == start_page_line)
          {
            start_pos = logical_rect.get_y() / 1024.0;
          }

          cairo_ctx->move_to(logical_rect.get_x() / 1024.0,
            baseline / 1024.0 - start_pos);

          layout_line->show_in_cairo_context(cairo_ctx);
        }

        line_index++;
      }
      while(line_index < end_page_line && iter.next_line());
    }

#### PrintDialog

The following example demonstrates how to print some input from a user interface using `PrintDialog`. The user interface is similar to the previous example.

##### Printing - PrintDialog

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class PrintFormDialog;

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow(const Glib::RefPtr<Gtk::Application>& app);
      ~ExampleWindow() override;

    protected:
      void build_main_menu(const Glib::RefPtr<Gtk::Application>& app);

      // Action signal handlers:
      void on_menu_file_new();
      void on_menu_file_print_setup();
      void on_menu_file_print();
      void on_menu_file_quit();

      // Printing-related objects:
      Glib::RefPtr<PrintFormDialog> m_refPrintFormDialog;

      // Child widgets:
      Gtk::Box m_VBox;
      Gtk::Grid m_Grid;

      Gtk::Label m_NameLabel;
      Gtk::Entry m_NameEntry;

      Gtk::Label m_SurnameLabel;
      Gtk::Entry m_SurnameEntry;

      Gtk::Label m_CommentsLabel;
      Gtk::ScrolledWindow m_ScrolledWindow;
      Gtk::TextView m_TextView;

      Glib::RefPtr<Gtk::TextBuffer> m_refTextBuffer;

      Glib::RefPtr<Gtk::Builder> m_refBuilder;
    };
    #endif //GTKMM_EXAMPLEWINDOW_H

File: `printformdialog.h` (For use with gtkmm 4)

    #ifndef GTKMM_PRINT_FORM_DIALOG_H
    #define GTKMM_PRINT_FORM_DIALOG_H

    #include <gtkmm.h>
    #include <pangomm.h>
    #include <vector>

    #define HAS_PRINT_DIALOG GTKMM_CHECK_VERSION(4,13,1)

    #if HAS_PRINT_DIALOG
    // We derive our own class from PrintDialog,
    // so we can put the actual print implementation here.
    class PrintFormDialog : public Gtk::PrintDialog
    {
    public:
      static Glib::RefPtr<PrintFormDialog> create();
      virtual ~PrintFormDialog();

      void set_name(const Glib::ustring& name) { m_Name = name; }
      void set_comments(const Glib::ustring& comments) { m_Comments = comments; }
      void do_setup(Gtk::Window* parent);
      void do_print(Gtk::Window* parent);

    protected:
      PrintFormDialog();

      // PrintDialog callback slots:
      void on_setup_finish(const Glib::RefPtr<Gio::AsyncResult>& result);
      void on_print_finish(const Glib::RefPtr<Gio::AsyncResult>& result);
      Cairo::ErrorStatus write_func(const unsigned char* data, unsigned int length,
        Glib::RefPtr<Gio::OutputStream>& stream);
      void do_printing(const Cairo::RefPtr<Cairo::Context>& cairo_ctx);

      Glib::ustring m_Name;
      Glib::ustring m_Comments;
      Glib::RefPtr<Pango::Layout> m_refLayout;
      Glib::RefPtr<Gtk::PrintSetup> m_refPrintSetup;
    };
    #endif // HAS_PRINT_DIALOG

    #endif // GTKMM_PRINT_FORM_DIALOG_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include "printformdialog.h"
    #include <iostream>

    ExampleWindow::ExampleWindow(const Glib::RefPtr<Gtk::Application>& app)
    : m_VBox(Gtk::Orientation::VERTICAL),
      m_NameLabel("Name"),
      m_SurnameLabel("Surname"),
      m_CommentsLabel("Comments")
    {
      set_title("gtkmm PrintDialog Example");
      set_default_size(400, 300);

    #if HAS_PRINT_DIALOG
      // Create a PrintDialog. (We use our derived PrintDialog class.)
      m_refPrintFormDialog = PrintFormDialog::create();
    #endif // HAS_PRINT_DIALOG

      set_child(m_VBox);

      build_main_menu(app);

      m_VBox.append(m_Grid);

      // Arrange the widgets inside the grid:
      m_Grid.set_expand(true);
      m_Grid.set_row_spacing(5);
      m_Grid.set_column_spacing(5);
      m_Grid.attach(m_NameLabel, 0, 0);
      m_Grid.attach(m_NameEntry, 1, 0);

      m_Grid.attach(m_SurnameLabel, 0, 1);
      m_Grid.attach(m_SurnameEntry, 1, 1);

      // Add the TextView, inside a ScrolledWindow:
      m_ScrolledWindow.set_child(m_TextView);

      // Only show the scrollbars when they are necessary:
      m_ScrolledWindow.set_policy(Gtk::PolicyType::AUTOMATIC, Gtk::PolicyType::AUTOMATIC);

      m_Grid.attach(m_CommentsLabel, 0, 2);
      m_Grid.attach(m_ScrolledWindow, 1, 2);
      m_ScrolledWindow.set_expand(true);

      m_refTextBuffer = Gtk::TextBuffer::create();
      m_TextView.set_buffer(m_refTextBuffer);
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::build_main_menu(const Glib::RefPtr<Gtk::Application>& app)
    {
      // Create actions for menus and toolbars:
      auto refActionGroup = Gio::SimpleActionGroup::create();

      // File menu:
      refActionGroup->add_action("new",
        sigc::mem_fun(*this, &ExampleWindow::on_menu_file_new));

      refActionGroup->add_action("printsetup",
        sigc::mem_fun(*this, &ExampleWindow::on_menu_file_print_setup));

      refActionGroup->add_action("print",
        sigc::mem_fun(*this, &ExampleWindow::on_menu_file_print));

      refActionGroup->add_action("quit",
        sigc::mem_fun(*this, &ExampleWindow::on_menu_file_quit));

      insert_action_group("example", refActionGroup);

      // When the menubar is a child of a Gtk::Window, keyboard accelerators are not
      // automatically fetched from the Gio::Menu.
      // See the examples/book/menus/main_menu example for an alternative way of
      // adding the menubar when using Gtk::ApplicationWindow.
      app->set_accel_for_action("example.new", "<Primary>n");
      app->set_accel_for_action("example.print", "<Primary>p");
      app->set_accel_for_action("example.quit", "<Primary>q");

      m_refBuilder = Gtk::Builder::create();

      // Layout the actions in a menubar:
      Glib::ustring ui_menu_info =
        "<interface>"
        "  <menu id='menu-example'>"
        "    <submenu>"
        "      <attribute name='label' translatable='yes'>_File</attribute>"
        "      <section>"
        "        <item>"
        "          <attribute name='label' translatable='yes'>_New</attribute>"
        "          <attribute name='action'>example.new</attribute>"
        "        </item>"
        "      </section>"
        "      <section>"
        "        <item>"
        "          <attribute name='label' translatable='yes'>Print _Setup...</attribute>"
        "          <attribute name='action'>example.printsetup</attribute>"
        "        </item>"
        "        <item>"
        "          <attribute name='label' translatable='yes'>_Print...</attribute>"
        "          <attribute name='action'>example.print</attribute>"
        "        </item>"
        "      </section>"
        "      <section>"
        "        <item>"
        "          <attribute name='label' translatable='yes'>_Quit</attribute>"
        "          <attribute name='action'>example.quit</attribute>"
        "        </item>"
        "      </section>"
        "    </submenu>"
        "  </menu>"
        "</interface>";

      try
      {
        m_refBuilder->add_from_string(ui_menu_info);
      }
      catch(const Glib::Error& ex)
      {
        std::cerr << "building menus failed: " << ex.what();
      }

      // Layout the actions in a toolbar:
      Glib::ustring ui_toolbar_info =
        "<!-- Generated with glade 3.18.3 and then changed manually -->"
        "<interface>"
          "<object class='GtkBox' id='toolbar'>"
            "<property name='can_focus'>False</property>"
            "<property name='spacing'>3</property>"
            "<child>"
              "<object class='GtkButton' id='toolbutton_new'>"
                "<property name='can_focus'>False</property>"
                "<property name='tooltip_text' translatable='yes'>New</property>"
                "<property name='action_name'>example.new</property>"
                "<property name='icon_name'>document-new</property>"
                "<property name='hexpand'>False</property>"
                "<property name='vexpand'>False</property>"
              "</object>"
            "</child>"
            "<child>"
              "<object class='GtkButton' id='toolbutton_print'>"
                "<property name='can_focus'>False</property>"
                "<property name='tooltip_text' translatable='yes'>Print</property>"
                "<property name='action_name'>example.print</property>"
                "<property name='icon_name'>document-print</property>"
                "<property name='hexpand'>False</property>"
                "<property name='vexpand'>False</property>"
              "</object>"
            "</child>"
            "<child>"
              "<object class='GtkSeparator' id='separator1'>"
                "<property name='can_focus'>False</property>"
                "<property name='hexpand'>False</property>"
                "<property name='vexpand'>False</property>"
              "</object>"
            "</child>"
            "<child>"
              "<object class='GtkButton' id='toolbutton_quit'>"
                "<property name='can_focus'>False</property>"
                "<property name='tooltip_text' translatable='yes'>Quit</property>"
                "<property name='action_name'>example.quit</property>"
                "<property name='icon_name'>application-exit</property>"
                "<property name='hexpand'>False</property>"
                "<property name='vexpand'>False</property>"
              "</object>"
            "</child>"
          "</object>"
        "</interface>";

      try
      {
        m_refBuilder->add_from_string(ui_toolbar_info);
      }
      catch(const Glib::Error& ex)
      {
        std::cerr << "building toolbar failed: " << ex.what();
      }

      // Get the menubar and add it to a container widget:
      auto object = m_refBuilder->get_object("menu-example");
      auto gmenu = std::dynamic_pointer_cast<Gio::Menu>(object);
      if (!gmenu)
        g_warning("GMenu not found");
      else
      {
        auto pMenuBar = Gtk::make_managed<Gtk::PopoverMenuBar>(gmenu);

        // Add the PopoverMenuBar to the window:
        m_VBox.append(*pMenuBar);
      }

      // Get the toolbar and add it to a container widget:
      auto toolbar = m_refBuilder->get_widget<Gtk::Box>("toolbar");
      if (!toolbar)
        g_warning("toolbar not found");
      else
        m_VBox.append(*toolbar);
    }

    void ExampleWindow::on_menu_file_new()
    {
      // Clear entries and textview:
      m_NameEntry.set_text("");
      m_SurnameEntry.set_text("");
      m_refTextBuffer->set_text("");
      m_TextView.set_buffer(m_refTextBuffer);
    }

    void ExampleWindow::on_menu_file_print_setup()
    {
    #if HAS_PRINT_DIALOG
      m_refPrintFormDialog->do_setup(this);
    #else
      std::cout << "Gtk::PrintDialog is not available.\n";
    #endif // HAS_PRINT_DIALOG
    }

    void ExampleWindow::on_menu_file_print()
    {
    #if HAS_PRINT_DIALOG
      m_refPrintFormDialog->set_name(m_NameEntry.get_text() + " " + m_SurnameEntry.get_text());
      m_refPrintFormDialog->set_comments(m_refTextBuffer->get_text(false /*Don't include hidden*/));
      m_refPrintFormDialog->do_print(this);
    #else
      std::cout << "Gtk::PrintDialog is not available.\n";
    #endif // HAS_PRINT_DIALOG
    }

    void ExampleWindow::on_menu_file_quit()
    {
      set_visible(false);
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char* argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      // Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv, app);
    }

File: `printformdialog.cc` (For use with gtkmm 4)

    #include "printformdialog.h"
    #include <iostream>

    #if HAS_PRINT_DIALOG
    PrintFormDialog::PrintFormDialog()
    {
      set_page_setup(Gtk::PageSetup::create());
      set_print_settings(Gtk::PrintSettings::create());
    }

    PrintFormDialog::~PrintFormDialog()
    {
    }

    Glib::RefPtr<PrintFormDialog> PrintFormDialog::create()
    {
      return Glib::make_refptr_for_instance<PrintFormDialog>(new PrintFormDialog());
    }

    void PrintFormDialog::do_setup(Gtk::Window* parent)
    {
      set_title("Print setup");
      if (parent)
        setup(*parent, sigc::mem_fun(*this, &PrintFormDialog::on_setup_finish));
      else
        setup(sigc::mem_fun(*this, &PrintFormDialog::on_setup_finish));
    }

    void PrintFormDialog::do_print(Gtk::Window* parent)
    {
      set_title("Printing");
      if (parent)
        print(*parent, sigc::mem_fun(*this, &PrintFormDialog::on_print_finish));
      else
        print(sigc::mem_fun(*this, &PrintFormDialog::on_print_finish));
    }

    void PrintFormDialog::on_setup_finish(const Glib::RefPtr<Gio::AsyncResult>& result)
    {
      try
      {
        m_refPrintSetup = setup_finish(result);
        if (m_refPrintSetup)
        {
          set_page_setup(m_refPrintSetup->get_page_setup());
          set_print_settings(m_refPrintSetup->get_print_settings());
        }
      }
      catch (const Gtk::DialogError& err)
      {
        // Can be thrown by setup_finish(result).
        std::cout << "No setup selected. " << err.what() << std::endl;
      }
      catch (const Glib::Error& err)
      {
        std::cout << "Unexpected exception. " << err.what() << std::endl;
      }
    }

    void PrintFormDialog::on_print_finish(const Glib::RefPtr<Gio::AsyncResult>& result)
    {
      Glib::RefPtr<Gio::OutputStream> outputStream;
      try
      {
        outputStream = print_finish(result);
      }
      catch (const Gtk::DialogError& err)
      {
        // Can be thrown by print_finish(result).
        std::cout << "No output stream. " << err.what() << std::endl;
        return;
      }
      catch (const Glib::Error& err)
      {
        std::cout << "Unexpected exception. " << err.what() << std::endl;
        return;
      }
      const double paper_width = get_page_setup()->get_paper_width(Gtk::Unit::POINTS);
      const double paper_height = get_page_setup()->get_paper_height(Gtk::Unit::POINTS);
      auto cairo_surface = Cairo::PdfSurface::create_for_stream(
        sigc::bind(sigc::mem_fun(*this, &PrintFormDialog::write_func), outputStream),
        paper_width, paper_height);
      auto cairo_ctx = Cairo::Context::create(cairo_surface);

      do_printing(cairo_ctx);

      // cairo_surface->finish() calls write_func(),
      // which must be done before the stream is closed.
      cairo_surface->finish();
      try
      {
        outputStream->close();
      }
      catch (const Glib::Error& err)
      {
        std::cout << "Error closing stream. " << err.what() << std::endl;
      }
    }

    Cairo::ErrorStatus PrintFormDialog::write_func(const unsigned char* data,
      unsigned int length, Glib::RefPtr<Gio::OutputStream>& stream)
    {
      try
      {
        gsize bytes_written = 0;
        stream->write_all(data, length, bytes_written);
      }
      catch (const Glib::Error& err)
      {
        std::cout << "Error writing to stream. " << err.what() << std::endl;
        return CAIRO_STATUS_WRITE_ERROR;
      }
      return CAIRO_STATUS_SUCCESS;
    }
    void PrintFormDialog::do_printing(const Cairo::RefPtr<Cairo::Context>& cairo_ctx)
    {
      m_refLayout = Pango::Layout::create(cairo_ctx);
      m_refLayout->set_font_description(Pango::FontDescription("sans 12"));

      const auto page_setup = get_page_setup();
      const double page_width = page_setup->get_page_width(Gtk::Unit::POINTS);
      const double page_height = page_setup->get_page_height(Gtk::Unit::POINTS);
      const double left_margin = page_setup->get_left_margin(Gtk::Unit::POINTS);
      const double top_margin = page_setup->get_top_margin(Gtk::Unit::POINTS);
      m_refLayout->set_width(static_cast<int>(page_width * Pango::SCALE));
      m_refLayout->set_wrap(Pango::WrapMode::WORD_CHAR);
      cairo_ctx->translate(left_margin, top_margin);

      // Set and mark up the text to print:
      Glib::ustring marked_up_form_text =
        "<b>Name</b>: " + m_Name + "\n\n" +
        "<b>Comments</b>: " + m_Comments;
      m_refLayout->set_markup(marked_up_form_text);

      // We'll use black letters:
      cairo_ctx->set_source_rgb(0, 0, 0);

      // Render Pango LayoutLines over the Cairo context:
      const double inverse_pango_scale = 1.0 / Pango::SCALE;
      double page_y = 0.0;
      auto iter = m_refLayout->get_iter();
      double start_y_pos = iter.get_line_logical_extents().get_y() * inverse_pango_scale;
      do
      {
        const auto layout_line = iter.get_line();
        const auto logical_rect = iter.get_line_logical_extents();
        const double line_height = logical_rect.get_height() * inverse_pango_scale;

        if (page_y + line_height > page_height)
        {
          // Start a new page.
          cairo_ctx->show_page();
          page_y = 0.0;
          start_y_pos = logical_rect.get_y() * inverse_pango_scale;
        }
        page_y += line_height;

        cairo_ctx->move_to(logical_rect.get_x() * inverse_pango_scale,
          iter.get_baseline() * inverse_pango_scale - start_y_pos);
        layout_line->show_in_cairo_context(cairo_ctx);
      }
      while (iter.next_line());

      cairo_ctx->show_page();
    }
    #endif // HAS_PRINT_DIALOG

## Nedávno použité dokumenty

gtkmm provides an easy way to manage recently used documents. This functionality is implemented in the `Gtk::RecentManager` class.

Jednotlivé položky v seznamu nedávno použitých souborů jsou identifikovány jejich adresou URI a mohou mít přiřazena metadata. Metadata se dají využít k určení, jak se má soubor zobrazovat, popisu souboru, jeho typu MIME, která aplikace jej má registrovaný, jestli je soukromý jen pro registrující aplikaci a dalším věcí.

### Správa nedávno použitých (RecentManager)

`RecentManager` funguje jako databáze nedávno použitých souborů. Tuto třídu můžete použít k registraci nových souborů, odstranění souborů ze seznamu a vyhledání nedávno použitých souborů. Každý uživatel má svůj vlastní seznam nedávno použitých souborů.

Můžete vytvořit nový `RecentManager`, ale nejspíše budete chtít používat výchozí. Ukazatel na výchozí `RecentManager` získáte pomocí metody `get_default()`.

#### Přidání položek do seznamu nedávných souborů

Když chcete do seznamu nedávných dokumentů přidat novou položku, v nejjednodušším případě stačí poskytnou adresu URI. Například:

    auto recent_manager = Gtk::RecentManager::get_default();
    recent_manager->add_item(uri);

Když chcete zaregistrovat soubor včetně metadat, můžete předat do `add_item()` parametr `RecentManager::Data`. Metadata mohou být nastavena pro konkrétní položku souboru následovně:

- `app_exec`: Příkazový řádek, který bude použitý ke spuštění tohoto prostředku. Tento řetězec může obsahovat ošetřené znaky „f“ a „u“, které se nahradí souborovou cestou prostředku, respektive jeho adresou URI.

- `app_name`: Název aplikace, která registruje prostředky.

- `description`: Krátký popis prostředku v podobě řetězce kódovaného v UTF-8.

- `display_name`: Název prostředku v podobě řetězce kódovaného v UTF-8, který se použije k zobrazení.

- `groups`: Seznam skupin přidružených k položce. Skupiny jsou v podstatě libovolné řetězce přidružené ke konkrétnímu prostředku. Můžete o nich uvažovat, jako o kategoriích (třeba „e-mail“, „grafika“, atd.) nebo o štítcích pro prostředek.

- `is_private`:Jestli má být tento prostředek viditelný jen aplikacím, které mají registraci, či nikoliv.

- `mime_type`: Typ MIME prostředku.

Mimo přidávání položek do seznamu, můžete položky v seznamu také vyhledávat a měnit nebo odebírat.

#### Vyhledávání položek v seznamu nedávných souborů

Pro vyhledání nedávno použitých souborů `RecentManager` poskytuje několik funkcí. K vyhledání konkrétní položky podle její URI můžete použít funkci `lookup_item()`, která vrací třídu `RecentInfo`. Pokud zadaná adresa URI v seznamu nedávných souborů neexistuje `lookup_item()` vyhodí výjimku `RecentManagerError`. Například:

    Glib::RefPtr<Gtk::RecentInfo> info;
    try
    {
      info = recent_manager->lookup_item(uri);
    }
    catch(const Gtk::RecentManagerError& ex)
    {
      std::cerr << "RecentManagerError: " << ex.what() << std::endl;
    }
    if (info)
    {
      // položka byla nalezena
    }

Objekt `RecentInfo` je v podstatě objekt obsahující všechna metadata o jednom nedávno použitém souboru. Můžete jej využít k vyhledání vlastností uvedených v předchozím.

Pokud nechcete vyhledávat podle konkrétní URI, ale místo toho chcete získat seznam všech nedávno použitých položek, poskytuje `RecentManager` funkci `get_items()`. Návratová hodnota této funkce je `std::vector` se všemi nedávno použitými soubory. Následující kód ukazuje, jak můžete seznam nedávno použitých souborů získat:

    auto info_list = recent_manager->get_items();

Maximální stáří položek v seznamu nedávno použitých položek se dá nastavit pomocí `Gtk::Settings::property_gtk_recent_files_max_age()`. Výchozí hodnota je 30 dní.

#### Změny seznamu nedávných souborů

Mohou nastat situace, kdy budete chtít seznam nedávných souborů změnit. Například, když je soubor přesunut nebo přejmenován, můžete potřebovat aktualizovat umístění souboru v seznamu nedávných souborů, aby neodkazoval na nesprávné místo. Aktualizovat umístění položky můžete pomocí `move_item()`.

Mimo změny URI souboru můžete také položky ze seznam odstranit, buď po jedné nebo smazat všechny naráz. Prvního zmíněného dosáhnete pomocí `remove_item()`, druhého pomocí `purge_items()`.

Funkce `move_item()`, `remove_item()` a `purge_items()` nemají žádný vliv na skutečné soubory, na které odkazují adresy URI, mění pouze seznam nedávných souborů.

### FileChooser and FileDialog

`FileChooser` is an interface that can be implemented by widgets displaying a list of files. gtkmm provides three built-in implementations for choosing recent files or other files: `FileChooserWidget`, `FileChooserDialog`, and `FileChooserNative`.

`FileChooserWidget` is a simple widget for displaying a list of recently used files or other files. `FileChooserWidget` is the basic building block for `FileChooserDialog`, but you can embed it into your user interface if you want to.

`FileChooser` and the classes that implement it are deprecated since gtkmm 4.10. They have been replaced by `FileDialog`, which is available since gtkmm 4.10.

#### Simple FileDialog example

Shown below is a simple example of how to use the `FileDialog` class in a program. This simple program has a menubar with a File Dialog menu item. When you select this menu item, a dialog pops up showing a list of files. If you select Recent in the sidebar, the list of recently used files is shown.

Když je to poprvé, co používáte program, který využívá nedávné soubory, může být dialogové okno napoprvé prázdné. Jinak v něm uvidíte zobrazený seznam nedávno použitých dokumentů zaregistrovaných jinými aplikacemi.

After selecting the File Dialog menu item and the Recent sidebar item, you should see something similar to the following window.

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow(const Glib::RefPtr<Gtk::Application>& app);
      ~ExampleWindow() override;

    protected:
      //Signal handlers:
      void on_menu_file_files_dialog();
      void on_menu_file_quit();
      void on_menu_file_new();
      void on_dialog_finish(Glib::RefPtr<Gio::AsyncResult>& result);

      //Child widgets:
      Gtk::Box m_Box;

      Glib::RefPtr<Gtk::Builder> m_refBuilder;
      Glib::RefPtr<Gio::SimpleActionGroup> m_refActionGroup;

      Glib::RefPtr<Gtk::RecentManager> m_refRecentManager;
      Glib::RefPtr<Gtk::FileDialog> m_refFileDialog;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow(const Glib::RefPtr<Gtk::Application>& app)
    : m_Box(Gtk::Orientation::VERTICAL),
      m_refRecentManager(Gtk::RecentManager::get_default())
    {
      set_title("Recent files example");
      set_default_size(300, 150);

      //We can put a PopoverMenuBar at the top of the box and other stuff below it.
      set_child(m_Box);

      //Create actions for menus and toolbars:
      m_refActionGroup = Gio::SimpleActionGroup::create();

      //File menu:
      m_refActionGroup->add_action("new",
        sigc::mem_fun(*this, &ExampleWindow::on_menu_file_new));

      //A menu item to open the file dialog:
      m_refActionGroup->add_action("files-dialog",
        sigc::mem_fun(*this, &ExampleWindow::on_menu_file_files_dialog));

      m_refActionGroup->add_action("quit",
        sigc::mem_fun(*this, &ExampleWindow::on_menu_file_quit) );

      insert_action_group("example", m_refActionGroup);

      m_refBuilder = Gtk::Builder::create();

      // When the menubar is a child of a Gtk::Window, keyboard accelerators are not
      // automatically fetched from the Gio::Menu.
      // See the examples/book/menus/main_menu example for an alternative way of
      // adding the menubar when using Gtk::ApplicationWindow.
      app->set_accel_for_action("example.new", "<Primary>n");
      app->set_accel_for_action("example.files-dialog", "<Primary>o");
      app->set_accel_for_action("example.quit", "<Primary>q");

      //Layout the actions in a menubar and a toolbar:
      const char* ui_info =
        "<interface>"
        "  <menu id='menubar'>"
        "    <submenu>"
        "      <attribute name='label' translatable='yes'>_File</attribute>"
        "      <item>"
        "        <attribute name='label' translatable='yes'>_New</attribute>"
        "        <attribute name='action'>example.new</attribute>"
        "        <attribute name='accel'>&lt;Primary&gt;n</attribute>"
        "      </item>"
        "      <item>"
        "        <attribute name='label' translatable='yes'>File _Dialog</attribute>"
        "        <attribute name='action'>example.files-dialog</attribute>"
        "        <attribute name='accel'>&lt;Primary&gt;o</attribute>"
        "      </item>"
        "      <item>"
        "        <attribute name='label' translatable='yes'>_Quit</attribute>"
        "        <attribute name='action'>example.quit</attribute>"
        "        <attribute name='accel'>&lt;Primary&gt;q</attribute>"
        "      </item>"
        "    </submenu>"
        "  </menu>"
        "  <object class='GtkBox' id='toolbar'>"
        "    <property name='can_focus'>False</property>"
        "    <child>"
        "      <object class='GtkButton' id='toolbutton_new'>"
        "        <property name='can_focus'>False</property>"
        "        <property name='tooltip_text' translatable='yes'>New</property>"
        "        <property name='action_name'>example.new</property>"
        "        <property name='icon_name'>document-new</property>"
        "        <property name='hexpand'>False</property>"
        "        <property name='vexpand'>False</property>"
        "      </object>"
        "    </child>"
        "    <child>"
        "      <object class='GtkButton' id='toolbutton_quit'>"
        "        <property name='can_focus'>False</property>"
        "        <property name='tooltip_text' translatable='yes'>Quit</property>"
        "        <property name='action_name'>example.quit</property>"
        "        <property name='icon_name'>application-exit</property>"
        "        <property name='hexpand'>False</property>"
        "        <property name='vexpand'>False</property>"
        "      </object>"
        "    </child>"
        "  </object>"
        "</interface>";

      try
      {
        m_refBuilder->add_from_string(ui_info);
      }
      catch(const Glib::Error& ex)
      {
        std::cerr << "building menubar and toolbar failed: " <<  ex.what();
      }

      //Get the menubar and toolbar widgets, and add them to a container widget:
      auto object = m_refBuilder->get_object("menubar");
      auto gmenu = std::dynamic_pointer_cast<Gio::Menu>(object);
      if (gmenu)
      {
        //Menubar:
        auto pMenubar = Gtk::make_managed<Gtk::PopoverMenuBar>(gmenu);
        m_Box.append(*pMenubar);
      }
      else
        g_warning("GMenu not found");

      auto pToolbar = m_refBuilder->get_widget<Gtk::Box>("toolbar");
      if (pToolbar)
        //Toolbar:
        m_Box.append(*pToolbar);
      else
        g_warning("toolbar not found");
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_menu_file_new()
    {
      std::cout << " New File" << std::endl;
    }

    void ExampleWindow::on_menu_file_quit()
    {
      set_visible(false); //Closes the main window to stop the app->make_window_and_run().
    }

    void ExampleWindow::on_menu_file_files_dialog()
    {
      if (!m_refFileDialog)
      {
        m_refFileDialog = Gtk::FileDialog::create();
        m_refFileDialog->set_modal(true);
      }
      m_refFileDialog->open(*this, sigc::mem_fun(*this, &ExampleWindow::on_dialog_finish));
    }

    void ExampleWindow::on_dialog_finish(Glib::RefPtr<Gio::AsyncResult>& result)
    {
      Glib::RefPtr<Gio::File> file;
      try
      {
        file = m_refFileDialog->open_finish(result);
      }
      catch (const Gtk::DialogError& err)
      {
        std::cout << "No file selected, " << err.what() << std::endl;
        return;
      }

      auto selected_uri = file->get_uri();
      std::cout << "URI selected = " << selected_uri << std::endl;
      std::cout << (m_refRecentManager->has_item(selected_uri) ? "A" : "Not a")
        << " recently used file" << std::endl;
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv, app);
    }

The constructor for `ExampleWindow` creates the menu and the toolbar using `Builder` (see for more information). It then adds the menu and the toolbar to the window.

#### Filtering Files

For any of the `FileChooser` classes, if you don't wish to display all of the items in the list of files, you can filter the list to show only those that you want. You can filter the list with the help of the `FileFilter` class. This class allows you to filter files by their name (`add_pattern()`), or their mime type (`add_mime_type()`).

After you've created and set up the filter to match only the items you want, you can apply a filter to a chooser widget with the `FileChooser::add_filter()` function.

## Události klávesnice

Event signals differ in some ways from other signals. These differences are described in the Event signals section in the appendix. Here we will use keyboard events to show how events can be used in a program.

### Přehled

Whenever you press or release a key, an event is emitted. You can add an event controller and connect a signal handler to handle such events.

The event signal handler will receive arguments that depend on the type of event. For key press events the arguments are (guint `keyval`, guint `keycode`, Gdk::ModifierType `state`). As described in the appendix, the key press event signal handler returns a bool value, to indicate that the signal is fully handled (`true`) or allow event propagation (`false`).

To determine which key was pressed or released, you read the value of the `keyval` argument and compare it with a constant in the `<gdk/gdkkeysyms.h>` header file. The states of modifier keys (shift, ctrl, etc.) are available as bit-flags in `state`.

Here's a simple example:

    bool MyClass::on_key_pressed(guint keyval, guint, Gdk::ModifierType state)
    {
      if (keyval == GDK_KEY_1 &&
        (state & (Gdk::ModifierType::SHIFT_MASK | Gdk::ModifierType::CONTROL_MASK |
         Gdk::ModifierType::ALT_MASK)) == Gdk::ModifierType::ALT_MASK)
      {
        handle_alt_press();
        return true;
      }
      return false;
    }

    // in MyClass constructor
    auto controller = Gtk::EventControllerKey::create();
    controller->signal_key_pressed().connect(
      sigc::mem_fun(*this, &MyClass::on_key_pressed), false);
    add_controller(controller);

#### Příklad

In this example there are three keyboard shortcuts: Alt+1 selects the first radio button, Alt+2 selects the second one, and the Esc key hides (closes) the window.

##### Události klávesnice – jednoduchý příklad

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:

      ExampleWindow();
      virtual ~ExampleWindow();

    private:
      // Signal handler:
      bool on_window_key_pressed(guint keyval, guint keycode, Gdk::ModifierType state);

      Gtk::Box m_container;
      Gtk::CheckButton m_first;
      Gtk::CheckButton m_second;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    {
      set_title("Keyboard Events");
      m_container.set_margin(10);
      set_child(m_container);

      // Radio buttons:
      m_first.set_label("First");
      m_second.set_label("Second");

      m_second.set_group(m_first);
      m_first.set_active();

      // Main Container:
      m_container.set_orientation(Gtk::Orientation::HORIZONTAL);
      m_container.append(m_first);
      m_container.append(m_second);

      // Events.
      auto controller = Gtk::EventControllerKey::create();
      controller->signal_key_pressed().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_window_key_pressed), false);
      add_controller(controller);
    }

    bool ExampleWindow::on_window_key_pressed(guint keyval, guint, Gdk::ModifierType state)
    {
      //Gdk::ModifierType::ALT_MASK -> the 'Alt' key(mask)
      //GDK_KEY_1 -> the '1' key
      //GDK_KEY_2 -> the '2' key

      //select the first radio button, when we press alt + 1
      if((keyval == GDK_KEY_1) &&
        (state & (Gdk::ModifierType::SHIFT_MASK | Gdk::ModifierType::CONTROL_MASK | Gdk::ModifierType::ALT_MASK)) == Gdk::ModifierType::ALT_MASK)
      {
        m_first.set_active();
        //returning true, cancels the propagation of the event
        return true;
      }
      else if((keyval == GDK_KEY_2) &&
        (state & (Gdk::ModifierType::SHIFT_MASK | Gdk::ModifierType::CONTROL_MASK | Gdk::ModifierType::ALT_MASK)) == Gdk::ModifierType::ALT_MASK)
      {
        //and the second radio button, when we press alt + 2
        m_second.set_active();
        return true;
      }
      else if(keyval == GDK_KEY_Escape)
      {
        //close the window, when the 'esc' key is pressed
        set_visible(false);
        return true;
      }

      //the event has not been handled
      return false;
    }

    ExampleWindow::~ExampleWindow()
    {
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

### Propagace události

As described in the appendix event signals are propagated in 3 phases:

1. Capture phase - runs from the toplevel down to the event widget.

2. Target phase - runs only on the event widget.

3. Bubble phase - runs from the event widget up to the toplevel.

A keyboard event is first sent to the toplevel window (`Gtk::Window`), where it will be checked for any keyboard shortcuts that may be set (accelerator keys and mnemonics, used for selecting menu items from the keyboard). After this (and assuming the event wasn't handled), it is propagated down until it reaches the widget which has keyboard focus. The event will then propagate up until it reaches the top-level widget, or until you stop the propagation by returning `true` from an event handler.

Dejte pozor na to, že po zastavení události nebude už zavolána žádná funkce (i kdyby byla z toho stejného widgetu).

#### Příklad

In this example there are 9 `EventControllerKey`s, 3 in each of a `Gtk::Window`, a `Gtk::Box` and a `Gtk::Label`. In each of the widgets there is one event controller for each propagation phase.

Účelem tohoto příkladu je ukázat kroky, které událost podstoupí, když je vyslána.

When you write in the label, a key press event will be emitted, which will go first, in the capture phase, to the toplevel window (`Gtk::Window`), then down to its child, the box, then to the box's child, the label with the keyboard focus. In the target phase the event goes only to the widget with the keyboard focus (the label). In the bubble phase the event goes first to the widget with the keyboard focus (the label), then to its parent (the box), then to the box's parent (the window). If the event propagates all the way down to the label and then up to the window without being stopped, the text you're writing will appear in the `Label` above the `Label` you're writing in.

##### Události klávesnice – propagace událostí

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EVENT_PROPAGATION_H
    #define GTKMM_EVENT_PROPAGATION_H

    #include <gtkmm.h>

    class ExampleWindow : public Gtk::Window
    {
    public:

      ExampleWindow();
      ~ExampleWindow() override;

    private:
      // Signal handlers:
      bool label2_key_pressed(guint keyval, guint keycode, Gdk::ModifierType state, const Glib::ustring& phase);
      bool box_key_pressed(guint keyval, guint keycode, Gdk::ModifierType state, const Glib::ustring& phase);
      bool window_key_pressed(guint keyval, guint keycode, Gdk::ModifierType state, const Glib::ustring& phase);

      bool m_first = true;
      Gtk::Box m_container;
      Gtk::Frame m_frame;
      Gtk::Label m_label1 {"A label"};
      Gtk::Label m_label2 {"Write here"};
      Gtk::CheckButton m_checkbutton_can_propagate_down {"Can propagate down in the capture phase"};
      Gtk::CheckButton m_checkbutton_can_propagate_up {"Can propagate up in the bubble phase"};
    };

    #endif //GTKMM_EVENT_PROPAGATION_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow()
    {
      set_title("Event Propagation");
      m_container.set_margin(10);
      set_child(m_container);

      m_frame.set_child(m_label2);
      m_label2.set_selectable();
      m_checkbutton_can_propagate_down.set_active();
      m_checkbutton_can_propagate_up.set_active();

      // Main container
      m_container.set_orientation(Gtk::Orientation::VERTICAL);
      m_container.append(m_label1);
      m_container.append(m_frame);
      m_container.append(m_checkbutton_can_propagate_down);
      m_container.append(m_checkbutton_can_propagate_up);

      // Event controllers
      const bool after = false; // Run before or after the default signal handlers.

      // Called in the capture phase of the event handling.
      auto controller = Gtk::EventControllerKey::create();
      controller->set_propagation_phase(Gtk::PropagationPhase::CAPTURE);
      controller->signal_key_pressed().connect(
        sigc::bind(sigc::mem_fun(*this, &ExampleWindow::label2_key_pressed), "capture"), after);
      m_label2.add_controller(controller);

      controller = Gtk::EventControllerKey::create();
      controller->set_propagation_phase(Gtk::PropagationPhase::CAPTURE);
      controller->signal_key_pressed().connect(
        sigc::bind(sigc::mem_fun(*this, &ExampleWindow::box_key_pressed), "capture"), after);
      m_container.add_controller(controller);

      controller = Gtk::EventControllerKey::create();
      controller->set_propagation_phase(Gtk::PropagationPhase::CAPTURE);
      controller->signal_key_pressed().connect(
        sigc::bind(sigc::mem_fun(*this, &ExampleWindow::window_key_pressed), "capture"), after);
      add_controller(controller);

      // Called in the target phase of the event handling.
      controller = Gtk::EventControllerKey::create();
      controller->set_propagation_phase(Gtk::PropagationPhase::TARGET);
      controller->signal_key_pressed().connect(
        sigc::bind(sigc::mem_fun(*this, &ExampleWindow::label2_key_pressed), "target"), after);
      m_label2.add_controller(controller);

      controller = Gtk::EventControllerKey::create();
      controller->set_propagation_phase(Gtk::PropagationPhase::TARGET);
      controller->signal_key_pressed().connect(
        sigc::bind(sigc::mem_fun(*this, &ExampleWindow::box_key_pressed), "target"), after);
      m_container.add_controller(controller);

      controller = Gtk::EventControllerKey::create();
      controller->set_propagation_phase(Gtk::PropagationPhase::TARGET);
      controller->signal_key_pressed().connect(
        sigc::bind(sigc::mem_fun(*this, &ExampleWindow::window_key_pressed), "target"), after);
      add_controller(controller);

      // Called in the bubble phase of the event handling.
      // This is the default, if set_propagation_phase() is not called.
      controller = Gtk::EventControllerKey::create();
      controller->set_propagation_phase(Gtk::PropagationPhase::BUBBLE);
      controller->signal_key_pressed().connect(
        sigc::bind(sigc::mem_fun(*this, &ExampleWindow::label2_key_pressed), "bubble"), after);
      m_label2.add_controller(controller);

      controller = Gtk::EventControllerKey::create();
      controller->set_propagation_phase(Gtk::PropagationPhase::BUBBLE);
      controller->signal_key_pressed().connect(
        sigc::bind(sigc::mem_fun(*this, &ExampleWindow::box_key_pressed), "bubble"), after);
      m_container.add_controller(controller);

      controller = Gtk::EventControllerKey::create();
      controller->set_propagation_phase(Gtk::PropagationPhase::BUBBLE);
      controller->signal_key_pressed().connect(
        sigc::bind(sigc::mem_fun(*this, &ExampleWindow::window_key_pressed), "bubble"), after);
      add_controller(controller);
    }

    // By changing the return value we allow, or don't allow, the event to propagate to other elements.
    bool ExampleWindow::label2_key_pressed(guint keyval, guint, Gdk::ModifierType, const Glib::ustring& phase)
    {
      std::cout << "Label,  " << phase << " phase" << std::endl;

      if (phase == "bubble")
      {
        const gunichar unichar = gdk_keyval_to_unicode(keyval);
        if (unichar != 0)
        {
          if (m_first)
          {
            m_label2.set_label("");
            m_first = false;
          }
          if (unichar == '\b')
            m_label2.set_label("");
          else
          {
            const Glib::ustring newchar(1, unichar);
            m_label2.set_label(m_label2.get_label() + newchar);
          }
        }

        if (!m_checkbutton_can_propagate_up.get_active())
          return true; // Don't propagate
      }
      return false;
    }

    bool ExampleWindow::box_key_pressed(guint, guint, Gdk::ModifierType, const Glib::ustring& phase)
    {
      std::cout << "Box,    " << phase << " phase" << std::endl;

      // Let it propagate
      return false;
    }

    // This will set the second label's text in the first label every time a key is pressed.
    bool ExampleWindow::window_key_pressed(guint, guint, Gdk::ModifierType, const Glib::ustring& phase)
    {
      if (phase == "capture")
        std::cout << std::endl;
      std::cout << "Window, " << phase << " phase";

      // Checking if the second label is on focus, otherwise the label would get
      // changed by pressing keys on the window (when the label is not on focus),
      // even if m_checkbutton_can_propagate_up wasn't active.
      if (phase == "bubble" && m_label2.has_focus())
      {
        m_label1.set_label(m_label2.get_label());
        std::cout << ", " << m_label2.get_label();
      }
      std::cout << std::endl;

      if (phase == "capture" && !m_checkbutton_can_propagate_down.get_active())
        return true; // Don't propagate
      return false;
    }

    ExampleWindow::~ExampleWindow()
    {
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

## Časové limity, V/V a funkce při nečinnosti

### Časové limity

Možná vás zajímá, jak to udělat, aby gtkmm dělalo něco užitečného, když je v nečinném stavu. Máte štěstí, protože máte dokonce hned několik možností, jak to udělat. Pomocí následujících metod můžete vytvořit časovanou metodu, která bude zavolaná každých pár milisekund.

    sigc::connection Glib::SignalTimeout::connect(const sigc::slot<bool()>& slot,
                                          unsigned int interval, int priority = Glib::PRIORITY_DEFAULT);

První argument je `slot`, který si přejete mít zavolaný, když doběhne časový odpočet. Druhý argument je počet milisekund mezi voláními této metody. Obdržíte objekt `sigc::connection`, který můžete použít k deaktivaci napojení pomocí metody `disconnect()`:

    my_connection.disconnect();

Another way of destroying the connection is your signal handler. It has to be of the type `sigc::slot<bool()>`. As you see from the definition your signal handler has to return a value of the type `bool`. A definition of a sample method might look like this:

    bool MyCallback() { std::cout << "Hello World!\n" << std::endl; return true; }

Metodu `timetout` můžete zastavit vrácením `false` z vaší obsluhy signálu. Pokud chcete, aby vaše metoda byla volána pravidelně, měli byste vrátit `true`.

