# Manual de GTK-Doc

1.24.1

Manual de usuarios para desenvolvedores con instrucións do uso de GTK-Doc.

Chris
Lyttle

     chris@wilddev.net

Dan
Mueth

     d-mueth@uchicago.edu

Stefan
Sauer (Kost)

     ensonic@users.sf.net

Proxecto GTK-Doc

    gtk-doc-list@gnome.org

2000, 2005
Dan Mueth and Chris Lyttle
2007-2019
Stefan Sauer (Kost)

Pode copiar, distribuír e modificar este documento baixo os termos da Licenza de Documentación Libre GNU, na súa versión 1.1 ou posterior, publicada pola Free Software Foundation, sen seccións invariantes e sen textos de portada ou de contraportada. Inclúese unha cópida da licenza.

Many of the names used by companies to distinguish their products and services are claimed as trademarks. Where those names appear in any GNOME documentation, and those trademarks are made aware to the members of the GNOME Documentation Project, the names have been printed in caps or initial caps.

1.33.0
1 Oct 2020
mc
gtk4 version
1.32.1
15 Aug 2019
ss
dev version
1.32
15 Aug 2019
ss
hotfix release
1.31
05 Aug 2019
ss
refactorings and more test coverage
1.30
08 May 2019
ss
more test coverage
1.29
28 Aug 2018
ss
bug fixes
1.28
24 Mar 2018
ss
bug fixes
1.27
07 Dec 2017
ss
fine tuning of the python port
1.26
11 Aug 2017
ss
port all tools from perl/bash to python
1.25
21 March 2016
ss
bug fixes, test cleanups
1.24
29 May 2015
ss
bug fix
1.23
17 May 2015
ss
bug fix
1.22
07 May 2015
ss
bug fixes, dropping deprecated features
1.21
17 de Xullo de 2014
ss
arranxos de erros, retirado de características obsoletas
1.20
16 de Febreiro de 2014
ss
arranxos de erros, compatibilidade de markdown, melloras de estilo
1.19
05 de Xuño de 2013
ss
arranxos de erros
1.18
14 de Setembro de 2011
ss
arranxos de erros, melloras de velocidade, compatibilidade de markdown
1.17
26 Feb 2011
sk
urgent bug fix update
1.16
14 Jan 2011
sk
bugfixes, layout improvements
1.15
21 May 2010
sk
bug and regression fixes
1.14
28 March 2010
sk
bugfixes and performance improvements
1.13
18 December 2009
sk
broken tarball update
1.12
18 December 2009
sk
new tool features and bugfixes
1.11
16 November 2008
mal
GNOME doc-utils migration
Fran Diéguez
frandieguez@gnome.org
2014.
Fran Diéguez

## Introduction

This chapter introduces GTK-Doc and gives an overview of what it is and how it is used.

### What is GTK-Doc?

GTK-Doc is used to document C code. It is typically used to document the public API of libraries, such as GLib-based libraries, but it can also be used to document application code.

### How Does GTK-Doc Work?

GTK-Doc works by reading specially-formatted comment blocks placed inside the source files to document symbols such as functions, macros, structs, enums, etc. (though note that for most kind of symbols GTK-Doc will only document the symbols that are declared in header files; for example it won't produce output for static functions).

GTK-Doc also reads template files where documentation can be added there as well.

GTK-Doc consists of a number of programs, each performing a different step in the process.

The main steps are:

1. Writing the documentation.

   The author fills in the source files with the documentation for each function, macro, structs or unions, etc.

2. Gathering information about the code.

   gtkdoc-scan scans the header files of the code looking for declarations of functions, macros, enums, structs, and unions. It creates the file `<module>-decl-list.txt` containing a list of the declarations, placing them into sections according to which header file they are in. On the first run this file is copied to `<module>-sections.txt`. The author can rearrange the sections, and the order of the declarations within them, to produce the final desired order. The second file it generates is `<module>-decl.txt`. This file contains the full declarations found by the scanner. If for some reason one would like some symbols to show up in the docs, where the full declaration cannot be found by the scanner or the declaration should appear differently, one can place entities similar to the ones in `<module>-decl.txt` into `<module>-overrides.txt`.

   gtkdoc-scangobj can also be used to dynamically query a library about any GObject subclasses it exports. It saves information about each object's position in the class hierarchy and about any GObject properties and signals it provides.

   gtkdoc-scanobj should not be used anymore. It was needed in the past when GObject was still GtkObject inside GTK.