Zde je příklad této techniky:

Source Code

File: `timerexample.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLE_TIMEREXAMPLE_H
    #define GTKMM_EXAMPLE_TIMEREXAMPLE_H

    #include <gtkmm.h>
    #include <iostream>
    #include <map>

    class TimerExample : public Gtk::Window
    {
    public:
      TimerExample();

    protected:
      // signal handlers
      void on_button_add_timer();
      void on_button_delete_timer();
      void on_button_quit();

      // This is the callback function the timeout will call
      bool on_timeout(int timer_number);

      // Member data:

      Gtk::Box m_Box;
      Gtk::Button m_ButtonAddTimer, m_ButtonDeleteTimer, m_ButtonQuit;

      // Keep track of the timers being added:
      int m_timer_number;

      // These two constants are initialized in the constructor's member initializer:
      const int count_value;
      const int timeout_value;

      // STL map for storing our connections
      std::map<int, sigc::connection> m_timers;

      // STL map for storing our timer values.
      // Each timer counts back from COUNT_VALUE to 0 and is removed when it reaches 0
      std::map<int, int> m_counters;
    };

    #endif // GTKMM_EXAMPLE_TIMEREXAMPLE_H

File: `main.cc` (For use with gtkmm 4)

    #include "timerexample.h"
    #include <gtkmm/application.h>

    int main (int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      return app->make_window_and_run<TimerExample>(argc, argv);
    }

File: `timerexample.cc` (For use with gtkmm 4)

    #include "timerexample.h"

    TimerExample::TimerExample() :
      m_Box(Gtk::Orientation::HORIZONTAL, 10),
      m_ButtonAddTimer("_Add", true),
      m_ButtonDeleteTimer("_Remove", true),
      m_ButtonQuit("_Quit", true),
      m_timer_number(0), // start numbering the timers at 0
      count_value(5), // each timer will count down 5 times before disconnecting
      timeout_value(1500) // 1500 ms = 1.5 seconds
    {
      m_Box.set_margin(10);
      set_child(m_Box);
      m_Box.append(m_ButtonAddTimer);
      m_Box.append(m_ButtonDeleteTimer);
      m_Box.append(m_ButtonQuit);
      m_ButtonAddTimer.set_expand();
      m_ButtonDeleteTimer.set_expand();
      m_ButtonQuit.set_expand();

      // Connect the three buttons:
      m_ButtonQuit.signal_clicked().connect(sigc::mem_fun(*this,
                  &TimerExample::on_button_quit));
      m_ButtonAddTimer.signal_clicked().connect(sigc::mem_fun(*this,
                  &TimerExample::on_button_add_timer));
      m_ButtonDeleteTimer.signal_clicked().connect(sigc::mem_fun(*this,
                  &TimerExample::on_button_delete_timer));
    }

    void TimerExample::on_button_quit()
    {
      set_visible(false);
    }

    void TimerExample::on_button_add_timer()
    {
      // Creation of a new object prevents long lines and shows us a little
      // how slots work.  We have 0 parameters and bool as a return value
      // after calling sigc::bind.
      sigc::slot<bool()> my_slot = sigc::bind(sigc::mem_fun(*this,
                  &TimerExample::on_timeout), m_timer_number);

      // This is where we connect the slot to the Glib::signal_timeout()
      auto conn = Glib::signal_timeout().connect(my_slot,
              timeout_value);

      // Remember the connection:
      m_timers[m_timer_number] = conn;

      // Initialize timer count:
      m_counters[m_timer_number] = count_value + 1;

      // Print some info to the console for the user:
      std::cout << "added timeout " << m_timer_number++ << std::endl;
    }

    void TimerExample::on_button_delete_timer()
    {
      // any timers?
      if(m_timers.empty())
      {
        // no timers left
        std::cout << "Sorry, there are no timers left." << std::endl;
      }
      else
      {
        // get the number of the first timer
        int timer_number = m_timers.begin()->first;

        // Give some info to the user:
        std::cout << "manually disconnecting timer " << timer_number
            << std::endl;

        // Remove the entry in the counter values
        m_counters.erase(timer_number);

        // Diconnect the signal handler:
        m_timers[timer_number].disconnect();

        // Forget the connection:
        m_timers.erase(timer_number);
      }
    }

    bool TimerExample::on_timeout(int timer_number)
    {
      // Print the timer:
      std::cout << "This is timer " << timer_number;

      // decrement and check counter value
      if (--m_counters[timer_number] == 0)
      {
        std::cout << " being disconnected" <<  std::endl;

        // delete the counter entry in the STL MAP
        m_counters.erase(timer_number);

        // delete the connection entry in the STL MAP
        m_timers.erase(timer_number);

        // Note that we do not have to explicitly call disconnect() on the
        // connection since Gtk::Main does this for us when we return false.
        return false;
      }

      // Print the timer value
      std::cout << " - " << m_counters[timer_number] << "/"
          << count_value << std::endl;

     // Keep going (do not disconnect yet):
      return true;
    }

### Sledování V/V

Šikovnou funkcí knihovny Glib (jedna z knihoven ležících pod gtkmm) je schopnost mít kontrolu nad daty z popisovače souborů pro vaše potřeby. To se hodí hlavně pro síťové aplikace. Následující metoda přesně tohle využívá:

    sigc::connection Glib::SignalIO::connect(const sigc::slot<bool(Glib::IOCondition)>& slot,
                                     Glib::PollFD::fd_t fd, Glib::IOCondition condition,
                                     int priority = Glib::PRIORITY_DEFAULT);

První argument je slot, který si přejete mít volaný, když nastane určená událost (viz třetí argument) na popisovači souboru, který jste určili druhým argumentem. Třetí argument může být jedna nebo více (pomocí `|`) hodnot z:

- Glib::IOCondition::IO_IN - Call your method when there is data ready for reading on your file descriptor.

- Glib::IOCondition::IO_OUT - Call your method when the file descriptor is ready for writing.

- Glib::IOCondition::IO_PRI - Call your method when the file descriptor has urgent data to be read.

- Glib::IOCondition::IO_ERR - Call your method when an error has occurred on the file descriptor.

- Glib::IOCondition::IO_HUP - Call your method when hung up (the connection has been broken usually for pipes and sockets).

Vrácená hodnota je `sigc::connection`, kterou můžete použít k zastavení sledování tohoto popisovače souboru pomocí jeho metody `disconnect()`. Obsluha signálu `slot` by měla být deklarovaná následovně:

    bool input_callback(Glib::IOCondition condition);

where `condition` is as specified above. As usual the slot is created with `sigc::mem_fun()` (for a member method of an object), or `sigc::ptr_fun()` (for a function). A lambda expression can be used, if you don't need the automatic disconnection that `sigc::mem_fun()` provides when the object goes out of scope.

Následuje menší příklad. Pokud jej chcete použít, spusťte jej z terminálu – nevytváří žádné okno. Co ale vytvoří, je pojmenovaná roura `testfifo` v aktuální složce. Pak spusťte další shell a v něm `echo "Hello" > testinfo`. Příklad bude vypisovat jednotlivé řádky, které takto zadáte, až dokud nespustíte `echo "Q" > testfifo`.

Source Code

File: `main.cc` (For use with gtkmm 4)

    #include <gtkmm/application.h>
    #include <glibmm/main.h>
    #include <glibmm/iochannel.h>
    #include <fcntl.h>
    #include <iostream>

    #include <unistd.h> //The SUN Forte compiler puts F_OK here.

    //The SUN Forte compiler needs these for mkfifo:
    #include <sys/types.h>
    #include <sys/stat.h>

    Glib::RefPtr<Gtk::Application> app;

    int read_fd;
    Glib::RefPtr<Glib::IOChannel> iochannel;

    /*
      send to the fifo with:
      echo "Hello" > testfifo

      quit the program with:
      echo "Q" > testfifo
    */

    // this will be our signal handler for read operations
    // it will print out the message sent to the fifo
    // and quit the program if the message was 'Q'.
    bool MyCallback(Glib::IOCondition io_condition)
    {
      if ((io_condition & Glib::IOCondition::IO_IN) != Glib::IOCondition::IO_IN)
      {
        std::cerr << "Invalid fifo response" << std::endl;
      }
      else
      {
       Glib::ustring buf;

       iochannel->read_line(buf);
       std::cout << buf;
       if (buf == "Q\n")
         app->quit();
      }
      return true;
    }

    int main(int argc, char *argv[])
    {
      app = Gtk::Application::create("org.gtkmm.example");

      if (access("testfifo", F_OK) == -1)
      {
        // fifo doesn't exist - create it
        #ifndef DONT_HAVE_MKFIFO
        if (mkfifo("testfifo", 0666) != 0)
        {
          std::cerr << "error creating fifo" << std::endl;
          return -1;
        }
        #else
          std::cerr << "error creating fifo: This platform does not have mkfifo()"
              << std::endl;
        #endif //DONT_HAVE_MKFIFO
      }

      // Although we will only read from the fifo, we open it in read/write mode.
      // Due to a peculiarity with the poll() system call, used deep down in glib,
      // this small program will use all available CPU time, if the fifo is opened
      // as O_RDONLY. See a discussion on the gtkmm-list, e.g.
      // https://mail.gnome.org/archives/gtkmm-list/2015-September/msg00034.html
      // and the link from there to stackoverflow.
      read_fd = open("testfifo", O_RDWR);
      if (read_fd == -1)
      {
        std::cerr << "error opening fifo" << std::endl;
        return -1;
      }

      // connect the signal handler
      Glib::signal_io().connect(
        [](Glib::IOCondition io_condition){ return MyCallback(io_condition); },
        read_fd, Glib::IOCondition::IO_IN);

      // Creates a iochannel from the file descriptor
      iochannel = Glib::IOChannel::create_from_fd(read_fd);

      // and last but not least - run the application main loop
      app->hold(); // keep the application running without a window
      app->run(argc, argv);

      // now remove the temporary fifo
      if(unlink("testfifo"))
        std::cerr << "error removing fifo" << std::endl;

      return 0;
    }

### Funkce při nečinnosti

Když chcete určit metodu, která má být zavolána, když se nic jiného neděje, použijte následující:

    sigc::connection  Glib::SignalIdle::connect(const sigc::slot<bool()>& slot,
                                        int priority = Glib::PRIORITY_DEFAULT_IDLE);

Způsobí to, že gtkmm zavolá určenou metodu kdykoliv, když se nic neděje. Můžete přidat prioritu (nižší čísla znamenají vyšší prioritu). Jsou dva způsoby, jak obsluhu signálu odstranit: zavolat `disconnect()` na objektu `sigc::connection`, nebo vrátit `false` z obsluhy signálu, která byla deklarována následovně:

    bool idleFunc();

Protože je tahle metoda velmi podobná metodě rozebrané v předchozím, mělo by tohle vysvětlení k pochopení fungování stačit. Pro jistotu je zde ale příklad:

Source Code

File: `idleexample.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLE_IDLEEXAMPLE_H
    #define GTKMM_EXAMPLE_IDLEEXAMPLE_H

    #include <gtkmm.h>
    #include <iostream>

    class IdleExample : public Gtk::Window
    {
    public:
      IdleExample();

    protected:
      // Signal Handlers:
      bool on_timer();
      bool on_idle();
      void on_button_clicked();

      // Member data:
      Gtk::Box m_Box;
      Gtk::Button m_ButtonQuit;
      Gtk::ProgressBar m_ProgressBar_c;
      Gtk::ProgressBar m_ProgressBar_d;
    };

    #endif // GTKMM_EXAMPLE_IDLEEXAMPLE_H

File: `idleexample.cc` (For use with gtkmm 4)

    #include "idleexample.h"

    IdleExample::IdleExample() :
      m_Box(Gtk::Orientation::VERTICAL, 5),
      m_ButtonQuit("_Quit", true)
    {
      m_Box.set_margin(5);

      // Put buttons into container

      // Adding a few widgets:
      set_child(m_Box);
      m_Box.append(*Gtk::make_managed<Gtk::Label>("Formatting Windows drive C:"));
      m_Box.append(*Gtk::make_managed<Gtk::Label>("100 MB"));
      m_Box.append(m_ProgressBar_c);
      m_ProgressBar_c.set_expand();

      m_Box.append(*Gtk::make_managed<Gtk::Label>(""));

      m_Box.append(*Gtk::make_managed<Gtk::Label>("Formatting Windows drive D:"));
      m_Box.append(*Gtk::make_managed<Gtk::Label>("5000 MB"));
      m_Box.append(m_ProgressBar_d);
      m_ProgressBar_d.set_expand();

      auto hbox = Gtk::make_managed<Gtk::Box>(Gtk::Orientation::HORIZONTAL,10);
      m_Box.append(*hbox);
      hbox->append(m_ButtonQuit);
      m_ButtonQuit.set_expand();
      m_ButtonQuit.set_halign(Gtk::Align::END);
      m_ButtonQuit.set_valign(Gtk::Align::END);

      // Connect the signal handlers:
      m_ButtonQuit.signal_clicked().connect( sigc::mem_fun(*this,
                  &IdleExample::on_button_clicked) );

      // formatting drive c in timeout signal handler - called once every 50ms
      Glib::signal_timeout().connect( sigc::mem_fun(*this, &IdleExample::on_timer),
              50 );

      // formatting drive d in idle signal handler - called as quickly as possible
      Glib::signal_idle().connect( sigc::mem_fun(*this, &IdleExample::on_idle) );
    }

    void IdleExample::on_button_clicked()
    {
      set_visible(false);
    }

    // this timer callback function is executed once every 50ms (set in connection
    // above).  Use timeouts when speed is not critical. (ie periodically updating
    // something).
    bool IdleExample::on_timer()
    {
      double value = m_ProgressBar_c.get_fraction();

      // Update progressbar 1/500th each time:
      m_ProgressBar_c.set_fraction(value + 0.002);

      return value < 0.99;  // return false when done
    }

    // This idle callback function is executed as often as possible, hence it is
    // ideal for processing intensive tasks.
    bool IdleExample::on_idle()
    {
      double value = m_ProgressBar_d.get_fraction();

      // Update progressbar 1/5000th each time:
      m_ProgressBar_d.set_fraction(value + 0.0002);

      return value < 0.99;  // return false when done
    }

File: `main.cc` (For use with gtkmm 4)

    #include "idleexample.h"
    #include <gtkmm/application.h>

    int main (int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      return app->make_window_and_run<IdleExample>(argc, argv);
    }

Tento příklad ukazuje malý rozdíl mezi metodou `idle` a `timeout`. Když potřebujete metodu, která je volána pravidelně a rychlost není důležitá, pak budete chtít metodu `timeout`. Pokud potřebujete takovou, která je volána tak často, jak je to možné (např. výpočet fraktálu na pozadí), pak použijte metodu `idle`.

Zkuste příklad spustit a zvýšit zátěž systému. Horní ukazatel průběhu bude nabývat rovnoměrně, dolní se zpomalí.

## Správa paměti

### Widgety

#### Normální správa paměti v C++

gtkmm dává programům kontrolu nad životností (tj. konstrukcí a destrukcí) kteréhokoliv widgetu stejným způsobme, jako nad kterýmkoliv jiným objektem C++. Díky této flexibilitě můžete použit `new` a `delete` k vytvoření a zničení objektu dynamicky, nebo můžete použít běžného člena třídy (který je zničen automaticky při zničení instance třídy), nebo použít lokální instanci (která zanikne při opuštění jejího rozsahu působnosti). Takovouto flexibilitu nenajdete v každé vývojářské sade GUI v C++, mnohé omezují programátory jen na nějakou podmnožinu funkcí správy paměti v C++.

An important difference in gtkmm-4.0 vs. older versions is that a C++ widgetʼs destruction no longer causes the widget to be destroyed if itʼs within a parent; in that case the C GtkWidget stays alive. If you had relied on that behavior in an older version, in gtkmm-4.0 you must now remove the widget from its parent first. See Changes in gtkmm-4.0.

Zde je nějaký příklad normální správy paměti v C++:

##### Widgety v rozsahu působnosti třídy

Pokud programátor nepotřebuje dynamickou alokaci paměti, dají se použít automatické widgety v rozsahu působnosti třídy. Jedním z přínosů automatických widgetů v rozsahu působnosti třídy je, že správa paměti je na jednom místě jako celek. Programátor neriskuje úniky paměti vlivem selhání `delete` u widgetu.

Hlavním přínosem použití widgetů v rozsahu působnosti třídy je odhalení implementace třídy, místo rozhraní třídy v hlavičce třídy.

    #include <gtkmm/button.h>
    #include <gtkmm/window.h>
    class Foo : public Gtk::Window
    {
    private:
      Gtk::Button theButton;
      // bude zlikvidováno, když je zlikvidován objekt Foo
    };

##### Widgety v rozsahu působnosti funkce

If a programmer does not need a class scope widget, a function scope widget may also be used. The advantages to function scope over class scope are the increased data hiding and reduced dependencies.

    {
      Gtk::Button aButton;
      aButton.set_visible(true);
      ...
      app->run();
    }

However, this technique is rarely useful. Most widgets can't safely be created before the application has been registered or activated. They can't safely be deleted after `Gtk::Application::run()` or `Gtk::Application::make_window_and_run()` returns.

##### Dynamická alokace pomocí new a delete

Usually, the programmer will prefer to allow containers to automatically destroy their children by creating them using `Gtk::make_managed()` (see below). This is not strictly required, as the `new` and `delete` operators may also be used, but modern C++ style discourages those in favor of safer models of memory management, so it is better to create widgets using `Gtk::make_managed()` and let their parent destroy them, than to manually perform dynamic allocation.

    auto pButton = new Gtk::Button("Test");
    // do something useful with pButton
    delete pButton;

Here, the programmer deletes `pButton` to prevent a memory leak.

#### Widgety pod správou

Alternatively, you can let a widget's container control when the widget is destroyed. In most cases, you want a widget to last only as long as the container it is in. To delegate the management of a widget's lifetime to its container, create it with `Gtk::make_managed()` and then pack it into its container with `Gtk::Box::append()` or a similar method. Now the widget will be destroyed whenever its container is destroyed.

##### Dynamic allocation with make_managed() and append()

gtkmm provides ways including the `make_managed()` function and `Gtk::Box::append()` method to simplify creation and destruction of widgets whose lifetime can be managed by a parent.

Every widget except a top-level window must be added to a parent container in order to be displayed. The `manage()` function marks a widget so that when that widget is added to a parent container, said container becomes responsible for deleting the widget, meaning the user no longer needs to do so. The original way to create widgets whose lifetime is managed by their parent in this way was to call `manage()`, passing in the result of a `new` expression that created a dynamically allocated widget.

However, usually, when you create such a widget, you will already know that its parent container should be responsible for destroying it. In addition, modern C++ style discourages use of the `new` operator, which was required when passing a newly created widget to `manage()`. Therefore, gtkmm has added `make_managed()`, which combines creation and marking with `manage()` into a single step. This avoids you having to write `new`, which is discouraged in modern C++ style, and more clearly expresses intent to create a managed widget.

    MyContainer::MyContainer()
    {
      auto pButton = Gtk::make_managed<Gtk::Button>("Test");
      append(*pButton); //add *pButton to MyContainer
    }

Now, when objects of type `MyContainer` are destroyed, the button will also be deleted. It is no longer necessary to delete `pButton` to free the button's memory; its deletion has been delegated to the `MyContainer` object.

If you never added the widget to any parent container, it's your responsibility to delete it. If you add it to a container widget, and later remove it (for instance with `Gtk::Box::remove()`), it's deleted by the container.

Of course, a top-level container will not be added to another container. The programmer is responsible for destroying the top-level container using one of the traditional C++ techniques. Or you can let `Gtk::Application::make_window_and_run()` create a top-level window and delete it when it's hidden.

### Sdílené prostředky

Některé objekty, jako jsou `Gdk::Pixbuf` a `Pango::Font`, se získávají ze sdíleného úložiště. Proto u nich nemůžete vytvářet své vlastní instance. Tyto třídy bývají typicky zděděné z `Glib::Object`. Místo aby gtkmm vyžadovalo reference a dereference na takovéto objekty, používá chytré ukazatele `Glib::RefPtr<>`. Cairomm má svůj vlastní chytrý ukazatel `Cairo::RefPtr<>`.

Objects such as `Gdk::Pixbuf` can only be instantiated with a `create()` function. For instance,

    auto pixbuf = Gdk::Pixbuf::create_from_file(filename);

You have no way of getting a bare `Gdk::Pixbuf`. In the example, `pixbuf` is a smart pointer, so you can do this, much like a normal pointer:

    auto width = 0;
    if(pixbuf)
    {
      width = pixbuf->get_width();
    }

Kdy `pixbuf` přejde mimo rozsah působnosti, provede se na pozadí `unref()` a dále se o něj již nemusíte starat. Nebylo zde žádné `new`, tak není ani žádné `delete`.

If you copy a `RefPtr`, for instance

    auto pixbuf2 = pixbuf;

, or if you pass it as a method argument or a return type, then `RefPtr` will do any necessary referencing to ensure that the instance will not be destroyed until the last `RefPtr` has gone out of scope.

Podrobné informace o RefPtr viz dodatek.

If you wish to learn more about smartpointers, you might look in these books:

- Bjarne Stroustrup, "The C++ Programming Language" Fourth Edition - section 34.3

- Nicolai M. Josuttis, "The C++ Standard Library" - section 4.2

## Gtk::Builder

Although you can use C++ code to instantiate and arrange widgets, this can soon become tedious and repetitive. And it requires a recompilation to show changes. The Cambalache application allows you to layout widgets on screen and then save an XML description of the arrangement. Your application can then use the Gtk::Builder API to load that XML file at runtime and obtain a pointer to specifically named widget instances.

This has the following advantages:

1. Less C++ code is required.

2. UI changes can be seen more quickly, so UIs are able to improve.

3. Designers without programming skills can create and edit UIs.

Stále budete potřebovat nějaký kód v C++ k obsluze změn v uživatelském rozhraní spouštěných uživatelovou činností, ale použití Gtk::Builder pro rozvržení vám uvolní ruce pro práci na funkcionalitě.

Cambalache replaces the Glade application. Glade can generate XML files to be used with gtk3/gtkmm3, but it does not support gtk4/gtkmm4.

### Loading the .ui file

`Gtk::Builder` must be used via a `Glib::RefPtr`. Like all such classes, you need to use a `create()` method to instantiate it. For instance,

    auto builder = Gtk::Builder::create_from_file("basic.ui");

This will instantiate the windows defined in the `.ui` file.

To instantiate just one window, or just one of the child widgets, you can specify the name of a widget as the second parameter. For instance,

    auto builder = Gtk::Builder::create_from_file("basic.ui", "treeview_products");

### Přístup k widgetům

To access a widget, for instance to show a dialog, use the `get_widget()` method, providing the widget's name. This name should be specified in the Cambalache window. If the widget could not be found, or is of the wrong type, then the pointer will be set to `nullptr`.

The dialogs in this chapter are derived from `Gtk::Window` because `Gtk::Dialog` is deprecated since gtkmm 4.10.

    auto pDialog = builder->get_widget<Gtk::Window>("DialogBasic");

`Gtk::Builder` checks for a null pointer, and checks that the widget is of the expected type, and will show warnings on the command line about these.

Pamatujte, že instanci widgetu nevytváříte pomocí metody `get_widget()`, tou jen získáváte ukazatel na instanci, která již existuje. Pokaždé, když zavoláte `get_widget()` na ten samý objekt `Gtk::Builder`, měli byste obdržet ukazatel na tu samou instanci. Instance widgetů se vytváří během `Gtk::Builder::create_from_file()`.

`get_widget()` returns child widgets that are `manage()`ed (see the Memory Management chapter), so they will be deleted when their parent container is deleted. `Window`s (such as `Dialog`s) cannot be managed because they have no parent container, so you must delete them at some point. The documentation of `Gtk::Builder` has more to say about the memory management of different kinds of objects.

Reference

#### Příklad

This simple example shows how to load a `.ui` file at runtime and access the widgets with `Gtk::Builder`.

Source Code

File: `main.cc` (For use with gtkmm 4)

    #include <gtkmm.h>
    #include <iostream>

    namespace
    {
    Gtk::Window* pDialog = nullptr;
    Glib::RefPtr<Gtk::Application> app;

    void on_button_clicked()
    {
      if (pDialog)
        pDialog->set_visible(false); // set_visible(false) will cause Gtk::Application::run() to end.
    }

    void on_app_activate()
    {
      // Load the GtkBuilder file and instantiate its widgets:
      auto refBuilder = Gtk::Builder::create();
      try
      {
        refBuilder->add_from_file("basic.ui");
      }
      catch(const Glib::FileError& ex)
      {
        std::cerr << "FileError: " << ex.what() << std::endl;
        return;
      }
      catch(const Glib::MarkupError& ex)
      {
        std::cerr << "MarkupError: " << ex.what() << std::endl;
        return;
      }
      catch(const Gtk::BuilderError& ex)
      {
        std::cerr << "BuilderError: " << ex.what() << std::endl;
        return;
      }

      // Get the GtkBuilder-instantiated dialog:
      pDialog = refBuilder->get_widget<Gtk::Window>("DialogBasic");
      if (!pDialog)
      {
        std::cerr << "Could not get the dialog" << std::endl;
        return;
      }

      // Get the GtkBuilder-instantiated button, and connect a signal handler:
      auto pButton = refBuilder->get_widget<Gtk::Button>("quit_button");
      if (pButton)
        pButton->signal_clicked().connect([] () { on_button_clicked(); });

      // It's not possible to delete widgets after app->run() has returned.
      // Delete the dialog with its child widgets before app->run() returns.
      pDialog->signal_hide().connect([] () { delete pDialog; });

      app->add_window(*pDialog);
      pDialog->set_visible(true);
    }
    } // anonymous namespace

    int main(int argc, char** argv)
    {
      app = Gtk::Application::create("org.gtkmm.example");

      // Instantiate a dialog when the application has been activated.
      // This can only be done after the application has been registered.
      // It's possible to call app->register_application() explicitly, but
      // usually it's easier to let app->run() do it for you.
      app->signal_activate().connect([] () { on_app_activate(); });

      return app->run(argc, argv);
    }

### Používání odvozených widgetů

You can use Cambalache and `Gtk::Builder` to layout your own custom widgets derived from gtkmm widget classes. This keeps your code organized and encapsulated, separating declarative presentation from business logic, avoiding having most of your source just be setting properties and packing in containers.

Use `Gtk::Builder::get_widget_derived()` like so:

    auto pDialog = Gtk::Builder::get_widget_derived<DerivedDialog>(builder, "DialogDerived");

Your derived class must have a constructor that takes a pointer to the underlying C type, and the `Gtk::Builder` instance. All relevant classes of gtkmm typedef their underlying C type as `BaseObjectType` (`Gtk::Window` typedefs `BaseObjectType` as GtkWindow, for instance).

You must call the base class's constructor in the initialization list, providing the C pointer. For instance,

    DerivedDialog::DerivedDialog(BaseObjectType* cobject, const Glib::RefPtr<Gtk::Builder>& builder)
    : Gtk::Window(cobject)
    {
    }

You could then encapsulate the manipulation of the child widgets in the constructor of the derived class, maybe using `get_widget()` or `get_widget_derived()` again. For instance,

    DerivedDialog::DerivedDialog(BaseObjectType* cobject, const Glib::RefPtr<Gtk::Builder>& builder)
    : Gtk::Window(cobject),
      m_builder(builder),
      // Get the GtkBuilder-instantiated Button, and connect a signal handler:
      m_pButton(m_builder->get_widget<Gtk::Button>("quit_button"))
    {
      if (m_pButton)
      {
        m_pButton->signal_clicked().connect( sigc::mem_fun(*this, &DerivedDialog::on_button_quit) );
      }
    }

It's possible to pass additional arguments from `get_widget_derived()` to the constructor of the derived widget. For instance, this call to `get_widget_derived()`

    auto pDialog = Gtk::Builder::get_widget_derived<DerivedDialog>(builder, "DialogDerived", true);

can invoke this constructor

    DerivedDialog::DerivedDialog(BaseObjectType* cobject,
      const Glib::RefPtr<Gtk::Builder>& builder, bool warning)
    : Gtk::Window(cobject),
      m_builder(builder),
      m_pButton(m_builder->get_widget<Gtk::Button>("quit_button"))
    {
      // ....
    }

#### Gtk::Builder and Glib::Property

If your derived widget uses `Glib::Property`, it becomes slightly more complicated. A derived widget that contains `Glib::Property` members must be registered with its own name in the GType system. It must be registered before any of the `create_from_*()` or `add_from_*()` methods are called, meaning that you may have to create an instance of your derived widget just to have its class registered. Your derived widget must have a constructor that has the parameters required by `get_widget_derived()` and calls the `Glib::ObjectBase` constructor to register the GType.

    DerivedButton::DerivedButton(BaseObjectType* cobject, const Glib::RefPtr<Gtk::Builder>& builder)
    : Glib::ObjectBase("MyButton"), // The GType name will be gtkmm__CustomObject_MyButton.
      Gtk::Button(cobject),
      prop_ustring(*this, "button-ustring"),
      prop_int(*this, "button-int", 10)
    {
      // ....
    }

It is possible also to specify properties of derived widgets, declared in C++ using gtkmm, within `.ui` files and load/set these using `Gtk::Builder`. See the documentation of `Gtk::Builder` for more details on how to achieve this. Cambalache won’t recognize such properties as-is, but you should be able to add a few lines of hand-coded XML to the XML code generated by Cambalache.

#### Příklad

This example shows how to load a `.ui` file at runtime and access the widgets via derived classes.

Source Code

File: `derivedbutton.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLE_DERIVED_BUTTON_H
    #define GTKMM_EXAMPLE_DERIVED_BUTTON_H

    #include <gtkmm.h>

    class DerivedButton : public Gtk::Button
    {
    public:
      DerivedButton();
      DerivedButton(BaseObjectType* cobject, const Glib::RefPtr<Gtk::Builder>& refBuilder);
      virtual ~DerivedButton();

      // Provide proxies for the properties. The proxy allows you to connect to
      // the 'changed' signal, etc.
      Glib::PropertyProxy<Glib::ustring> property_ustring() { return prop_ustring.get_proxy(); }
      Glib::PropertyProxy<int> property_int() { return prop_int.get_proxy(); }

    private:
      Glib::Property<Glib::ustring> prop_ustring;
      Glib::Property<int> prop_int;
    };

    #endif //GTKMM_EXAMPLE_DERIVED_BUTTON_H

File: `deriveddialog.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLE_DERIVED_DIALOG_H
    #define GTKMM_EXAMPLE_DERIVED_DIALOG_H

    #include <gtkmm.h>
    #include "derivedbutton.h"

    class DerivedDialog : public Gtk::Window
    {
    public:
      DerivedDialog(BaseObjectType* cobject, const Glib::RefPtr<Gtk::Builder>& refBuilder);
      DerivedDialog(BaseObjectType* cobject, const Glib::RefPtr<Gtk::Builder>& refBuilder,
        bool is_glad);
      ~DerivedDialog() override;

    protected:
      //Signal handlers:
      void on_button_quit();

      Glib::RefPtr<Gtk::Builder> m_refBuilder;
      DerivedButton* m_pButton;
    };

    #endif //GTKMM_EXAMPLE_DERIVED_DIALOG_H

File: `derivedbutton.cc` (For use with gtkmm 4)

    #include "derivedbutton.h"
    #include <iostream>

    // For creating a dummy object in main.cc.
    DerivedButton::DerivedButton()
    : Glib::ObjectBase("MyButton"),
      prop_ustring(*this, "button-ustring"),
      prop_int(*this, "button-int", 10)
    {
    }

    DerivedButton::DerivedButton(BaseObjectType* cobject, const Glib::RefPtr<Gtk::Builder>& /* refBuilder */)
    : // To register custom properties, you must register a custom GType.  If
      // you don't know what that means, don't worry, just remember to add
      // this Glib::ObjectBase constructor call to your class' constructor.
      // The GType name will be gtkmm__CustomObject_MyButton.
      Glib::ObjectBase("MyButton"),
      Gtk::Button(cobject),
      // register the properties with the object and give them names
      prop_ustring(*this, "button-ustring"),
      // this one has a default value
      prop_int(*this, "button-int", 10)
    {
      // Register some handlers that will be called when the values of the
      // specified parameters are changed.
      property_ustring().signal_changed().connect(
        [](){ std::cout << "- ustring property changed!" << std::endl; }
      );
      property_int().signal_changed().connect(
        [](){ std::cout << "- int property changed!" << std::endl; }
      );
    }

    DerivedButton::~DerivedButton()
    {
    }

File: `deriveddialog.cc` (For use with gtkmm 4)

    #include "deriveddialog.h"
    #include <iostream>

    DerivedDialog::DerivedDialog(BaseObjectType* cobject, const Glib::RefPtr<Gtk::Builder>& refBuilder)
    : Gtk::Window(cobject),
      m_refBuilder(refBuilder),
      m_pButton(nullptr)
    {
      // Get the GtkBuilder-instantiated Button, and connect a signal handler:
      m_pButton = Gtk::Builder::get_widget_derived<DerivedButton>(m_refBuilder, "quit_button");
      if (m_pButton)
      {
        m_pButton->signal_clicked().connect( sigc::mem_fun(*this, &DerivedDialog::on_button_quit) );
        std::cout << "ustring, int: " << m_pButton->property_ustring()
                  << ", " << m_pButton->property_int() << std::endl;
        m_pButton->property_int() = 99;
        std::cout << "ustring, int: " << m_pButton->property_ustring()
                  << ", " << m_pButton->property_int() << std::endl;
      }
    }

    // The first two parameters are mandatory in a constructor that will be called
    // from Gtk::Builder::get_widget_derived().
    // Additional parameters, if any, correspond to additional arguments in the call
    // to Gtk::Builder::get_widget_derived().
    DerivedDialog::DerivedDialog(BaseObjectType* cobject, const Glib::RefPtr<Gtk::Builder>& refBuilder,
      bool is_glad)
    : DerivedDialog(cobject, refBuilder) // Delegate to the other constructor
    {
      // Show an icon.
      auto content_area = refBuilder->get_widget<Gtk::Box>("dialog-content_area");
      if (!content_area)
      {
        std::cerr << "Could not get the content area" << std::endl;
        return;
      }
      auto pImage = Gtk::make_managed<Gtk::Image>();
      pImage->set_from_icon_name(is_glad ? "face-smile" : "face-sad");
      pImage->set_icon_size(Gtk::IconSize::LARGE);
      pImage->set_expand();
      content_area->append(*pImage);
    }

    DerivedDialog::~DerivedDialog()
    {
    }

    void DerivedDialog::on_button_quit()
    {
      set_visible(false); // set_visible(false) will cause Gtk::Application::run() to end.
    }

File: `main.cc` (For use with gtkmm 4)

    #include "deriveddialog.h"
    #include <iostream>
    #include <cstring>

    namespace
    {
    bool show_icon = false;
    bool is_glad = true;

    DerivedDialog* pDialog = nullptr;
    Glib::RefPtr<Gtk::Application> app;

    void on_app_activate()
    {
      // Create a dummy instance before the call to refBuilder->add_from_file().
      // This creation registers DerivedButton's class in the GType system.
      // This is necessary because DerivedButton contains user-defined properties
      // (Glib::Property) and is created by Gtk::Builder.
      static_cast<void>(DerivedButton());

      // Load the GtkBuilder file and instantiate its widgets:
      auto refBuilder = Gtk::Builder::create();
      try
      {
        refBuilder->add_from_file("derived.ui");
      }
      catch(const Glib::FileError& ex)
      {
        std::cerr << "FileError: " << ex.what() << std::endl;
        return;
      }
      catch(const Glib::MarkupError& ex)
      {
        std::cerr << "MarkupError: " << ex.what() << std::endl;
        return;
      }
      catch(const Gtk::BuilderError& ex)
      {
        std::cerr << "BuilderError: " << ex.what() << std::endl;
        return;
      }

      // Get the GtkBuilder-instantiated dialog:
      if (show_icon)
        pDialog = Gtk::Builder::get_widget_derived<DerivedDialog>(refBuilder, "DialogDerived", is_glad);
      else
        pDialog = Gtk::Builder::get_widget_derived<DerivedDialog>(refBuilder, "DialogDerived");

      if (!pDialog)
      {
        std::cerr << "Could not get the dialog" << std::endl;
        return;
      }

      // It's not possible to delete widgets after app->run() has returned.
      // Delete the dialog with its child widgets before app->run() returns.
      pDialog->signal_hide().connect([] () { delete pDialog; });

      app->add_window(*pDialog);
      pDialog->set_visible(true);
    }
    } // anonymous namespace

    int main(int argc, char** argv)
    {
      int argc1 = argc;
      if (argc > 1)
      {
        if (std::strcmp(argv[1], "--glad") == 0)
        {
          show_icon = true;
          is_glad = true;
          argc1 = 1; // Don't give the command line arguments to Gtk::Application.
        }
        else if (std::strcmp(argv[1], "--sad") == 0)
        {
          show_icon = true;
          is_glad = false;
          argc1 = 1; // Don't give the command line arguments to Gtk::Application.
        }
      }

      app = Gtk::Application::create("org.gtkmm.example");

      // Instantiate a dialog when the application has been activated.
      // This can only be done after the application has been registered.
      // It's possible to call app->register_application() explicitly, but
      // usually it's easier to let app->run() do it for you.
      app->signal_activate().connect([] () { on_app_activate(); });

      return app->run(argc1, argv);
    }

## Internacionalizace a lokalizace

Aplikace s gtkmm mohou jednoduše podporovat více jazyků, včetně neevropských, jako je čínština nebo zprava doleva psaná arabština. Správně napsaná a přeložená aplikace s gtkmm použije za běhu správný jazyk podle toho, jaké národní prostředí má uživatel nastavené.

Možná nebudete předpokládat potřebu podpory dalších jazyků, ale nikdy neříkejte nikdy. A je jednodušší aplikace hned ze začátku napsat správně, než ji později celou opravovat.

Proces psaní zdrojového kódu, který umožňuje jazykové překlady, se nazývá `internacionalizace`, což je často zkracováno na `i18n`. `Lokalizace`, zkracovaná na `l10n` je pak vlastní překlad textů vycházejících ze zdrojového kódu do jiných jazyků.

Hlavní činností při internacionalizaci je vyhledání řetězců, které uživatele uvidí a jejich označení k překladu. Nemusíte je všechny označit naráz – když správně nastavíte potřebnou infrastrukturu projektu, bude vaše aplikace normálně fungovat bez ohledu na to, kolik řetězců jste internacionalizací pokryli.

Řetězcové literály byste měli ve zdrojovém kódu psát v angličtině, ale obalené do makra. Nástroj gettext (nebo intltool) umí vytáhnout takto označené řetězce pro překladatele a za běhu je pak nahrazovat překlady.

### Příprava vašeho projektu

In the instructions below we will assume that you will not be using gettext directly, but intltool, which was written specifically for `GNOME`. intltool uses `gettext()`, which extracts strings from source code, but intltool can also combine strings from other files, for example from desktop menu details, and GUI resource files such as `.ui` files, into standard gettext `.pot/.po` files.

We also assume that you are using autotools (automake and autoconf) to build your project (although autotools is not recommended for new applications), and that you are using `./autogen.sh` from gnome-common or a similar `autogen.sh` file, which, among other things, takes care of some intltool initialization.

If you are using meson (recommended), see the Localisation chapter in Meson's manual. You can then skip this section.

An alternative to gnome-common's `autogen.sh` may look like this:

    #! /bin/sh -e
    test -n "$srcdir" || srcdir=`dirname "$0"`
    test -n "$srcdir" || srcdir=.

    autoreconf --force --install --verbose --warnings=all "$srcdir"
    echo "Running intltoolize --copy --force --automake"
    intltoolize --copy --force --automake
    test -n "$NOCONFIGURE" || "$srcdir/configure" "$@"

Vytvořte v kořenové složce vašeho projektu podsložku s názvem `po`. V budoucnu bude obsahovat všechny překlady. V ní vytvořte soubory s názvy `LINGUAS` a `POTFILES.in`. Je běžnou praxí v ní vytvořit také soubor `ChangeLog`, aby si překladatelé mohli udržovat přehled o změnách v překladech.

Soubor `LINGUAS` obsahuje abecedně seřazený seznam kódů identifikujících jazyky, do kterých je aplikace přeložená (řádky začínající # jsou komentáře a jsou ignorovány). Jednotlivé kódy jazyků uvedené v `LINGUAS` musí odpovídat názvům souborů `.po`. Když má například aplikace překlad do češtiny a japonštiny, měl by váš soubor `LINGUAS` vypadat nějak takto:

    # keep this file sorted alphabetically, one language code per line
    cs
    ja

(In addition, you'd have the files `de.po` and `ja.po` in your `po` directory which contain the German and Japanese translations, respectively.)

Soubor `POTFILES.in` je seznam cest ke všem souborům, které obsahují řetězce označené k překladu, počínaje kořenovou složkou projektu. Takže když například má váš projekt zdrojové kódy umístěné v podsložce s názvem `src` a v ní jsou dva soubory obsahující řetězce, které chcete přeložit, může váš soubor `POTFILES.in` vypadat nějak takto:

    src/main.cc
    src/other.cc

If you are using gettext directly, you can only mark strings for translation if they are in source code file. However, if you use intltool, you can mark strings for translation in a variety of other file formats, including `.ui` files, xml, .desktop files and several more. So, if you have designed some of the application UI in xml files then also add your `.ui` files to the list in `POTFILES.in`.

Nyní máte místo, kam dávat překlady, a teď potřebujete inicializovat intltool a gettext. Přidejte následující kód do svého souboru `configure.ac`, přičemž „nazevaplikace“ nahraďte názvem svojí aplikace (platí pro celou kapitolu).

    IT_PROG_INTLTOOL([0.35.0])

    GETTEXT_PACKAGE=programname
    AC_SUBST(GETTEXT_PACKAGE)
    AC_DEFINE_UNQUOTED([GETTEXT_PACKAGE], ["$GETTEXT_PACKAGE"],
                       [The domain to use with gettext])
    AM_GNU_GETTEXT([external])
    AM_GNU_GETTEXT_VERSION([0.17])

    PROGRAMNAME_LOCALEDIR=[${datadir}/locale]
    AC_SUBST(PROGRAMNAME_LOCALEDIR)

Proměnná `NAZEVAPLIKACE_LOCALEDIR` bude použita později v souboru `Makefile.am` k definici makra, které se použije až budeme ve zdrojovém kódu inicializovat gettext.

`AM_GLIB_GNU_GETTEXT` has been an alternative to `AM_GNU_GETTEXT` and `AM_GNU_GETTEXT_VERSION`, but `AM_GLIB_GNU_GETTEXT` is now deprecated, and shall not be used in new code.

In the top-level Makefile.am:

- Add `po` to the `SUBDIRS` variable. Without this, your translations won't get built and installed when you build the program

- Define `INTLTOOL_FILES` as:

      INTLTOOL_FILES = intltool-extract.in \
                       intltool-merge.in \
                       intltool-update.in

- Add `INTLTOOL_FILES` to the `EXTRA_DIST` list of files. This ensures that when you do a `make dist`, these files will be included in the source tarball.

- Update your `DISTCLEANFILES`:

      DISTCLEANFILES = ... intltool-extract \
                       intltool-merge \
                       intltool-update \
                       po/.intltool-merge-cache

- Depending on the types of files that contain translatable strings, add code such as

      desktopdir = $(datadir)/applications
      desktop_in_files = programname.desktop.in
      desktop_DATA = $(desktop_in_files:.desktop.in=.desktop)
      @INTLTOOL_DESKTOP_RULE@

V souboru `src/Makefile.am` aktualizujte `AM_CPPFLAGS` přidáním následujících definic maker preprocesoru:

    AM_CPPFLAGS = ... -DNAZEVAPLIKACE_LOCALEDIR=\"${NAZEVAPLIKACE_LOCALEDIR}\"

Toto makro se použije, když inicializujete `gettext` ve svém zdrojovém kódu.

### Označení řetězců k překladu

Řetězcové literály by se měly ve zdrojovém kódu psát v angličtině a zároveň by měly být uzavřeny do volání funkce `gettext()`. Pak budou vytaženy pro překlad a překlad bude použit za běhu místo původního anglického řetězce.

Balíček GNU gettext umožňuje označit řetězce ve zdrojovém kódu k překladu, vytáhnout tyto řetězce pro překlad a použít přeložené řetězce v aplikaci.

However, Glib defines `gettext()` support macros which are shorter wrappers in an easy-to-use form. To use these macros, include `<glibmm/i18n.h>`, and then, for example, substitute:

    display_message("Getting ready for i18n.");

with:

    display_message(_("Getting ready for i18n."));

For reference, it is possible to generate a file which contains all strings which appear in your code, even if they are not marked for translation, together with file name and line number references. To generate such a file named `my-strings`, execute the following command, within the source code directory:

    xgettext -a -o moje-řetězce --omit-header *.cc *.h

Finally, to let your program use the translation for the current locale, add this code to the beginning of your `main.cc` file, to initialize gettext.

    bindtextdomain(GETTEXT_PACKAGE, PROGRAMNAME_LOCALEDIR);
    bind_textdomain_codeset(GETTEXT_PACKAGE, "UTF-8");
    textdomain(GETTEXT_PACKAGE);

#### Jak gettext funguje

The intltool-update or xgettext script extracts the strings and puts them in a `mypackage.pot` file. The translators of your application create their translations by first copying this `.pot` file to a `localename.po` file. A locale identifies a language and an encoding for that language, including date and numerical formats. Later, when the text in your source code has changed, the msgmerge or intltool-update script is used to update the `localename.po` files from the regenerated `.pot` file.

Před instalací jsou soubory `.po` převedeny do binárního formátu (s příponou `.mo`) a při instalaci se nakopírují do systémové složky pro lokalizační soubory, například `/usr/share/locale/`.

Když je aplikace spuštěna, knihovna gettext zkontroluje systémovou složku, jestli v ní je soubor `.mo` pro národní prostředí uživatele (národní prostředí můžete nastavit například příkazem „export LANG=cs_CZ.UTF-8“ z příkazové řádky). Až později běžící aplikace narazí na volání `gettext`, podívá se po překladu konkrétního řetězce. Pokud jej nenajde, použije se řetězec původní.

#### Testování a přidávání překladů

To convince yourself that you've done well, you may wish to add a translation for a new locale. In order to do that, go to the `po` subdirectory of your project and execute the following command:

    intltool-update --pot

Vytvoří se tím soubor `nazevaplikace.pot`. Zkopírujte tento soubor do `kodjazyka.po`, třeba `cs.po` nebo `hu.po`. Příslušný jazyk také přidejte do souboru `LINGUAS`. Soubor `.po` obsahuje hlavičku a seznam anglických řetězců s rezervovaným místem pro zadání přeložených řetězců. Ujistěte se, že je kódování souboru `.po` nastavené na `UTF-8` (je to uvedené v hlavičce a musí být v tomto kódování i řetězce).

It's possible that certain strings will be marked as `fuzzy` in the `.po` file. These translations will not substitute the original string. To make them appear, simply remove the `fuzzy` tag. A `fuzzy` tag appears if a string content changed, but the location is still the same.

#### Zdroje

More information about what lies behind the internationalization and localization process is presented and demonstrated in:

- L10N Guidelines for Developers

- Intltool README

- How to use Git for GNOME translators

- gettext manual

- `gtkmm_hello` example package

- `gnomemm_hello` example package

### Očekává se UTF-8

Správně internacializovaná aplikace nebude mít žádné předpoklady ohledně počtu bajtů na znak. To znamená, že byste neměli používat ukazatelovou aritmetiku k procházení řetězců po znacích a neměli byste používat `std::string` nebo standardní funkce C, jako je `strlen()`, protože ty takové předpoklady mají.

Místo obyčejných polí char* a ukazatelové aritmetiky už stejně nejspíše používáte třídu `std::string`, takže stačí, když přejdete místo ní na používání `Glib::ustring`. Viz kapitola Základy o `Glib::ustring`.

#### Glib::ustring and std::iostreams

Unfortunately, the integration with the standard iostreams is not completely foolproof. gtkmm converts `Glib::ustring`s to a locale-specific encoding (which usually is not UTF-8) if you output them to an `ostream` with `operator<<`. Likewise, retrieving `Glib::ustring`s from `istream` with `operator>>` causes a conversion in the opposite direction. But this scheme breaks down if you go through a `std::string`, e.g. by inputting text from a stream to a `std::string` and then implicitly converting it to a `Glib::ustring`. If the string contained non-ASCII characters and the current locale is not UTF-8 encoded, the result is a corrupted `Glib::ustring`. You can work around this with a manual conversion. For instance, to retrieve the `std::string` from a `ostringstream`:

    std::locale::global(std::locale("")); // Set the global locale to the user's preferred locale.
                                          // Usually unnecessary here, because Glib::init()
                                          // or Gtk::Application::create() does it for you.
    std::ostringstream output;
    output << percentage << " % done";
    label->set_text(Glib::locale_to_utf8(output.str()));

### Úskalí

Existuje několik běžných omylů, na které byste si jistě přišli sami. Tato kapitola vám pomůže se jim vyhnout.

#### Stejné řetězce, jiný význam

Sometimes two English strings are identical but have different meanings in different contexts, so they would probably not be identical when translated. Since the English strings are used as look-up keys, this causes problems.

V takovémto případě byste měli přidat do řetězce nějaké další znaky. Například použít `"jumps[noun]"` a `"jumps[verb]"` místo prostého `"jumps"` a po zavolání funkce `gettext` je odříznout. Když něco takového provedete, měli byste také přidat komentář pro překladatele před volání `gettext`. Tyto komentáře se objeví v souborech `.po`. Například:

    // note to translators: don't translate the "[noun]" part - it is
    // just here to distinguish the string from another "jumps" string
    text = strip(gettext("jumps[noun]"), "[noun]");

If you use Glib's support macros, it's easier. Use `C_()` instead of `_()`. For instance:

    GLib::ustring text(C_("noun", "jumps"));

#### Skládání řetězců

C programmers use `sprintf()` to compose and concatenate strings. C++ favors streams, but unfortunately, this approach makes translation difficult, because each fragment of text is translated separately, without allowing the translators to rearrange them according to the grammar of the language.

Například takovýto kód by mohl přinést problémy:

    std::cout << _("Current amount: ") << amount
              << _(" Future: ") << future << std::endl;

    label.set_text(_("Really delete ") + filename + _(" now?"));

So you should either avoid this situation or use `Glib::ustring::compose()` which supports syntax such as:

    std::cout << Glib::ustring::compose(
                 _("Current amount: %1 Future: %2"), amount, future) << std::endl;

    label.set_text(Glib::ustring::compose(_("Really delete %1 now?"), filename));

#### Počítejte s dostatečnou šířkou pro zobrazení řetězců

Nemůžete dopředu vědět, kolik místa na obrazovce řetězec zabere po překladu. Je klidně možné, že bude dvakrát delší, než anglický originál. Naštěstí se většina widgetů gtkmm za běhu roztáhne na velikost, která se po nich chce.

#### Neobvyklá slova

Měli byste se vyhnout tajuplným zkratkám, slangu a nářečím. Většinou bývá nesnadné je přeložit a někdy jim nerozumí ani rodilý mluvčí. Například raději používejte „application“ než „app“.

#### Používání jiných znaků než ASCII v řetězcích

V současnosti gettext nepodporuje jiné znaky než ASCII (tj. znaky s kódem vyšším než 127) ve zdrojovém kódu. Například nemůžete použít znak copyright (©).

To work around this, you could write a comment in the source code just before the string, telling the translators to use the special character if it is available in their languages. For English, you could then make an American English `en_US.po` translation which used that special character.

### Získání pomoci s překladem

If your program is free software, there is a whole `GNOME` subproject devoted to helping you make translations, the `GNOME` Translation Project.

The way it works is that you upload your source code to a git repository where translators can access it, then contact the gnome-i18n mailing list and ask to have your program added to the list of modules to translate.

Then you make sure you update the file `POTFILES.in` in the `po/` subdirectory (`intltool-update -m` can help with this) so that the translators always access updated `myprogram.pot` files, and simply freeze the strings at least a couple of days before you make a new release, announcing it on gnome-i18n. Depending on the number of strings your program contains and how popular it is, the translations will then start to tick in as `languagename.po` files.

Upozorňujeme, že většina překladatelských týmů se skládá jen z jednoho až tří lidí, takže pokud vaše aplikace obsahuje spoustu řetězců, může to chvíli trvat, něž si někdo najde čas se na ni podívat. Navíc většina překladatelů nechce ztrácet svůj čas (překládání je časově velmi náročné) na nesolidních projektech (ve smyslu, že je dotažený do použitelného stavu a udržovaný) a mohou se věnovat raději jinému projektu.

## Vlastní widgety

gtkmm makes it very easy to derive new widgets by inheriting from an existing widget class, either by deriving from a container and adding child widgets, or by deriving from a single-item widget, and changing its behavior. But you might occasionally find that no suitable starting point already exists. In this case, you can implement a widget from scratch.

### Vlastní kontejnery

When deriving a custom container widget directly from `Gtk::Widget`, you should override the following virtual methods:

- `get_request_mode_vfunc()`: Return what `Gtk::SizeRequestMode` is preferred by the container.

- `measure_vfunc()`: Calculate the minimum and natural width or height of the container.

- `size_allocate_vfunc()`: Position the child widgets, given the height and width that the container has actually been given.

The `get_request_mode_vfunc()`, `measure_vfunc()`, and `size_allocate_vfunc()` virtual methods control the layout of the child widgets. For instance, if your container has 2 child widgets, with one below the other, your `get_request_mode_vfunc()` might request height-for-width layout. Then your `measure_vfunc()` might report the maximum of the widths of the child widgets when asked to report width, and it might report the sum of their heights when asked to report height. If you want padding between the child widgets then you would add that to the width and height too. Your widget's container will use this result to ensure that your widget gets enough space, and not less. By examining each widget's parent, and its parent, this logic will eventually decide the size of the top-level window.

You are not guaranteed to get the `Gtk::SizeRequestMode` that you request. Therefore `measure_vfunc()` must return sensible values for all reasonable values of its input parameters. For a description of `measure_vfunc()`'s parameters see also the description of `Gtk::Widget::measure()`, which may be better documented than `measure_vfunc()`.

`size_allocate_vfunc()` receives the actual height and width that the parent container has decided to give to your widget. This might be more than the minimum, or even more than the natural size, for instance if the top-level window has been expanded. You might choose to ignore the extra space and leave a blank area, or you might choose to expand your child widgets to fill the space, or you might choose to expand the padding between your widgets. It's your container, so you decide.

Your container must unparent its children before the underlying C object (a `gtkmm__GtkWidget`) is finalized. If your container is used as a managed widget, it shall unparent its children in a `Gtk::Widget::signal_destroy()` handler (available since gtkmm 4.8). If your container is not managed, that signal handler is not called. Instead the children shall be unparented in the C++ destructor. If you want your container to be useful both ways, unparent the children both in the destructor and in a signal handler. See the example code.

#### Příklad

This example implements a container with child widgets, one above the other. Of course, in this case it would be far simpler just to use a vertical `Gtk::Box` or `Gtk::Grid`.

##### Vlastní kontejner

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>
    #include "mycontainer.h"

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      ~ExampleWindow() override;

    protected:
      //Signal handlers:
      void on_button_quit();

      //Child widgets:
      Gtk::Box m_VBox;
      MyContainer m_MyContainer;
      Gtk::Button m_Button_Child;
      Gtk::Label m_Label_Child;
      Gtk::Box m_ButtonBox;
      Gtk::Button m_Button_Quit;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `mycontainer.h` (For use with gtkmm 4)

    #ifndef GTKMM_CUSTOM_CONTAINER_MYCONTAINER_H
    #define GTKMM_CUSTOM_CONTAINER_MYCONTAINER_H

    #include <gtkmm/widget.h>
    #include <gtkmm/version.h>

    #define HAS_SIGNAL_DESTROY GTKMM_CHECK_VERSION(4,7,1)

    class MyContainer : public Gtk::Widget
    {
    public:
      MyContainer();
      ~MyContainer() override;

      void append(Gtk::Widget& child);
      void prepend(Gtk::Widget& child);
      void remove(Gtk::Widget& child);

    protected:
      int get_nvis_children() const;

      //Overrides:
      Gtk::SizeRequestMode get_request_mode_vfunc() const override;
      void measure_vfunc(Gtk::Orientation orientation, int for_size, int& minimum, int& natural,
        int& minimum_baseline, int& natural_baseline) const override;
      void size_allocate_vfunc(int width, int height, int baseline) override;

    #if HAS_SIGNAL_DESTROY
      // Signal handler:
      void on_container_destroy();
    #endif
    };

    #endif //GTKMM_CUSTOM_CONTAINER_MYCONTAINER_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::Orientation::VERTICAL),
      m_Button_Child("Child button"),
      m_Label_Child("Child label", Gtk::Align::END, Gtk::Align::CENTER),
      m_Button_Quit("Quit")
    {
      set_title("Custom Container example");
      set_default_size(400, 200);

      m_VBox.set_margin(6);
      set_child(m_VBox);

      //Add the child widgets to the custom container:
      m_MyContainer.append(m_Button_Child);
      m_MyContainer.append(m_Label_Child);
      m_MyContainer.prepend(*Gtk::make_managed<Gtk::Label>(
        "First line\nSecond line\nThird line"));
      m_MyContainer.set_expand();
      m_VBox.append(m_MyContainer);

    #if HAS_SIGNAL_DESTROY
      // A managed custom container.
      auto container = Gtk::make_managed<MyContainer>();
      container->prepend(*Gtk::make_managed<Gtk::Label>("Second custom container"));
      container->set_expand();
      m_VBox.append(*container);
    #endif
      m_VBox.append(m_ButtonBox);

      m_ButtonBox.append(m_Button_Quit);
      m_ButtonBox.set_margin(6);
      m_Button_Quit.set_hexpand(true);
      m_Button_Quit.set_halign(Gtk::Align::END);
      m_Button_Quit.signal_clicked().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_button_quit) );
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_quit()
    {
      set_visible(false);
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

File: `mycontainer.cc` (For use with gtkmm 4)

    #include "mycontainer.h"

    #include <algorithm> // std::max()

    // This example container is a simplified vertical Box.
    //
    // It can't be used as a managed widget, managed by another container
    // unless Gtk::Widget::signal_destroy() exists.
    // It would cause an error like
    // Gtk-WARNING **: 08:31:48.137: Finalizing gtkmm__GtkWidget 0x561b777462c0, but it still has children left:

    MyContainer::MyContainer()
    {
    #if HAS_SIGNAL_DESTROY
      signal_destroy().connect(sigc::mem_fun(*this, &MyContainer::on_container_destroy));
    #endif
    }

    MyContainer::~MyContainer()
    {
      // If MyContainer is a managed widget, the underlying C object is destructed
      // before this C++ destructor is executed.
      if (!gobj())
        return;

      // If MyContainer is not a managed widget, unparent all children here.
      while (Widget* child = get_first_child())
        child->unparent();
    }

    #if HAS_SIGNAL_DESTROY
    // This signal handler is called only if MyContainer is a managed widget.
    void MyContainer::on_container_destroy()
    {
      while (Widget* child = get_first_child())
        child->unparent();
    }
    #endif

    // Get number of visible children.
    int MyContainer::get_nvis_children() const
    {
      int nvis_children = 0;
      for (const Widget* child = get_first_child(); child; child = child->get_next_sibling())
        if (child->get_visible())
          ++nvis_children;

      return nvis_children;
    }

    Gtk::SizeRequestMode MyContainer::get_request_mode_vfunc() const
    {
      return Gtk::SizeRequestMode::HEIGHT_FOR_WIDTH;
    }

    // Discover the total amount of minimum space and natural space needed by
    // this container and its children.
    void MyContainer::measure_vfunc(Gtk::Orientation orientation, int for_size,
      int& minimum, int& natural, int& minimum_baseline, int& natural_baseline) const
    {
      // Don't use baseline alignment.
      minimum_baseline = -1;
      natural_baseline = -1;

      minimum = 0;
      natural = 0;

      // Number of visible children.
      const int nvis_children = get_nvis_children();

      if (orientation == Gtk::Orientation::HORIZONTAL)
      {
        // Divide the height equally among the visible children.
        if (for_size > 0 && nvis_children > 0)
          for_size /= nvis_children;

        // Request a width equal to the width of the widest visible child.
      }

      for (const Widget* child = get_first_child(); child; child = child->get_next_sibling())
        if (child->get_visible())
        {
          int child_minimum, child_natural, ignore;
          child->measure(orientation, for_size, child_minimum, child_natural, ignore, ignore);
          minimum = std::max(minimum, child_minimum);
          natural = std::max(natural, child_natural);
        }

      if (orientation == Gtk::Orientation::VERTICAL)
      {
        // The allocated height will be divided equally among the visible children.
        // Request a height equal to the number of visible children times the height
        // of the highest child.
        minimum *= nvis_children;
        natural *= nvis_children;
      }
    }

    void MyContainer::size_allocate_vfunc(int width, int height, int baseline)
    {
      //Do something with the space that we have actually been given:
      //(We will not be given heights or widths less than we have requested, though
      //we might get more.)

      // Number of visible children.
      const int nvis_children = get_nvis_children();

      if (nvis_children <= 0)
      {
        // No visible child.
        return;
      }

      //Assign space to the children:
      Gtk::Allocation child_allocation;
      const int height_per_child = height / nvis_children;

      //Place the first visible child at the top-left:
      child_allocation.set_x(0);
      child_allocation.set_y(0);

      //Make it take up the full width available:
      child_allocation.set_width(width);
      child_allocation.set_height(height_per_child);

      //Divide the height equally among the visible children.
      for (Widget* child = get_first_child(); child; child = child->get_next_sibling())
        if (child->get_visible())
        {
          child->size_allocate(child_allocation, baseline);
          child_allocation.set_y(child_allocation.get_y() + height_per_child);
        }
    }

    void MyContainer::append(Gtk::Widget& child)
    {
       child.insert_at_end(*this);
    }

    void MyContainer::prepend(Gtk::Widget& child)
    {
       child.insert_at_start(*this);
    }

    void MyContainer::remove(Gtk::Widget& child)
    {
      child.unparent();
    }

### Vlastní widgety

Při odvození z `Gtk::Widget` můžete provádět veškeré kreslení pro svůj widget přímo, místo abyste jen uspořádali synovské widgety. Například `Gtk::Label` kreslí text popisku, ale nedělá to to pomocí jiných widgetů.

When deriving from `Gtk::Widget`, you should override the following virtual methods. The methods marked (optional) need not be overridden in all custom widgets. The base class's methods may be appropriate.

- `get_request_mode_vfunc()`: (optional) Return what `Gtk::SizeRequestMode` is preferred by the widget.

- `measure_vfunc()`: Calculate the minimum and natural width or height of the widget.

- `size_allocate_vfunc()`: (optional) Position the widget, given the height and width that it has actually been given.

- `on_realize()`: (optional)

- `on_unrealize()`: (optional)

- `on_map()`: (optional)

- `on_unmap()`: (optional)

- `snapshot_vfunc()`: Create a render node, e.g. a `Cairo::Context` node, and draw on it.

The first 3 methods in the previous table are also overridden in custom containers. They are briefly described in the Custom Containers section.

#### Class Init and Instance Init Functions

Some GTK functions, if called at all, must be called from the class init function. Some other GTK functions, if called, must be called from the instance init function. If your custom widget must call any of those functions, you can derive a class from `Glib::ExtraClassInit` and derive your custom class from that class. The custom CSS name example shows how that's done.

#### Příklad

This example implements a widget which draws Penrose triangles.

##### Vlastní widget

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>
    #include "mywidget.h"

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      virtual ~ExampleWindow();

    protected:
      //Signal handlers:
      void on_button_quit();

      //Child widgets:
      Gtk::Grid m_Grid;
      MyWidget m_MyWidgetS1;
      MyWidget m_MyWidgetS2;
      Gtk::Box m_ButtonBox;
      Gtk::Button m_Button_Quit;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `mywidget.h` (For use with gtkmm 4)

    #ifndef GTKMM_CUSTOM_WIDGET_MYWIDGET_H
    #define GTKMM_CUSTOM_WIDGET_MYWIDGET_H

    #include <gtkmm/widget.h>
    #include <gtkmm/border.h>
    #include <gdkmm/rgba.h>

    class MyWidget : public Gtk::Widget
    {
    public:
      MyWidget();
      ~MyWidget() override;

    protected:
      // Overrides:
      Gtk::SizeRequestMode get_request_mode_vfunc() const override;
      void measure_vfunc(Gtk::Orientation orientation, int for_size, int& minimum, int& natural,
        int& minimum_baseline, int& natural_baseline) const override;
      void on_map() override;
      void on_unmap() override;
      void on_realize() override;
      void on_unrealize() override;
      void snapshot_vfunc(const Glib::RefPtr<Gtk::Snapshot>& snapshot) override;

      Gtk::Border m_padding;
      Gdk::RGBA m_foreground{0.0, 0.0, 1.0};
      Gdk::RGBA m_background{1.0, 0.0, 0.0};
    };

    #endif //GTKMM_CUSTOM_WIDGET_MYWIDGET_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"

    ExampleWindow::ExampleWindow()
    : m_Button_Quit("Quit")
    {
      set_title("Custom Widget example");
      set_default_size(600, 400);

      m_Grid.set_margin(6);
      m_Grid.set_row_spacing(10);
      m_Grid.set_column_spacing(10);

      set_child(m_Grid);

      m_Grid.attach(m_MyWidgetS1, 0, 0);
      m_Grid.attach(m_MyWidgetS2, 1, 1);

      m_Grid.attach(m_ButtonBox, 0, 2, 2, 1);

      m_ButtonBox.append(m_Button_Quit);
      m_ButtonBox.set_margin(6);
      m_Button_Quit.set_hexpand(true);
      m_Button_Quit.set_halign(Gtk::Align::END);
      m_Button_Quit.signal_clicked().connect( sigc::mem_fun(*this, &ExampleWindow::on_button_quit) );
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_quit()
    {
      set_visible(false);
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char *argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

File: `mywidget.cc` (For use with gtkmm 4)

    #include "mywidget.h"
    #include <gdkmm/general.h>  // for Gdk::Cairo:: functions
    #include <gtkmm/snapshot.h>

    MyWidget::MyWidget()
    {
      // Expand, if there is extra space.
      set_expand(true);

      m_padding.set_left(5);
      m_padding.set_right(15);
      m_padding.set_top(10);
      m_padding.set_bottom(20);
    }

    MyWidget::~MyWidget()
    {
    }

    Gtk::SizeRequestMode MyWidget::get_request_mode_vfunc() const
    {
      //Accept the default value supplied by the base class.
      return Gtk::Widget::get_request_mode_vfunc();
    }

    //Discover the total amount of minimum space and natural space needed by
    //this widget.
    //Let's make this simple example widget always need minimum 60 by 50 and
    //natural 100 by 70.
    void MyWidget::measure_vfunc(Gtk::Orientation orientation, int /* for_size */,
      int& minimum, int& natural, int& minimum_baseline, int& natural_baseline) const
    {
      if (orientation == Gtk::Orientation::HORIZONTAL)
      {
        minimum = 60;
        natural = 100;
      }
      else
      {
        minimum = 50;
        natural = 70;
      }

      // Don't use baseline alignment.
      minimum_baseline = -1;
      natural_baseline = -1;
    }

    void MyWidget::on_map()
    {
      //Call base class:
      Gtk::Widget::on_map();
    }

    void MyWidget::on_unmap()
    {
      //Call base class:
      Gtk::Widget::on_unmap();
    }

    void MyWidget::on_realize()
    {
      //Call base class:
      Gtk::Widget::on_realize();
    }

    void MyWidget::on_unrealize()
    {
      //Call base class:
      Gtk::Widget::on_unrealize();
    }

    void MyWidget::snapshot_vfunc(const Glib::RefPtr<Gtk::Snapshot>& snapshot)
    {
      const auto allocation = get_allocation();
      const Gdk::Rectangle rect(0, 0, allocation.get_width(), allocation.get_height());

      // Create a cairo context to draw on.
      auto cr = snapshot->append_cairo(rect);

      // paint the background
      Gdk::Cairo::set_source_rgba(cr, m_background);
      Gdk::Cairo::add_rectangle_to_path(cr, rect);
      cr->fill();

      // draw the foreground
      const double scale_x = 0.001 * (allocation.get_width() - m_padding.get_left() - m_padding.get_right());
      const double scale_y = 0.001 * (allocation.get_height() - m_padding.get_top() - m_padding.get_bottom());
      Gdk::Cairo::set_source_rgba(cr, m_foreground);
      cr->translate(m_padding.get_left(), m_padding.get_top());
      cr->rectangle(0.0, 0.0, 1000.0*scale_x, 1000.0*scale_y);
      cr->move_to(155.*scale_x, 165.*scale_y);
      cr->line_to(155.*scale_x, 838.*scale_y);
      cr->line_to(265.*scale_x, 900.*scale_y);
      cr->line_to(849.*scale_x, 564.*scale_y);
      cr->line_to(849.*scale_x, 438.*scale_y);
      cr->line_to(265.*scale_x, 100.*scale_y);
      cr->line_to(155.*scale_x, 165.*scale_y);
      cr->move_to(265.*scale_x, 100.*scale_y);
      cr->line_to(265.*scale_x, 652.*scale_y);
      cr->line_to(526.*scale_x, 502.*scale_y);
      cr->move_to(369.*scale_x, 411.*scale_y);
      cr->line_to(633.*scale_x, 564.*scale_y);
      cr->move_to(369.*scale_x, 286.*scale_y);
      cr->line_to(369.*scale_x, 592.*scale_y);
      cr->move_to(369.*scale_x, 286.*scale_y);
      cr->line_to(849.*scale_x, 564.*scale_y);
      cr->move_to(633.*scale_x, 564.*scale_y);
      cr->line_to(155.*scale_x, 838.*scale_y);
      cr->stroke();
    }

### Custom CSS Names

Many aspects of the look of widgets are controlled by CSS (Cascading Style Sheet) files. With CSS files you can choose color, font, line thickness, etc. If you give some widgets their own names or their own CSS classes, you can define CSS rules that apply only to those widgets, for instance certain buttons, without affecting other similar widgets.

#### CSS Node Name, Widget Name, CSS Class Name

There are three ways of referring from a widget to data in a CSS file:

- `gtk_widget_class_set_css_name()` can only be called from the class init function. It sets the CSS node name of all instances of a class (a GType). See the Class Init and Instance Init Functions section.

- `Gtk::Widget::set_name()` can be called from a C++ constructor. It sets the name of a widget instance.

- `Gtk::Widget::add_class_name()` can be called from a C++ constructor. It adds the name of a CSS class, used by a widget instance.

The following example shows a button with its own CSS node name, a label with a widget name and a label that uses its own CSS class.

#### Custom Style Information

To add a style sheet to an application, use one of the `Gtk::CssProvider::load_from_*()` methods. Then add it with `Gtk::StyleProvider::add_provider_for_display()` (available since gtkmm 4.10) or `Gtk::StyleContext::add_provider_for_display()`. `Gtk::StyleContext` also contains methods to read some style information, but this class is deprecated since gtkmm 4.10.

CSS files are described in the documentation of GTK.

#### Příklad

This example implements a button and two labels with custom style information.

##### Custom CSS Name

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>
    #include "mybutton.h"

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();
      ~ExampleWindow() override;

    protected:
      // Signal handlers:
      void on_button_quit();
      static void on_parsing_error(const Glib::RefPtr<const Gtk::CssSection>& section,
        const Glib::Error& error);

      // Child widgets:
      Gtk::Box m_VBox;
      MyButton m_Button_Child;
      Gtk::Label m_Label_Child1;
      Gtk::Label m_Label_Child2;
      Gtk::Box m_ButtonBox;
      Gtk::Button m_Button_Quit;

      Glib::RefPtr<Gtk::CssProvider> m_refCssProvider;
    };

    #endif //GTKMM_EXAMPLEWINDOW_H

File: `mybutton.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLE_MYBUTTON_H
    #define GTKMM_EXAMPLE_MYBUTTON_H

    #include <gtkmm/button.h>
    #include "myextrainit.h"

    class MyButton : public MyExtraInit, public Gtk::Button
    {
    public:
      MyButton(const Glib::ustring& label, bool mnemonic=false);
      ~MyButton() override;
    };

    #endif //GTKMM_EXAMPLE_MYBUTTON_H

File: `myextrainit.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLE_MYEXTRAINIT_H
    #define GTKMM_EXAMPLE_MYEXTRAINIT_H

    #include <glibmm/extraclassinit.h>
    #include <glibmm/ustring.h>

    // Calls gtk_widget_class_set_css_name() in the class init function.
    class MyExtraInit : public Glib::ExtraClassInit
    {
    public:
      MyExtraInit(const Glib::ustring& css_name);

    private:
      Glib::ustring m_css_name;
    };

    #endif //GTKMM_EXAMPLE_MYEXTRAINIT_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <iostream>
    #include <gtkmm/version.h>

    #define HAS_STYLE_PROVIDER_ADD_PROVIDER_FOR_DISPLAY GTKMM_CHECK_VERSION(4,9,1)

    ExampleWindow::ExampleWindow()
    : m_VBox(Gtk::Orientation::VERTICAL),
      m_Button_Child("Button with custom CSS node name"),
      m_Label_Child1("Label with custom name"),
      m_Label_Child2("Label with custom CSS class"),
      m_Button_Quit("Quit")
    {
      set_title("Custom CSS name example");
      set_default_size(400, 200);

      m_VBox.set_margin(10);
      m_VBox.set_spacing(5);
      set_child(m_VBox);

      // There are 3 ways to set custom CSS data for a widget:
      // 1. The CSS name can be set for a GType with gtk_widget_class_set_css_name().
      // 2. The CSS name can be set for a widget instance with gtk_widget_set_name()
      //    (Gtk::Widget::set_name()).
      // 3. A CSS class can be set for a widget instance with
      //    gtk_widget_add_css_class() (Gtk::Widget::add_css_class()).
      //
      // gtk_widget_class_set_css_name(), if used, must be called in the class init
      // function. It has not been wrapped in a C++ function.
      // Gtk::Widget::set_name() and Gtk::Widget::add_css_class() can be called in
      // a C++ constructor.

      // CSS widget name, which must be used in the CSS file, preceded by "#".
      m_Label_Child1.set_name("my-label1");

      // CSS class name, which must be used in the CSS file, preceded by ".".
      m_Label_Child2.add_css_class("my-label2");

      // Add the child widgets to m_VBox:
      m_VBox.append(*Gtk::make_managed<Gtk::Label>("Ordinary label"));
      m_VBox.append(m_Button_Child);
      m_VBox.append(m_Label_Child1);
      m_VBox.append(m_Label_Child2);
      m_VBox.set_expand();
      m_VBox.append(m_ButtonBox);

      m_ButtonBox.append(m_Button_Quit);
      m_ButtonBox.set_margin(6);
      m_Button_Quit.set_hexpand(true);
      m_Button_Quit.set_halign(Gtk::Align::END);
      m_Button_Quit.signal_clicked().connect( sigc::mem_fun(*this,
                  &ExampleWindow::on_button_quit) );

      // Load extra CSS file.
      m_refCssProvider = Gtk::CssProvider::create();
    #if HAS_STYLE_PROVIDER_ADD_PROVIDER_FOR_DISPLAY
      Gtk::StyleProvider::add_provider_for_display(get_display(), m_refCssProvider,
        GTK_STYLE_PROVIDER_PRIORITY_APPLICATION);
    #else
      Gtk::StyleContext::add_provider_for_display(get_display(), m_refCssProvider,
        GTK_STYLE_PROVIDER_PRIORITY_APPLICATION);
    #endif

      m_refCssProvider->signal_parsing_error().connect(
        [](const auto& section, const auto& error)
        { on_parsing_error(section, error); }
      );
      m_refCssProvider->load_from_path("custom_gtkmm.css");
    }

    ExampleWindow::~ExampleWindow()
    {
    }

    void ExampleWindow::on_button_quit()
    {
      set_visible(false);
    }

    void ExampleWindow::on_parsing_error(const Glib::RefPtr<const Gtk::CssSection>& section,
      const Glib::Error& error)
    {
      std::cerr << "on_parsing_error(): " << error.what() << std::endl;
      if (section)
      {
        const auto file = section->get_file();
        if (file)
        {
          std::cerr << "  URI = " << file->get_uri() << std::endl;
        }

        auto start_location = section->get_start_location();
        auto end_location = section->get_end_location();
        std::cerr << "  start_line = " << start_location.get_lines()+1
                  << ", end_line = " << end_location.get_lines()+1 << std::endl;
        std::cerr << "  start_position = " << start_location.get_line_chars()
                  << ", end_position = " << end_location.get_line_chars() << std::endl;
      }
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char* argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      // Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

File: `mybutton.cc` (For use with gtkmm 4)

    #include "mybutton.h"
    #include <gtk/gtk.h> // For GTK_IS_BUTTON()
    #include <iostream>

    MyButton::MyButton(const Glib::ustring& label, bool mnemonic)
      :
      // The GType name will actually be gtkmm__CustomObject_MyButton
      Glib::ObjectBase("MyButton"),
      MyExtraInit("my-button"), // CSS node name, which must be used in the CSS file.
      Gtk::Button(label, mnemonic)
    {
      // This shows the GType name:
      std::cout << "GType name: " << G_OBJECT_TYPE_NAME(gobj()) << std::endl;

      // This shows that the GType still derives from GtkButton:
      std::cout << "Gtype is a GtkButton?: " << GTK_IS_BUTTON(gobj()) << std::endl;

      // The CSS name can be set either
      // - for a GType (in this case for your custom class) with gtk_widget_class_set_css_name(), or
      // - for a widget instance with gtk_widget_set_name() (Gtk::Widget::set_name()).
      //
      // gtk_widget_class_set_css_name(), if used, must be called in the class init function.
      // It has not been wrapped in a C++ function.
      // Gtk::Widget::set_name() can be called in a C++ constructor.
      //
      // Another alternative: The custom button inherits the CSS name "button" from
      // GtkButton. That name can be used in the CSS file.
    }

    MyButton::~MyButton()
    {
    }

File: `myextrainit.cc` (For use with gtkmm 4)

    #include "myextrainit.h"
    #include <gtkmm/widget.h>
    #include <gtk/gtk.h>

    namespace
    {
    using BaseObjectType = GtkWidget;
    using BaseClassType = GtkWidgetClass;

    // These callback functions are called from GLib (a C library).
    // They shall have C linkage. (Many compilers accept callback functions
    // with C++ linkage, but such a program has undefined behavior.)
    //
    // If you want the functions with C linkage to have internal linkage,
    // they must be declared 'static', even though they are defined in an anonymous
    // namespace. The compiler respects namespace declarations of functions
    // with C linkage, but the linker does not.
    extern "C"
    {
    // Extra class init function.
    static void class_init_function(void* g_class, void* class_data)
    {
      g_return_if_fail(GTK_IS_WIDGET_CLASS(g_class));

      const auto klass = static_cast<BaseClassType*>(g_class);
      const auto css_name = static_cast<Glib::ustring*>(class_data);

      gtk_widget_class_set_css_name(klass, css_name->c_str());
    }

    // Extra instance init function.
    static void instance_init_function(GTypeInstance* instance, void* /* g_class */)
    {
      g_return_if_fail(GTK_IS_WIDGET(instance));

      // Nothing to do here.
      // This extra instance init function just shows how such a function can
      // be added to a custom widget, if necessary.
    }
    } // extern "C"
    } // anonymous namespace

    MyExtraInit::MyExtraInit(const Glib::ustring& css_name)
    :
    Glib::ExtraClassInit(class_init_function, &m_css_name, instance_init_function),
    m_css_name(css_name)
    {
    }

File: `custom_gtkmm.css` (For use with gtkmm 4)

    /* Example of a CSS style sheet. */

    my-button {
      background-color: red;
      color:            blue;
      padding:          10px 15px 20px 5px; /* top right bottom left */
      border:           solid black 2px;
      border-radius:    8px;
    }
    my-button:active {
      background-color: rgb(0,255,0);
    }
    #my-label1 {
      background-color: rgb(180,180,180);
      color:            rgb(0,255,255);
      padding:          10px 15px 10px 25px; /* top right bottom left */
    }
    #my-label1:hover {
      background-color: rgb(220,220,220);
    }
    .my-label2 {
      background-color: rgb(180,180,100);
      color:            black;
      padding:          5px 15px 5px 25px; /* top right bottom left */
    }
    .my-label2:hover {
      background-color: rgb(220,220,140);
    }

## Vícevláknové programy

### Omezení

Care is required when writing programs based on gtkmm using multiple threads of execution, arising from the fact that libsigc++, and in particular `sigc::trackable`, are not thread-safe. That's because none of the complex interactions that occur behind the scenes when using libsigc++ are protected by a mutex or other means of synchronization. These interactions arise from the fact that, amongst other things, a class inheriting from `sigc::trackable` will, via that inheritance, have a `std::list` object keeping track of slots created by calls to `sigc::mem_fun()` representing any of its non-static methods (more particularly it keeps a list of callbacks which will null the connected slots on its destruction). Each `sigc::slot` object also keeps, via `sigc::slot_rep`, its own `sigc::trackable` object to track any `sigc::connection` objects which it needs to inform about its demise, and also has a function to deregister itself from any `sigc::trackable` on disconnection or destruction. `sigc::signal` objects also keep lists of slots, which will be updated by a call to their `connect()` method or calls to any `sigc::connection` object relating to such a connection.