3. Generating the XML and HTML/PDF.

   gtkdoc-mkdb turns the template files into XML files in the `xml/` subdirectory. If the source code contains documentation for symbols, using the special comment blocks, it gets merged in here. If there are no tmpl files used it only reads docs from sources and introspection data.

   gtkdoc-mkhtml turns the XML files into HTML files in the `html/` subdirectory. Likewise gtkdoc-mkpdf turns the XML files into a PDF document called `<package>.pdf`.

   Files in `xml/` and `html/` directories are always overwritten. One should never edit them directly.

4. Fixing up cross-references between documents.

   After installing the HTML files, gtkdoc-fixxref can be run to fix up any cross-references between separate documents. For example, the GTK documentation contains many cross-references to types documented in the GLib manual.

   When creating the source tarball for distribution, gtkdoc-rebase turns all external links into web-links. When installing distributed (pregenerated) docs the same application will try to turn links back to local links (where those docs are installed).

### Getting GTK-Doc

#### Requirements

python 2/3 - the main scripts are written in python.

xsltproc - the xslt processor from libxslt xmlsoft.org/XSLT/

docbook-xsl - the docbook xsl stylesheets sourceforge.net/projects/docbook/files/docbook-xsl

One of source-highlight, highlight or vim - optional - used for syntax highlighting of examples

### About GTK-Doc

Historically GTK-Doc was used to generate template files from the sources code. These template files could be used by developers to enter the API documentation. This approach was rather inconvenient because it required to keep the generated files under version control. Since GTK-Doc 1.9 it became possible to place all API information into source comments, which made the template support obsolete. In version 1.26 template support has been removed.

(FIXME)

(authors, web pages, mailing list, license, future plans, comparison with other similar systems.)

### About this Manual

(FIXME)

(who it is meant for, where you can get it, license)

## Project Setup

This Chapter describes the steps that are necessary to integrate GTK-Doc into your project. The integration of GTK-Doc into a project includes the following steps:

- Preparation of the directory structure and creating required configuration files for your GTK-Doc documentation (see Setting up a skeleton documentation).

- Adjusting the build system to build your documentation using the GTK-Doc tools. Multiple build systems are supported, in this manual we describe how to integrate GTK-Doc with Autotools, CMake, and plain Makefiles.

- Adding GTK-Doc specific files to version control and deciding which files to ignore (see Integration with version control systems).

The following sections assume we work on a project called `meep`. This project contains two packages (or modules), a library called `libmeep` and an end-user app called `meeper`.

### Setting up a skeleton documentation

A common convention is to place documentation into a folder called `docs` inside your top-level project directory. We usually distinguish between reference documentation intended for developers and an user manual intended for end-users. Again the convention is to have separate folders for both. We usually place the reference documentation in a folder named `reference` and the end-user manual in a folder named `help` as.

According to the above convention the documentation for our `libmeep` package would be placed into: `docs/reference/libmeep`.

For packages with just one library or application the documentation could also be placed directly into `docs/reference`.

It is not mandatory to use the above convention, but if you choose to use a different directory structure you must adjust your build system configuration to match your directory structure.

In the following sections we will assume a directory structure for our meep project that uses the above conventions.

#### Example directory structure of meep project

    meep/
      docs/
        reference/  # reference documentation
          libmeep/
          meeper/
        help/       # optional: user manual
          meeper/
      src/
        libmeep/
        meeper/

### Integration with Autotools

Integration of GTK-Doc into an autotools-based build system requires the following steps:

- Ensure that gtkdocize is run once before the `configure` script. If an `autogen.sh` script is present, adjust it to check for GTK-Doc and add a call to gtkdocize.

  The main purpose of gtkdocize is to make the `gtk-doc.make` Makefile and the `gtk-doc.m4` macro definition file available to the build system, either by copying or linking it into the project.

- Add the necessary autoconf macros to `configure.ac` to enable GTK-Doc in your build system to allow configuration of GTK-Doc via the generated `configure` script.

  Among others with registers the `--enable-gtk-doc` option with the `configure` script.

- Create an automake script for each application or library in your project. In the example used in this documentation this step applies to both `meeper` and `libmeep`.

In the following sections, we will perform the above steps in reverse order. We start with the automake scripts and work our way up to `configure.ac` and `autogen.sh`. Then we show how enable Gtk-Doc in the build system and how to build the documentation.

#### Integration with automake

First copy the `Makefile.am` from the `examples` sub-directory of the gtkdoc-sources to your project's reference documentation directory (e.g. `docs/reference/<package>`). A local copy should be available under e.g. `/usr/share/doc/gtk-doc-tools/examples/Makefile.am`. If you have multiple packages repeat this for each one.

Do not forget to add each `Makefile.am` to the `AC_CONFIG_FILES` macro in `configure.ac`. For `docs/reference/libmeep/Makefile.am` you will need to add the entry `docs/reference/libmeep/Makefile` to `AC_CONFIG_FILES`.

##### Example directory structure with `Makefiles.am`

    meep/
      docs/
        reference/  # reference documentation
          libmeep/
            Makefile.am
          meeper/
            Makefile.am
        help/       # optional: user manual
          meeper/
      src/
        libmeep/
        meeper/

Next, you need to customize the copied Makefiles and provide values for the various parameters in each `Makefile.am`.

All settings have a comment above them that describes their purpose and how to customize the setting.

Most settings are used to supply extra flags to the respective tools to which they apply. Every tool has a variable of the form `<TOOLNAME>_OPTIONS` (e.g. the tool gtkdoc-mkhtml has an option named `MKHTML_OPTIONS`).

All the tools support `--help` to list the supported options.

The following list explains the most relevant options. Check the example `Makefile.am` for additional options.

- `DOC_MODULE` is used to provide the name of the package that is being documentated (e.g. `meeper`, or `libmeep`).

- `DOC_SOURCE_DIR` is used to specify the location of source directory which GTK-Doc searches for your API documentation. This will usually be `DOC_SOURCE_DIR=$(top_srcdir)/src` or a sub-directory of that directory.

- `HFILE_GLOB` and `CFILE_GLOB` are used for dependencies. Each option take a file-glob (e.g. `HFILE_GLOB=$(top_srcdir)/src/*.c`). The documentation will be rebuilt if any of the matched files change.

- `EXTRA_HFILES` allows to specify extra header files to include when scanning for API documentation, which are not found under `DOC_SOURCE_DIR` (e.g. `EXTRA_HFILES=$(top_srcdir}/contrib/extra.h`).

- `IGNORE_HFILES` allows to specify header files or directories to ignore when scanning for API documentation. Use the basename of the file or directory (e.g. `IGNORE_HFILES=gtkdebug.h gtkintl.h private_code_folder`).

- `HTML_IMAGES` allows to specify images files which will be copied into the `html/` directory of the generated documentation. If your API documentation includes any images they need to be added to this option (e.g. `HTML_IMAGES=$(top_srcdir)/gtk/stock-icons/stock_about_24.png`).

- `content_files` allows to specify extra files that are included by `$(DOC_MAIN_SGML_FILE)` (e.g. `content_files=running.xml building.xml changes-2.0.xml`).

- `expand_content_files` allows to specify files where gtk-doc abbreviations such as `#GtkWidget` are expanded (e.g. `expand_content_files=running.xml`).

#### Integration with autoconf

Integration with autoconf is very simple and includes one required step and an additional optional (but recommended) step.