#### Pravidla

Celé to vyžaduje řadu pravidel, kterých je třeba se držet při psaní vícevláknových aplikací pomocí gtkmm. Jsou uvedena níže, ale jedna věc stojí zvlášť za pozornost, a to, že je potřeba věnovat speciální péči odvozování tříd z `sigc::trackable`, protože efekty jsou nepředvidatelné (viz hlavně body 4 a 5 níže).

1. Použijte `Glib::Dispatcher` k vyvolání funkcí gtkmm z pracovních vláken (podrobněji bude rozebráno dále).

2. Objekt `sigc::signal` by měl být považován za vlastněný vláknem, které jej vytvořilo. Pouze toto vlákno by mělo napojit objekt `sigc::slot` na objekt signálu a pouze toto vlákno by mělo vyslat signál pomocí `emit()`, nebo na signál zavolat `operator()()`, nebo napojený objekt `sigc::slot` anulovat. Z toho vyplývá (mimo jiné), že objekt signálu poskytovaný widgetem gtkmm by měl operovat jen v hlavním vlákně starajícím se o grafické uživatelské rozhraní a objekt odvozený z `sigc::trackable` mající nestatické metody, na které se odkazuje slot napojený na objekt signálu, by měl být zlikvidován v tomto vlákně.

3. Objekt `sigc::connection` by měl být považován za vlastněný vláknem, ve kterém byl metoda vracející objekt `sigc::connection` zavolána. Jen toto vlákno by mělo volat metody `sigc::connection` na objektu.

4. A `sigc::slot` object created by a call to `sigc::mem_fun()` which references a method of a class deriving from `sigc::trackable` should never be copied to another thread, nor destroyed by a different thread than the one which created it.

5. Pokud je určitý objekt třídy odvozený z `sigc::trackable`, jen jedno vlákno by mělo vytvářet objekty `sigc::slot` představující některou z nestatických metod třídy volánm `sigc::mem_fun()`. První vlákno, které má vytvořit takovýto slot, by mělo být považováno za vlastníka příslušného objektu za účelem vytváření dalších slotů odkazujících na kteroukoliv z jeho nestatických metod používajících tuto funkci, nebo anulovat tyto sloty jejich odpojením nebo zničeném sledovacího objektu.

6. Ačkoliv glib je sama o sobě z hlediska vláken bezpečná, některé obalující funkce z glibmm, které používají libsigc++, bezpečné nebudou. Takže například jen vlákno, ve kterém běží hlavní smyčka by mělo volat `Glib::SignalIdle::connect()`, `Glib::SignalIO::connect()`, `Glib::SignalTimeout::connect()`, `Glib::SignalTimeout::connect_seconds` pro hlavní smyčku, nebo manipulovat s objektem `sigc::connection`, který vrací.

   The connect*_once() variants, `Glib::SignalIdle::connect_once()`, `Glib::SignalTimeout::connect_once()`, `Glib::SignalTimeout::connect_seconds_once()`, are thread-safe for any case where the slot is not created by a call to `sigc::mem_fun()` which represents a method of a class deriving from `sigc::trackable`.

### Používání Glib::Dispatcher

Sloty napojené na objekty `sigc::signal` běží ve vlákně, které volá na signál `emit()` nebo `operator()`. `Glib::Dispatcher` se takto nechová: místo toho jeho napojené sloty běží ve vlákně, ve kterém byl objekt `Glib::Dispatcher` vytvořen (které musí mít hlavní smyčku glib). Pokud je objekt `Glib::Dispatcher` vytvořen v hlavním vlákně grafického uživatelského rozhraní (který tedy bude mít přijímací vlákno), libovolné pracovním vlákno pro něj může vysílat a mít napojené sloty, které mohou bezpečně spouštět funkce gtkmm.

Některá bezpečnostní pravidla pro vlákna při použití `Glib::Dispatcher` stále platí. Jak bylo zmíněno, objekt `Glib::Dispatcher` musí být vytvořen ve vlákně příjemce (vlákno, ve kterém hlavní smyčka spustí jeho napojené sloty). Standardně je to hlavní vlákno programu, ačkoliv existuje konstruktor třídy `Glib::Dispatcher`, který umí převzít objekt `Glib::MainContext` libovolného vlákna, které má hlavní smyčku. Jen vlákno příjemce by mělo volat `connect()` na objekt `Glib::Dispatcher`, nebo manipulovat s souvisejícím objektem `sigc::connection`, pokud není zajištěna dodatečná synchronizace. Na druhou stranu, libovolné vlákno může bezpečně vyslat objekt `Glib::Dispatcher` bez zamykání, jakmile má vlákno příjemce napojené sloty, za předpokladu, že je vytvořen před spuštěním pracovního vlákna (jestliže je vytvořen po spuštění vlákna, je pro zajištění viditelnosti vyžadována dodatečná synchronizace).

Aside from the fact that connected slots always execute in the receiver thread, `Glib::Dispatcher` objects are similar to `sigc::signal<void()>` objects. They therefore cannot pass unbound arguments nor return a value. The best way to pass unbound arguments is with a thread-safe (asynchronous) queue. At the time of writing glibmm does not have one, although most people writing multi-threaded code will have one available to them (they are relatively easy to write although there are subtleties in combining thread safety with strong exception safety).

A `Glib::Dispatcher` object can be emitted on by the receiver thread as well as by a worker thread, although this should be done within reasonable bounds. On unix-like systems `Glib::Dispatcher` objects share a single common pipe, which could in theory at least fill up on a very heavily loaded system running a program with a very large number of `Dispatcher` objects in use. Were the pipe to fill up before the receiver thread's main loop has had an opportunity to read from it to empty it, and the receiver thread attempt to emit and so write to it when it is in that condition, the receiver thread would block on the write, so deadlocking. Where the receiver thread is to emit, a normal `sigc::signal<void()>` object could of course be used instead.

### Příklad

Jedná se o příklad programu se dvěma vlákny, jedním vláknem pro grafické uživatelské rozhraní, podobně jako ve všech programech gtkmm, a jedním pracovním vláknem. Pracovní vlákno se vytvoří, když zmáčknete tlačítko `Start work`. Smaže se, když je práce dokončena, když zmáčknete tlačítko `Stop work`, nebo když zmáčknete tlačítko `Quit`.

A `Glib::Dispatcher` is used for sending notifications from the worker thread to the GUI thread. The `ExampleWorker` class contains data which is accessed by both threads. This data is protected by a `std::mutex`. Only the GUI thread updates the GUI.

Compiling and linking a multi-threaded program can require special compiler and linker options. If you use the g++ compiler, add the `-pthread` option. Other compilers may require other options. If you build with meson, it handles the multi-threading complications for you, if you add `dependency('threads')`.

#### Vícevláknový program

Source Code

File: `examplewindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWINDOW_H
    #define GTKMM_EXAMPLEWINDOW_H

    #include <gtkmm.h>
    #include "exampleworker.h"

    class ExampleWindow : public Gtk::Window
    {
    public:
      ExampleWindow();

      // Called from the worker thread.
      void notify();

    private:
      // Signal handlers.
      void on_start_button_clicked();
      void on_stop_button_clicked();
      void on_quit_button_clicked();

      void update_start_stop_buttons();
      void update_widgets();

      // Dispatcher handler.
      void on_notification_from_worker_thread();

      // Member data.
      Gtk::Box m_VBox;
      Gtk::Box m_ButtonBox;
      Gtk::Button m_ButtonStart;
      Gtk::Button m_ButtonStop;
      Gtk::Button m_ButtonQuit;
      Gtk::ProgressBar m_ProgressBar;
      Gtk::ScrolledWindow m_ScrolledWindow;
      Gtk::TextView m_TextView;

      Glib::Dispatcher m_Dispatcher;
      ExampleWorker m_Worker;
      std::thread* m_WorkerThread;
    };

    #endif // GTKMM_EXAMPLEWINDOW_H

File: `exampleworker.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEWORKER_H
    #define GTKMM_EXAMPLEWORKER_H

    #include <gtkmm.h>
    #include <thread>
    #include <mutex>

    class ExampleWindow;

    class ExampleWorker
    {
    public:
      ExampleWorker();

      // Thread function.
      void do_work(ExampleWindow* caller);

      void get_data(double* fraction_done, Glib::ustring* message) const;
      void stop_work();
      bool has_stopped() const;

    private:
      // Synchronizes access to member data.
      mutable std::mutex m_Mutex;

      // Data used by both GUI thread and worker thread.
      bool m_shall_stop;
      bool m_has_stopped;
      double m_fraction_done;
      Glib::ustring m_message;
    };

    #endif // GTKMM_EXAMPLEWORKER_H

File: `examplewindow.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <iostream>

    ExampleWindow::ExampleWindow() :
      m_VBox(Gtk::Orientation::VERTICAL, 5),
      m_ButtonBox(Gtk::Orientation::HORIZONTAL),
      m_ButtonStart("Start work"),
      m_ButtonStop("Stop work"),
      m_ButtonQuit("_Quit", /* mnemonic= */ true),
      m_ProgressBar(),
      m_ScrolledWindow(),
      m_TextView(),
      m_Dispatcher(),
      m_Worker(),
      m_WorkerThread(nullptr)
    {
      set_title("Multi-threaded example");
      set_default_size(300, 300);

      m_VBox.set_margin(5);
      set_child(m_VBox);

      // Add the ProgressBar.
      m_VBox.append(m_ProgressBar);

      m_ProgressBar.set_text("Fraction done");
      m_ProgressBar.set_show_text();

      // Add the TextView, inside a ScrolledWindow.
      m_ScrolledWindow.set_child(m_TextView);

      // Only show the scrollbars when they are necessary.
      m_ScrolledWindow.set_policy(Gtk::PolicyType::AUTOMATIC, Gtk::PolicyType::AUTOMATIC);
      m_ScrolledWindow.set_expand();

      m_VBox.append(m_ScrolledWindow);

      m_TextView.set_editable(false);

      // Add the buttons to the ButtonBox.
      m_VBox.append(m_ButtonBox);

      m_ButtonBox.append(m_ButtonStart);
      m_ButtonBox.append(m_ButtonStop);
      m_ButtonBox.append(m_ButtonQuit);
      m_ButtonBox.set_margin(5);
      m_ButtonBox.set_spacing(5);
      m_ButtonStart.set_hexpand(true);
      m_ButtonStart.set_halign(Gtk::Align::END);

      // Connect the signal handlers to the buttons.
      m_ButtonStart.signal_clicked().connect(sigc::mem_fun(*this, &ExampleWindow::on_start_button_clicked));
      m_ButtonStop.signal_clicked().connect(sigc::mem_fun(*this, &ExampleWindow::on_stop_button_clicked));
      m_ButtonQuit.signal_clicked().connect(sigc::mem_fun(*this, &ExampleWindow::on_quit_button_clicked));

      // Connect the handler to the dispatcher.
      m_Dispatcher.connect(sigc::mem_fun(*this, &ExampleWindow::on_notification_from_worker_thread));

      // Create a text buffer mark for use in update_widgets().
      auto buffer = m_TextView.get_buffer();
      buffer->create_mark("last_line", buffer->end(), /* left_gravity= */ true);

      update_start_stop_buttons();
    }

    void ExampleWindow::on_start_button_clicked()
    {
      if (m_WorkerThread)
      {
        std::cout << "Can't start a worker thread while another one is running." << std::endl;
      }
      else
      {
        // Start a new worker thread.
        m_WorkerThread = new std::thread(
          [this]
          {
            m_Worker.do_work(this);
          });
      }
      update_start_stop_buttons();
    }

    void ExampleWindow::on_stop_button_clicked()
    {
      if (!m_WorkerThread)
      {
        std::cout << "Can't stop a worker thread. None is running." << std::endl;
      }
      else
      {
       // Order the worker thread to stop.
        m_Worker.stop_work();
        m_ButtonStop.set_sensitive(false);
      }
    }

    void ExampleWindow::update_start_stop_buttons()
    {
      const bool thread_is_running = m_WorkerThread != nullptr;

      m_ButtonStart.set_sensitive(!thread_is_running);
      m_ButtonStop.set_sensitive(thread_is_running);
    }

    void ExampleWindow::update_widgets()
    {
      double fraction_done;
      Glib::ustring message_from_worker_thread;
      m_Worker.get_data(&fraction_done, &message_from_worker_thread);

      m_ProgressBar.set_fraction(fraction_done);

      if (message_from_worker_thread != m_TextView.get_buffer()->get_text())
      {
        auto buffer = m_TextView.get_buffer();
        buffer->set_text(message_from_worker_thread);

        // Scroll the last inserted line into view. That's somewhat complicated.
        auto iter = buffer->end();
        iter.set_line_offset(0); // Beginning of last line
        auto mark = buffer->get_mark("last_line");
        buffer->move_mark(mark, iter);
        m_TextView.scroll_to(mark);
        // TextView::scroll_to(iter) is not perfect.
        // We do need a TextMark to always get the last line into view.
      }
    }

    void ExampleWindow::on_quit_button_clicked()
    {
      if (m_WorkerThread)
      {
        // Order the worker thread to stop and wait for it to stop.
        m_Worker.stop_work();
        if (m_WorkerThread->joinable())
          m_WorkerThread->join();
      }
      set_visible(false);
    }

    // notify() is called from ExampleWorker::do_work(). It is executed in the worker
    // thread. It triggers a call to on_notification_from_worker_thread(), which is
    // executed in the GUI thread.
    void ExampleWindow::notify()
    {
      m_Dispatcher.emit();
    }

    void ExampleWindow::on_notification_from_worker_thread()
    {
      if (m_WorkerThread && m_Worker.has_stopped())
      {
        // Work is done.
        if (m_WorkerThread->joinable())
          m_WorkerThread->join();
        delete m_WorkerThread;
        m_WorkerThread = nullptr;
        update_start_stop_buttons();
      }
      update_widgets();
    }

File: `exampleworker.cc` (For use with gtkmm 4)

    #include "exampleworker.h"
    #include "examplewindow.h"
    #include <sstream>
    #include <chrono>

    ExampleWorker::ExampleWorker() :
      m_Mutex(),
      m_shall_stop(false),
      m_has_stopped(false),
      m_fraction_done(0.0),
      m_message()
    {
    }

    // Accesses to these data are synchronized by a mutex.
    // Some microseconds can be saved by getting all data at once, instead of having
    // separate get_fraction_done() and get_message() methods.
    void ExampleWorker::get_data(double* fraction_done, Glib::ustring* message) const
    {
      std::lock_guard<std::mutex> lock(m_Mutex);

      if (fraction_done)
        *fraction_done = m_fraction_done;

      if (message)
        *message = m_message;
    }

    void ExampleWorker::stop_work()
    {
      std::lock_guard<std::mutex> lock(m_Mutex);
      m_shall_stop = true;
    }

    bool ExampleWorker::has_stopped() const
    {
      std::lock_guard<std::mutex> lock(m_Mutex);
      return m_has_stopped;
    }

    void ExampleWorker::do_work(ExampleWindow* caller)
    {
      {
        std::lock_guard<std::mutex> lock(m_Mutex);
        m_has_stopped = false;
        m_fraction_done = 0.0;
        m_message = "";
      } // The mutex is unlocked here by lock's destructor.

      // Simulate a long calculation.
      for (int i = 0; ; ++i) // do until break
      {
        std::this_thread::sleep_for(std::chrono::milliseconds(250));

        {
          std::lock_guard<std::mutex> lock(m_Mutex);

          m_fraction_done += 0.01;

          if (i % 4 == 3)
          {
            std::ostringstream ostr;
            ostr << (m_fraction_done * 100.0) << "% done\n";
            m_message += ostr.str();
          }

          if (m_fraction_done >= 1.0)
          {
            m_message += "Finished";
            break;
          }
          if (m_shall_stop)
          {
            m_message += "Stopped";
            break;
          }
        }

        caller->notify();
      }

      {
        std::lock_guard<std::mutex> lock(m_Mutex);
        m_shall_stop = false;
        m_has_stopped = true;
      }

      caller->notify();
    }

File: `main.cc` (For use with gtkmm 4)

    #include "examplewindow.h"
    #include <gtkmm/application.h>

    int main(int argc, char* argv[])
    {
      auto app = Gtk::Application::create("org.gtkmm.example");

      //Shows the window and returns when it is closed.
      return app->make_window_and_run<ExampleWindow>(argc, argv);
    }

## Doporučené techniky

V této kapitole je taková všehochuť mouder, obecných pokynů a rad k vytváření aplikací s gtkmm.

Use Meson! It is your friend :) It examines C and C++ files, determines how they depend on each other, and generates `build.ninja` or an equivalent file so the files can be compiled in the correct order. Meson permits automatic configuration of software installation, handling a large number of system quirks to increase portability.

Odvozujte podtřídy widgetů kvůli lepší přehlednosti kódu. Pravděpodobně odvodíte minimálně podtřídu z `Window`. Pak můžete ze synovských widgetů a obsluh signálů udělat členy této třídy.

Create your own signals instead of passing pointers around. Objects can communicate with each other via signals and signal handlers. This is much simpler than objects holding pointers to each other and calling each other's methods. gtkmm's classes use special versions of `sigc::signal`, but you should use normal `sigc::signal`s, as described in the libsigc++ documentation.

### Životnost aplikace

Most applications will have only one `Window`, or only one main window. These applications can use `Gtk::Application::make_window_and_run(int argc, char** argv, T_Args&&... args)`. It creates and shows a window. When the window is hidden, `make_window_and_run()` deletes the window and returns to the caller. This might happen when the user closes the window, or when your code decides to hide the window with `set_visible(false)`. You can prevent the user from closing the window (for instance, if there are unsaved changes) by overriding `Gtk::Window::on_close_request()`.

Většina našich příkladů používá tuto techniku.

### Používání widgetů gtkmm

Všechny naše příklady se snaží mít stejnou strukturu. V použití třídy `Widget` se snaží držet těchto kroků:

1. Declare a variable of the type of `Widget` you wish to use, generally as member variable of a derived container class. You could also declare a pointer to the widget type, and then create it with `new` or `Gtk::make_managed()` in your code.

2. Set the attributes of the widget. If the widget has no default constructor, then you will need to initialize the widget in the initializer list of your container class's constructor.

3. Napojit případné signály, které si přejete používat s příslušnou obsluhou.

4. Pack the widget into a container using the appropriate call, e.g. `Gtk::Box::append()`.

If you don't want all widgets to be shown, call `Gtk::Widget::set_visible(false)` on the widgets that you don't want to show. If a container widget is hidden, all of its child widgets are also hidden, even if `set_visible(false)` is not called on the child widgets.

## Building applications

This chapter is similar to Building applications and following sections in the Getting Started chapter in the GTK documentation. The same application is built, but gtkmm is used instead of GTK.

An application consists of a number of files:

The binary file

  This gets installed in `/usr/bin`.

A desktop file

  The desktop file provides important information about the application to the desktop shell, such as its name, icon, D-Bus name, commandline to launch it, etc. It is installed in `/usr/share/applications`.

An icon

  The icon gets installed in `/usr/share/icons/hicolor/48x48/apps`, where it will be found regardless of the current theme.

A settings schema

  If the application uses `Gio::Settings`, it will install its schema in `/usr/share/glib-2.0/schemas`, so that tools like dconf-editor can find it.

Other resources

  Other files, such as `Gtk::Builder` ui files, are best loaded from resources stored in the application binary itself. This eliminates the need for most of the files that would traditionally be installed in an application-specific location in `/usr/share`.

gtkmm includes application support that is built on top of `Gio::Application`. In this chapter we'll build a simple application by starting from scratch, adding more and more pieces over time. Along the way, we'll learn about `Gtk::Application`, `Gtk::Builder`, resources, menus, settings, `Gtk::HeaderBar`, `Gtk::Stack`, `Gtk::SearchBar`, `Gtk::ListBox`, and more.

The full, buildable sources for these examples can be found in the `examples/book/buildapp` directory of the gtkmm-documentation source distribution, or online in the gtkmm-documentation git repository. You can build each example separately by using `meson` and `ninja` with the `meson.build` file or by using `make` with the `Makefile.example` file. For more information, see the `README` included in the `buildapp` directory.

### A trivial application

When using `Gtk::Application`, the `main()` function can be very simple. We just call `Gtk::Application::run()` on an instance of our application class.

All the application logic is in the application class, which is a subclass of `Gtk::Application`. Our example does not yet have any interesting functionality. All it does is open a window when it is activated without arguments, and open the files it is given, if it is started with arguments. (Or rather, our application class tries to open the files, but our subclassed application window does not yet do what it's told to do.)

To handle these two cases, we override `signal_activate()`'s default handler, which gets called when the application is launched without commandline arguments, and `signal_open()`'s default handler, which gets called when the application is launched with commandline arguments.

Gio::Application Reference

Gtk::Application Reference

Another important class that is part of the application support in gtkmm is `Gtk::ApplicationWindow`. It is typically subclassed as well. Our subclass does not do anything yet, so we will just get an empty window.

As part of the initial setup of our application, we also create an icon and a desktop file. Note that @bindir@ in the desktop file needs to be replaced with the actual path to the binary before this desktop file can be used.

Here is what we've achieved so far:

#### A trivial application

This does not look very impressive yet, but our application is already presenting itself on the session bus, it has single-instance semantics, and it accepts files as commandline arguments.

Source Code

File: `exampleapplication.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEAPPLICATION_H
    #define GTKMM_EXAMPLEAPPLICATION_H

    #include <gtkmm.h>

    class ExampleAppWindow;

    class ExampleApplication: public Gtk::Application
    {
    protected:
      ExampleApplication();

    public:
      static Glib::RefPtr<ExampleApplication> create();

    protected:
      // Override default signal handlers:
      void on_activate() override;
      void on_open(const Gio::Application::type_vec_files& files,
        const Glib::ustring& hint) override;

    private:
      ExampleAppWindow* create_appwindow();
    };

    #endif /* GTKMM_EXAMPLEAPPLICATION_H */

File: `exampleappwindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEAPPWINDOW_H_
    #define GTKMM_EXAMPLEAPPWINDOW_H_

    #include <gtkmm.h>

    class ExampleAppWindow : public Gtk::ApplicationWindow
    {
    public:
      ExampleAppWindow();

      void open_file_view(const Glib::RefPtr<Gio::File>& file);
    };

    #endif /* GTKMM_EXAMPLEAPPWINDOW_H */

File: `exampleapplication.cc` (For use with gtkmm 4)

    #include "exampleapplication.h"
    #include "exampleappwindow.h"

    ExampleApplication::ExampleApplication()
    : Gtk::Application("org.gtkmm.examples.application", Gio::Application::Flags::HANDLES_OPEN)
    {
    }

    Glib::RefPtr<ExampleApplication> ExampleApplication::create()
    {
      return Glib::make_refptr_for_instance<ExampleApplication>(new ExampleApplication());
    }

    ExampleAppWindow* ExampleApplication::create_appwindow()
    {
      auto appwindow = new ExampleAppWindow();

      // Make sure that the application runs for as long this window is still open.
      add_window(*appwindow);

      // A window can be added to an application with Gtk::Application::add_window()
      // or Gtk::Window::set_application(). When all added windows have been hidden
      // or removed, the application stops running (Gtk::Application::run() returns()),
      // unless Gio::Application::hold() has been called.

      // Delete the window when it is hidden.
      appwindow->signal_hide().connect([appwindow](){ delete appwindow; });

      return appwindow;
    }

    void ExampleApplication::on_activate()
    {
      // The application has been started, so let's show a window.
      auto appwindow = create_appwindow();
      appwindow->present();
    }

    void ExampleApplication::on_open(const Gio::Application::type_vec_files& files,
      const Glib::ustring& /* hint */)
    {
      // The application has been asked to open some files,
      // so let's open a new view for each one.
      ExampleAppWindow* appwindow = nullptr;
      auto windows = get_windows();
      if (windows.size() > 0)
        appwindow = dynamic_cast<ExampleAppWindow*>(windows[0]);

      if (!appwindow)
        appwindow = create_appwindow();

      for (const auto& file : files)
        appwindow->open_file_view(file);

      appwindow->present();
    }

File: `exampleappwindow.cc` (For use with gtkmm 4)

    #include "exampleappwindow.h"

    ExampleAppWindow::ExampleAppWindow()
    : Gtk::ApplicationWindow()
    {
    }

    void ExampleAppWindow::open_file_view(const Glib::RefPtr<Gio::File>& /* file */)
    {
    }

File: `main.cc` (For use with gtkmm 4)

    #include "exampleapplication.h"

    int main(int argc, char* argv[])
    {
      auto application = ExampleApplication::create();

      // Start the application, showing the initial window,
      // and opening extra views for any files that it is asked to open,
      // for instance as a command-line parameter.
      // run() will return when the last window has been closed.
      return application->run(argc, argv);
    }

File: `exampleapp.desktop.in` (For use with gtkmm 4)

    [Desktop Entry]
    Type=Application
    Name=Gtkmm example
    GenericName=Example
    Comment=From the "Programming with gtkmm 4" tutorial
    Icon=exampleapp
    StartupNotify=true
    Exec=@bindir@/exampleapp %U
    Categories=GNOME;GTK;Utility

### Populating the window

In this step, we use a `Gtk::Builder` instance to associate a `Gtk::Builder` ui file with our application window class.

Our simple ui file gives the window a title, and puts a `Gtk::Stack` widget as the main content.

To make use of this file in our application, we revisit our `Gtk::ApplicationWindow` subclass, and call `Gtk::Builder::create_from_resource()` and `Gtk::Builder::get_widget_derived()` from the `ExampleAppWindow::create()` method to get an instance of our subclassed `Gtk::ApplicationWindow`. See the Using derived widgets section for more information about `get_widget_derived()`.

You may have noticed that we use the `_from_resource()` variant of the method that reads the ui file. Now we need to use GLib's resource functionality to include the ui file in the binary. This is commonly done by listing all resources in a .gresource.xml file. This file has to be converted into a C source file that will be compiled and linked into the application together with the other source files. To do so, we use the glib-compile-resources utility:

    $ glib-compile-resources --target=resources.c --generate-source exampleapp.gresource.xml

The Gio::Resource and glib-compile-resources section contains more information about resource files. If you build with Meson, use the `compile_resources()` function in Meson's GNOME module.

Our application now looks like this:

#### Populating the window

Source Code

File: `exampleapplication.h` (For use with gtkmm 4)

    #include "../step1/exampleapplication.h"
    // Equal to the corresponding file in step1

File: `exampleappwindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEAPPWINDOW_H_
    #define GTKMM_EXAMPLEAPPWINDOW_H_

    #include <gtkmm.h>

    class ExampleAppWindow : public Gtk::ApplicationWindow
    {
    public:
      ExampleAppWindow(BaseObjectType* cobject,
        const Glib::RefPtr<Gtk::Builder>& refBuilder);

      static ExampleAppWindow* create();

      void open_file_view(const Glib::RefPtr<Gio::File>& file);

    protected:
      Glib::RefPtr<Gtk::Builder> m_refBuilder;
    };

    #endif /* GTKMM_EXAMPLEAPPWINDOW_H */

File: `exampleapplication.cc` (For use with gtkmm 4)

    #include "exampleapplication.h"
    #include "exampleappwindow.h"
    #include <iostream>
    #include <exception>

    ExampleApplication::ExampleApplication()
    : Gtk::Application("org.gtkmm.examples.application", Gio::Application::Flags::HANDLES_OPEN)
    {
    }

    Glib::RefPtr<ExampleApplication> ExampleApplication::create()
    {
      return Glib::make_refptr_for_instance<ExampleApplication>(new ExampleApplication());
    }

    ExampleAppWindow* ExampleApplication::create_appwindow()
    {
      auto appwindow = ExampleAppWindow::create();

      // Make sure that the application runs for as long this window is still open.
      add_window(*appwindow);

      // A window can be added to an application with Gtk::Application::add_window()
      // or Gtk::Window::set_application(). When all added windows have been hidden
      // or removed, the application stops running (Gtk::Application::run() returns()),
      // unless Gio::Application::hold() has been called.

      // Delete the window when it is hidden.
      appwindow->signal_hide().connect([appwindow](){ delete appwindow; });

      return appwindow;
    }

    void ExampleApplication::on_activate()
    {
      try
      {
        // The application has been started, so let's show a window.
        auto appwindow = create_appwindow();
        appwindow->present();
      }
      // If create_appwindow() throws an exception (perhaps from Gtk::Builder),
      // no window has been created, no window has been added to the application,
      // and therefore the application will stop running.
      catch (const Glib::Error& ex)
      {
        std::cerr << "ExampleApplication::on_activate(): " << ex.what() << std::endl;
      }
      catch (const std::exception& ex)
      {
        std::cerr << "ExampleApplication::on_activate(): " << ex.what() << std::endl;
      }
    }

    void ExampleApplication::on_open(const Gio::Application::type_vec_files& files,
      const Glib::ustring& /* hint */)
    {
      // The application has been asked to open some files,
      // so let's open a new view for each one.
      ExampleAppWindow* appwindow = nullptr;
      auto windows = get_windows();
      if (windows.size() > 0)
        appwindow = dynamic_cast<ExampleAppWindow*>(windows[0]);

      try
      {
        if (!appwindow)
          appwindow = create_appwindow();

        for (const auto& file : files)
          appwindow->open_file_view(file);

        appwindow->present();
      }
      catch (const Glib::Error& ex)
      {
        std::cerr << "ExampleApplication::on_open(): " << ex.what() << std::endl;
      }
      catch (const std::exception& ex)
      {
        std::cerr << "ExampleApplication::on_open(): " << ex.what() << std::endl;
      }
    }

File: `exampleappwindow.cc` (For use with gtkmm 4)

    #include "exampleappwindow.h"
    #include <stdexcept>

    ExampleAppWindow::ExampleAppWindow(BaseObjectType* cobject,
      const Glib::RefPtr<Gtk::Builder>& refBuilder)
    : Gtk::ApplicationWindow(cobject),
      m_refBuilder(refBuilder)
    {
    }

    //static
    ExampleAppWindow* ExampleAppWindow::create()
    {
      // Load the Builder file and instantiate its widgets.
      auto refBuilder = Gtk::Builder::create_from_resource("/org/gtkmm/exampleapp/window.ui");

      auto window = Gtk::Builder::get_widget_derived<ExampleAppWindow>(refBuilder, "app_window");
      if (!window)
        throw std::runtime_error("No \"app_window\" object in window.ui");

      return window;
    }

    void ExampleAppWindow::open_file_view(const Glib::RefPtr<Gio::File>& /* file */)
    {
    }

File: `main.cc` (For use with gtkmm 4)

    #include "../step1/main.cc"
    // Equal to the corresponding file in step1

File: `exampleapp.gresource.xml` (For use with gtkmm 4)

    <?xml version="1.0" encoding="UTF-8"?>
    <gresources>
      <gresource prefix="/org/gtkmm/exampleapp">
        <file preprocess="xml-stripblanks">window.ui</file>
      </gresource>
    </gresources>

File: `window.ui` (For use with gtkmm 4)

    <?xml version="1.0" encoding="UTF-8"?>
    <interface>
      <object class="GtkApplicationWindow" id="app_window">
        <property name="title" translatable="yes">Example Application</property>
        <property name="default-width">600</property>
        <property name="default-height">400</property>
        <property name="hide-on-close">True</property>
        <child>
          <object class="GtkBox" id="content_box">
            <property name="orientation">vertical</property>
            <child>
              <object class="GtkStack" id="stack"/>
            </child>
          </object>
        </child>
      </object>
    </interface>

### Opening files

In this step, we make our application show the contents of all the files that it is given on the commandline.

To this end, we add a data member to our application window and keep a pointer to the `Gtk::Stack` there. We get the pointer with a call to `Gtk::Builder::get_widget()` in the application window's constructor.

Now we revisit the `ExampleAppWindow::open_file_view()` method that is called for each commandline argument, and construct a `Gtk::TextView` that we then add as a page to the stack.

Lastly, we add a `Gtk::StackSwitcher` to the titlebar area in the ui file, and we tell it to display information about our stack.

The stack switcher gets all its information it needs to display tabs from the stack that it belongs to. Here, we are passing the label to show for each file as the last argument to the `Gtk::Stack::add()` method.

Our application is beginning to take shape:

#### Opening files

Source Code

File: `exampleapplication.h` (For use with gtkmm 4)

    #include "../step1/exampleapplication.h"
    // Equal to the corresponding file in step1

File: `exampleappwindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEAPPWINDOW_H_
    #define GTKMM_EXAMPLEAPPWINDOW_H_

    #include <gtkmm.h>

    class ExampleAppWindow : public Gtk::ApplicationWindow
    {
    public:
      ExampleAppWindow(BaseObjectType* cobject,
        const Glib::RefPtr<Gtk::Builder>& refBuilder);

      static ExampleAppWindow* create();

      void open_file_view(const Glib::RefPtr<Gio::File>& file);

    protected:
      Glib::RefPtr<Gtk::Builder> m_refBuilder;
      Gtk::Stack* m_stack {nullptr};
    };

    #endif /* GTKMM_EXAMPLEAPPWINDOW_H */

File: `exampleapplication.cc` (For use with gtkmm 4)

    #include "../step2/exampleapplication.cc"
    // Equal to the corresponding file in step2

File: `exampleappwindow.cc` (For use with gtkmm 4)

    #include "exampleappwindow.h"
    #include <iostream>
    #include <stdexcept>

    ExampleAppWindow::ExampleAppWindow(BaseObjectType* cobject,
      const Glib::RefPtr<Gtk::Builder>& refBuilder)
    : Gtk::ApplicationWindow(cobject),
      m_refBuilder(refBuilder)
    {
      m_stack = m_refBuilder->get_widget<Gtk::Stack>("stack");
      if (!m_stack)
        throw std::runtime_error("No \"stack\" object in window.ui");
    }

    //static
    ExampleAppWindow* ExampleAppWindow::create()
    {
      // Load the Builder file and instantiate its widgets.
      auto refBuilder = Gtk::Builder::create_from_resource("/org/gtkmm/exampleapp/window.ui");

      auto window = Gtk::Builder::get_widget_derived<ExampleAppWindow>(refBuilder, "app_window");
      if (!window)
        throw std::runtime_error("No \"app_window\" object in window.ui");

      return window;
    }

    void ExampleAppWindow::open_file_view(const Glib::RefPtr<Gio::File>& file)
    {
      const Glib::ustring basename = file->get_basename();

      auto scrolled = Gtk::make_managed<Gtk::ScrolledWindow>();
      scrolled->set_expand(true);
      auto view = Gtk::make_managed<Gtk::TextView>();
      view->set_editable(false);
      view->set_cursor_visible(false);
      scrolled->set_child(*view);
      m_stack->add(*scrolled, basename, basename);

      try
      {
        char* contents = nullptr;
        gsize length = 0;

        file->load_contents(contents, length);
        view->get_buffer()->set_text(contents, contents+length);
        g_free(contents);
      }
      catch (const Glib::Error& ex)
      {
        std::cout << "ExampleAppWindow::open_file_view(\"" << file->get_parse_name()
          << "\"):\n  " << ex.what() << std::endl;
      }
    }

File: `main.cc` (For use with gtkmm 4)

    #include "../step1/main.cc"
    // Equal to the corresponding file in step1

File: `window.ui` (For use with gtkmm 4)

    <?xml version="1.0" encoding="UTF-8"?>
    <interface>
      <object class="GtkApplicationWindow" id="app_window">
        <property name="title" translatable="yes">Example Application</property>
        <property name="default-width">600</property>
        <property name="default-height">400</property>
        <property name="hide-on-close">True</property>
        <child type="titlebar">
          <object class="GtkHeaderBar" id="header">
            <child type="title">
              <object class="GtkStackSwitcher" id="tabs">
                <property name="stack">stack</property>
              </object>
            </child>
          </object>
        </child>
        <child>
          <object class="GtkBox" id="content_box">
            <property name="orientation">vertical</property>
            <child>
              <object class="GtkStack" id="stack"/>
            </child>
          </object>
        </child>
      </object>
    </interface>

### A menu

The menu is shown at the right side of the headerbar. It is meant to collect infrequently used actions that affect the whole application.

Just like the application window, we specify our menu in a ui file, and add it as a resource to our binary.

To make the menu appear, we have to load the ui file and associate the resulting menu model with the menu button that we've added to the headerbar. Since menus work by activating `Gio::Action`s, we also have to add a suitable set of actions to our application.

Adding the actions is best done in the `on_startup()` default signal handler, which is guaranteed to be called once for each primary application instance.

Our preferences menu item does not do anything yet, but the Quit menu item is fully functional. It can also be activated by the usual Ctrl-Q shortcut. The shortcut is added with `Gtk::Application::set_accel_for_action()`.