The first step is to add the `GTK_DOC_CHECK` macro to your `configure.ac` script. This registers several configure options to enable GTK-Doc and allows you to set default arguments for gtkdocize.

Make sure that the `GTK_DOC_CHECK` macro is not indented. The macro must start at the beginning of the line and should not start with whitespace.

The second step is to add the `AC_CONFIG_MACRO_DIR(m4)` to your `configure.ac`. This is not required but helps gtkdocize to automatically copy the macro definition (e.g `gtk-doc.m4`) which contains the `GTK_DOC_CHECK` macro to your project's macro directory. Without this, the GTK_DOC_CHECK macro might not be found and you would need to explicitly tell the aclocal tool where to find the macro definition file.

##### Minimal integration with autoconf

    # recommended: set m4 directory
    AC_CONFIG_MACRO_DIR(m4)
    # optional: register gtk-doc in configure
    GTK_DOC_CHECK([1.28])

The above example works, but will require all developers to have gtk-doc installed. A better way is to make building the documentation optional as shown in the next example:

##### Integration with optional gtk-doc dependency

    m4_ifdef([GTK_DOC_CHECK], [
    # recommended: set m4 directory
    AC_CONFIG_MACRO_DIR(m4)
    # optional: register gtk-doc in configure
    GTK_DOC_CHECK([1.28])
    ],[
    AM_CONDITIONAL([ENABLE_GTK_DOC], false)
    ])

The first argument is used to check for the Gtk-Doc version at configure time. The 2nd, optional argument is used by gtkdocize. The GTK_DOC_CHECK macro also adds several configure switches:

1. --with-html-dir=PATH : path to installed docs

2. --enable-gtk-doc : use gtk-doc to build documentation [default=no]

3. --enable-gtk-doc-html : build documentation in html format [default=yes]

4. --enable-gtk-doc-pdf : build documentation in pdf format [default=no]

GTK-Doc is disabled by default! Remember to pass the option `'--enable-gtk-doc'` to the next `configure` run. Otherwise pregenerated documentation is installed (which makes sense for users but not for developers).

After all changes to `configure.ac` are made, update the `configure` file. This can be done by re-running `autogen.sh`.

#### Integration with autogen

Most projects will have an `autogen.sh` script to setup the build infrastructure after the project was checked out from a version control system (such as git or svn). GTK-Doc comes with a script called gtkdocize which can be used to copy the necessary files needed by Gtk-Doc to the source directory.

It should be run before autoreconf, autoheader, automake or autoconf.

##### Running gtkdocize from autogen.sh

    gtkdocize || exit 1

##### Conditionally run gtkdocize from autogen.sh

    GTKDOCIZE=$(which gtkdocize 2>/dev/null)
    if test $? -ne 0; then
      echo "No gtk-doc support found. You can't build the docs."
    else
      $GTKDOCIZE || exit 1
    fi

When running gtkdocize it copies `gtk-doc.make` to your project root (or any directory specified by the `--docdir` option).

gtkdocize checks your `configure.ac` script for the `GTK_DOC_CHECK` macro. The `GTK_DOC_CHECK` macro can be used to pass extra arguments to the gtkdocize script. the 2nd parameter in the `GTK_DOC_CHECK` macro.

Alternatively, additional arguments can also be passed to gtkdocize via the `GTKDOCIZE_FLAGS` environment variable, or by directly specifying them to gtkdocize in `autogen.sh`.

#### Executing GTK-Doc from the Build System

After the previous steps it's time to run the build. First we need to rerun `autogen.sh`. If this script runs configure for you, then give it the `--enable-gtk-doc` option. Otherwise manually run `configure` with this option afterwards.

The first make run generates several additional files in the doc-directories. The important ones are: `<package>.types`, `<package>-docs.xml` (in the past .sgml), `<package>-sections.txt`.

##### Running the doc build

    ./autogen.sh --enable-gtk-doc
    make

Now you can point your browser to `docs/reference/<package>/index.html`. With this initial setup you will only see a very simple document. The next chapter will teach you how to add API documentation to your code via special comment blocks. The Chapter afterwards introduces additional files and shows how to edit the master template to add additional chapters and sections to your documentation files.

### Integration with CMake build systems

GTK-Doc now provides a `GtkDocConfig.cmake` module (and the corresponding `GtkDocConfigVersion.cmake` module). This provides a `gtk_doc_add_module` command that you can set in your `CMakeLists.txt` file.

The following example shows how to use this command.

#### Example of using GTK-Doc from CMake

    find_package(GtkDoc 1.25 REQUIRED)

    # Create the doc-libmeep target.
    gtk_doc_add_module(
       libmeep ${CMAKE_SOURCE_DIR}/libmeep
          XML meep-docs.xml
          LIBRARIES libmeep
    )

    # Build doc-libmeep as part of the default target. Without this, you would
    # have to explicitly run something like `make doc-libmeep` to build the docs.
    add_custom_target(documentation ALL DEPENDS doc-libmeep)

    # Install the docs. (This assumes you're using the GNUInstallDirs CMake module
    # to set the CMAKE_INSTALL_DOCDIR variable correctly).
    install(DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/libmeep/html
            DESTINATION ${CMAKE_INSTALL_DOCDIR})

### Integration with plain makefiles or other build systems

In the case one does not want to use automake and therefore `gtk-doc.mak` one will need to call the gtkdoc tools in the right order in own makefiles (or other build tools).

#### Documentation build steps

    DOC_MODULE=meep
    // sources have changed
    gtkdoc-scan --module=$(DOC_MODULE) <source-dir>
    gtkdoc-scangobj --module=$(DOC_MODULE)
    gtkdoc-mkdb --module=$(DOC_MODULE) --output-format=xml --source-dir=<source-dir>
    // xml files have changed
    mkdir html
    cd html && gtkdoc-mkhtml $(DOC_MODULE) ../meep-docs.xml
    gtkdoc-fixxref --module=$(DOC_MODULE) --module-dir=html

One will need to look at the `Makefile.am` and `gtk-doc.mak` to pick the extra options needed.

### Integration with version control systems

As a rule of thumb, it's the files you edit which should go under version control. For typical projects it's these files: `<package>.types`, `<package>-docs.xml` (in the past .sgml), `<package>-sections.txt`, `Makefile.am`.

Files in the `xml/` and `html/` directories should not go under version control. Neither should any of the `.stamp` files.

## Documenting the code

GTK-Doc uses source code comment with a special syntax for code documentation. Further it retrieves information about your project structure from other sources. During the next section you will find all information about the syntax of the comments.

The GTK-Doc scanner can handle the majority of C headers fine. In the case of receiving warnings from the scanner that look like a special case, one can hint GTK-Doc to skip over them.

### GTK-Doc comment block

    #ifndef __GTK_DOC_IGNORE__
    /* unparseable code here */
    #endif

### Limitations

Note, that GTK-Doc's supports `#ifndef(__GTK_DOC_IGNORE__)` but not `#if !defined(__GTK_DOC_IGNORE__)` or other combinations.

### Documentation comments

A multiline comment that starts with an additional '*' marks a documentation block that will be processed by the GTK-Doc tools.

#### GTK-Doc comment block

    /**
     * identifier:
     * documentation ...
     */

The 'identifier' is one line with the name of the item the comment is related to. The syntax differs a little depending on the item. (TODO add table showing identifiers)

The 'documentation' block is also different for each symbol type. Symbol types that get parameters such as functions or macros have the parameter description first followed by a blank line (just a '*'). Afterwards follows the detailed description. All lines (outside program listings and CDATA sections) just containing a ' *' (blank-asterisk) are converted to paragraph breaks. If you don't want a paragraph break, change that into ' * ' (blank-asterisk-blank-blank). This is useful in preformatted text (code listings).

When documenting code, describe two aspects:

- What it is: The name for a class or function can sometimes be misleading for people coming from a different background.

- What it does: Tell about common uses. Put it in relation with the other API.