The menu looks like this:

#### A menu

Source Code

File: `exampleapplication.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEAPPLICATION_H
    #define GTKMM_EXAMPLEAPPLICATION_H

    #include <gtkmm.h>

    class ExampleAppWindow;

    class ExampleApplication: public Gtk::Application
    {
    protected:
      ExampleApplication();

    public:
      static Glib::RefPtr<ExampleApplication> create();

    protected:
      // Override default signal handlers:
      void on_startup() override;
      void on_activate() override;
      void on_open(const Gio::Application::type_vec_files& files,
        const Glib::ustring& hint) override;

    private:
      ExampleAppWindow* create_appwindow();
      void on_action_preferences();
      void on_action_quit();
    };

    #endif /* GTKMM_EXAMPLEAPPLICATION_H */

File: `exampleappwindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEAPPWINDOW_H_
    #define GTKMM_EXAMPLEAPPWINDOW_H_

    #include <gtkmm.h>

    class ExampleAppWindow : public Gtk::ApplicationWindow
    {
    public:
      ExampleAppWindow(BaseObjectType* cobject,
        const Glib::RefPtr<Gtk::Builder>& refBuilder);

      static ExampleAppWindow* create();

      void open_file_view(const Glib::RefPtr<Gio::File>& file);

    protected:
      Glib::RefPtr<Gtk::Builder> m_refBuilder;
      Gtk::Stack* m_stack {nullptr};
      Gtk::MenuButton* m_gears {nullptr};
    };

    #endif /* GTKMM_EXAMPLEAPPWINDOW_H */

File: `exampleapplication.cc` (For use with gtkmm 4)

    #include "exampleapplication.h"
    #include "exampleappwindow.h"
    #include <iostream>
    #include <exception>

    ExampleApplication::ExampleApplication()
    : Gtk::Application("org.gtkmm.examples.application", Gio::Application::Flags::HANDLES_OPEN)
    {
    }

    Glib::RefPtr<ExampleApplication> ExampleApplication::create()
    {
      return Glib::make_refptr_for_instance<ExampleApplication>(new ExampleApplication());
    }

    ExampleAppWindow* ExampleApplication::create_appwindow()
    {
      auto appwindow = ExampleAppWindow::create();

      // Make sure that the application runs for as long this window is still open.
      add_window(*appwindow);

      // A window can be added to an application with Gtk::Application::add_window()
      // or Gtk::Window::set_application(). When all added windows have been hidden
      // or removed, the application stops running (Gtk::Application::run() returns()),
      // unless Gio::Application::hold() has been called.

      // Delete the window when it is hidden.
      appwindow->signal_hide().connect([appwindow](){ delete appwindow; });

      return appwindow;
    }

    void ExampleApplication::on_startup()
    {
      // Call the base class's implementation.
      Gtk::Application::on_startup();

      // Add actions and keyboard accelerators for the menu.
      add_action("preferences", sigc::mem_fun(*this, &ExampleApplication::on_action_preferences));
      add_action("quit", sigc::mem_fun(*this, &ExampleApplication::on_action_quit));
      set_accel_for_action("app.quit", "<Ctrl>Q");
    }

    void ExampleApplication::on_activate()
    {
      try
      {
        // The application has been started, so let's show a window.
        auto appwindow = create_appwindow();
        appwindow->present();
      }
      // If create_appwindow() throws an exception (perhaps from Gtk::Builder),
      // no window has been created, no window has been added to the application,
      // and therefore the application will stop running.
      catch (const Glib::Error& ex)
      {
        std::cerr << "ExampleApplication::on_activate(): " << ex.what() << std::endl;
      }
      catch (const std::exception& ex)
      {
        std::cerr << "ExampleApplication::on_activate(): " << ex.what() << std::endl;
      }
    }

    void ExampleApplication::on_open(const Gio::Application::type_vec_files& files,
      const Glib::ustring& /* hint */)
    {
      // The application has been asked to open some files,
      // so let's open a new view for each one.
      ExampleAppWindow* appwindow = nullptr;
      auto windows = get_windows();
      if (windows.size() > 0)
        appwindow = dynamic_cast<ExampleAppWindow*>(windows[0]);

      try
      {
        if (!appwindow)
          appwindow = create_appwindow();

        for (const auto& file : files)
          appwindow->open_file_view(file);

        appwindow->present();
      }
      catch (const Glib::Error& ex)
      {
        std::cerr << "ExampleApplication::on_open(): " << ex.what() << std::endl;
      }
      catch (const std::exception& ex)
      {
        std::cerr << "ExampleApplication::on_open(): " << ex.what() << std::endl;
      }
    }

    void ExampleApplication::on_action_preferences()
    {

    }

    void ExampleApplication::on_action_quit()
    {
      // Gio::Application::quit() will make Gio::Application::run() return,
      // but it's a crude way of ending the program. The window is not removed
      // from the application. Neither the window's nor the application's
      // destructors will be called, because there will be remaining reference
      // counts in both of them. If we want the destructors to be called, we
      // must remove the window from the application. One way of doing this
      // is to hide the window. See comment in create_appwindow().
      auto windows = get_windows();
      for (auto window : windows)
        window->set_visible(false);

      // Not really necessary, when Gtk::Widget::set_visible(false) is called,
      // unless Gio::Application::hold() has been called without a corresponding
      // call to Gio::Application::release().
      quit();
    }

File: `exampleappwindow.cc` (For use with gtkmm 4)

    #include "exampleappwindow.h"
    #include <iostream>
    #include <stdexcept>

    ExampleAppWindow::ExampleAppWindow(BaseObjectType* cobject,
      const Glib::RefPtr<Gtk::Builder>& refBuilder)
    : Gtk::ApplicationWindow(cobject),
      m_refBuilder(refBuilder)
    {
      // Get widgets from the Gtk::Builder file.
      m_stack = m_refBuilder->get_widget<Gtk::Stack>("stack");
      if (!m_stack)
        throw std::runtime_error("No \"stack\" object in window.ui");

      m_gears = m_refBuilder->get_widget<Gtk::MenuButton>("gears");
      if (!m_gears)
        throw std::runtime_error("No \"gears\" object in window.ui");

      // Connect the menu to the MenuButton m_gears.
      // (The connection between action and menu item is specified in gears_menu.ui.)
      auto menu_builder = Gtk::Builder::create_from_resource("/org/gtkmm/exampleapp/gears_menu.ui");
      auto menu = menu_builder->get_object<Gio::MenuModel>("menu");
      if (!menu)
        throw std::runtime_error("No \"menu\" object in gears_menu.ui");

      m_gears->set_menu_model(menu);
    }

    //static
    ExampleAppWindow* ExampleAppWindow::create()
    {
      // Load the Builder file and instantiate its widgets.
      auto refBuilder = Gtk::Builder::create_from_resource("/org/gtkmm/exampleapp/window.ui");

      auto window = Gtk::Builder::get_widget_derived<ExampleAppWindow>(refBuilder, "app_window");
      if (!window)
        throw std::runtime_error("No \"app_window\" object in window.ui");

      return window;
    }

    void ExampleAppWindow::open_file_view(const Glib::RefPtr<Gio::File>& file)
    {
      const Glib::ustring basename = file->get_basename();

      auto scrolled = Gtk::make_managed<Gtk::ScrolledWindow>();
      scrolled->set_expand(true);
      auto view = Gtk::make_managed<Gtk::TextView>();
      view->set_editable(false);
      view->set_cursor_visible(false);
      scrolled->set_child(*view);
      m_stack->add(*scrolled, basename, basename);

      try
      {
        char* contents = nullptr;
        gsize length = 0;

        file->load_contents(contents, length);
        view->get_buffer()->set_text(contents, contents+length);
        g_free(contents);
      }
      catch (const Glib::Error& ex)
      {
        std::cout << "ExampleAppWindow::open_file_view(\"" << file->get_parse_name()
          << "\"):\n  " << ex.what() << std::endl;
      }
    }

File: `main.cc` (For use with gtkmm 4)

    #include "../step1/main.cc"
    // Equal to the corresponding file in step1

File: `exampleapp.gresource.xml` (For use with gtkmm 4)

    <?xml version="1.0" encoding="UTF-8"?>
    <gresources>
      <gresource prefix="/org/gtkmm/exampleapp">
        <file preprocess="xml-stripblanks">window.ui</file>
        <file preprocess="xml-stripblanks">gears_menu.ui</file>
      </gresource>
    </gresources>

File: `gears_menu.ui` (For use with gtkmm 4)

    <?xml version="1.0" encoding="UTF-8"?>
    <interface>
      <menu id="menu">
        <section>
          <item>
            <attribute name="label" translatable="yes">_Preferences</attribute>
            <attribute name="action">app.preferences</attribute>
          </item>
        </section>
        <section>
          <item>
            <attribute name="label" translatable="yes">_Quit</attribute>
            <attribute name="action">app.quit</attribute>
          </item>
        </section>
      </menu>
    </interface>

File: `window.ui` (For use with gtkmm 4)

    <?xml version="1.0" encoding="UTF-8"?>
    <interface>
      <object class="GtkApplicationWindow" id="app_window">
        <property name="title" translatable="yes">Example Application</property>
        <property name="default-width">600</property>
        <property name="default-height">400</property>
        <property name="hide-on-close">True</property>
        <child type="titlebar">
          <object class="GtkHeaderBar" id="header">
            <child type="title">
              <object class="GtkStackSwitcher" id="tabs">
                <property name="stack">stack</property>
              </object>
            </child>
            <child type="end">
              <object class="GtkMenuButton" id="gears">
                <property name="direction">none</property>
              </object>
            </child>
          </object>
        </child>
        <child>
          <object class="GtkBox" id="content_box">
            <property name="orientation">vertical</property>
            <child>
              <object class="GtkStack" id="stack"/>
            </child>
          </object>
        </child>
      </object>
    </interface>

### A preference dialog

A typical application will have some preferences that should be remembered from one run to the next. Even for our simple example application, we may want to change the font that is used for the content.

We are going to use `Gio::Settings` to store our preferences. `Gio::Settings` requires a schema that describes our settings, in our case the `org.gtkmm.exampleapp.gschema.xml` file.

Before we can make use of this schema in our application, we need to compile it into the binary form that `Gio::Settings` expects. GIO provides macros to do this in autotools-based projects. See the description of GSettings. Meson provides the `compile_schemas()` function in the GNOME module.

Next, we need to connect our settings to the widgets that they are supposed to control. One convenient way to do this is to use `Gio::Settings::bind()` to bind settings keys to object properties, as we do for the transition setting in `ExampleAppWindow`'s constructor.

    m_settings = Gio::Settings::create("org.gtkmm.exampleapp");
    m_settings->bind("transition", m_stack->property_transition_type());

The code to connect the font setting is a little more involved, since it corresponds to an object property in a `Gtk::TextTag` that we must first create. The code is in `ExampleAppWindow::open_file_view()`.

    auto tag = buffer->create_tag();
    m_settings->bind("font", tag->property_font());
    buffer->apply_tag(tag, buffer->begin(), buffer->end());

At this point, the application will already react if you change one of the settings, e.g. using the `gsettings` commandline tool. Of course, we expect the application to provide a preference dialog for these. So lets do that now. Our preference dialog will be a subclass of `Gtk::Window`, and we'll use the same techniques that we've already seen in `ExampleAppWindow`: a `Gtk::Builder` ui file and settings bindings. In this case the bindings are more involved, though. We use `Gtk::FontDialogButton` and `Gtk::DropDown` in the preference dialog. The types of the properties in these classes can't be automatically converted to the string type that `Gio::Settings` requires.

When we've created the `prefs.ui` file and the `ExampleAppPrefs` class, we revisit the `ExampleApplication::on_action_preferences()` method in our application class, and make it open a new preference dialog.

    auto prefs_dialog = ExampleAppPrefs::create(*get_active_window());
    prefs_dialog->present();

After all this work, our application can now show a preference dialog like this:

#### A preference dialog

Source Code

File: `exampleapplication.h` (For use with gtkmm 4)

    #include "../step4/exampleapplication.h"
    // Equal to the corresponding file in step4

File: `exampleappprefs.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEAPPPREFS_H_
    #define GTKMM_EXAMPLEAPPPREFS_H_

    #include <gtkmm.h>

    #ifdef GLIBMM_CHECK_VERSION
    #define HAS_GIO_SETTINGS_BIND_WITH_MAPPING GLIBMM_CHECK_VERSION(2,75,0)
    #else
    #define HAS_GIO_SETTINGS_BIND_WITH_MAPPING 0
    #endif

    class ExampleAppPrefs : public Gtk::Window
    {
    public:
      ExampleAppPrefs(BaseObjectType* cobject,
        const Glib::RefPtr<Gtk::Builder>& refBuilder);

      static ExampleAppPrefs* create(Gtk::Window& parent);

    protected:
    #if HAS_GIO_SETTINGS_BIND_WITH_MAPPING
      // Mappings from Gio::Settings to properties
      static std::optional<unsigned int> map_from_ustring_to_int(const Glib::ustring& transition);
      static std::optional<Glib::ustring> map_from_int_to_ustring(const unsigned int& pos);
    #else
      // Signal handlers
      void on_font_setting_changed(const Glib::ustring& key);
      void on_font_selection_changed();
      void on_transition_setting_changed(const Glib::ustring& key);
      void on_transition_selection_changed();
    #endif
      Glib::RefPtr<Gtk::Builder> m_refBuilder;
      Glib::RefPtr<Gio::Settings> m_settings;
      Gtk::FontDialogButton* m_font {nullptr};
      Gtk::DropDown* m_transition {nullptr};
    };

    #endif /* GTKMM_EXAMPLEAPPPREFS_H_ */

File: `exampleappwindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEAPPWINDOW_H_
    #define GTKMM_EXAMPLEAPPWINDOW_H_

    #include <gtkmm.h>

    class ExampleAppWindow : public Gtk::ApplicationWindow
    {
    public:
      ExampleAppWindow(BaseObjectType* cobject,
        const Glib::RefPtr<Gtk::Builder>& refBuilder);

      static ExampleAppWindow* create();

      void open_file_view(const Glib::RefPtr<Gio::File>& file);

    protected:
      Glib::RefPtr<Gtk::Builder> m_refBuilder;
      Glib::RefPtr<Gio::Settings> m_settings;
      Gtk::Stack* m_stack {nullptr};
      Gtk::MenuButton* m_gears {nullptr};
    };

    #endif /* GTKMM_EXAMPLEAPPWINDOW_H */

File: `exampleapplication.cc` (For use with gtkmm 4)

    #include "exampleapplication.h"
    #include "exampleappwindow.h"
    #include "exampleappprefs.h"
    #include <iostream>
    #include <exception>

    ExampleApplication::ExampleApplication()
    : Gtk::Application("org.gtkmm.examples.application", Gio::Application::Flags::HANDLES_OPEN)
    {
    }

    Glib::RefPtr<ExampleApplication> ExampleApplication::create()
    {
      return Glib::make_refptr_for_instance<ExampleApplication>(new ExampleApplication());
    }

    ExampleAppWindow* ExampleApplication::create_appwindow()
    {
      auto appwindow = ExampleAppWindow::create();

      // Make sure that the application runs for as long this window is still open.
      add_window(*appwindow);

      // A window can be added to an application with Gtk::Application::add_window()
      // or Gtk::Window::set_application(). When all added windows have been hidden
      // or removed, the application stops running (Gtk::Application::run() returns()),
      // unless Gio::Application::hold() has been called.

      // Delete the window when it is hidden.
      appwindow->signal_hide().connect([appwindow](){ delete appwindow; });

      return appwindow;
    }

    void ExampleApplication::on_startup()
    {
      // Call the base class's implementation.
      Gtk::Application::on_startup();

      // Add actions and keyboard accelerators for the menu.
      add_action("preferences", sigc::mem_fun(*this, &ExampleApplication::on_action_preferences));
      add_action("quit", sigc::mem_fun(*this, &ExampleApplication::on_action_quit));
      set_accel_for_action("app.quit", "<Ctrl>Q");
    }

    void ExampleApplication::on_activate()
    {
      try
      {
        // The application has been started, so let's show a window.
        auto appwindow = create_appwindow();
        appwindow->present();
      }
      // If create_appwindow() throws an exception (perhaps from Gtk::Builder),
      // no window has been created, no window has been added to the application,
      // and therefore the application will stop running.
      catch (const Glib::Error& ex)
      {
        std::cerr << "ExampleApplication::on_activate(): " << ex.what() << std::endl;
      }
      catch (const std::exception& ex)
      {
        std::cerr << "ExampleApplication::on_activate(): " << ex.what() << std::endl;
      }
    }

    void ExampleApplication::on_open(const Gio::Application::type_vec_files& files,
      const Glib::ustring& /* hint */)
    {
      // The application has been asked to open some files,
      // so let's open a new view for each one.
      ExampleAppWindow* appwindow = nullptr;
      auto windows = get_windows();
      if (windows.size() > 0)
        appwindow = dynamic_cast<ExampleAppWindow*>(windows[0]);

      try
      {
        if (!appwindow)
          appwindow = create_appwindow();

        for (const auto& file : files)
          appwindow->open_file_view(file);

        appwindow->present();
      }
      catch (const Glib::Error& ex)
      {
        std::cerr << "ExampleApplication::on_open(): " << ex.what() << std::endl;
      }
      catch (const std::exception& ex)
      {
        std::cerr << "ExampleApplication::on_open(): " << ex.what() << std::endl;
      }
    }

    void ExampleApplication::on_action_preferences()
    {
      try
      {
        auto prefs_dialog = ExampleAppPrefs::create(*get_active_window());
        prefs_dialog->present();

        // Delete the dialog when it is hidden.
        prefs_dialog->signal_hide().connect([prefs_dialog](){ delete prefs_dialog; });
      }
      catch (const Glib::Error& ex)
      {
        std::cerr << "ExampleApplication::on_action_preferences(): " << ex.what() << std::endl;
      }
      catch (const std::exception& ex)
      {
        std::cerr << "ExampleApplication::on_action_preferences(): " << ex.what() << std::endl;
      }
    }

    void ExampleApplication::on_action_quit()
    {
      // Gio::Application::quit() will make Gio::Application::run() return,
      // but it's a crude way of ending the program. The window is not removed
      // from the application. Neither the window's nor the application's
      // destructors will be called, because there will be remaining reference
      // counts in both of them. If we want the destructors to be called, we
      // must remove the window from the application. One way of doing this
      // is to hide the window. See comment in create_appwindow().
      auto windows = get_windows();
      for (auto window : windows)
        window->set_visible(false);

      // Not really necessary, when Gtk::Widget::set_visible(false) is called,
      // unless Gio::Application::hold() has been called without a corresponding
      // call to Gio::Application::release().
      quit();
    }

File: `exampleappprefs.cc` (For use with gtkmm 4)

    #include "exampleappprefs.h"
    #include "exampleappwindow.h"
    #include <array>
    #include <stdexcept>

    namespace
    {
    struct TransitionTypeStruct
    {
      Glib::ustring id;   // Value of "transition" key in Gio::Settings
      Glib::ustring text; // Text in the DropDown list
    };

    const std::array<TransitionTypeStruct, 3> transitionTypes =
    {
      TransitionTypeStruct{"none",             "None"},
      TransitionTypeStruct{"crossfade",        "Fade"},
      TransitionTypeStruct{"slide-left-right", "Slide"}
    };

    } // anonymous namespace

    ExampleAppPrefs::ExampleAppPrefs(BaseObjectType* cobject,
      const Glib::RefPtr<Gtk::Builder>& refBuilder)
    : Gtk::Window(cobject),
      m_refBuilder(refBuilder)
    {
      m_font = m_refBuilder->get_widget<Gtk::FontDialogButton>("font");
      if (!m_font)
        throw std::runtime_error("No \"font\" object in prefs.ui");

      m_transition = m_refBuilder->get_widget<Gtk::DropDown>("transition");
      if (!m_transition)
        throw std::runtime_error("No \"transition\" object in prefs.ui");

      // DropDown for transition type.
      auto string_list = Gtk::StringList::create();
      for (const auto& transitionType : transitionTypes)
        string_list->append(transitionType.text);

      m_transition->set_model(string_list);

      m_settings = Gio::Settings::create("org.gtkmm.exampleapp");

      // Connect preference properties to the Gio::Settings.
    #if HAS_GIO_SETTINGS_BIND_WITH_MAPPING
      m_settings->bind<Glib::ustring, Pango::FontDescription>("font",
        m_font->property_font_desc(), Gio::Settings::BindFlags::DEFAULT,
        [](const auto& font) { return Pango::FontDescription(font); },
        [](const auto& fontdesc) { return fontdesc.to_string(); }
      );
      m_settings->bind<Glib::ustring, unsigned int>("transition",
        m_transition->property_selected(), Gio::Settings::BindFlags::DEFAULT,
        [](const auto& transition) { return map_from_ustring_to_int(transition); },
        [](const auto& pos) { return map_from_int_to_ustring(pos); }
      );
    #else
      // This is easier when g_settings_bind_with_mapping() is
      // wrapped in a Gio::Settings method.
      m_settings->signal_changed("font").connect(
        sigc::mem_fun(*this, &ExampleAppPrefs::on_font_setting_changed));
      m_font->property_font_desc().signal_changed().connect(
        sigc::mem_fun(*this, &ExampleAppPrefs::on_font_selection_changed));

      m_settings->signal_changed("transition").connect(
        sigc::mem_fun(*this, &ExampleAppPrefs::on_transition_setting_changed));
      m_transition->property_selected().signal_changed().connect(
        sigc::mem_fun(*this, &ExampleAppPrefs::on_transition_selection_changed));

      // Synchronize the preferences dialog with m_settings.
      on_font_setting_changed("font");
      on_transition_setting_changed("transition");
    #endif
    }

    //static
    ExampleAppPrefs* ExampleAppPrefs::create(Gtk::Window& parent)
    {
      // Load the Builder file and instantiate its widgets.
      auto refBuilder = Gtk::Builder::create_from_resource("/org/gtkmm/exampleapp/prefs.ui");

      auto dialog = Gtk::Builder::get_widget_derived<ExampleAppPrefs>(refBuilder, "prefs_dialog");
      if (!dialog)
        throw std::runtime_error("No \"prefs_dialog\" object in prefs.ui");

      dialog->set_transient_for(parent);

      return dialog;
    }

    #if HAS_GIO_SETTINGS_BIND_WITH_MAPPING
    std::optional<unsigned int> ExampleAppPrefs::map_from_ustring_to_int(const Glib::ustring& transition)
    {
      for (std::size_t i = 0; i < transitionTypes.size(); ++i)
      {
        if (transitionTypes[i].id == transition)
          return i;
      }
      return std::nullopt;
    }

    std::optional<Glib::ustring> ExampleAppPrefs::map_from_int_to_ustring(const unsigned int& pos)
    {
      if (pos >= transitionTypes.size())
        return std::nullopt;
      return transitionTypes[pos].id;
    }
    #else
    void ExampleAppPrefs::on_font_setting_changed(const Glib::ustring& /* key */)
    {
      const auto font_setting = m_settings->get_string("font");
      const auto font_button = m_font->get_font_desc().to_string();
      if (font_setting != font_button)
        m_font->set_font_desc(Pango::FontDescription(font_setting));
    }

    void ExampleAppPrefs::on_font_selection_changed()
    {
      const auto font_setting = m_settings->get_string("font");
      const auto font_button = m_font->get_font_desc().to_string();
      if (font_setting != font_button)
        m_settings->set_string("font", font_button);
    }

    void ExampleAppPrefs::on_transition_setting_changed(const Glib::ustring& /* key */)
    {
      const auto transition_setting = m_settings->get_string("transition");
      const auto transition_button = transitionTypes[m_transition->get_selected()].id;
      if (transition_setting != transition_button)
      {
        for (std::size_t i = 0; i < transitionTypes.size(); ++i)
        {
          if (transitionTypes[i].id == transition_setting)
          {
            m_transition->set_selected(i);
            break;
          }
        }
      }
    }

    void ExampleAppPrefs::on_transition_selection_changed()
    {
      const auto pos = m_transition->get_selected();
      if (pos >= transitionTypes.size())
        return;
      const auto transition_setting = m_settings->get_string("transition");
      const auto transition_button = transitionTypes[pos].id;
      if (transition_setting != transition_button)
        m_settings->set_string("transition", transition_button);
    }
    #endif

File: `exampleappwindow.cc` (For use with gtkmm 4)

    #include "exampleappwindow.h"
    #include <iostream>
    #include <stdexcept>

    ExampleAppWindow::ExampleAppWindow(BaseObjectType* cobject,
      const Glib::RefPtr<Gtk::Builder>& refBuilder)
    : Gtk::ApplicationWindow(cobject),
      m_refBuilder(refBuilder)
    {
      // Get widgets from the Gtk::Builder file.
      m_stack = m_refBuilder->get_widget<Gtk::Stack>("stack");
      if (!m_stack)
        throw std::runtime_error("No \"stack\" object in window.ui");

      m_gears = m_refBuilder->get_widget<Gtk::MenuButton>("gears");
      if (!m_gears)
        throw std::runtime_error("No \"gears\" object in window.ui");

      // Bind settings.
      m_settings = Gio::Settings::create("org.gtkmm.exampleapp");
      m_settings->bind("transition", m_stack->property_transition_type());

      // Connect the menu to the MenuButton m_gears.
      // (The connection between action and menu item is specified in gears_menu.ui.)
      auto menu_builder = Gtk::Builder::create_from_resource("/org/gtkmm/exampleapp/gears_menu.ui");
      auto menu = menu_builder->get_object<Gio::MenuModel>("menu");
      if (!menu)
        throw std::runtime_error("No \"menu\" object in gears_menu.ui");

      m_gears->set_menu_model(menu);
    }

    //static
    ExampleAppWindow* ExampleAppWindow::create()
    {
      // Load the Builder file and instantiate its widgets.
      auto refBuilder = Gtk::Builder::create_from_resource("/org/gtkmm/exampleapp/window.ui");

      auto window = Gtk::Builder::get_widget_derived<ExampleAppWindow>(refBuilder, "app_window");
      if (!window)
        throw std::runtime_error("No \"app_window\" object in window.ui");

      return window;
    }

    void ExampleAppWindow::open_file_view(const Glib::RefPtr<Gio::File>& file)
    {
      const Glib::ustring basename = file->get_basename();

      auto scrolled = Gtk::make_managed<Gtk::ScrolledWindow>();
      scrolled->set_expand(true);
      auto view = Gtk::make_managed<Gtk::TextView>();
      view->set_editable(false);
      view->set_cursor_visible(false);
      scrolled->set_child(*view);
      m_stack->add(*scrolled, basename, basename);

      auto buffer = view->get_buffer();
      try
      {
        char* contents = nullptr;
        gsize length = 0;

        file->load_contents(contents, length);
        buffer->set_text(contents, contents+length);
        g_free(contents);
      }
      catch (const Glib::Error& ex)
      {
        std::cout << "ExampleAppWindow::open_file_view(\"" << file->get_parse_name()
          << "\"):\n  " << ex.what() << std::endl;
      }

      auto tag = buffer->create_tag();
      m_settings->bind("font", tag->property_font());
      buffer->apply_tag(tag, buffer->begin(), buffer->end());
    }

File: `main.cc` (For use with gtkmm 4)

    #include "exampleapplication.h"

    int main(int argc, char* argv[])
    {
      // Since this example is running uninstalled, we have to help it find its
      // schema. This is *not* necessary in a properly installed application.
      Glib::setenv ("GSETTINGS_SCHEMA_DIR", ".", false);

      auto application = ExampleApplication::create();

      // Start the application, showing the initial window,
      // and opening extra views for any files that it is asked to open,
      // for instance as a command-line parameter.
      // run() will return when the last window has been closed.
      return application->run(argc, argv);
    }

File: `exampleapp.gresource.xml` (For use with gtkmm 4)

    <?xml version="1.0" encoding="UTF-8"?>
    <gresources>
      <gresource prefix="/org/gtkmm/exampleapp">
        <file preprocess="xml-stripblanks">window.ui</file>
        <file preprocess="xml-stripblanks">gears_menu.ui</file>
        <file preprocess="xml-stripblanks">prefs.ui</file>
      </gresource>
    </gresources>

File: `prefs.ui` (For use with gtkmm 4)

    <?xml version="1.0" encoding="UTF-8"?>
    <interface>
      <object class="GtkWindow" id="prefs_dialog">
        <property name="title" translatable="yes">Preferences</property>
        <property name="resizable">False</property>
        <property name="modal">True</property>
        <property name="hide_on_close">True</property>
        <child>
          <object class="GtkGrid" id="grid">
            <property name="margin-start">12</property>
            <property name="margin-end">12</property>
            <property name="margin-top">12</property>
            <property name="margin-bottom">12</property>
            <property name="row-spacing">12</property>
            <property name="column-spacing">12</property>
            <child>
              <object class="GtkLabel" id="fontlabel">
                <property name="label">_Font:</property>
                <property name="use-underline">True</property>
                <property name="mnemonic-widget">font</property>
                <property name="xalign">1</property>
                <layout>
                  <property name="column">0</property>
                  <property name="row">0</property>
                </layout>
              </object>
            </child>
            <child>
              <object class="GtkFontDialogButton" id="font">
                <property name="dialog">
                  <object class="GtkFontDialog"/>
                </property>
                <layout>
                  <property name="column">1</property>
                  <property name="row">0</property>
                </layout>
              </object>
            </child>
            <child>
              <object class="GtkLabel" id="transitionlabel">
                <property name="label">_Transition:</property>
                <property name="use-underline">True</property>
                <property name="mnemonic-widget">transition</property>
                <property name="xalign">1</property>
                <layout>
                  <property name="column">0</property>
                  <property name="row">1</property>
                </layout>
              </object>
            </child>
            <child>
              <object class="GtkDropDown" id="transition">
                <layout>
                  <property name="column">1</property>
                  <property name="row">1</property>
                </layout>
              </object>
            </child>
          </object>
        </child>
      </object>
    </interface>

File: `org.gtkmm.exampleapp.gschema.xml` (For use with gtkmm 4)

    <?xml version="1.0" encoding="UTF-8"?>
    <schemalist>
      <schema path="/org/gtkmm/exampleapp/" id="org.gtkmm.exampleapp">
        <key name="font" type="s">
          <default>'Monospace 12'</default>
          <summary>Font</summary>
          <description>The font to be used for content.</description>
        </key>
        <key name="transition" type="s">
          <choices>
            <choice value='none'/>
            <choice value='crossfade'/>
            <choice value='slide-left-right'/>
          </choices>
          <default>'none'</default>
          <summary>Transition</summary>
          <description>The transition to use when switching tabs.</description>
        </key>
      </schema>
    </schemalist>

### Adding a search bar

We continue to flesh out the functionality of our application. For now, we add search. gtkmm supports this with `Gtk::SearchEntry` and `Gtk::SearchBar`. The search bar is a widget that can slide in from the top to present a search entry.

We add a toggle button to the header bar, which can be used to slide out the search bar below the header bar. The new widgets are added in the `window.ui` file.

Implementing the search needs quite a few code changes that we are not going to completely go over here. The central piece of the search implementation is a signal handler that listens for text changes in the search entry, shown here without error handling.

    void ExampleAppWindow::on_search_text_changed()
    {
      const auto text = m_searchentry->get_text();
      auto tab = dynamic_cast<Gtk::ScrolledWindow*>(m_stack->get_visible_child());
      auto view = dynamic_cast<Gtk::TextView*>(tab->get_child());

      // Very simple-minded search implementation.
      auto buffer = view->get_buffer();
      Gtk::TextIter match_start;
      Gtk::TextIter match_end;
      if (buffer->begin().forward_search(text, Gtk::TextSearchFlags::CASE_INSENSITIVE,
          match_start, match_end))
      {
        buffer->select_range(match_start, match_end);
        view->scroll_to(match_start);
      }
    }

With the search bar, our application now looks like this:

#### Adding a search bar

Source Code

File: `exampleapplication.h` (For use with gtkmm 4)

    #include "../step4/exampleapplication.h"
    // Equal to the corresponding file in step4

File: `exampleappprefs.h` (For use with gtkmm 4)

    #include "../step5/exampleappprefs.h"
    // Equal to the corresponding file in step5

File: `exampleappwindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEAPPWINDOW_H_
    #define GTKMM_EXAMPLEAPPWINDOW_H_

    #include <gtkmm.h>

    class ExampleAppWindow : public Gtk::ApplicationWindow
    {
    public:
      ExampleAppWindow(BaseObjectType* cobject,
        const Glib::RefPtr<Gtk::Builder>& refBuilder);

      static ExampleAppWindow* create();

      void open_file_view(const Glib::RefPtr<Gio::File>& file);

    protected:
      // Signal handlers
      void on_search_text_changed();
      void on_visible_child_changed();

      Glib::RefPtr<Gtk::Builder> m_refBuilder;
      Glib::RefPtr<Gio::Settings> m_settings;
      Gtk::Stack* m_stack {nullptr};
      Gtk::ToggleButton* m_search {nullptr};
      Gtk::SearchBar* m_searchbar {nullptr};
      Gtk::SearchEntry* m_searchentry {nullptr};
      Gtk::MenuButton* m_gears {nullptr};
      Glib::RefPtr<Glib::Binding> m_prop_binding;
    };

    #endif /* GTKMM_EXAMPLEAPPWINDOW_H */

File: `exampleapplication.cc` (For use with gtkmm 4)

    #include "../step5/exampleapplication.cc"
    // Equal to the corresponding file in step5

File: `exampleappprefs.cc` (For use with gtkmm 4)

    #include "../step5/exampleappprefs.cc"
    // Equal to the corresponding file in step5

File: `exampleappwindow.cc` (For use with gtkmm 4)

    #include "exampleappwindow.h"
    #include <iostream>
    #include <stdexcept>

    ExampleAppWindow::ExampleAppWindow(BaseObjectType* cobject,
      const Glib::RefPtr<Gtk::Builder>& refBuilder)
    : Gtk::ApplicationWindow(cobject),
      m_refBuilder(refBuilder)
    {
      // Get widgets from the Gtk::Builder file.
      m_stack = m_refBuilder->get_widget<Gtk::Stack>("stack");
      if (!m_stack)
        throw std::runtime_error("No \"stack\" object in window.ui");

      m_search = m_refBuilder->get_widget<Gtk::ToggleButton>("search");
      if (!m_search)
        throw std::runtime_error("No \"search\" object in window.ui");

      m_searchbar = m_refBuilder->get_widget<Gtk::SearchBar>("searchbar");
      if (!m_searchbar)
        throw std::runtime_error("No \"searchbar\" object in window.ui");

      m_searchentry = m_refBuilder->get_widget<Gtk::SearchEntry>("searchentry");
      if (!m_searchentry)
        throw std::runtime_error("No \"searchentry\" object in window.ui");

      m_gears = m_refBuilder->get_widget<Gtk::MenuButton>("gears");
      if (!m_gears)
        throw std::runtime_error("No \"gears\" object in window.ui");

      // Bind settings.
      m_settings = Gio::Settings::create("org.gtkmm.exampleapp");
      m_settings->bind("transition", m_stack->property_transition_type());

      // Bind properties.
      m_prop_binding = Glib::Binding::bind_property(m_search->property_active(),
        m_searchbar->property_search_mode_enabled(), Glib::Binding::Flags::BIDIRECTIONAL);

      // Connect signal handlers.
      m_searchentry->signal_search_changed().connect(
        sigc::mem_fun(*this, &ExampleAppWindow::on_search_text_changed));
      m_stack->property_visible_child().signal_changed().connect(
        sigc::mem_fun(*this, &ExampleAppWindow::on_visible_child_changed));

      // Connect the menu to the MenuButton m_gears.
      // (The connection between action and menu item is specified in gears_menu.ui.)
      auto menu_builder = Gtk::Builder::create_from_resource("/org/gtkmm/exampleapp/gears_menu.ui");
      auto menu = menu_builder->get_object<Gio::MenuModel>("menu");
      if (!menu)
        throw std::runtime_error("No \"menu\" object in gears_menu.ui");

      m_gears->set_menu_model(menu);
    }

    //static
    ExampleAppWindow* ExampleAppWindow::create()
    {
      // Load the Builder file and instantiate its widgets.
      auto refBuilder = Gtk::Builder::create_from_resource("/org/gtkmm/exampleapp/window.ui");

      auto window = Gtk::Builder::get_widget_derived<ExampleAppWindow>(refBuilder, "app_window");
      if (!window)
        throw std::runtime_error("No \"app_window\" object in window.ui");

      return window;
    }

    void ExampleAppWindow::open_file_view(const Glib::RefPtr<Gio::File>& file)
    {
      const Glib::ustring basename = file->get_basename();

      auto scrolled = Gtk::make_managed<Gtk::ScrolledWindow>();
      scrolled->set_expand(true);
      auto view = Gtk::make_managed<Gtk::TextView>();
      view->set_editable(false);
      view->set_cursor_visible(false);
      scrolled->set_child(*view);
      m_stack->add(*scrolled, basename, basename);

      auto buffer = view->get_buffer();
      try
      {
        char* contents = nullptr;
        gsize length = 0;

        file->load_contents(contents, length);
        buffer->set_text(contents, contents+length);
        g_free(contents);
      }
      catch (const Glib::Error& ex)
      {
        std::cout << "ExampleAppWindow::open_file_view(\"" << file->get_parse_name()
          << "\"):\n  " << ex.what() << std::endl;
        return;
      }

      auto tag = buffer->create_tag();
      m_settings->bind("font", tag->property_font());
      buffer->apply_tag(tag, buffer->begin(), buffer->end());

      m_search->set_sensitive(true);
    }

    void ExampleAppWindow::on_search_text_changed()
    {
      const auto text = m_searchentry->get_text();
      if (text.empty())
        return;

      auto tab = dynamic_cast<Gtk::ScrolledWindow*>(m_stack->get_visible_child());
      if (!tab)
      {
        std::cout << "ExampleAppWindow::on_search_text_changed(): No visible child." << std::endl;
        return;
      }

      auto view = dynamic_cast<Gtk::TextView*>(tab->get_child());
      if (!view)
      {
        std::cout << "ExampleAppWindow::on_search_text_changed(): No visible text view." << std::endl;
        return;
      }

      // Very simple-minded search implementation.
      auto buffer = view->get_buffer();
      Gtk::TextIter match_start;
      Gtk::TextIter match_end;
      if (buffer->begin().forward_search(text, Gtk::TextSearchFlags::CASE_INSENSITIVE,
          match_start, match_end))
      {
        buffer->select_range(match_start, match_end);
        view->scroll_to(match_start);
      }
    }

    void ExampleAppWindow::on_visible_child_changed()
    {
      m_searchbar->set_search_mode(false);
    }

File: `main.cc` (For use with gtkmm 4)

    #include "../step5/main.cc"
    // Equal to the corresponding file in step5

File: `window.ui` (For use with gtkmm 4)

    <?xml version="1.0" encoding="UTF-8"?>
    <interface>
      <object class="GtkApplicationWindow" id="app_window">
        <property name="title" translatable="yes">Example Application</property>
        <property name="default-width">600</property>
        <property name="default-height">400</property>
        <property name="hide-on-close">True</property>
        <child type="titlebar">
          <object class="GtkHeaderBar" id="header">
            <child type="title">
              <object class="GtkStackSwitcher" id="tabs">
                <property name="stack">stack</property>
              </object>
            </child>
            <child type="end">
              <object class="GtkMenuButton" id="gears">
                <property name="direction">none</property>
              </object>
            </child>
            <child type="end">
              <object class="GtkToggleButton" id="search">
                <property name="sensitive">False</property>
                <property name="icon-name">edit-find-symbolic</property>
              </object>
            </child>
          </object>
        </child>
        <child>
          <object class="GtkBox" id="content_box">
            <property name="orientation">vertical</property>
            <child>
              <object class="GtkSearchBar" id="searchbar">
                <child>
                  <object class="GtkSearchEntry" id="searchentry">
                  </object>
                </child>
              </object>
            </child>
            <child>
              <object class="GtkStack" id="stack">
                <property name="transition-duration">500</property>
              </object>
            </child>
          </object>
        </child>
      </object>
    </interface>

### Adding a side bar

As another piece of functionality, we are adding a sidebar, which demonstrates `Gtk::Revealer` and `Gtk::ListBox`. The new widgets are added in the `window.ui` file.

The code to populate the sidebar with buttons for the words found in each file is a little too involved to go into here. But we'll look at the code to add a checkbutton for the new feature to the menu. A menu item is added to the ui file `gears_menu.ui`.