One advantage of hyper-text over plain-text is the ability to have links in the document. Writing the correct markup for a link can be tedious though. GTK-Doc comes to help by providing several useful abbreviations.

- Use function() to refer to functions or macros which take arguments.

- Use @param to refer to parameters. Also use this when referring to parameters of other functions, related to the one being described.

- Use %constant to refer to a constant, e.g. %G_TRAVERSE_LEAFS.

- Use #symbol to refer to other types of symbol, e.g. structs and enums and macros which don't take arguments.

- Use #Object::signal to refer to a GObject signal.

- Use #Object:property to refer to a GObject property.

- Use #Struct.field to refer to a field inside a structure and #GObjectClass.foo_bar() to refer to a vmethod.

If you need to use the special characters '<', '>', '()', '@', '%', or '#' in your documentation without GTK-Doc changing them you can use the XML entities "&lt;", "&gt;", "&lpar;", "&rpar;", "&commat;", "&percnt;" and "&num;" respectively or escape them with a backslash '\'.

DocBook can do more than just links. One can also have lists, examples, headings, and images. As of version 1.20, the preferred way is to use a subset of the basic text formatting syntax called Markdown. On older GTK-Doc versions any documentation that includes Markdown will be rendered as is. For example, list items will appear as lines starting with a dash.

While markdown is now preferred one can mix both. One limitation here is that one can use docbook xml within markdown, but markdown within docbook xml is not supported.

In older GTK-Doc releases, if you need support for additional formatting, you would need to enable the usage of docbook XML tags inside doc-comments by putting `--xml-mode` (or `--sgml-mode`) in the variable MKDB_OPTIONS inside `Makefile.am`.

#### GTK-Doc comment block using Markdown

    /**
     * identifier:
     *
     * documentation paragraph ...
     *
     * # Sub Heading #
     *
     * ## Second Sub Heading
     *
     * # Sub Heading With a Link Anchor # {#heading-two}
     *
     * more documentation:
     *
     * - list item 1
     *
     *   Paragraph inside a list item.
     *
     * - list item 2
     *
     * 1. numbered list item
     *
     * 2. another numbered list item
     *
     * Another paragraph. [A Link to the GNOME Website](http://www.gnome.org/)
     *
     * ![an inline image](plot-result.png)
     *
     * [A link to the heading anchor above][heading-two]
     *
     * A C-language example:
     * |[<!-- language="C" -->
     * GtkWidget *label = gtk_label_new ("Gorgeous!");
     * ]|
     */

More examples of what markdown tags are supported can be found in the GTK Documentation Markdown Syntax Reference.

As already mentioned earlier GTK-Doc is for documenting public API. Thus one cannot write documentation for static symbols. Nevertheless it is good to comment those symbols too. This helps other developers to understand your code. Therefore we recommend to comment these using normal comments (without the 2nd '*' in the first line). If later the function needs to be made public, all one needs to do is to add another '*' in the comment block and insert the symbol name at the right place inside the sections file.

### Documenting sections

Each section of the documentation contains information about one class or module. To introduce the component one can write a section block. The short description is also used inside the table of contents. All the @fields are optional.

#### Section comment block

    /**
     * SECTION:meepapp
     * @short_description: the application class
     * @title: Meep application
     * @section_id:
     * @see_also: #MeepSettings
     * @stability: Stable
     * @include: meep/app.h
     * @image: application.png
     *
     * The application class handles ...
     */

SECTION:<name>

  The name links the section documentation to the respective part in the `<package>-sections.txt` file. The name given here should match the <FILE> tag in the `<package>-sections.txt` file.

@short_description

  A one line description of the section, that later will appear after the links in the TOC and at the top of the section page.

@title

  The section title defaults to <name> from the SECTION declaration. It can be overridden with the @title field.

@section_id

  Overrides the use of title as a section identifier. For GObjects the <title> is used as a section_id and for other sections it is <MODULE>-<title>.

@see_also

  A list of symbols that are related to this section.

@stability

  An informal description of the stability level this API has. We recommend the use of one of these terms:

  - Stable - The intention of a Stable interface is to enable arbitrary third parties to develop applications to these interfaces, release them, and have confidence that they will run on all minor releases of the product (after the one in which the interface was introduced, and within the same major release). Even at a major release, incompatible changes are expected to be rare, and to have strong justifications.

  - Unstable - Unstable interfaces are experimental or transitional. They are typically used to give outside developers early access to new or rapidly changing technology, or to provide an interim solution to a problem where a more general solution is anticipated. No claims are made about either source or binary compatibility from one minor release to the next.

  - Private - An interface that can be used within the GNOME stack itself, but that is not documented for end-users. Such functions should only be used in specified and documented ways.

  - Internal - An interface that is internal to a module and does not require end-user documentation. Functions that are undocumented are assumed to be Internal.

@include

  The `#include` files to show in the section synopsis (a comma separated list), overriding the global value from the section file or command line. This item is optional.

@image

  The image to display at the top of the reference page for this section. This will often be some sort of a diagram to illustrate the visual appearance of a class or a diagram of its relationship to other classes. This item is optional.

To avoid unnecessary recompilation after doc-changes put the section docs into the c-source where possible.

### Documenting symbols

Each symbol (function, macro, struct, enum, signal and property) is documented in a separate block. The block is best placed close to the definition of the symbols so that it is easy to keep them in sync. Thus functions are usually documented in the c-source and macros, structs and enums in the header file.

#### General tags

You can add versioning information to all documentation elements to tell when an API was introduced, or when it was deprecated.

##### Versioning Tags

Since:

  Description since which version of the code the API is available.

Deprecated:

  Paragraph denoting that this function should no be used anymore. The description should point the reader to the new API.

You can also add stability information to all documentation elements to indicate whether API stability is guaranteed for them for all future minor releases of the project.

The default stability level for all documentation elements can be set by passing the `--default-stability` argument to gtkdoc-mkdb with one of the values below.

##### Stability Tags

Stability: Stable

  Mark the element as stable. This is for public APIs which are guaranteed to remain stable for all future minor releases of the project.

Stability: Unstable

  Mark the element as unstable. This is for public APIs which are released as a preview before being stabilised.

Stability: Private

  Mark the element as private. This is for interfaces which can be used by tightly coupled modules, but not by arbitrary third parties.

##### General tags

    /**
     * foo_get_bar:
     * @foo: some foo
     *
     * Retrieves @foo's bar.
     *
     * Returns: @foo's bar
     *
     * Since: 2.6
     * Deprecated: 2.12: Use foo_baz_get_bar() instead.
     */
    Bar *
    foo_get_bar(Foo *foo)
    {
    ...

#### Annotations

Documentation blocks can contain annotation-tags. These tags will be rendered with tooltips describing their meaning. The tags are used by GObject Introspection to generate language bindings. A detailed list of the supported tags can be found in the GObject Introspection documentation.

##### Annotations

    /**
     * foo_get_bar: (annotation)
     * @foo: (annotation): some foo
     *
     * Retrieves @foo's bar.
     *
     * Returns: (annotation): @foo's bar
     */
    ...
    /**
     * foo_set_bar_using_the_frobnicator: (annotation) (another annotation)
     *                                    (and another annotation)
     * @foo: (annotation) (another annotation): some foo
     *
     * Sets bar on @foo.
     */

#### Function comment block

Please remember to:

- Document whether returned objects, lists, strings, etc, should be freed/unrefed/released.

- Document whether parameters can be NULL, and what happens if they are.

- Mention interesting pre-conditions and post-conditions where appropriate.

Gtk-doc assumes all symbols (macros, functions) starting with '_' are private. They are treated like static functions.