To connect the menu item to the new `show-words` setting, we use a `Gio::Action` corresponding to the given `Gio::Settings` key. In `ExampleAppWindow`'s constructor:

    // Connect the menu to the MenuButton m_gears, and bind the show-words setting
    // to the win.show-words action and the "Words" menu item.
    // (The connection between action and menu item is specified in gears_menu.ui.)
    auto menu_builder = Gtk::Builder::create_from_resource("/org/gtkmm/exampleapp/gears_menu.ui");
    auto menu = menu_builder->get_object<Gio::MenuModel>("menu");
    m_gears->set_menu_model(menu);
    add_action(m_settings->create_action("show-words"));

What our application looks like now:

#### Adding a side bar

Source Code

File: `exampleapplication.h` (For use with gtkmm 4)

    #include "../step4/exampleapplication.h"
    // Equal to the corresponding file in step4

File: `exampleappprefs.h` (For use with gtkmm 4)

    #include "../step5/exampleappprefs.h"
    // Equal to the corresponding file in step5

File: `exampleappwindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEAPPWINDOW_H_
    #define GTKMM_EXAMPLEAPPWINDOW_H_

    #include <gtkmm.h>

    class ExampleAppWindow : public Gtk::ApplicationWindow
    {
    public:
      ExampleAppWindow(BaseObjectType* cobject,
        const Glib::RefPtr<Gtk::Builder>& refBuilder);

      static ExampleAppWindow* create();

      void open_file_view(const Glib::RefPtr<Gio::File>& file);

    protected:
      // Signal handlers
      void on_search_text_changed();
      void on_visible_child_changed();
      void on_find_word(const Gtk::Button* button);
      void on_reveal_child_changed();

      void update_words();

      Glib::RefPtr<Gtk::Builder> m_refBuilder;
      Glib::RefPtr<Gio::Settings> m_settings;
      Gtk::Stack* m_stack {nullptr};
      Gtk::ToggleButton* m_search {nullptr};
      Gtk::SearchBar* m_searchbar {nullptr};
      Gtk::SearchEntry* m_searchentry {nullptr};
      Gtk::MenuButton* m_gears {nullptr};
      Gtk::Revealer* m_sidebar {nullptr};
      Gtk::ListBox* m_words {nullptr};
      Glib::RefPtr<Glib::Binding> m_prop_binding;
    };

    #endif /* GTKMM_EXAMPLEAPPWINDOW_H */

File: `exampleapplication.cc` (For use with gtkmm 4)

    #include "../step5/exampleapplication.cc"
    // Equal to the corresponding file in step5

File: `exampleappprefs.cc` (For use with gtkmm 4)

    #include "../step5/exampleappprefs.cc"
    // Equal to the corresponding file in step5

File: `exampleappwindow.cc` (For use with gtkmm 4)

    #include "exampleappwindow.h"
    #include <iostream>
    #include <stdexcept>
    #include <set>

    ExampleAppWindow::ExampleAppWindow(BaseObjectType* cobject,
      const Glib::RefPtr<Gtk::Builder>& refBuilder)
    : Gtk::ApplicationWindow(cobject),
      m_refBuilder(refBuilder)
    {
      // Get widgets from the Gtk::Builder file.
      m_stack = m_refBuilder->get_widget<Gtk::Stack>("stack");
      if (!m_stack)
        throw std::runtime_error("No \"stack\" object in window.ui");

      m_search = m_refBuilder->get_widget<Gtk::ToggleButton>("search");
      if (!m_search)
        throw std::runtime_error("No \"search\" object in window.ui");

      m_searchbar = m_refBuilder->get_widget<Gtk::SearchBar>("searchbar");
      if (!m_searchbar)
        throw std::runtime_error("No \"searchbar\" object in window.ui");

      m_searchentry = m_refBuilder->get_widget<Gtk::SearchEntry>("searchentry");
      if (!m_searchentry)
        throw std::runtime_error("No \"searchentry\" object in window.ui");

      m_gears = m_refBuilder->get_widget<Gtk::MenuButton>("gears");
      if (!m_gears)
        throw std::runtime_error("No \"gears\" object in window.ui");

      m_sidebar = m_refBuilder->get_widget<Gtk::Revealer>("sidebar");
      if (!m_sidebar)
        throw std::runtime_error("No \"sidebar\" object in window.ui");

      m_words = m_refBuilder->get_widget<Gtk::ListBox>("words");
      if (!m_words)
        throw std::runtime_error("No \"words\" object in window.ui");

      // Bind settings.
      m_settings = Gio::Settings::create("org.gtkmm.exampleapp");
      m_settings->bind("transition", m_stack->property_transition_type());
      m_settings->bind("show-words", m_sidebar->property_reveal_child());

      // Bind properties.
      m_prop_binding = Glib::Binding::bind_property(m_search->property_active(),
        m_searchbar->property_search_mode_enabled(), Glib::Binding::Flags::BIDIRECTIONAL);

      // Connect signal handlers.
      m_searchentry->signal_search_changed().connect(
        sigc::mem_fun(*this, &ExampleAppWindow::on_search_text_changed));
      m_stack->property_visible_child().signal_changed().connect(
        sigc::mem_fun(*this, &ExampleAppWindow::on_visible_child_changed));
      m_sidebar->property_reveal_child().signal_changed().connect(
        sigc::mem_fun(*this, &ExampleAppWindow::on_reveal_child_changed));

      // Connect the menu to the MenuButton m_gears, and bind the show-words setting
      // to the win.show-words action and the "Words" menu item.
      // (The connection between action and menu item is specified in gears_menu.ui.)
      auto menu_builder = Gtk::Builder::create_from_resource("/org/gtkmm/exampleapp/gears_menu.ui");
      auto menu = menu_builder->get_object<Gio::MenuModel>("menu");
      if (!menu)
        throw std::runtime_error("No \"menu\" object in gears_menu.ui");

      m_gears->set_menu_model(menu);
      add_action(m_settings->create_action("show-words"));
    }

    //static
    ExampleAppWindow* ExampleAppWindow::create()
    {
      // Load the Builder file and instantiate its widgets.
      auto refBuilder = Gtk::Builder::create_from_resource("/org/gtkmm/exampleapp/window.ui");

      auto window = Gtk::Builder::get_widget_derived<ExampleAppWindow>(refBuilder, "app_window");
      if (!window)
        throw std::runtime_error("No \"app_window\" object in window.ui");

      return window;
    }

    void ExampleAppWindow::open_file_view(const Glib::RefPtr<Gio::File>& file)
    {
      const Glib::ustring basename = file->get_basename();

      auto scrolled = Gtk::make_managed<Gtk::ScrolledWindow>();
      scrolled->set_expand(true);
      auto view = Gtk::make_managed<Gtk::TextView>();
      view->set_editable(false);
      view->set_cursor_visible(false);
      scrolled->set_child(*view);
      m_stack->add(*scrolled, basename, basename);

      auto buffer = view->get_buffer();
      try
      {
        char* contents = nullptr;
        gsize length = 0;

        file->load_contents(contents, length);
        buffer->set_text(contents, contents+length);
        g_free(contents);
      }
      catch (const Glib::Error& ex)
      {
        std::cout << "ExampleAppWindow::open_file_view(\"" << file->get_parse_name()
          << "\"):\n  " << ex.what() << std::endl;
        return;
      }

      auto tag = buffer->create_tag();
      m_settings->bind("font", tag->property_font());
      buffer->apply_tag(tag, buffer->begin(), buffer->end());

      m_search->set_sensitive(true);
      update_words();
    }

    void ExampleAppWindow::on_search_text_changed()
    {
      const auto text = m_searchentry->get_text();
      if (text.empty())
        return;

      auto tab = dynamic_cast<Gtk::ScrolledWindow*>(m_stack->get_visible_child());
      if (!tab)
      {
        std::cout << "ExampleAppWindow::on_search_text_changed(): No visible child." << std::endl;
        return;
      }

      auto view = dynamic_cast<Gtk::TextView*>(tab->get_child());
      if (!view)
      {
        std::cout << "ExampleAppWindow::on_search_text_changed(): No visible text view." << std::endl;
        return;
      }

      // Very simple-minded search implementation.
      auto buffer = view->get_buffer();
      Gtk::TextIter match_start;
      Gtk::TextIter match_end;
      if (buffer->begin().forward_search(text, Gtk::TextSearchFlags::CASE_INSENSITIVE,
          match_start, match_end))
      {
        buffer->select_range(match_start, match_end);
        view->scroll_to(match_start);
      }
    }

    void ExampleAppWindow::on_visible_child_changed()
    {
      m_searchbar->set_search_mode(false);
      update_words();
    }

    void ExampleAppWindow::on_find_word(const Gtk::Button* button)
    {
      m_searchentry->set_text(button->get_label());
    }

    void ExampleAppWindow::on_reveal_child_changed()
    {
      update_words();
    }

    void ExampleAppWindow::update_words()
    {
      auto tab = dynamic_cast<Gtk::ScrolledWindow*>(m_stack->get_visible_child());
      if (!tab)
        return;

      auto view = dynamic_cast<Gtk::TextView*>(tab->get_child());
      if (!view)
      {
        std::cout << "ExampleAppWindow::update_words(): No visible text view." << std::endl;
        return;
      }
      auto buffer = view->get_buffer();

      // Find all words in the text buffer.
      std::set<Glib::ustring> words;
      auto start = buffer->begin();
      Gtk::TextIter end;
      while (start)
      {
        while (start && !start.starts_word())
          ++start;

        if (!start)
          break;

        end = start;
        end.forward_word_end();
        if (start == end)
          break;

        auto word = buffer->get_text(start, end, false);
        words.insert(word.lowercase());
        start = end;
      }

      // Remove old children from the ListBox.
      while (auto child = m_words->get_first_child())
        m_words->remove(*child);

      // Add new child buttons, one per unique word.
      for (const auto& word : words)
      {
        auto row = Gtk::make_managed<Gtk::Button>(word);
        row->signal_clicked().connect(sigc::bind(sigc::mem_fun(*this,
          &ExampleAppWindow::on_find_word), row));
        m_words->append(*row);
      }
    }

File: `main.cc` (For use with gtkmm 4)

    #include "../step5/main.cc"
    // Equal to the corresponding file in step5

File: `gears_menu.ui` (For use with gtkmm 4)

    <?xml version="1.0" encoding="UTF-8"?>
    <interface>
      <menu id="menu">
        <section>
          <item>
            <attribute name="label" translatable="yes">_Words</attribute>
            <attribute name="action">win.show-words</attribute>
          </item>
          <item>
            <attribute name="label" translatable="yes">_Preferences</attribute>
            <attribute name="action">app.preferences</attribute>
          </item>
        </section>
        <section>
          <item>
            <attribute name="label" translatable="yes">_Quit</attribute>
            <attribute name="action">app.quit</attribute>
          </item>
        </section>
      </menu>
    </interface>

File: `window.ui` (For use with gtkmm 4)

    <?xml version="1.0" encoding="UTF-8"?>
    <interface>
      <object class="GtkApplicationWindow" id="app_window">
        <property name="title" translatable="yes">Example Application</property>
        <property name="default-width">600</property>
        <property name="default-height">400</property>
        <property name="hide-on-close">True</property>
        <child type="titlebar">
          <object class="GtkHeaderBar" id="header">
            <child type="title">
              <object class="GtkStackSwitcher" id="tabs">
                <property name="stack">stack</property>
              </object>
            </child>
            <child type="end">
              <object class="GtkToggleButton" id="search">
                <property name="sensitive">False</property>
                <property name="icon-name">edit-find-symbolic</property>
              </object>
            </child>
            <child type="end">
              <object class="GtkMenuButton" id="gears">
                <property name="direction">none</property>
              </object>
            </child>
          </object>
        </child>
        <child>
          <object class="GtkBox" id="content_box">
            <property name="orientation">vertical</property>
            <child>
              <object class="GtkSearchBar" id="searchbar">
                <child>
                  <object class="GtkSearchEntry" id="searchentry">
                  </object>
                </child>
              </object>
            </child>
            <child>
              <object class="GtkBox" id="hbox">
                <child>
                  <object class="GtkRevealer" id="sidebar">
                    <property name="transition-type">slide-right</property>
                    <child>
                     <object class="GtkScrolledWindow" id="sidebar-sw">
                       <property name="hscrollbar-policy">never</property>
                       <child>
                         <object class="GtkListBox" id="words">
                           <property name="selection-mode">none</property>
                         </object>
                       </child>
                     </object>
                    </child>
                  </object>
                </child>
                <child>
                  <object class="GtkStack" id="stack">
                    <property name="transition-duration">500</property>
                  </object>
                </child>
              </object>
            </child>
          </object>
        </child>
      </object>
    </interface>

File: `org.gtkmm.exampleapp.gschema.xml` (For use with gtkmm 4)

    <?xml version="1.0" encoding="UTF-8"?>
    <schemalist>
      <schema path="/org/gtkmm/exampleapp/" id="org.gtkmm.exampleapp">
        <key name="font" type="s">
          <default>'Monospace 12'</default>
          <summary>Font</summary>
          <description>The font to be used for content.</description>
        </key>
        <key name="transition" type="s">
          <choices>
            <choice value='none'/>
            <choice value='crossfade'/>
            <choice value='slide-left-right'/>
          </choices>
          <default>'none'</default>
          <summary>Transition</summary>
          <description>The transition to use when switching tabs.</description>
        </key>
        <key name="show-words" type="b">
          <default>false</default>
          <summary>Show words</summary>
          <description>Whether to show a word list in the sidebar.</description>
        </key>
      </schema>
    </schemalist>

### Properties

Widgets and other objects have many useful properties. Here we show some ways to use them in new and flexible ways, by wrapping them in actions with `Gio::PropertyAction` or by binding them with `Glib::Binding`.

To set this up, we add two labels to the header bar in our `window.ui` file, named `lines_label` and `lines`, and get pointers to them in the application window's constructor, as we've seen a couple of times by now. We add a new "Lines" menu item to the gears menu, which triggers the `show-lines` action.

To make this menu item do something, we create a property action for the `visible` property of the `lines` label, and add it to the actions of the window. The effect of this is that the visibility of the label gets toggled every time the action is activated. Since we want both labels to appear and disappear together, we bind the `visible` property of the `lines_label` widget to the same property of the `lines` widget. In `ExampleAppWindow`'s constructor:

    add_action(Gio::PropertyAction::create("show-lines", m_lines->property_visible()));
    m_binding_lines_visible = Glib::Binding::bind_property(m_lines->property_visible(),
      m_lines_label->property_visible());

We also need a function that counts the lines of the currently active tab, and updates the `lines` label. See the full source if you are interested in the details.

This brings our example application to this appearance:

#### Properties

Source Code

File: `exampleapplication.h` (For use with gtkmm 4)

    #include "../step4/exampleapplication.h"
    // Equal to the corresponding file in step4

File: `exampleappprefs.h` (For use with gtkmm 4)

    #include "../step5/exampleappprefs.h"
    // Equal to the corresponding file in step5

File: `exampleappwindow.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLEAPPWINDOW_H_
    #define GTKMM_EXAMPLEAPPWINDOW_H_

    #include <gtkmm.h>

    class ExampleAppWindow : public Gtk::ApplicationWindow
    {
    public:
      ExampleAppWindow(BaseObjectType* cobject,
        const Glib::RefPtr<Gtk::Builder>& refBuilder);

      static ExampleAppWindow* create();

      void open_file_view(const Glib::RefPtr<Gio::File>& file);

    protected:
      // Signal handlers
      void on_search_text_changed();
      void on_visible_child_changed();
      void on_find_word(const Gtk::Button* button);
      void on_reveal_child_changed();

      void update_words();
      void update_lines();

      Glib::RefPtr<Gtk::Builder> m_refBuilder;
      Glib::RefPtr<Gio::Settings> m_settings;
      Gtk::Stack* m_stack {nullptr};
      Gtk::ToggleButton* m_search {nullptr};
      Gtk::SearchBar* m_searchbar {nullptr};
      Gtk::SearchEntry* m_searchentry {nullptr};
      Gtk::MenuButton* m_gears {nullptr};
      Gtk::Revealer* m_sidebar {nullptr};
      Gtk::ListBox* m_words {nullptr};
      Gtk::Label* m_lines {nullptr};
      Gtk::Label* m_lines_label {nullptr};
      Glib::RefPtr<Glib::Binding> m_binding_search_enabled;
      Glib::RefPtr<Glib::Binding> m_binding_lines_visible;
    };

    #endif /* GTKMM_EXAMPLEAPPWINDOW_H */

File: `exampleapplication.cc` (For use with gtkmm 4)

    #include "../step5/exampleapplication.cc"
    // Equal to the corresponding file in step5

File: `exampleappprefs.cc` (For use with gtkmm 4)

    #include "../step5/exampleappprefs.cc"
    // Equal to the corresponding file in step5

File: `exampleappwindow.cc` (For use with gtkmm 4)

    #include "exampleappwindow.h"
    #include <iostream>
    #include <stdexcept>
    #include <set>

    ExampleAppWindow::ExampleAppWindow(BaseObjectType* cobject,
      const Glib::RefPtr<Gtk::Builder>& refBuilder)
    : Gtk::ApplicationWindow(cobject),
      m_refBuilder(refBuilder)
    {
      // Get widgets from the Gtk::Builder file.
      m_stack = m_refBuilder->get_widget<Gtk::Stack>("stack");
      if (!m_stack)
        throw std::runtime_error("No \"stack\" object in window.ui");

      m_search = m_refBuilder->get_widget<Gtk::ToggleButton>("search");
      if (!m_search)
        throw std::runtime_error("No \"search\" object in window.ui");

      m_searchbar = m_refBuilder->get_widget<Gtk::SearchBar>("searchbar");
      if (!m_searchbar)
        throw std::runtime_error("No \"searchbar\" object in window.ui");

      m_searchentry = m_refBuilder->get_widget<Gtk::SearchEntry>("searchentry");
      if (!m_searchentry)
        throw std::runtime_error("No \"searchentry\" object in window.ui");

      m_gears = m_refBuilder->get_widget<Gtk::MenuButton>("gears");
      if (!m_gears)
        throw std::runtime_error("No \"gears\" object in window.ui");

      m_sidebar = m_refBuilder->get_widget<Gtk::Revealer>("sidebar");
      if (!m_sidebar)
        throw std::runtime_error("No \"sidebar\" object in window.ui");

      m_words = m_refBuilder->get_widget<Gtk::ListBox>("words");
      if (!m_words)
        throw std::runtime_error("No \"words\" object in window.ui");

      m_lines = m_refBuilder->get_widget<Gtk::Label>("lines");
      if (!m_lines)
        throw std::runtime_error("No \"lines\" object in window.ui");

      m_lines_label = m_refBuilder->get_widget<Gtk::Label>("lines_label");
      if (!m_lines_label)
        throw std::runtime_error("No \"lines_label\" object in window.ui");

      // Bind settings.
      m_settings = Gio::Settings::create("org.gtkmm.exampleapp");
      m_settings->bind("transition", m_stack->property_transition_type());
      m_settings->bind("show-words", m_sidebar->property_reveal_child());

      // Bind properties of the search button to the search bar.
      m_binding_search_enabled = Glib::Binding::bind_property(m_search->property_active(),
        m_searchbar->property_search_mode_enabled(), Glib::Binding::Flags::BIDIRECTIONAL);

      // Connect signal handlers.
      m_searchentry->signal_search_changed().connect(
        sigc::mem_fun(*this, &ExampleAppWindow::on_search_text_changed));
      m_stack->property_visible_child().signal_changed().connect(
        sigc::mem_fun(*this, &ExampleAppWindow::on_visible_child_changed));
      m_sidebar->property_reveal_child().signal_changed().connect(
        sigc::mem_fun(*this, &ExampleAppWindow::on_reveal_child_changed));

      // Connect the menu to the MenuButton m_gears, and bind the show-words setting
      // to the win.show-words action and the "Words" menu item.
      // (The connection between action and menu item is specified in gears_menu.ui.)
      auto menu_builder = Gtk::Builder::create_from_resource("/org/gtkmm/exampleapp/gears_menu.ui");
      auto menu = menu_builder->get_object<Gio::MenuModel>("menu");
      if (!menu)
        throw std::runtime_error("No \"menu\" object in gears_menu.ui");

      m_gears->set_menu_model(menu);
      add_action(m_settings->create_action("show-words"));

      // Bind the "visible" property of m_lines to the win.show-lines action, to
      // the "Lines" menu item and to the "visible" property of m_lines_label.
      add_action(Gio::PropertyAction::create("show-lines", m_lines->property_visible()));
      m_binding_lines_visible = Glib::Binding::bind_property(m_lines->property_visible(),
        m_lines_label->property_visible());
    }

    //static
    ExampleAppWindow* ExampleAppWindow::create()
    {
      // Load the Builder file and instantiate its widgets.
      auto refBuilder = Gtk::Builder::create_from_resource("/org/gtkmm/exampleapp/window.ui");

      auto window = Gtk::Builder::get_widget_derived<ExampleAppWindow>(refBuilder, "app_window");
      if (!window)
        throw std::runtime_error("No \"app_window\" object in window.ui");

      return window;
    }

    void ExampleAppWindow::open_file_view(const Glib::RefPtr<Gio::File>& file)
    {
      const Glib::ustring basename = file->get_basename();

      auto scrolled = Gtk::make_managed<Gtk::ScrolledWindow>();
      scrolled->set_expand(true);
      auto view = Gtk::make_managed<Gtk::TextView>();
      view->set_editable(false);
      view->set_cursor_visible(false);
      scrolled->set_child(*view);
      m_stack->add(*scrolled, basename, basename);

      auto buffer = view->get_buffer();
      try
      {
        char* contents = nullptr;
        gsize length = 0;

        file->load_contents(contents, length);
        buffer->set_text(contents, contents+length);
        g_free(contents);
      }
      catch (const Glib::Error& ex)
      {
        std::cout << "ExampleAppWindow::open_file_view(\"" << file->get_parse_name()
          << "\"):\n  " << ex.what() << std::endl;
        return;
      }

      auto tag = buffer->create_tag();
      m_settings->bind("font", tag->property_font());
      buffer->apply_tag(tag, buffer->begin(), buffer->end());

      m_search->set_sensitive(true);
      update_words();
      update_lines();
    }

    void ExampleAppWindow::on_search_text_changed()
    {
      const auto text = m_searchentry->get_text();
      if (text.empty())
        return;

      auto tab = dynamic_cast<Gtk::ScrolledWindow*>(m_stack->get_visible_child());
      if (!tab)
      {
        std::cout << "ExampleAppWindow::on_search_text_changed(): No visible child." << std::endl;
        return;
      }

      auto view = dynamic_cast<Gtk::TextView*>(tab->get_child());
      if (!view)
      {
        std::cout << "ExampleAppWindow::on_search_text_changed(): No visible text view." << std::endl;
        return;
      }

      // Very simple-minded search implementation.
      auto buffer = view->get_buffer();
      Gtk::TextIter match_start;
      Gtk::TextIter match_end;
      if (buffer->begin().forward_search(text, Gtk::TextSearchFlags::CASE_INSENSITIVE,
          match_start, match_end))
      {
        buffer->select_range(match_start, match_end);
        view->scroll_to(match_start);
      }
    }

    void ExampleAppWindow::on_visible_child_changed()
    {
      m_searchbar->set_search_mode(false);
      update_words();
      update_lines();
    }

    void ExampleAppWindow::on_find_word(const Gtk::Button* button)
    {
      m_searchentry->set_text(button->get_label());
    }

    void ExampleAppWindow::on_reveal_child_changed()
    {
      update_words();
    }

    void ExampleAppWindow::update_words()
    {
      auto tab = dynamic_cast<Gtk::ScrolledWindow*>(m_stack->get_visible_child());
      if (!tab)
        return;

      auto view = dynamic_cast<Gtk::TextView*>(tab->get_child());
      if (!view)
      {
        std::cout << "ExampleAppWindow::update_words(): No visible text view." << std::endl;
        return;
      }
      auto buffer = view->get_buffer();

      // Find all words in the text buffer.
      std::set<Glib::ustring> words;
      auto start = buffer->begin();
      Gtk::TextIter end;
      while (start)
      {
        while (start && !start.starts_word())
          ++start;

        if (!start)
          break;

        end = start;
        end.forward_word_end();
        if (start == end)
          break;

        auto word = buffer->get_text(start, end, false);
        words.insert(word.lowercase());
        start = end;
      }

      // Remove old children from the ListBox.
      while (auto child = m_words->get_first_child())
        m_words->remove(*child);

      // Add new child buttons, one per unique word.
      for (const auto& word : words)
      {
        auto row = Gtk::make_managed<Gtk::Button>(word);
        row->signal_clicked().connect(sigc::bind(sigc::mem_fun(*this,
          &ExampleAppWindow::on_find_word), row));
        m_words->append(*row);
      }
    }

    void ExampleAppWindow::update_lines()
    {
      auto tab = dynamic_cast<Gtk::ScrolledWindow*>(m_stack->get_visible_child());
      if (!tab)
        return;

      auto view = dynamic_cast<Gtk::TextView*>(tab->get_child());
      if (!view)
      {
        std::cout << "ExampleAppWindow::update_lines(): No visible text view." << std::endl;
        return;
      }
      auto buffer = view->get_buffer();

      int count = 0;
      auto iter = buffer->begin();
      while (iter)
      {
        ++count;
        if (!iter.forward_line())
          break;
      }
      m_lines->set_text(Glib::ustring::format(count));
    }

File: `main.cc` (For use with gtkmm 4)

    #include "../step5/main.cc"
    // Equal to the corresponding file in step5

File: `gears_menu.ui` (For use with gtkmm 4)

    <?xml version="1.0" encoding="UTF-8"?>
    <interface>
      <menu id="menu">
        <section>
          <item>
            <attribute name="label" translatable="yes">_Words</attribute>
            <attribute name="action">win.show-words</attribute>
          </item>
          <item>
            <attribute name="label" translatable="yes">_Lines</attribute>
            <attribute name="action">win.show-lines</attribute>
          </item>
          <item>
            <attribute name="label" translatable="yes">_Preferences</attribute>
            <attribute name="action">app.preferences</attribute>
          </item>
        </section>
        <section>
          <item>
            <attribute name="label" translatable="yes">_Quit</attribute>
            <attribute name="action">app.quit</attribute>
          </item>
        </section>
      </menu>
    </interface>

File: `window.ui` (For use with gtkmm 4)

    <?xml version="1.0" encoding="UTF-8"?>
    <interface>
      <object class="GtkApplicationWindow" id="app_window">
        <property name="title" translatable="yes">Example Application</property>
        <property name="default-width">600</property>
        <property name="default-height">400</property>
        <property name="hide-on-close">True</property>
        <child type="titlebar">
          <object class="GtkHeaderBar" id="header">
            <child>
              <object class="GtkLabel" id="lines_label">
                <property name="visible">False</property>
                <property name="label" translatable="yes">Lines:</property>
              </object>
            </child>
            <child>
              <object class="GtkLabel" id="lines">
                <property name="visible">False</property>
              </object>
            </child>
            <child type="title">
              <object class="GtkStackSwitcher" id="tabs">
                <property name="stack">stack</property>
              </object>
            </child>
            <child type="end">
              <object class="GtkToggleButton" id="search">
                <property name="sensitive">False</property>
                <property name="icon-name">edit-find-symbolic</property>
              </object>
            </child>
            <child type="end">
              <object class="GtkMenuButton" id="gears">
                <property name="direction">none</property>
              </object>
            </child>
          </object>
        </child>
        <child>
          <object class="GtkBox" id="content_box">
            <property name="orientation">vertical</property>
            <child>
              <object class="GtkSearchBar" id="searchbar">
                <child>
                  <object class="GtkSearchEntry" id="searchentry">
                  </object>
                </child>
              </object>
            </child>
            <child>
              <object class="GtkBox" id="hbox">
                <child>
                  <object class="GtkRevealer" id="sidebar">
                    <property name="transition-type">slide-right</property>
                    <child>
                      <object class="GtkScrolledWindow" id="sidebar-sw">
                        <property name="hscrollbar-policy">never</property>
                        <child>
                          <object class="GtkListBox" id="words">
                            <property name="selection-mode">none</property>
                          </object>
                        </child>
                      </object>
                    </child>
                  </object>
                </child>
                <child>
                  <object class="GtkStack" id="stack">
                    <property name="transition-duration">500</property>
                  </object>
                </child>
              </object>
            </child>
          </object>
        </child>
      </object>
    </interface>

### Header bar

Our application already uses a `Gtk::HeaderBar` instead of a 'normal' window titlebar. The header bar is a direct child of the window, and its type is `titlebar`. This is set in the `window.ui` file.

Here we'll just make two small changes to the header bar. The `decoration-layout` property is set in the `window.ui` file, to show only the close button, and hide the minimize and maximize buttons. We also include an icon in the resource file, and set up this icon as the window icon. In `ExampleAppWindow`'s constructor:

    Gtk::IconTheme::get_for_display(get_display())->add_resource_path("/org/gtkmm/exampleapp");
    set_icon_name("exampleapp");

Here is how the application now looks:

#### Header bar

The `window.ui` file sets a header bar title, but this title is not shown. That's because the stack switcher is a child of type `title`. The stack switcher becomes a custom title that hides the title label.

Source Code

File: `exampleapplication.h` (For use with gtkmm 4)

    #include "../step4/exampleapplication.h"
    // Equal to the corresponding file in step4

File: `exampleappprefs.h` (For use with gtkmm 4)

    #include "../step5/exampleappprefs.h"
    // Equal to the corresponding file in step5

File: `exampleappwindow.h` (For use with gtkmm 4)

    #include "../step8/exampleappwindow.h"
    // Equal to the corresponding file in step8

File: `exampleapplication.cc` (For use with gtkmm 4)

    #include "../step5/exampleapplication.cc"
    // Equal to the corresponding file in step5

File: `exampleappprefs.cc` (For use with gtkmm 4)

    #include "../step5/exampleappprefs.cc"
    // Equal to the corresponding file in step5

File: `exampleappwindow.cc` (For use with gtkmm 4)

    #include "exampleappwindow.h"
    #include <iostream>
    #include <stdexcept>
    #include <set>

    ExampleAppWindow::ExampleAppWindow(BaseObjectType* cobject,
      const Glib::RefPtr<Gtk::Builder>& refBuilder)
    : Gtk::ApplicationWindow(cobject),
      m_refBuilder(refBuilder)
    {
      // Get widgets from the Gtk::Builder file.
      m_stack = m_refBuilder->get_widget<Gtk::Stack>("stack");
      if (!m_stack)
        throw std::runtime_error("No \"stack\" object in window.ui");

      m_search = m_refBuilder->get_widget<Gtk::ToggleButton>("search");
      if (!m_search)
        throw std::runtime_error("No \"search\" object in window.ui");

      m_searchbar = m_refBuilder->get_widget<Gtk::SearchBar>("searchbar");
      if (!m_searchbar)
        throw std::runtime_error("No \"searchbar\" object in window.ui");

      m_searchentry = m_refBuilder->get_widget<Gtk::SearchEntry>("searchentry");
      if (!m_searchentry)
        throw std::runtime_error("No \"searchentry\" object in window.ui");

      m_gears = m_refBuilder->get_widget<Gtk::MenuButton>("gears");
      if (!m_gears)
        throw std::runtime_error("No \"gears\" object in window.ui");

      m_sidebar = m_refBuilder->get_widget<Gtk::Revealer>("sidebar");
      if (!m_sidebar)
        throw std::runtime_error("No \"sidebar\" object in window.ui");

      m_words = m_refBuilder->get_widget<Gtk::ListBox>("words");
      if (!m_words)
        throw std::runtime_error("No \"words\" object in window.ui");

      m_lines = m_refBuilder->get_widget<Gtk::Label>("lines");
      if (!m_lines)
        throw std::runtime_error("No \"lines\" object in window.ui");

      m_lines_label = m_refBuilder->get_widget<Gtk::Label>("lines_label");
      if (!m_lines_label)
        throw std::runtime_error("No \"lines_label\" object in window.ui");

      // Bind settings.
      m_settings = Gio::Settings::create("org.gtkmm.exampleapp");
      m_settings->bind("transition", m_stack->property_transition_type());
      m_settings->bind("show-words", m_sidebar->property_reveal_child());

      // Bind properties of the search button to the search bar.
      m_binding_search_enabled = Glib::Binding::bind_property(m_search->property_active(),
        m_searchbar->property_search_mode_enabled(), Glib::Binding::Flags::BIDIRECTIONAL);

      // Connect signal handlers.
      m_searchentry->signal_search_changed().connect(
        sigc::mem_fun(*this, &ExampleAppWindow::on_search_text_changed));
      m_stack->property_visible_child().signal_changed().connect(
        sigc::mem_fun(*this, &ExampleAppWindow::on_visible_child_changed));
      m_sidebar->property_reveal_child().signal_changed().connect(
        sigc::mem_fun(*this, &ExampleAppWindow::on_reveal_child_changed));

      // Connect the menu to the MenuButton m_gears, and bind the show-words setting
      // to the win.show-words action and the "Words" menu item.
      // (The connection between action and menu item is specified in gears_menu.ui.)
      auto menu_builder = Gtk::Builder::create_from_resource("/org/gtkmm/exampleapp/gears_menu.ui");
      auto menu = menu_builder->get_object<Gio::MenuModel>("menu");
      if (!menu)
        throw std::runtime_error("No \"menu\" object in gears_menu.ui");

      m_gears->set_menu_model(menu);
      add_action(m_settings->create_action("show-words"));

      // Bind the "visible" property of m_lines to the win.show-lines action, to
      // the "Lines" menu item and to the "visible" property of m_lines_label.
      add_action(Gio::PropertyAction::create("show-lines", m_lines->property_visible()));
      m_binding_lines_visible = Glib::Binding::bind_property(m_lines->property_visible(),
        m_lines_label->property_visible());

      // Set the window icon.
      Gtk::IconTheme::get_for_display(get_display())->add_resource_path("/org/gtkmm/exampleapp");
      set_icon_name("exampleapp");
    }

    //static
    ExampleAppWindow* ExampleAppWindow::create()
    {
      // Load the Builder file and instantiate its widgets.
      auto refBuilder = Gtk::Builder::create_from_resource("/org/gtkmm/exampleapp/window.ui");

      auto window = Gtk::Builder::get_widget_derived<ExampleAppWindow>(refBuilder, "app_window");
      if (!window)
        throw std::runtime_error("No \"app_window\" object in window.ui");

      return window;
    }

    void ExampleAppWindow::open_file_view(const Glib::RefPtr<Gio::File>& file)
    {
      const Glib::ustring basename = file->get_basename();

      auto scrolled = Gtk::make_managed<Gtk::ScrolledWindow>();
      scrolled->set_expand(true);
      auto view = Gtk::make_managed<Gtk::TextView>();
      view->set_editable(false);
      view->set_cursor_visible(false);
      scrolled->set_child(*view);
      m_stack->add(*scrolled, basename, basename);

      auto buffer = view->get_buffer();
      try
      {
        char* contents = nullptr;
        gsize length = 0;

        file->load_contents(contents, length);
        buffer->set_text(contents, contents+length);
        g_free(contents);
      }
      catch (const Glib::Error& ex)
      {
        std::cout << "ExampleAppWindow::open_file_view(\"" << file->get_parse_name()
          << "\"):\n  " << ex.what() << std::endl;
        return;
      }

      auto tag = buffer->create_tag();
      m_settings->bind("font", tag->property_font());
      buffer->apply_tag(tag, buffer->begin(), buffer->end());

      m_search->set_sensitive(true);
      update_words();
      update_lines();
    }

    void ExampleAppWindow::on_search_text_changed()
    {
      const auto text = m_searchentry->get_text();
      if (text.empty())
        return;

      auto tab = dynamic_cast<Gtk::ScrolledWindow*>(m_stack->get_visible_child());
      if (!tab)
      {
        std::cout << "ExampleAppWindow::on_search_text_changed(): No visible child." << std::endl;
        return;
      }

      auto view = dynamic_cast<Gtk::TextView*>(tab->get_child());
      if (!view)
      {
        std::cout << "ExampleAppWindow::on_search_text_changed(): No visible text view." << std::endl;
        return;
      }

      // Very simple-minded search implementation.
      auto buffer = view->get_buffer();
      Gtk::TextIter match_start;
      Gtk::TextIter match_end;
      if (buffer->begin().forward_search(text, Gtk::TextSearchFlags::CASE_INSENSITIVE,
          match_start, match_end))
      {
        buffer->select_range(match_start, match_end);
        view->scroll_to(match_start);
      }
    }

    void ExampleAppWindow::on_visible_child_changed()
    {
      m_searchbar->set_search_mode(false);
      update_words();
      update_lines();
    }

    void ExampleAppWindow::on_find_word(const Gtk::Button* button)
    {
      m_searchentry->set_text(button->get_label());
    }

    void ExampleAppWindow::on_reveal_child_changed()
    {
      update_words();
    }

    void ExampleAppWindow::update_words()
    {
      auto tab = dynamic_cast<Gtk::ScrolledWindow*>(m_stack->get_visible_child());
      if (!tab)
        return;

      auto view = dynamic_cast<Gtk::TextView*>(tab->get_child());
      if (!view)
      {
        std::cout << "ExampleAppWindow::update_words(): No visible text view." << std::endl;
        return;
      }
      auto buffer = view->get_buffer();

      // Find all words in the text buffer.
      std::set<Glib::ustring> words;
      auto start = buffer->begin();
      Gtk::TextIter end;
      while (start)
      {
        while (start && !start.starts_word())
          ++start;

        if (!start)
          break;

        end = start;
        end.forward_word_end();
        if (start == end)
          break;

        auto word = buffer->get_text(start, end, false);
        words.insert(word.lowercase());
        start = end;
      }

      // Remove old children from the ListBox.
      while (auto child = m_words->get_first_child())
        m_words->remove(*child);

      // Add new child buttons, one per unique word.
      for (const auto& word : words)
      {
        auto row = Gtk::make_managed<Gtk::Button>(word);
        row->signal_clicked().connect(sigc::bind(sigc::mem_fun(*this,
          &ExampleAppWindow::on_find_word), row));
        m_words->append(*row);
      }
    }

    void ExampleAppWindow::update_lines()
    {
      auto tab = dynamic_cast<Gtk::ScrolledWindow*>(m_stack->get_visible_child());
      if (!tab)
        return;

      auto view = dynamic_cast<Gtk::TextView*>(tab->get_child());
      if (!view)
      {
        std::cout << "ExampleAppWindow::update_lines(): No visible text view." << std::endl;
        return;
      }
      auto buffer = view->get_buffer();

      int count = 0;
      auto iter = buffer->begin();
      while (iter)
      {
        ++count;
        if (!iter.forward_line())
          break;
      }
      m_lines->set_text(Glib::ustring::format(count));
    }

File: `main.cc` (For use with gtkmm 4)

    #include "../step5/main.cc"
    // Equal to the corresponding file in step5

File: `exampleapp.gresource.xml` (For use with gtkmm 4)

    <?xml version="1.0" encoding="UTF-8"?>
    <gresources>
      <gresource prefix="/org/gtkmm/exampleapp">
        <file preprocess="xml-stripblanks">window.ui</file>
        <file preprocess="xml-stripblanks">gears_menu.ui</file>
        <file preprocess="xml-stripblanks">prefs.ui</file>
        <file>exampleapp.png</file>
      </gresource>
    </gresources>

File: `window.ui` (For use with gtkmm 4)

    <?xml version="1.0" encoding="UTF-8"?>
    <interface>
      <object class="GtkApplicationWindow" id="app_window">
        <property name="title" translatable="yes">Example Application</property>
        <property name="default-width">600</property>
        <property name="default-height">400</property>
        <property name="hide-on-close">True</property>
        <child type="titlebar">
          <object class="GtkHeaderBar" id="header">
            <property name="decoration-layout">icon:close</property>
            <child>
              <object class="GtkLabel" id="lines_label">
                <property name="visible">False</property>
                <property name="label" translatable="yes">Lines:</property>
              </object>
            </child>
            <child>
              <object class="GtkLabel" id="lines">
                <property name="visible">False</property>
              </object>
            </child>
            <child type="title">
              <object class="GtkStackSwitcher" id="tabs">
                <property name="stack">stack</property>
              </object>
            </child>
            <child type="end">
              <object class="GtkToggleButton" id="search">
                <property name="sensitive">False</property>
                <property name="icon-name">edit-find-symbolic</property>
              </object>
            </child>
            <child type="end">
              <object class="GtkMenuButton" id="gears">
                <property name="direction">none</property>
              </object>
            </child>
          </object>
        </child>
        <child>
          <object class="GtkBox" id="content_box">
            <property name="orientation">vertical</property>
            <child>
              <object class="GtkSearchBar" id="searchbar">
                <child>
                  <object class="GtkSearchEntry" id="searchentry">
                  </object>
                </child>
              </object>
            </child>
            <child>
              <object class="GtkBox" id="hbox">
                <child>
                  <object class="GtkRevealer" id="sidebar">
                    <property name="transition-type">slide-right</property>
                    <child>
                      <object class="GtkScrolledWindow" id="sidebar-sw">
                        <property name="hscrollbar-policy">never</property>
                        <child>
                          <object class="GtkListBox" id="words">
                            <property name="selection-mode">none</property>
                          </object>
                        </child>
                      </object>
                    </child>
                  </object>
                </child>
                <child>
                  <object class="GtkStack" id="stack">
                    <property name="transition-duration">500</property>
                  </object>
                </child>
              </object>
            </child>
          </object>
        </child>
      </object>
    </interface>

## Přispívání

Tento dokument, stejně jako mnoho dalšího skvělého softwaru, byl vytvořen zdarma dobrovolníky. Pokud víte o čemkoliv z gtkmm, co není ještě zdokumentováno, pouvažujte prosím o přispění do tohoto dokumentu.

Ideally, we would like you to provide a merge request to the `docs/tutorial/C/index-in.docbook` file. This file is in the `gtkmm-documentation` module in GNOME git.

If you do decide to contribute, please post your contribution as an issue or merge request to GitLab. You can also discuss your ideas on GNOME's Discourse instance, under the Platform/Language bindings category with a `cplusplus` tag. Also, be aware that the entirety of this document is free, and any addition you provide must also be free. That is, people must be able to use any portion of your examples in their programs, and copies of this document (including your contribution) may be distributed freely.

## Chytrý ukazatel RefPtr

`Glib::RefPtr` is a smartpointer. Specifically, it is a reference-counting smartpointer. You might be familiar with `std::unique_ptr<>` and `std::shared_ptr<>`, which are also smartpointers. In gtkmm-4.0 `Glib::RefPtr<>` is an alias for `std::shared_ptr<>`, which is reference-counting. `Glib::RefPtr<>` was introduced long before there was a reference-counting smartpointer in the C++ Standard Library.

If you make your own `Glib::ObjectBase`-derived classes with `create()` methods that return a `Glib::RefPtr`, you must use `Glib::make_refptr_for_instance()` in your `create()` methods. This function creates a `std::shared_ptr` with a special deleter, which handles the reference-count for the wrapped C object.

Reference

Chytré ukazatele fungují hodně podobně jako normální ukazatele.Zde je pár příkladů.

### Kopírování

`RefPtr` můžete kopírovat stejně jako normální ukazatele. Ale na rozdíl od nich se nemusíte starat o smazání podkladové instance.

    auto refPixbuf = Gdk::Pixbuf::create_from_file(filename);
    auto refPixbuf2 = refPixbuf;

To samozřejmě znamená, že můžete uchovávat `RefPtr` ve standardních kontejnerech, jako je `std::vector` nebo `std::list`.

    std::list<Glib::RefPtr<Gdk::Pixbuf>> listPixbufs;
    auto refPixbuf = Gdk::Pixbuf::create_from_file(filename);
    listPixbufs.push_back(refPixbuf);

### Snižování referencí

Počitadlo referencí chytrého ukazatele můžete snížit (dereference) pomocí operátoru ->, který zavolá metodu podkladové instance, jako u normálního ukazatele.

    auto refPixbuf = Gdk::Pixbuf::create_from_file(filename);
    auto width = refPixbuf->get_width();

You can also use the * operator and the `get()` method to access the underlying instance, but it's usually a bad idea to do so. Unless you are careful, you can end up with a pointer or a reference which is not included in the reference count.

    auto refPixbuf = Gdk::Pixbuf::create_from_file(filename);
    auto& underlying = *refPixbuf; // Possible, but not recommended

### Přetypování

`RefPtr` můžete přetypovat na základní typy, stejně jako normální ukazatele.

    auto refStore = Gtk::TreeStore::create(columns);
    Glib::RefPtr<Gtk::TreeModel> refModel = refStore;

This means that any method which takes a const Glib::RefPtr<BaseType>& argument can also take a const Glib::RefPtr<DerivedType>&. The cast is implicit, just as it would be for a normal pointer.

Můžete také přetypovat na zděděné typy, ale syntax je trochu rozdílná, než s normálním ukazatelem.

    auto refStore = std::dynamic_pointer_cast<Gtk::TreeStore>(refModel);
    auto refStore2 = std::static_pointer_cast<Gtk::TreeStore>(refModel);

### Checking for nullptr

Stejně jako u normálních ukazatelů můžete kontrolovat, jestli `RefPtr` neukazuje na nic.

    auto refModel = m_TreeView.get_model();
    if (refModel)
    {
      auto cols_count = refModel->get_n_columns();
      ...
    }

But unlike normal pointers, `RefPtr`s are automatically initialized to `nullptr` so you don't need to remember to do that yourself.

### Bezkonstantnost

The use of the `const` keyword in C++ is not always clear. You might not realize that const Something* declares a pointer to a const Something. The pointer can be changed, but not the Something that it points to.

Proto `RefPtr` stejné jako Neco* pro parametr metody je const Glib::RefPtr<Neco>& a stejné jako const Neco* je const Glib::RefPtr<const Neco>&.

`const … &` je u obou jen kvůli efektivitě, podobně jako použití `const std::string&` místo `std::string` pro parametr metody, aby se zabránilo zbytečnému kopírování.

## Signály

### Napojení obsluhy signálu

gtkmm widget classes have signal accessor methods, such as `Gtk::Button::signal_clicked()`, which allow you to connect your signal handler. Thanks to the flexibility of libsigc++, the callback library used by gtkmm, the signal handler can be almost any kind of function, but you will probably want to use a class method. Among GTK C coders, these signal handlers are often named callbacks.

Zde je příklad napojení obsluhy signálu na signál:

    #include <gtkmm/button.h>

    void on_button_clicked()
    {
      std::cout << "Hello World" << std::endl;
    }

    class some_class
    {
    public:
      some_class
      {
        button.signal_clicked().connect(sigc::ptr_fun(&on_button_clicked));
      }
    private:
      Gtk::Button button {"Hello World"};
    };

V tomto (nefunkčním) kódu je toho hodně k zamyšlení. Nejdříve pojďme pojmenovat zúčastněné věci:

- Obsluha signálu je `on_button_clicked()`.

- Zaháčkovali jsme ji k objektu `Gtk::Button` nazvanému `button`.

- Když `Button` vyšle svůj signál `clicked`, zavolá se `on_button_clicked()`.

Nyní se pojďme znovu podívat na přípojení:

        ...
        button.signal_clicked().connect(sigc::ptr_fun(&on_button_clicked));
        ...

Všimněte si, že ukazatel na `on_button_clicked()` nepředáváme přímo do metody `connect()` patřící signálu. Místo toho zavoláme `sigc::ptr_fun()` a do `connect()` předáme výsledek.

`sigc::ptr_fun()` generuje `sigc::slot`. Slot je objekt, který vypadá a působí jako funkce. Někdy se můžete setkat i s označením funkční objekt nebo functor. `sigc::ptr_fun()` generuje slot pro samostatnou funkci nebo statickou metodu. `sigc::mem_fun()` generuje slot pro členskou metodu konkrétní instance.

A C++ lambda expression is a functor which can be implicitly converted to a `sigc::slot` in the call to `connect()`. A lambda expression can be used instead of `sigc::ptr_fun()`. It's also possible to use a lambda expression instead of `sigc::mem_fun()`, but then you won't get automatic disconnection of the signal handler when a `sigc::trackable`-derived object goes out of scope.

Zde je trochu rozsáhlejší příklad slotů v činnosti:

    #include <gtkmm/button.h>

    void on_button_clicked()
    {
      std::cout << "Hello World" << std::endl;
    }

    class some_class
    {
    public:
      some_class
      {
        button.signal_clicked().connect(sigc::ptr_fun(&on_button_clicked));
        button.signal_clicked().connect(sigc::mem_fun(*this, &some_class::on_button_clicked));
      }
      void on_button_clicked();
    private:
      Gtk::Button button {"Hello World"};
    };

První volání `connect()` je stejné, jak jsme již viděli minule, nic nového.

The next is more interesting. `sigc::mem_fun()` is called with two arguments. The first argument is `*this`, which is the object that our new slot will be pointing at. The second argument is a pointer to one of its methods. This particular version of `sigc::mem_fun()` creates a slot which will, when "called", call the pointed-to method of the specified object.

Další věcí, která stojí v tomto příkladu za zmínku, je, že voláme `connect()` dvakrát pro ten samý objekt signálu. To je úplně v pořádku – když je na tlačítko kliknuto, jsou zavolány obě obsluhy signálu.

Právě jsme vám řekli, že signál `clicked` tlačítka očekává volání metody bez argumentu. Všechny signály mají obdobné požadavky – nemůžete zaháčkovat funkci se dvěma argumenty na signál, který neočekává žádný (ledaže použijete adaptér, jako je `sigc::bind()`). Proto je důležité znát, jaký typ obsluhy signálu byste měli očekávat, že se k danému signálu napojí.

### Psaní obsluhy signálů

Když chcete zjistit, které typy obsluhy signálu můžete na signál napojit, podívejte se do referenční dokumentace nebo do hlavičkového souboru. Zde je příklad deklarace signálu, která můžete vidět v hlavičkových souborech gtkmm:

    Glib::SignalProxy<bool(Gtk::DirectionType)> signal_focus()

Other than the signal's name (`focus`), the template arguments are important to note here. The first argument, bool, is the type that the signal handler should return; and the type within parentheses, Gtk::DirectionType, is the type of this signal's first, and only, argument. By looking at the reference documentation, you can see the names of the arguments too.

Stejné principy se používají pro signály, které mají více argumentů. Zde je jeden se třemi (pochází z `<gtkmm/textbuffer.h>`):

    Glib::SignalProxy<void(TextBuffer::iterator&, const Glib::ustrin&, int)> signal_insert();

It follows the same form. The first type is void, so that should be our signal handler's return type. The following three types are the argument types, in order. Our signal handler's prototype could look like this:

    void on_insert(TextBuffer::iterator& pos, const Glib::ustring& text, int bytes)

### Odpojení obsluhy signálu

Podívejme se ještě jednou na metodu `connect()` signálu:

    sigc::connection signal<void(int)>::connect(const sigc::slot<void(int)>&);

The returned `sigc::connection` can be used to control the connection. By keeping a connection object you can disconnect its associated signal handler using the `sigc::connection::disconnect()` method.

### Přepisování výchozí obsluhy signálu

Doposud jste se dozvěděli, jak provést nějakou činnost na základě zmáčknutí tlačítka a jak obsluhovat signály. To je samozřejmě dobrý způsob, jak dělat věci, ale není jediný.

Namísto pracného napojení obsluhy signálu na signál můžete jednoduše vytvořit novou třídu, která bude zděděná z widgetu – řekněme tlačítka – a přepsat jeho výchozí obsluhu signálu, jako je Button::on_clicked(). To může být mnohem jednodušší, než se zaháčkovat na obsluhu signálu pro všechno.

Tvorba podtříd není ale vždy nejlepším způsobem, jak dosáhnout kýženého. Je použitelná jen, když widget obsluhuje své vlastní signály. Když chcete, aby signál obsluhovala jiná třída, potřebujete napojit samostatnou obsluhu. Platí to o to víc, když chcete aby stejný signál obsluhovalo několik objektů, nebo chcete, aby jedna obsluha reagovala na stejný signál z více různých objektů.

Třídy gtkmm jsou navržené přímo s ohledem na přepisování. Obsahují virtuální členské metody speciálně zamýšlené za účelem přepsání.

Pojďme se podívat na příklad s přepsáním:

    #include <gtkmm/button.h>

    class OverriddenButton : public Gtk::Button
    {
    protected:
      void on_clicked() override;
    }

    void OverriddenButton::on_clicked()
    {
      std::cout << "Hello World" << std::endl;

      // call the base class's version of the method:
      Gtk::Button::on_clicked();
    }

Zde definujeme novou třídu nazvanou `OverriddenButton`, která je zděděná z `Gtk::Button`. Jedinou věcí, kterou měníme, je metoda `on_clicked()`, která je zavolaná, kdykoliv `Gtk::Button` vyšle signál `clicked`. Tato metoda vypíše „Hello World“ na `stdout` a pak zavolá původní, přepsanou metodu, aby třída `Gtk::Button` mohla udělat to, co by dělala, kdybychom ji nepřepsali.

You don't always need to call the parent's method; there are times when you might not want to. Note that we called the parent method after writing "Hello World", but we could have called it before. In this simple example, it hardly matters much, but there are times when it will. With connected signal handlers, it's not quite so easy to change details like this, and you can do something here which you can't do at all with connected signal handlers: you can call the parent method in the middle of your custom code.

### Navázání dodatečných argumentů

If you use one signal handler to catch the same signal from several widgets, you might like that signal handler to receive some extra information. For instance, you might want to know which button was clicked. You can do this with `sigc::bind()`. Here's some code from the helloworld2 example.

    m_button1.signal_clicked().connect(sigc::bind(sigc::mem_fun(*this, &HelloWorld::on_button_clicked), "button 1"));

This says that we want the signal to send an extra `Glib::ustring` argument to the signal handler, and that the value of that argument should be "button 1". Of course we will need to add that extra argument to the declaration of our signal handler:

    void on_button_clicked(const Glib::ustring& data);

Of course, a normal "clicked" signal handler would have no arguments.

`sigc::bind()` is not commonly used, but you might find it helpful sometimes. If you are familiar with GTK programming then you have probably noticed that this is similar to the extra `gpointer data` arguments which all GTK callbacks have. This is generally overused in GTK to pass information that should be stored as member data in a derived widget, but widget derivation is very difficult in C. We have far less need of this hack in gtkmm.

### Event signals

Event signals are emitted as a result of some user input, for instance a key press or a mouse motion. Usually you don't handle these events directly. Instead, you use a subclass of `Gtk::EventController`, such as `Gtk::EventControllerKey` or `Gtk::GestureClick`. Event controllers can be added to a widget with `Gtk::Widget::add_controller()`.

You might occasionally find it useful to handle events when there's something you can't accomplish with normal signals. `Gtk::Button`, for example, does not send mouse-pointer coordinates with its `clicked` signal, but you could handle `Gtk::GestureClick::signal_pressed()` if you needed this information. `Gtk::EventControllerKey::signal_key_pressed()` is often used to handle key-presses.

Some event controller signals behave slightly differently. The value returned from the signal handler indicates whether it has fully "handled" the event. If the value is `false` then gtkmm will pass the event on to the next signal handler. If the value is `true` then no other signal handlers will need to be called.

Handling an event doesn't affect the Widget's other signals. If you handle `Gtk::GestureClick::signal_pressed()` for `Gtk::Button`, you'll still be able to get the `clicked` signal. They are emitted at (nearly) the same time.

Here's a simple example:

    void on_button_press(int n_press, double x, double y);
    Gtk::Button button("label");
    auto controller = Gtk::GestureClick::create();
    controller->set_propagation_phase(Gtk::PropagationPhase::CAPTURE);
    controller->signal_pressed().connect(sigc::ptr_fun(&on_button_press));
    button.add_controller(controller);

Když je ukazatel myši nad tlačítkem a zmáčknete tlačítko myši, je zavoláno `on_button_press()`.

The call to `set_propagation_phase()` is necessary in this case because the `GtkButton` C class adds an event controller, handling button clicks in the capture phase. `GtkButton` claims the event, meaning that the event is not propagated in the bubble phase, where event controllers handle events by default.

#### Posloupnost obsluhy signálu

By default, signal handlers that return void are called after any previously-connected signal handlers. However, this can be a problem with event signals that can stop event propagation by returning `true`. For instance, the existing signal handlers, or the default signal handler, might return `true` to stop other signal handlers from being called. To specify that your signal handler should be called before the other signal handlers, you can specify `false` for the `after` parameter. This `connect()` parameter is optional, if the signal handler returns void. For instance,

    key_controller->signal_key_pressed().connect(sigc::ptr_fun(&on_mywindow_key_pressed), false);

The event is propagated between widgets in 3 phases.

1. Capture phase - runs from the toplevel down to the event widget.

2. Target phase - runs only on the event widget.

3. Bubble phase - runs from the event widget up to the toplevel.

The Input Handling chapter in the GTK documentation describes user input handling in more detail.

### Výjimky v obsluze signálu

Když je program přerušen kvůli neobsloužené výjimce C++, je občas možné použít ladicí program k nalezení místa, kde byla výjimka vyhozena. Pokud je výjimka vyhozena v obsluze signálu, je to náročnější, než obvykle.

This section describes primarily what you can expect on a Linux system, when you use the gdb debugger.

First, let's look at a simple example where an exception is thrown from a normal function (no signal handler).

    // without_signal.cc
    #include <gtkmm.h>

    bool throwSomething()
    {
      throw "Something";
      return true;
    }

    int main(int argc, char** argv)
    {
      throwSomething();
      auto app = Gtk::Application::create("org.gtkmm.without_signal");
      return app->run();
    }

Here is an excerpt from a gdb session. Only the most interesting parts of the output are shown.

    > gdb without_signal
    (gdb) run
    terminate called after throwing an instance of 'char const*'

    Program received signal SIGABRT, Aborted.
    (gdb) backtrace
    #7  0x08048864 in throwSomething () at without_signal.cc:6
    #8  0x0804887d in main (argc=1, argv=0xbfffecd4) at without_signal.cc:12

You can see that the exception was thrown from `without_signal.cc`, line 6 (`throw "Something";`).

Now let's see what happens when an exception is thrown from a signal handler. Here's the source code.

    // with_signal.cc
    #include <gtkmm.h>

    bool throwSomething()
    {
      throw "Something";
      return true;
    }

    int main(int argc, char** argv)
    {
      Glib::signal_timeout().connect(sigc::ptr_fun(throwSomething), 500);
      auto app = Gtk::Application::create("org.gtkmm.with_signal");
      app->hold();
      return app->run();
    }

And here's an excerpt from a gdb session.

    > gdb with_signal
    (gdb) run
    (with_signal:2703): glibmm-ERROR **:
    unhandled exception (type unknown) in signal handler

    Program received signal SIGTRAP, Trace/breakpoint trap.
    (gdb) backtrace
    #2  0x0063c6ab in glibmm_unexpected_exception () at exceptionhandler.cc:77
    #3  Glib::exception_handlers_invoke () at exceptionhandler.cc:150
    #4  0x0063d370 in glibmm_source_callback (data=0x804d620) at main.cc:212
    #13 0x002e1b31 in Gtk::Application::run (this=0x804f300) at application.cc:178
    #14 0x08048ccc in main (argc=1, argv=0xbfffecd4) at with_signal.cc:16

The exception is caught in glibmm, and the program ends with a call to `g_error()`. Other exceptions may result in different behavior, but in any case the exception from a signal handler is caught in glibmm or gtkmm, and gdb can't see where it was thrown.

To see where the exception is thrown, you can use the gdb command `catch throw`.

    > gdb with_signal
    (gdb) catch throw
    Catchpoint 1 (throw)
    (gdb) run
    Catchpoint 1 (exception thrown), 0x00714ff0 in __cxa_throw ()
    (gdb) backtrace
    #0  0x00714ff0 in __cxa_throw () from /usr/lib/i386-linux-gnu/libstdc++.so.6
    #1  0x08048bd4 in throwSomething () at with_signal.cc:6
    (gdb) continue
    Continuing.
    (with_signal:2375): glibmm-ERROR **
    unhandled exception (type unknown) in signal handler

    Program received signal SIGTRAP, Trace/breakpoint trap.

If there are many caught exceptions before the interesting uncaught one, this method can be tedious. It can be automated with the following gdb commands.

    (gdb) catch throw
    (gdb) commands
    (gdb)   backtrace
    (gdb)   continue
    (gdb)   end
    (gdb) set pagination off
    (gdb) run

These commands will print a backtrace from each `throw` and continue. The backtrace from the last (or possibly the last but one) `throw` before the program stops, is the interesting one.

## Vytváření vlastních signálů

Nyní, když jste poznali signály a obsluhu signálů v gtkmm, budete možná chtít používat stejnou techniku ke komunikaci mezi vašimi vlastními třídami. Je to skutečně velmi jednoduché díky přímému použití knihovny libsigc++.

This isn't purely a gtkmm or GUI issue. gtkmm uses libsigc++ to implement its proxy wrappers for the GTK signal system, but for new, non-GTK signals, you can create pure C++ signals, using the `sigc::signal<>` template.

For instance, to create a signal that sends 2 parameters, a bool and an int, just declare a `sigc::signal`, like so:

    sigc::signal<void(bool, int)> signal_something;

You could just declare that signal as a public member variable, but some people find that distasteful and prefer to make it available via an accessor method, like so:

    class Server
    {
    public:
      //signal accessor:
      using type_signal_something = sigc::signal<void(bool, int)>;
      type_signal_something signal_something();

    protected:
      type_signal_something m_signal_something;
    };

    Server::type_signal_something Server::signal_something()
    {
      return m_signal_something;
    }

You can then connect to the signal using the same syntax used when connecting to gtkmm signals. For instance,

    server.signal_something().connect(
      sigc::mem_fun(client, &Client::on_server_something) );

### Příklad

Jedná se o úplný funkční příklad, který definuje a používá vlastní signály.

Source Code

File: `client.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLE_CLIENT_H
    #define GTKMM_EXAMPLE_CLIENT_H

    #include <sigc++/sigc++.h>

    //Client must inherit from sigc::trackable.
    //because libsigc++ needs to keep track of the lifetime of signal handlers.
    class Client : public sigc::trackable
    {
    public:
      Client();
      virtual ~Client();

      //Signal handler:
      void on_server_something(bool a, int b);
    };

    #endif //GTKMM_EXAMPLE_CLIENT_H

File: `server.h` (For use with gtkmm 4)

    #ifndef GTKMM_EXAMPLE_SERVER_H
    #define GTKMM_EXAMPLE_SERVER_H

    #include <sigc++/sigc++.h>

    class Server
    {
    public:
      Server();
      virtual ~Server();

      void do_something();

      //signal accessor:
      using type_signal_something = sigc::signal<void(bool, int)>;
      type_signal_something signal_something();

    protected:
      type_signal_something m_signal_something;
    };

    #endif //GTKMM_EXAMPLE_SERVER_H

File: `client.cc` (For use with gtkmm 4)

    #include "client.h"
    #include <iostream>

    Client::Client()
    {
    }

    Client::~Client()
    {
    }

    void Client::on_server_something(bool a, int b)
    {
      std::cout << "Client::on_server_something() called with these parameters: "
          << a << ", " << b << std::endl;
    }

File: `main.cc` (For use with gtkmm 4)

    #include "server.h"
    #include "client.h"
    #include <iostream>

    int main(int, char**)
    {
      Server server;
      Client client;

      //Connect a Server signal to the signal handler in Client.
      server.signal_something().connect(sigc::mem_fun(client,
                  &Client::on_server_something) );

      std::cout << "Before Server::do_something()" << std::endl;

      //Tell the server to do something that will eventually cause it to emit the
      //"something" signal.
      server.do_something();    // Client::on_server_something() will run before
                                // Server::do_something() has completed.

      std::cout << "After Server::do_something()" << std::endl;

      return 0;
    }

File: `server.cc` (For use with gtkmm 4)

    #include "server.h"
    #include <iostream>

    Server::Server()
    {
    }

    Server::~Server()
    {
    }

    Server::type_signal_something Server::signal_something()
    {
      return m_signal_something;
    }

    void Server::do_something()
    {
      m_signal_something.emit(false, 5);
    }

## Srovnání s jinými signalizačními systémy

(An aside: GTK calls this scheme "signalling"; the sharp-eyed reader with GUI toolkit experience will note that this same design is often seen under the name of "broadcaster-listener" (e.g., in Metrowerks' PowerPlant framework for the Macintosh). It works in much the same way: one sets up `broadcasters`, and then connects `listeners` to them; the broadcaster keeps a list of the objects listening to it, and when someone gives the broadcaster a message, it calls all of its objects in its list with the message. In gtkmm, signal objects play the role of broadcasters, and slots play the role of listeners - sort of. More on this later.)

gtkmm signal handlers are strongly-typed, whereas GTK C code allows you to connect a callback with the wrong number and type of arguments, leading to a segfault at runtime. And, unlike Qt, gtkmm achieves this without modifying the C++ language.

Re. Overriding signal handlers: You can do this in the straight-C world of GTK too; that's what GTK's object system is for. But in GTK, you have to go through some complicated procedures to get object-oriented features like inheritance and overloading. In C++, it's simple, since those features are supported in the language itself; you can let the compiler do the dirty work.

This is one of the places where the beauty of C++ really comes out. One wouldn't think of subclassing a GTK widget simply to override its action method; it's just too much trouble. In GTK, you almost always use signals to get things done, unless you're writing a new widget. But because overriding methods is so easy in C++, it's entirely practical - and sensible - to subclass a button for that purpose.

## gtkmm a Win32

Jedním z hlavních přínosů gtkmm je, že je multiplatformní. Programy gtkmm napsané na jiných platformách, jako je GNU/Linux, mohou být obecně vzato přenesené do Windows (a naopak) jen s pár změnami ve zdrojových kódech.

gtkmm currently works with the MinGW/GCC compiler with a compiler version that supports C++17, such as gcc 7 or 8. It also works with Microsoft Visual C++ 2017 15.7.x or later (including the freely available express/community editions) on the Windows platform. There is an installer available for gtkmm on Microsoft Windows, but as of this writing (October 2020) it has not been updated for a long time. Please be aware that although normally it is fine to mix builds done with Visual Studio 2017 and 2019, please do not do so when building gtkmm with its -mm dependencies.

Refer to the README.win32, as well as the README files in the gtkmm, pangomm and glibmm for instructions on how to build gtkmm on Windows.

## Práce se zdrojovým kódem gtkmm

Pokud byste měli zájem pomoci nám s vývojem gtkmm nebo s opravou chyb v gtkmm, budete nejspíše potřebovat sestavit vývojovou verzi gtkmm. Neměli byste ale instalovat vývojovou verzi přes stabilní verzi. Místo toho byste ji měli nainstalovat vedle stávající instalace gtkmm do samostatné cesty.

The easiest way to do this is using jhbuild. jhbuild is a program that makes building GNOME software much easier by calculating dependencies and building things in the correct order. This section will give a brief explanation of how to set up jhbuild to build and install gtkmm from the source repository (git). For up-to-date information on jhbuild, please refer to the jhbuild manual.

Upozorňujeme, že k sestavení gtkmm z repozitáře git je často zapotřebí sestavení také mnoha jeho závislostí. jhbuild to velmi usnadňuje oproti normálnímu postupu, ale sestavení a instalace zabere poměrně hodně času. Pravděpodobně také narazíte na nějaké problémy se sestavováním, ale když je nahlásíte, tak bývají poměrně rychle opravené.

gnome-build-meta is an alternative to jhbuild. It is described at the Building system components wiki page, but here we concentrate on jhbuild.

### Nastavení systému jhbuild

To set up jhbuild, follow the basic installation instructions from the jhbuild manual. After you have installed jhbuild, you should copy the sample jhbuild configuration file into your home directory by executing the following command from the jhbuild directory:

    $ cp examples/sample.jhbuildrc ~/.config/jhbuildrc

The gtkmm module is defined in the `gnome-suites-core-deps-latest.modules` moduleset. So edit your `jhbuildrc` file and set your moduleset setting like so:

    moduleset = 'gnome-suites-core-deps-latest'

After setting the correct moduleset, you need to tell jhbuild which module or modules to build. To build gtkmm and all of its dependencies, set `modules` like so:

    modules = [ 'gtkmm' ]

Můžete sestavit několik modulů nastavením proměnné `modules` na metabalíček, např. `meta-gnome-core`, nebo vypsáním více než jednoho názvu modulu. Proměnná `modules` určuje, které moduly budou sestavené, když žádný výslovně neuvedete na příkazové řádce. Vždy můžete sestavit jinou sadu modulů později jejich zadáním na příkazové řádce (např. `jhbuild build gtkmm`).

#### Nastavení prefixu

By default, jhbuild's configuration is configured to install all software built with jhbuild under the `~/jhbuild/install` prefix. You can choose a different prefix, but it is recommended that you keep this prefix different from other software that you've installed (don't set it to `/usr`!) If you've followed the jhbuild instructions then this prefix belongs to your user, so you don't need to run jhbuild as `root`.

You should also set `buildroot` in `jhbuildrc`. jhbuild builds gtkmm and many of its dependencies with Meson. Meson does not allow building in the source tree. jhbuild's default action is to build in a `build` directory directly below the source root directory. Some modules have a `build` directory with files used when building with Autotools. Those files can be destroyed if you let jhbuild build in that directory.

When you downloaded jhbuild from the git repository, you got a number of `.modules` files, specifying dependencies between modules. By default jhbuild does not use the downloaded versions of these files, but reads the latest versions in the git repository. This is usually what you want. If you don't want it, use the `use_local_modulesets` variable in `jhbuildrc`.

### Instalace a používání vývojové verze gtkmm z repozitáře git

Once you've configured jhbuild as described above, building gtkmm should be relatively straightforward. The first time you run jhbuild, you should run the following sequence of commands to ensure that jhbuild has the required tools and verify that it is set up correctly:

    $ jhbuild bootstrap
    $ jhbuild sanitycheck

#### Instalace gtkmm pomocí programu jhbuild

Pokud je vše správně, měli byste být schopni sestavit gtkmm a všechny jeho závislosti z repozitáře git pomocí příkazu `jhbuild build` (nebo, pokud neurčíte gtkmm v proměnné `modules`, pomocí příkazu `jhbuild build gtkmm`).

Tento příkaz sestaví a nainstaluje sérii modulů a bude pravděpodobně napoprvé trvat dosti dlouho. Při následujících spuštění by už ale měl být o něco rychlejší, protože bude potřebovat sestavit jen soubory, které se změnily od předchozího sestavení. Jinou variantou je, že po té co napoprvé sestavíte a nainstalujete gtkmm, můžete gtkmm znovu sestavit sebou samým (bez opětovného sestavování všech jeho závislostí) pomocí příkazu `jhbuild buildone gtkmm`.

#### Používání vývojové verze gtkmm z repozitáře git

After you've installed the git version of gtkmm, you're ready to start using and experimenting with it. In order to use the new version of gtkmm you've just installed, you need to set some environment variables so that your `configure` or `meson.build` script knows where to find the new libraries. Fortunately, jhbuild offers an easy solution to this problem. Executing the command `jhbuild shell` will start a new shell with all of the correct environment variables set. Now if you re-configure and build your project just as you usually do, it should link against the newly installed libraries. To return to your previous environment, simply exit the jhbuild shell.

Jakmile máte svůj software sestavený, potřebujete jej spustit ve stejném prostředí systému jhbuild. K tomu můžete znovu spustit příkaz `jhbuild shell`, aby se spustil nový shell s nastaveným prostředím pro jhbuild. Případně můžete jednorázově spustit příkaz v prostředí systému jhbuild následujícím příkazem: `jhbuild run command-name`. V tomto případě bude příkaz spuštěn s nastavenými správnými proměnnými prostředí, ale po jeho ukončení dojde návratu do předchozího prostředí.

## Obalení knihoven C pomocí gmmproc

gtkmm využívá nástroj `gmmproc` k vygenerování většiny svých zdrojových kódů pomocí souborů .defs, které definují API knihoven založených na `GObject`. Je tak velmi snadné vytvořit další obalující kód ve stylu gtkmm pro další knihovny založené na glib/GObject.

Ve skutečnosti se jedná o několik nástrojů, z nichž některé jsou záludnější, ale určitě fungují a byly použité v několika projektech.

### Struktura sestavení

Generation of the source code for a gtkmm-style wrapper API requires use of tools such as `gmmproc` and `generate_wrap_init.pl`, which are included in glibmm. In theory you could write your own build files to use these appropriately, but a much better option is to make use of the build infrastructure provided by the mm-common module. To get started, it helps a lot to pick an existing binding module as an example to look at.

Například si představme, že obalujeme knihovnu C nazvanou libneco a že poskytuje API na základě `GObject` s typy nazvanými například `NecoWidget` a `NecoNejakeho`.

#### Kopírování kostry projektu

Typically our wrapper library would be called libsomethingmm. We can start by copying the skeleton source tree from the mm-common module. Starting with mm-common 1.0.0 this skeleton application is built with the Meson build system.

      $ git clone https://gitlab.gnome.org/GNOME/mm-common.git
      $ cp -a mm-common/skeletonmm libsomethingmm

This provides a directory structure for the source .hg and .ccg files and the hand-written .h and .cc files, with `meson.build` files that can specify the various files in use, in terms of Meson variables. The directory structure usually looks like this, after we have renamed the directories appropriately:

- `libsomethingmm`: The top-level directory.

  - `libsomething`: Contains the main include file and the pkg-config .pc file.

    - `src`: Contains .hg and .ccg source files.

    - `libsomethingmm`: Contains hand-written .h and .cc files.

As well as renaming the directories, we should rename some of the source files. For instance:

    $ for f in $(find libsomethingmm -depth -name '*skeleton*'); do \
        d="${f%/*}"; b="${f##*/}"; mv "$f" "$d/${b//skeleton/libsomething}"; \
      done

A number of the skeleton files must still be filled in with project-specific content later.

Soubory končící na `.in` budou použity k vygenerování souborů se stejným názvem, ale bez přípony `.in`. Během konfigurační fáze se v nich nahradí některé proměnné skutečnými hodnotami.

Generated files are saved in the build tree, which is separated from the source tree when `meson` and `ninja` are used.

#### Úprava souborů řídících sestavení

Now we edit the files to adapt them to our needs. You might prefer to use a multiple-file search-replace utility for this, such as `regexxer`. Note that nearly all of the files provided with the skeleton source tree contain placeholder text. Thus, the substitutions should be performed globally, and not be limited to the Meson files.

Všechny výskyty `skeleton` by měly být nahrazeny správným názvem knihovny C, kterou obalujete, např. za „neco“ a „libneco“. Stejně tak všechny výskyty `SKELETON` by měly být nahrazeny za „NECO“ a „LIBNECO“ a všechny výskyty `Skeleton` za „Neco“.

Obdobně nahraďte všechny výskyty `Joe Hacker` za zamýšleného držitele práv, což budete nejspíše vy. To stejné proveďte s e-mailovou adresou `joe@example.com`.

##### meson.build in the top-level directory

- Pro vazební moduly je běžné, že sledují číslo verze knihovny, kterou obalují. Takže například, když knihovna C je ve verzi 1.23.4, počáteční verze vazebního modulu by byla 1.23.0. Vyhněte se ale počátku se sudým vedlejším číslem verze, protože obvykle indikuje stabilní vydání.

- In the `project()` function, change the license and the C++ version, if necessary.

- You probably need to add more required modules than glibmm and skeleton (libsomething).

##### Other meson.build files

Next we must adapt the other `meson.build` files:

- `skeleton/meson.build`: Perhaps not much to change here more than the global name substitutions.

- `skeleton/skeletonmm/meson.build`

  `defs_basefiles`

    If we have more .defs and docs.xml files, we add them here.

  `hg_ccg_basenames`

    We must mention all of our `.hg` and `.ccg` files here.

  `extra_cc_files, extra_h_files`

    Any additional hand-written `.h` and `.cc` source files go here.

##### Vytváření souborů .hg a .ccg

Měli bychom vytvořit své první soubory `.hg` a `.ccg` pro obalení některého z objektů v knihovně C. Jeden pár ukázkových zdrojových souborů již existuje: `skeleton.ccg` a `skeleton.hg`. Podle potřeby si vytvořte kopie těchto souborů.

V kapitole soubory .hg a .ccg se můžete dozvědět více o syntaxi používané v těchto souborech.

### Generování souborů .defs

The `.defs` files are text files, in a lisp format, that describe the API of a C library, including its

- objects (GObjects, widgets, interfaces, boxed-types and plain structs)

- functions

- enums

- signals

- properties

- vfuncs

At the moment, we have separate tools for generating different parts of these `.defs`, so we split them up into separate files. For instance, in the `gtk/src` directory of the gtkmm sources, you will find these files:

`gtk.defs`

  Includes the other files.

`gtk_methods.defs`

  Objects and functions.

`gtk_enums.defs`

  Enumerations.

`gtk_signals.defs`

  Signals and properties.

`gtk_vfuncs.defs`

  vfuncs (function pointer member fields in structs), written by hand.

The `skeletonmm/tools/generate_defs_and_docs.sh` script generates all `.defs` files and the `*_docs.xml` file, described in the Documentation section.

#### Generování .defs pro metody

This `.defs` file describes objects and their functions. It is generated by the `h2def.py` script which you can find in glibmm's `tools/defs_gen` directory. For instance,

    $ ./h2def.py /usr/include/gtk-4.0/gtk/*.h > gtk_methods.defs

#### Generování .defs pro výčty

This `.defs` file describes enum types and their possible values. It is generated by the `enumextract.py` script which you can also find in glibmm's `tools/defs_gen` directory. For instance,

    $ ./enumextract.py /usr/include/gtk-4.0/gtk/*.h > gtk_enums.defs

#### Generování .defs pro signály a vlastnosti

This `.defs` file describes signals and properties. It is generated by the special `generate_extra_defs` utility that is in every wrapping project, such as `gtkmm/tools/extra_defs_gen/`. For instance

    $ cd tools/extra_defs_gen
    $ ./generate_extra_defs > gtk_signals.defs

You must edit the source code of your own `generate_extra_defs` tool in order to generate the `.defs` for the GObject C types that you wish to wrap. In the skeleton source tree, the source file is named `tools/extra_defs_gen/generate_defs_skeleton.cc`. If not done so already, the file should be renamed, with the basename of your new binding substituted for the `skeleton` placeholder. The `tools/extra_defs_gen/meson.build` file should also mention the new source filename.

Then edit the `.cc` file to specify the correct types. For instance, your `main()` function might look like this:

    #include <glibmm_generate_extra_defs/generate_extra_defs.h>
    #include <libsomething.h>
    #include <iostream>

    int main(int, char**)
    {
      something_init();

      std::cout << get_defs(SOME_TYPE_WIDGET)
                << get_defs(SOME_TYPE_STUFF);
      return 0;
    }

#### Psaní .defs pro virtuální funkce

Tento soubor `.defs` popisuje virtuální funkce. Musíte jej napsat ručně. Existuje k tomu připravená kostra `skeleton/src/skeleton_vfunc.defs`, ze které můžete vyjít. Můžete se také podívat na soubor `gtk/src/gtk_vfuncs.defs` z gtkmm.

### Soubory .hg a .ccg

Zdrojové soubory `.hg` a `.ccg` se velmi podobají zdrojovým souborům `.h` a `.cc`, ale mohou obsahovat další makra, jako je `_CLASS_GOBJECT()` a `_WRAP_METHOD()`, ze kterých `gmmproc` generuje příslušný zdrojový kód C++, obvykle na stejném místě v hlavičkovém souboru. Případný doplňující zdrojový kód C++ bude doslovně nakopírován do příslušného souboru `.h` nebo `.cc`.

A .hg file will typically include some headers and then declare a class, using some macros to add API or behavior to this class. For instance, gtkmm's `button.hg` looks roughly like this:

    #include <gtkmm/widget.h>
    #include <gtkmm/actionable.h>
    _DEFS(gtkmm,gtk)
    _PINCLUDE(gtkmm/private/widget_p.h)

    namespace Gtk
    {

    class Button
      : public Widget,
        public Actionable
    {
      _CLASS_GTKOBJECT(Button, GtkButton, GTK_BUTTON, Gtk::Widget, GtkWidget)
      _IMPLEMENTS_INTERFACE(Actionable)
    public:

      _CTOR_DEFAULT
      explicit Button(const Glib::ustring& label, bool mnemonic = false);

      _WRAP_METHOD(void set_label(const Glib::ustring& label), gtk_button_set_label)

      ...

      _WRAP_SIGNAL(void clicked(), "clicked")

      ...

      _WRAP_PROPERTY("label", Glib::ustring)
    };

    } // namespace Gtk

The macros in this example do the following:

`_DEFS()`

  Specifies the destination directory for generated sources, and the name of the main .defs file that `gmmproc` should parse.

`_PINCLUDE()`

  Tells `gmmproc` to include a header in the generated `private/button_p.h` file.

`_CLASS_GTKOBJECT()`

  Tells `gmmproc` to add some typedefs, constructors, and standard methods to this class, as appropriate when wrapping a widget.

`_IMPLEMENTS_INTERFACE()`

  Tells `gmmproc` to add initialization code for the interface.

`_CTOR_DEFAULT`

  Adds a default constructor.

`_WRAP_METHOD()`, `_WRAP_SIGNAL()`, and `_WRAP_PROPERTY()`

  Add methods to wrap parts of the C API.

The .h and .cc files will be generated from the .hg and .ccg files by processing them with `gmmproc` like so, though this happens automatically when using the above build structure:

    $ cd gtk/src
    $ /usr/lib/glibmm-2.68/proc/gmmproc -I ../../tools/m4 --defs . button . ./../gtkmm

Všimněte si, že `gmmproc` poskytujeme cestu k převodním souborům `.m4`, cestu k souboru `.defs`, název souboru `.hg`, složku se zdrojovými kódy a cílovou složku.

Měli byste se vyhnout vložení hlavičkového souboru C z vašeho hlavičkového souboru C++, aby se předešlo šíření globálního jmenného prostoru a exportu nepotřebného veřejného API. Budete ale potřebovat vložit nutné hlavičkové soubory C ze souboru `.ccg`.

V následujících oddílech jsou podrobně rozebrána makra.

#### Konverze m4

The macros that you use in the .hg and .ccg files often need to know how to convert a C++ type to a C type, or vice-versa. `gmmproc` takes this information from an .m4 file in your `tools/m4/` or `codegen/m4/` directory. This allows it to call a C function in the implementation of your C++ method, passing the appropriate parameters to that C function. For instance, this tells `gmmproc` how to convert a `GtkTreeView` pointer to a `Gtk::TreeView` pointer:

    _CONVERSION(`GtkTreeView*',`TreeView*',`Glib::wrap($3)')

`$3` will be replaced by the parameter name when this conversion is used by `gmmproc`.

Some extra macros make this easier and consistent. Look in gtkmm's .m4 files for examples. For instance:

    _CONVERSION(`PrintSettings&',`GtkPrintSettings*',__FR2P)
    _CONVERSION(`const PrintSettings&',`GtkPrintSettings*',__FCR2P)
    _CONVERSION(`const Glib::RefPtr<Printer>&',`GtkPrinter*',__CONVERT_REFPTR_TO_P($3))

#### Inicializace m4

Often when wrapping methods, it is desirable to store the return of the C function in what is called an output parameter. In this case, the C++ method returns void but an output parameter in which to store the value of the C function is included in the argument list of the C++ method. `gmmproc` allows such functionality, but appropriate initialization macros must be included to tell `gmmproc` how to initialize the C++ parameter from the return of the C function.

For example, if there was a C function that returned a GtkWidget* and for some reason, instead of having the C++ method also return the widget, it was desirable to have the C++ method place the widget in a specified output parameter, an initialization macro such as the following would be necessary:

    _INITIALIZATION(`Gtk::Widget&',`GtkWidget*',`$3 = Glib::wrap($4)')

`$3` will be replaced by the output parameter name of the C++ method and `$4` will be replaced by the return of the C function when this initialization is used by `gmmproc`. For convenience, `$1` will also be replaced by the C++ type without the ampersand (&) and `$2` will be replaced by the C type.

#### Makra pro třídy

Makro deklaruje samotnou třídu a její vztah k podkladovému typu v C. Generuje některé interní konstruktory, definice členských typů `gobject`, příslušníky `gobj()`, registraci typu a metodu `Glib::wrap()`, spolu s dalšími věcmi.

Ostatní makra, jako je `_WRAP_METHOD()` a `_WRAP_SIGNAL()` mohou být použita jen po zavolání makra `_CLASS_*`.

##### _CLASS_GOBJECT

Toto makro deklaruje obalení pro typ, který je odvozený z `GObject`, ale jeho obalení není odvozené z `Gtk::Object`.

`_CLASS_GOBJECT( C++ class, C class, C casting macro, C++ base class, C base class )`

For instance, from `adjustment.hg`:

    _CLASS_GOBJECT(Adjustment, GtkAdjustment, GTK_ADJUSTMENT, Glib::Object, GObject)

##### _CLASS_GTKOBJECT

Toto makro deklaruje obalení pro typ, jehož obalení je odvozené z `Gtk::Object`, jako je widget nebo dialog.

`_CLASS_GTKOBJECT( C++ class, C class, C casting macro, C++ base class, C base class )`

For instance, from `button.hg`:

    _CLASS_GTKOBJECT(Button, GtkButton, GTK_BUTTON, Gtk::Widget, GtkWidget)

You will typically use this macro when the class already derives from `Gtk::Object`. For instance, you will use it when wrapping a GTK Widget, because `Gtk::Widget` derives from `Gtk::Object`.

You might also derive non-widget classes from `Gtk::Object` so they can be used without `Glib::RefPtr`. For instance, they could then be instantiated with `Gtk::make_managed()` or on the stack as a member variable. This is convenient, but you should use this only when you are sure that true reference-counting is not needed. We consider it useful for widgets.

##### _CLASS_BOXEDTYPE

Toto makro deklaruje obalení pro jinou strukturu než `GObject` registrovanou pomocí `g_boxed_type_register_static()`.

`_CLASS_BOXEDTYPE( C++ class, C class, new function, copy function, free function )`

For instance, from `Gdk::RGBA`:

    _CLASS_BOXEDTYPE(RGBA, GdkRGBA, NONE, gdk_rgba_copy, gdk_rgba_free)

##### _CLASS_BOXEDTYPE_STATIC

Toto makro deklaruje obalení pro jednoduchou přiřaditelnou strukturu, jako je `GdkRectangle`. Je to podobné, jako u `_CLASS_BOXEDTYPE`, jen struktura v C se nealokuje dynamicky.

`_CLASS_BOXEDTYPE_STATIC( C++ class, C class )`

For instance, for `Gdk::Rectangle`:

    _CLASS_BOXEDTYPE_STATIC(Rectangle, GdkRectangle)

##### _CLASS_OPAQUE_COPYABLE

Toto makro deklaruje obalení pro neprůhlednou strukturu, která má funkce copy a free. Funkce new, copy a free se použijí pro vytváření instancí pomocí výchozího konstruktoru, pro kopírovací konstruktor a pro destruktor.

`_CLASS_OPAQUE_COPYABLE( C++ class, C class, new function, copy function, free function )`

For instance, from `Glib::VariantType`:

    _CLASS_OPAQUE_COPYABLE(VariantType, GVariantType, NONE, g_variant_type_copy, g_variant_type_free)

##### _CLASS_OPAQUE_REFCOUNTED

Toto makro deklaruje obalení pro neprůhlednou strukturu s počítáním referencí. Pro obalení v C++ nelze přímo vytvářet instance a lze je použít jen pomocí `Glib::RefPtr`.

`_CLASS_OPAQUE_REFCOUNTED( C++ class, C class, new function, ref function, unref function )`

For instance, for `Gtk::CssSection`:

    _CLASS_OPAQUE_REFCOUNTED(CssSection, GtkCssSection, NONE, gtk_css_section_ref, gtk_css_section_unref)

##### _CLASS_GENERIC

Toto makro se dá použít k obalení struktur, které nezapadají do žádné speciální kategorie.

`_CLASS_GENERIC( C++ class, C class )`

For instance, for `Gdk::TimeCoord`:

    _CLASS_GENERIC(TimeCoord, GdkTimeCoord)

##### _CLASS_INTERFACE

Toto makro deklaruje obalení pro typ, který je odvozený z `GTypeInterface`.

`_CLASS_INTERFACE( C++ class, C class, C casting macro, C interface struct, Base C++ class (optional), Base C class (optional) )`

For instance, from `celleditable.hg`:

    _CLASS_INTERFACE(CellEditable, GtkCellEditable, GTK_CELL_EDITABLE, GtkCellEditableIface)

Two extra optional parameters were once added, for the case that the interface derives from another interface, which was believed to be the case when the GInterface has another GInterface as a prerequisite. This is a misunderstanding, though. When GInterface A has GInterface B as a prerequisite, it means that every class that implements A shall also implement B. For instance, from `loadableicon.hg` in glibmm-2.4:

    _CLASS_INTERFACE(LoadableIcon, GLoadableIcon, G_LOADABLE_ICON, GLoadableIconIface, Icon, GIcon)

#### Makra pro konstruktory

The `_CTOR_DEFAULT()` and `_WRAP_CTOR()` macros add constructors, wrapping the specified `*_new()` C functions. These macros assume that the C object has properties with the same names as the function parameters, as is usually the case, so that it can supply the parameters directly to a `g_object_new()` call. These constructors never actually call the `*_new()` C functions, because gtkmm must actually instantiate derived GTypes, and the `*_new()` C functions are meant only as convenience functions for C programmers.

When using `_CLASS_GOBJECT()`, the constructors should be protected (rather than public) and each constructor should have a corresponding `_WRAP_CREATE()` in the public section. This prevents the class from being instantiated without using a `RefPtr`. For instance:

    class TextMark : public Glib::Object
    {
      _CLASS_GOBJECT(TextMark, GtkTextMark, GTK_TEXT_MARK, Glib::Object, GObject)

    protected:
      _WRAP_CTOR(TextMark(const Glib::ustring& name, bool left_gravity = true), gtk_text_mark_new)

    public:
      _WRAP_CREATE(const Glib::ustring& name, bool left_gravity = true)

##### _CTOR_DEFAULT

Toto makro vytváří výchozí konstruktor bez argumentů.

##### _WRAP_CTOR

Toto makro vytvoří konstruktor s argumenty ekvivalentní funkci `*_new()` v C. Ve skutečnosti se nebude volat funkce `*_new()`, ale jednoduše vytvoří ekvivalentní konstruktor se stejnými typy argumentů. Vyžadována je hlavička konstruktoru v C++ a název funkce v C.

It also takes an optional extra argument:

errthrow

  This tells `gmmproc` that the C `*_new()` has a final GError** parameter which should be ignored.

##### Ruční psaní konstruktorů

When a constructor must be partly hand written because, for instance, the `*_new()` C function's parameters do not correspond directly to object properties, or because the `*_new()` C function does more than call `g_object_new()`, the `_CONSTRUCT()` macro may be used in the .ccg file to save some work. The `_CONSTRUCT` macro takes a series of property names and values. For instance, from `button.ccg`:

    Button::Button(const Glib::ustring& label, bool mnemonic)
    :
      _CONSTRUCT("label", label.c_str(), "use_underline", gboolean(mnemonic))
    {}

#### Macros that suppress generation of some code

Some macros suppress the generation of some code when they are used after a `_CLASS_*` macro. Some suppress the definition in the generated .cc file, others suppress both the declaration in the .h file and the definition in the .cc file.

##### _CUSTOM_DEFAULT_CTOR

Suppresses declaration and definition of default constructor in `_CLASS_BOXEDTYPE`, `_CLASS_BOXEDTYPE_STATIC` and `_CLASS_OPAQUE_COPYABLE`.

##### _CUSTOM_CTOR_CAST

Suppresses declaration and definition of the constructor that takes a pointer to the wrapped C object in `_CLASS_BOXEDTYPE` and `_CLASS_BOXEDTYPE_STATIC`.

Suppresses definition of the constructor that takes a pointer to the wrapped C object in `_CLASS_INTERFACE` and `_CLASS_OPAQUE_COPYABLE`.

Suppresses definition of the constructor that takes a pointer to the wrapped C object and the constructor that takes construct_params in `_CLASS_GOBJECT` and `_CLASS_GTKOBJECT`.

##### _CUSTOM_DTOR

Suppresses definition of destructor in `_CLASS_GOBJECT` and `_CLASS_GTKOBJECT`.

##### _CUSTOM_MOVE_OPERATIONS

Suppresses declaration and definition of move constructor and move assignment operator in `_CLASS_GOBJECT` and `_CLASS_GTKOBJECT`.

For example:

    class Derived : public Glib::Object
    {
      _CLASS_GOBJECT(Derived, GDerived, G_DERIVED, Glib::Object, GObject)

      _CUSTOM_MOVE_OPERATIONS

    public:
      Derived(Derived&& src) noexcept;
      Derived& operator=(Derived&& src) noexcept;
      // ...
    };

##### _CUSTOM_WRAP_NEW

Suppresses definition of `Glib::wrap_new()` function in `_CLASS_GOBJECT`.

##### _CUSTOM_WRAP_FUNCTION

Suppresses definition of `Glib::wrap()` function in `_CLASS_GOBJECT` and `_CLASS_GTKOBJECT`.

##### _NO_WRAP_FUNCTION

Suppresses declaration and definition of `Glib::wrap()` function in `_CLASS_GOBJECT`, `_CLASS_BOXEDTYPE`, `_CLASS_BOXEDTYPE_STATIC`, `_CLASS_OPAQUE_COPYABLE`, `_CLASS_INTERFACE` and `_CLASS_GTKOBJECT`.

#### Makra pro metody

##### _WRAP_METHOD

Toto makro generuje metodu v C++ pro obalení funkce v C.

`_WRAP_METHOD( C++ method signature, C function name)`

For instance, from `entry.hg`:

    _WRAP_METHOD(void set_text(const Glib::ustring& text), gtk_entry_set_text)

Funkce v C (např. `gtk_entry_set_text`) je více popsaná v souboru `.defs` a soubory `convert*.m4` obsahují nutné převody z typů parametrů v C++ na typy parametrů v C. Toto makro také generuje dokumentační komentáře Doxygen na základě souborů `*_docs.xml` a `*_docs_override.xml`.

There are some optional extra arguments:

refreturn

  Do an extra `reference()` on the return value, in case the C function does not provide a reference.

errthrow ["<exceptions>"]

  Use the last GError** parameter of the C function to throw an exception. The optional "<exceptions>" is a comma-separated list of exceptions that can be thrown. It determines which @throws Doxygen commands are added to the documentation. Default value is `Glib::Error`. If you want a comma in the description of an exception, precede it by a backslash. Example: `errthrow "Glib::OptionError Hello\, world, Glib::ConvertError"`

deprecated ["<text>"]

  Puts the generated code in #ifdef blocks. Text about the deprecation can be specified as an optional parameter.

ignore_deprecations

  Puts the generated code in the .cc file in a G_GNUC_BEGIN_IGNORE_DEPRECATIONS / G_GNUC_END_IGNORE_DEPRECATIONS block. (Only in glibmm >= 2.70.1)

constversion

  Just call the non-const version of the same function, instead of generating almost duplicate code.

newin "<version>"

  Adds a @newin Doxygen command to the documentation, or replaces the @newin command generated from the C documentation.

ifdef <identifier>

  Puts the generated code in #ifdef blocks.

slot_name <parameter_name>

  Specifies the name of the slot parameter of the method, if it has one. This enables `gmmproc` to generate code to copy the slot and pass the copy on to the C function in its final `gpointer user_data` parameter. The `slot_callback` option must also be used to specify the name of the glue callback function to also pass on to the C function.

slot_callback <function_name>

  Used in conjunction with the `slot_name` option to specify the name of the glue callback function that handles extracting the slot and then calling it. The address of this callback is also passed on to the C function that the method wraps.

no_slot_copy

  Tells `gmmproc` not to pass a copy of the slot to the C function, if the method has one. Instead the slot itself is passed. The slot parameter name and the glue callback function must have been specified with the `slot_name` and `slot_callback` options respectively.

Selecting which C++ types should be used is also important when wrapping C API. Though it's usually obvious what C++ types should be used in the C++ method, here are some hints:

- Objects used via `RefPtr`: Pass the `RefPtr` as a const reference. For instance, `const Glib::RefPtr<Gtk::FileFilter>& filter`.

- Const Objects used via `RefPtr`: If the object should not be changed by the function, then make sure that the object is const, even if the `RefPtr` is already const. For instance, `const Glib::RefPtr<const Gtk::FileFilter>& filter`.

- Wrapping `GList*` and `GSList*` parameters: First, you need to discover what objects are contained in the list's data field for each item, usually by reading the documentation for the C function. The list can then be wrapped by a `std::vector` type. For instance, `std::vector<Glib::RefPtr<Gdk::Pixbuf>>`. You may need to define a Traits type to specify how the C and C++ types should be converted.

- Wrapping `GList*` and `GSList*` return types: You must discover whether the caller should free the list and whether it should release the items in the list, again by reading the documentation of the C function. With this information you can choose the ownership (none, shallow or deep) for the m4 conversion rule, which you should probably put directly into the .hg file because the ownership depends on the function rather than the type. For instance:

      #m4 _CONVERSION(`GSList*',`std::vector<Widget*>',`Glib::SListHandler<Widget*>::slist_to_vector($3, Glib::OWNERSHIP_SHALLOW)')

##### _WRAP_METHOD_DOCS_ONLY

Toto makro je podobné jako `_WRAP_METHOD()`, ale generuje jen dokumentaci pro metodu v C++, která obaluje funkci v C. Použijte v situaci, kdy musíte ručně napsat metodu, ale chcete použít dokumentaci, která by byla vygenerovaná, kdyby se generovala metoda.

`_WRAP_METHOD_DOCS_ONLY(C function name)`

For instance, from `recentinfo.hg`:

    _WRAP_METHOD_DOCS_ONLY(gtk_recent_info_get_applications)

There are some optional extra arguments:

errthrow ["<exceptions>"]

  Excludes documentation of the last GError** parameter of the C function. The optional "<exceptions>" is a comma-separated list of exceptions that can be thrown. It determines which @throws Doxygen commands are added to the documentation. Default value is `Glib::Error`. If you want a comma in the description of an exception, precede it by a backslash. Example: `errthrow "Glib::OptionError Hello\, world, Glib::ConvertError"`

newin "<version>"

  Adds a @newin Doxygen command to the documentation, or replaces the @newin command generated from the C documentation.

voidreturn

  Don't include a @return Doxygen command in the documentation. Useful if the wrapped C function returns a value, but the corresponding C++ method returns void.

##### _IGNORE, _IGNORE_SIGNAL, _IGNORE_PROPERTY

`gmmproc` will warn you on stdout about functions, signals, properties and child properties that you have forgotten to wrap, helping to ensure that you are wrapping the complete API. But if you don't want to wrap some functions, signals, properties or child properties, or if you chose to hand-code some methods then you can use the _IGNORE(), _IGNORE_SIGNAL() or _IGNORE_PROPERTY() macro to make `gmmproc` stop complaining.

    _IGNORE(C function name 1, C function name 2, etc)
    _IGNORE_SIGNAL(C signal name 1, C signal name 2, etc)
    _IGNORE_PROPERTY(C property name 1, C property name 2, etc)

For instance, from `flowbox.hg`:

    _IGNORE(gtk_flow_box_set_filter_func, gtk_flow_box_set_sort_func)
    _IGNORE_SIGNAL(activate-cursor-child, toggle-cursor-child, move-cursor)

##### _WRAP_SIGNAL

Toto makro generuje signál v C++ ve stylu libsigc++ pro obalení signálu objektu GObject v C. Ve skutečnosti generuje veřejně přístupnou metodu, jako je `signal_clicked()`, která vrací zástupný objekt. `gmmproc` používá soubor `.defs` k vyhledání typů parametrů C a převodní soubory `.m4` k vyhledání příslušných typů převodů.

`_WRAP_SIGNAL( C++ signal handler signature, C signal name)`

For instance, from `button.hg`:

    _WRAP_SIGNAL(void clicked(),"clicked")

Signály obvykle mají ve struktuře GTK ukazatel na funkci s příslušnou výčtovou hodnotou a `g_signal_new()` v souboru `.c`.

There are some optional extra arguments:

no_default_handler

  Do not generate an `on_something()` virtual method to allow easy overriding of the default signal handler. Use this when adding a signal with a default signal handler would break the ABI by increasing the size of the class's virtual function table, and when adding a signal without a public C default handler.

custom_default_handler

  Generate a declaration of the `on_something()` virtual method in the `.h` file, but do not generate a definition in the `.cc` file. Use this when you must generate the definition by hand.

custom_c_callback

  Do not generate a C callback function for the signal. Use this when you must generate the callback function by hand.

refreturn

  Do an extra `reference()` on the return value of the `on_something()` virtual method, in case the C function does not provide a reference.

deprecated ["<text>"]

  Puts the generated code in #ifdef blocks. Text about the deprecation can be specified as an optional parameter.

newin "<version>"

  Adds a @newin Doxygen command to the documentation, or replaces the @newin command generated from the C documentation.

ifdef <identifier>

  Puts the generated code in #ifdef blocks.

exception_handler <method_name>

  Allows to use custom exception handler instead of default one. Exception might be rethrown by user-defined handler, and it will be caught by default handler.

detail_name <parameter_name>

  Adds a const Glib::ustring& parameter to the `signal_something()` method. Use it, if the signal accepts a detailed signal name, i.e. if the underlying C code registers the signal with the `G_SIGNAL_DETAILED` flag.

two_signal_methods

  Used in conjunction with the `detail_name` option to generate two `signal_something()` methods, one without a parameter and one with a parameter without a default value. With only the `detail_name` option one method is generated, with a parameter with default value. Use the `two_signal_methods` option, if it's necessary in order to preserve ABI.

##### _WRAP_PROPERTY

Toto makro generuje metodu C++ pro obalení vlastnosti objektu GObject v C. Musíte správně uvést název vlastnosti a typ C++, který chcete. `gmmproc` používá soubor `.defs` k vyhledání typu C a převodní soubory `.m4` k vyhledání příslušného typu převodů.

`_WRAP_PROPERTY(C property name, C++ type)`

For instance, from `button.hg`:

    _WRAP_PROPERTY("label", Glib::ustring)

There are some optional extra arguments:

deprecated ["<text>"]

  Puts the generated code in #ifdef blocks. Text about the deprecation can be specified as an optional parameter.

newin "<version>"

  Adds a @newin Doxygen command to the documentation, or replaces the @newin command generated from the C documentation.

##### _WRAP_VFUNC

Toto makro generuje metodu v C++ pro obalení virtuální funkce v C.

`_WRAP_VFUNC( C++ method signature, C function name)`

For instance, from `widget.hg`:

    _WRAP_VFUNC(SizeRequestMode get_request_mode() const, get_request_mode)

The C function (e.g. `get_request_mode`) is described more fully in the `*_vfuncs.defs` file, and the `convert*.m4` files contain the necessary conversion from the C++ parameter type to the C parameter type. Conversions can also be written in the .hg file. Virtual functions often require special conversions that are best kept local to the .hg file where they are used.

There are some optional extra arguments:

refreturn

  Do an extra `reference()` on the return value of the `something_vfunc()` function, in case the virtual C function does not provide a reference.

refreturn_ctype

  Do an extra `reference()` on the return value of an overridden `something_vfunc()` function in the C callback function, in case the calling C function expects it to provide a reference.

keep_return

  Keep a copy of the return value in the C callback function, in case the calling C function does not expect to get its own reference.

errthrow

  Use the last GError** parameter of the C virtual function (if there is one) to throw an exception.

custom_vfunc

  Do not generate a definition of the vfunc in the `.cc` file. Use this when you must generate the vfunc by hand.

custom_vfunc_callback

  Do not generate a C callback function for the vfunc. Use this when you must generate the callback function by hand.

ifdef <identifier>

  Puts the generated code in #ifdef blocks.

slot_name <parameter_name>

  Specifies the name of the slot parameter of the method, if it has one. This enables `gmmproc` to generate code to copy the slot and pass the copy on to the C function in its final `gpointer user_data` parameter. The `slot_callback` option must also be used to specify the name of the glue callback function to also pass on to the C function.

slot_callback <function_name>

  Used in conjunction with the `slot_name` option to specify the name of the glue callback function that handles extracting the slot and then calling it. The address of this callback is also passed on to the C function that the method wraps.

no_slot_copy

  Tells `gmmproc` not to pass a copy of the slot to the C function, if the method has one. Instead the slot itself is passed. The slot parameter name and the glue callback function must have been specified with the `slot_name` and `slot_callback` options respectively.

return_value <value>

  Defines a non-default return value.

err_return_value <value>

  Defines a non-default return value, used only if the C++ `something_vfunc()` function throws an exception which is propagated to the C callback function. If return_value is specified, but err_return_value is not, then return_value is used also when an exception is propagated.

exception_handler <method_name>

  Allows to use custom exception handler instead of default one. Exception might be rethrown by user-defined handler, and it will be caught by default handler.

Pravidlo, ze kterého mohou existovat výjimky: V případě, že virtuální funkce v C vrací ukazatel na objekt odvozený z `GObject`, tj. objekt s počítáním referencí, pak virtuální funkce v C++ vrátí objekt `Glib::RefPtr<>`. Je vyžadován jeden z doplňující argumentů `refreturn` nebo `refreturn_ctype`.

#### Ostatní makra

##### _IMPLEMENTS_INTERFACE

Toto makro generuje inicializační kód pro rozhraní.

`_IMPLEMENTS_INTERFACE(C++ interface name)`

For instance, from `grid.hg`:

    _IMPLEMENTS_INTERFACE(Orientable)

There is one optional extra argument:

ifdef <identifier>

  Puts the generated code in #ifdef blocks.

##### _WRAP_ENUM

Toto makro generuje výčet v C++ pro obalení výčtu v C. Musíte uvést požadovaný název v C++ a název podkladového výčtu v C.

For instance, from `enums.hg`:

    _WRAP_ENUM(Orientation, GtkOrientation)

There are some optional extra arguments:

NO_GTYPE

  Use this option, if the enum is not a `GType`. This is the case when there is no `*_get_type()` function for the C enum, but be careful that you don't just need to include an extra header for that function. You should also file a bug against the C API, because all enums should be registered as GTypes.

  If you specify `NO_GTYPE`, don't use that enum as the type in _WRAP_PROPERTY. It would cause a runtime error, when the generated `property_*()` method is called.

  For example, from `icontheme.hg`:

      _WRAP_ENUM(IconLookupFlags, GtkIconLookupFlags, NO_GTYPE)

gtype_func <function_name>

  Specifies the name of the `*_get_type()` function for the C enum. Use this parameter if `gmmproc` can't deduce the correct function name from the name of the C enum type.

  For example, from `dbusproxy.hg` in glibmm:

      _WRAP_ENUM(ProxyFlags, GDBusProxyFlags, gtype_func g_dbus_proxy_flags_get_type)

CONV_TO_INT

  "Convertible to int." Generates a plain enum (not an enum class) within a class. Such an enum is scoped like an enum class, but unlike an enum class, it can be implicitly converted to int.

  For example, from `dialog.hg`:

      _WRAP_ENUM(ResponseType, GtkResponseType, CONV_TO_INT)

s#<from>#<to>#

  Substitutes (part of) the name of one or more enum constants. You can add any number of substitutions.

  For example, from `iochannel.hg` in glibmm:

      _WRAP_ENUM(SeekType, GSeekType, NO_GTYPE, s#^SEEK_#SEEK_TYPE_#)

deprecated ["<text>"]

  Puts the generated code in #ifdef blocks. Text about the deprecation can be specified as an optional parameter.

newin "<version>"

  Adds a @newin Doxygen command to the documentation, or replaces the @newin command generated from the C documentation.

##### _WRAP_ENUM_DOCS_ONLY

This macro just generates a Doxygen documentation block for the enum. This is useful for enums that can't be wrapped with `_WRAP_ENUM()` because they are complexly defined (maybe using C macros) but including the generated enum documentation is still desired. It is used with the same syntax as `_WRAP_ENUM()` and also processes the same options (though NO_GTYPE, gtype_func <function_name> and CONV_TO_INT are ignored because they make no difference when just generating the enum's documentation).

##### _WRAP_GERROR

This macro generates a C++ exception class, derived from `Glib::Error`, with a Code enum and a `code()` method. You must specify the desired C++ name, the name of the corresponding C enum, and the prefix for the C enum values.

Tato výjimka může být vyhozená metodou, která je vygenerovaná pomocí _WRAP_METOD() s volbou errthrow.

For instance, from `pixbuf.hg`:

    _WRAP_GERROR(PixbufError, GdkPixbufError, GDK_PIXBUF_ERROR)

_WRAP_GERROR() accepts the same optional arguments as _WRAP_ENUM() (though CONV_TO_INT is ignored because all exception class enums are plain enums within a class).

##### _MEMBER_GET / _MEMBER_SET

Tato makra použijte, když obalujete jednoduchou strukturu nebo boxovyný typ, který poskytuje přímý přístup ke svým datovým členům, aby se vytvořily funkce pro získávání a nastavování datových členů.

`_MEMBER_GET(C++ name, C name, C++ type, C type)`

`_MEMBER_SET(C++ name, C name, C++ type, C type)`

For example, in `rectangle.hg`:

    _MEMBER_GET(x, x, int, int)

##### _MEMBER_GET_PTR / _MEMBER_SET_PTR

Tato makra použijte k poskytnutí funkcí pro získávání a nastavování datového člena, který je typu ukazatel. Pro funkci na získávání to vytvoří dvě metody, jednu konstantní a jednu nekonstantní.

`_MEMBER_GET_PTR(C++ name, C name, C++ type, C type)`

`_MEMBER_SET_PTR(C++ name, C name, C++ type, C type)`

For example, for `Pango::Analysis` in `item.hg`:

    // _MEMBER_GET_PTR(engine_lang, lang_engine, EngineLang*, PangoEngineLang*)
    // Je to jen komentáře. Je těžké najít skutečný příklad ze života.

##### _MEMBER_GET_GOBJECT / _MEMBER_SET_GOBJECT

Tato makra použijte k poskytnutí funkcí pro získávání a nastavování datového člena typu `GObject`, u kterého musí být před jeho vrácením zvýšeno počitadlo referencí.

`_MEMBER_GET_GOBJECT(C++ name, C name, C++ type, C type)`

`_MEMBER_SET_GOBJECT(C++ name, C name, C++ type, C type)`

For example, in Pangomm, `layoutline.hg`:

    _MEMBER_GET_GOBJECT(layout, layout, Pango::Layout, PangoLayout*)

#### Zpracování parametrů gmmproc

`gmmproc` umožňuje zpracování parametrů v hlavičkách metod různým způsobem pro makra, které zpracovávají hlavičky metod (jako jsou `_WRAP_METHOD()`, `_WRAP_CTOR()` and `_WRAP_CREATE()`):

##### Změna pořadí parametrů

For all the macros that process method signatures, it is possible to specify a different order for the C++ parameters than the existing order in the C function, virtual function or signal. For example, say that the following C function were being wrapped as a C++ method for the `Gtk::Widget` class:

    void gtk_widget_set_device_events(GtkWidget* widget, GdkDevice* device,
      GdkEventMask events);

However, changing the order of the C++ method's two parameters is necessary. Something like the following would wrap the function as a C++ method with a different order for the two parameters:

    _WRAP_METHOD(void set_device_events(Gdk::EventMask events{events},
      const Glib::RefPtr<const Gdk::Device>& device{device}),
      gtk_widget_set_device_events)

The `{c_param_name}` following the method parameter names tells `gmmproc` to map the C++ parameter to the specified C parameter within the `{}`. Since the C++ parameter names correspond to the C ones, the above could be re-written as:

    _WRAP_METHOD(void set_device_events(Gdk::EventMask events{.},
      const Glib::RefPtr<const Gdk::Device>& device{.}),
      gtk_widget_set_device_events)

Pamatujte, že při změně pořadí parametrů pro hlavičku metody `_WRAP_SIGNAL()`, budou názvy parametrů v C vždy `p0`, `p1` atd., protože nástroj `generate_extrac_defs` používá tyto názvy parametrů bez ohledu na názvy parametrů v API C. Takto prostě zmíněný nástroj v současnosti funguje.

##### Zpracování volitelných parametrů

For all macros processing method signatures except `_WRAP_SIGNAL()` and `_WRAP_VFUNC()` it is also possible to make the parameters optional so that extra C++ methods are generated without the specified optional parameter. For example, say that the following `*_new()` function were being wrapped as a constructor in the `Gtk::ToolButton` class:

    GtkToolItem* gtk_tool_button_new(GtkWidget* icon_widget, const gchar* label);

Also, say that the C API allowed NULL for the function's `label` parameter so that that parameter is optional. It would be possible to have `gmmproc` generate the original constructor (with all the parameters) along with an additional constructor without that optional parameter by appending a `{?}` to the parameter name like so:

    _WRAP_CTOR(ToolButton(Widget& icon_widget, const Glib::ustring& label{?}),
      gtk_tool_button_new)

In this case, two constructors would be generated: One with the optional parameter and one without it.

##### Zpracování výstupních parametrů

With `_WRAP_METHOD()` it is also possible for the return of the wrapped C function (if it has one) to be placed in an output parameter of the C++ method instead of having the C++ method also return a value like the C function does. To do that, simply include the output parameter in the C++ method parameter list appending a `{OUT}` to the output parameter name. For example, if `gtk_widget_get_request_mode()` is declared as the following:

    GtkSizeRequestMode gtk_widget_get_request_mode(GtkWidget* widget);

And having the C++ method set an output parameter is desired instead of returning a SizeRequestMode, something like the following could be used:

    _WRAP_METHOD(void get_request_mode(SizeRequestMode& mode{OUT}) const,
      gtk_widget_get_request_mode)

The `{OUT}` appended to the name of the `mode` output parameter tells `gmmproc` to place the return of the C function in that output parameter. In this case, however, a necessary initialization macro like the following would also have to be specified:

    _INITIALIZATION(`SizeRequestMode&',`GtkSizeRequestMode',`$3 = (SizeRequestMode)($4)')

Which could also be written as:

    _INITIALIZATION(`SizeRequestMode&',`GtkSizeRequestMode',`$3 = ($1)($4)')

`_WRAP_METHOD()` also supports setting C++ output parameters from C output parameters if the C function being wrapped has any. Suppose, for example, that we want to wrap the following C function that returns a value in its C output parameter `out_mime_type`:

    GInputStream* gdk_clipboard_read_finish(GdkClipboard* clipboard,
      GAsyncResult* result, const char** out_mime_type, GError** error)

To have `gmmproc` place the value returned in the C++ `out_mime_type` output parameter, something like the following `_WRAP_METHOD()` macro could be used:

    _WRAP_METHOD(Glib::RefPtr<Gio::InputStream> read_finish(
      const Glib::RefPtr<Gio::AsyncResult>& result,
      Glib::ustring& out_mime_type{>>}), gdk_clipboard_read_finish, errthrow)

The `{>>}` following the `out_mime_type` parameter name indicates that the C++ output parameter should be set from the value returned in the C parameter from the C function. `gmmproc` will generate a declaration of a temporary variable in which to store the value of the C output parameter and a statement that sets the C++ output parameter from the temporary variable. In this case it may be necessary to have an `_INITIALIZATION()` describing how to set a `Glib::ustring&` from a `const char**` such as the following:

    _INITIALIZATION(`Glib::ustring&',`const char*',`$3 = Glib::convert_const_gchar_ptr_to_ustring($4)')

##### String Parameter Processing

A string-valued input parameter in a C++ method is usually a const Glib::ustring& or a const std::string&. In C code it's a const gchar*. When an empty string is converted to const gchar*, it can be converted either to `nullptr` or to a pointer to an empty string (with `c_str()`). Some parameters in some C functions accept a `nullptr`, and interpret it in a special way. Other parameters must not be `nullptr`.

The default conversion in `_WRAP_METHOD()` and similar macros is

- for mandatory parameters (with or without default values): empty string to empty string,

- for optional parameters (with appended `{?}`): empty string to `nullptr`.

If the default conversion is not the best conversion, append `{NULL}` to a mandatory parameter or `{?!NULL}` to an optional parameter (`!NULL` = not `NULL`). If you append both a C parameter name and `NULL`, separate them with a space: `{c_param_name NULL}`.

#### Základní typy

Některé základní typy, které se používají v API v C mají lepší náhrady v C++. Například, není potřeba používat typ gboolean, protože C++ má bool. Následující seznam uvádí některé běžně používané typy v API v C a na co je můžete převést v obalující knihovně C++.

Typ v C
Typ v C++
gboolean
bool
gint
int
guint
guint
gdouble
double
gunichar
gunichar
gchar*
Glib::ustring
(or `std::string` for filenames)

### Ručně psané soubory se zdrojovými kódy

You might want to include additional source files that will not be generated by `gmmproc` from `.hg` and `.ccg` files. You can simply place these in your `libsomething/libsomethingmm` directory and mention them in the `meson.build` in the `extra_h_files` and `extra_cc_files` variables.

### Inicializace

Your library must be initialized before it can be used, to register the new types that it makes available. Also, the C library that you are wrapping might have its own initialization function that you should call. You can do this in an `init()` function that you can place in hand-coded `init.h` and `init.cc` files. This function should initialize your dependencies (such as the C function, and gtkmm) and call your generated `wrap_init()` function. For instance:

    void init()
    {
      Gtk::init_gtkmm_internals(); //Sets up the g type system and the Glib::wrap() table.
      wrap_init(); //Tells the Glib::wrap() table about the libsomethingmm classes.
    }

Implementace metody `wrap_init()` ve `wrap_init.cc` je generovaná skriptem `generate_wrap_init.pl`, ale deklarace ve `wrap_init.h` je psaná ručně, takže musíte upravit `wrap_init.h`, aby se funkce `wrap_init()` vyskytovala ve správném jmenném prostoru C++.

### Problémy v API v C

Nejspíše se setkáte s některými problémy v knihovně, kterou balíte, zejména pokud jde o nový projekt. Zde jsou některé běžné problémy včetně řešení.

#### Nejde předeklarovat struktury

By convention, structs are declared in glib/GTK-style headers like so:

    typedef struct _ExampleWidget ExampleWidget;

    struct _ExampleWidget
    {
      …
    };

Doplňující typedef umožňuje použít strukturu v hlavičkovém souboru bez vložení její plné definice, pouze jejím předeklarováním pomocí zopakování tohoto typedef. To znamená, že nemusíte vkládat hlavičkový soubor knihovny v C do svého hlavičkového souboru v C++ a tím ji udržet mimo veřejné API. `gmmproc` předpokládá, že je tato technika použita, takže pokud tomu tak není, uvidíte chybové hlášení kompilátoru.

This compiler error might look like this:

    example-widget.h:56: error: using typedef-name 'ExampleWidget' after 'struct'
    ../../libexample/libexamplemm/example-widget.h:34: error: 'ExampleWidget' has a previous declaration here
    make[4]: *** [example-widget.lo] Error 1

or this:

    example-widget.h:60: error: '_ExampleWidget ExampleWidget' redeclared as different kind of symbol
    ../../libexample/libexamplemm/example-widget.h:34: error: previous declaration of 'typedef struct _ExampleWidget ExampleWidget'

Takovéto věci se v knihovně v jazyce C opravují snadno, tak neváhejte poslat příslušnému správci záplatu.

#### Chybějící vlastnosti

By convention, glib/GTK-style objects have `*_new()` functions, such as `example_widget_new()` that do nothing more than call `g_object_new()` and return the result. The input parameters are supplied to `g_object_new()` along with the names of the properties for which they are values. For instance,

    GtkWidget* example_widget_new(int something, const char* thing)
    {
            return g_object_new (EXAMPLE_TYPE_WIDGET, "something", something, "thing", thing, NULL);
    }

To umožňuje vazbám mezi různými programovacími jazyky implementovat jejich vlastní ekvivalenty (jako jsou konstruktory v C++), bez použití funkce `*_new()`. Často je to nutné, protože mohou ve skutečnosti vytvářet instanci odvozenin GType, do kterých přidají vlastní háčky pro obsluhu signálů a virtuálních funkcí.

Minimálně by funkce `_new()` neměla používat žádné privátní API (funkce, které jsou jen v souboru .c). Dokonce i v případě, že neexistují žádné funkce, můžeme napsat dva až tři řádky kódu s implementací funkce `_new()`, pokud tyto řádky kódu používají API, které je pro nás dostupné.

Another workaround is to add a `*_construct()` function that the C++ constructor can call after instantiating its own type. For instance,

    GtkWidget* example_widget_new(int something, const char* thing)
    {
            ExampleWidget* widget;
            widget = g_object_new (EXAMPLE_TYPE_WIDGET, NULL);
            example_widget_construct(widget, "something", something, "thing", thing);
    }

    void example_widget_construct(ExampleWidget* widget, int something, const char* thing)
    {
            //Do stuff that uses private API:
            widget->priv->thing = thing;
            do_something(something);
    }

Provést opravu přidání vlastností a zajištěním, že budou spolu navzájem správně komunikovat, je v knihovně v jazyce C relativně obtížné, ale není to nemožné. Takže vyplňte chybové hlášení a zkuste příslušnému správci poslat záplatu.

### Dokumentace

Obecně používají projekty ve stylu gtkmm Doxygen, který čte speciálně formátované komentáře jazyka C++ a generuje z nich dokumentaci v HTML. Tyto komentáře můžete zapisovat přímo do hlavičkových souborů.

#### Recyklace dokumentace ke knihovnám C

You might wish to reuse documentation that exists for the C library that you are wrapping. GTK-style C libraries typically use gtk-doc or gi-docgen and therefore have source code comments formatted for gtk-doc or gi-docgen and some extra documentation in .sgml and .xml files. The docextract_to_xml.py script, from glibmm's `tools/defs_gen` directory, can read these files and generate an .xml file that `gmmproc` can use to generate doxygen comments. `gmmproc` will even try to transform the documentation to make it more appropriate for a C++ API.

Například

    ./docextract_to_xml.py -s ~/checkout/gnome/gtk/gtk/ > gtk_docs.xml

Because this automatic transformation is not always appropriate, you might want to provide hand-written text for a particular method. You can do this by copying the XML node for the function from your `something_docs.xml` file to the `something_docs_override.xml` file and changing the contents. Alternatively you can write your own documentation in the `.hg` file.

#### Struktura pro sestavení dokumentace

If you copied the skeleton source tree in mm-common and substituted the placeholder text, then you will already have suitable `meson.build` and `Doxyfile.in` files in the `doc/reference/` directory. You probably need to modify the `tag_file_modules` variable in `meson.build`, though. With the mm-common build setup, the list of Doxygen input files is not defined in the Doxygen configuration file, but passed along from `meson/ninja` to the standard input of `doxygen`.