##### Function comment block

    /**
     * function_name:
     * @par1:  description of parameter 1. These can extend over more than
     * one line.
     * @par2:  description of parameter 2
     * @...: a %NULL-terminated list of bars
     *
     * The function description goes here. You can use @par1 to refer to parameters
     * so that they are highlighted in the output. You can also use %constant
     * for constants, function_name2() for functions and #GtkWidget for links to
     * other declarations (which may be documented elsewhere).
     *
     * Returns: an integer.
     *
     * Since: 2.2
     * Deprecated: 2.18: Use other_function() instead.
     */

##### Function tags

Returns:

  Paragraph describing the returned result.

@...:

  In case the function has variadic arguments, you should use this tag (@Varargs: does also work for historic reasons).

#### Property comment block

##### Property comment block

    /**
     * SomeWidget:some-property:
     *
     * Here you can document a property.
     */
    g_object_class_install_property (object_class, PROP_SOME_PROPERTY, ...);

#### Signal comment block

Please remember to:

- Document when the signal is emitted and whether it is emitted before or after other signals.

- Document what an application might do in the signal handler.

##### Signal comment block

    /**
     * FooWidget::foobarized:
     * @widget: the widget that received the signal
     * @foo: some foo
     * @bar: some bar
     *
     * The ::foobarized signal is emitted each time someone tries to foobarize @widget.
     */
    foo_signals[FOOBARIZED] =
      g_signal_new ("foobarized",
                    ...

#### Struct comment block

##### Struct comment block

    /**
     * FooWidget:
     * @bar: some #gboolean
     *
     * This is the best widget, ever.
     */
    typedef struct _FooWidget {
      GtkWidget parent_instance;

      gboolean bar;
    } FooWidget;

Use `/*< private >*/` before the private struct fields you want to hide. Use `/*< public >*/` for the reverse behaviour.

If the first field is "g_iface", "parent_instance" or "parent_class" it will be considered private automatically and doesn't need to be mentioned in the comment block.

Struct comment blocks can also be used for GObjects and GObjectClasses. It is usually a good idea to add a comment block for a class, if it has vmethods (as this is how they can be documented). For the GObject itself one can use the related section docs, having a separate block for the instance struct would be useful if the instance has public fields. One disadvantage here is that this creates two index entries of the same name (the structure and the section).

#### Enum comment block

##### Enum comment block

    /**
     * Something:
     * @SOMETHING_FOO: something foo
     * @SOMETHING_BAR: something bar
     *
     * Enum values used for the thing, to specify the thing.
     */
    typedef enum {
      SOMETHING_FOO,
      SOMETHING_BAR,
      /*< private >*/
      SOMETHING_COUNT
    } Something;

Use `/*< private >*/` before the private enum values you want to hide. Use `/*< public >*/` for the reverse behaviour.

### Inline program documentation

You can document programs and their commandline interface using inline documentation.

#### Tags

PROGRAM

  Defines the start of a program documentation.

@short_description:

  Defines a short description of the program. (Optional)

@synopsis:

  Defines the arguments, or list of arguments that the program can take. (Optional)

@see_also:

  See Also manual page section. (Optional)

@arg:

  Argument(s) passed to the program and their description. (Optional)

Description:

  A longer description of the program.

Returns:

  Specify what value(s) the program returns. (Optional)

#### Example of program documentation.

##### Program documentation block

    /**
     * PROGRAM:test-program
     * @short_description: A test program
     * @synopsis: test-program [*OPTIONS*...] --arg1 *arg* *FILE*
     * @see_also: test(1)
     * @--arg1 *arg*: set arg1 to *arg*
     * @--arg2 *arg*: set arg2 to *arg*
     * @-v, --version: Print the version number
     * @-h, --help: Print the help message
     *
     * Long description of program.
     *
     * Returns: Zero on success, non-zero on failure
     */
    int main(int argc, char *argv[])
    {
    	return 0;
    }

### Useful DocBook tags

Here are some DocBook tags which are most useful when documenting the code.

To link to another section in the GTK docs:

    <link linkend="glib-Hash-Tables">Hash Tables</link>

The linkend is the SGML/XML id on the top item of the page you want to link to. For most pages this is currently the part ("gtk", "gdk", "glib") and then the page title ("Hash Tables"). For widgets it is just the class name. Spaces and underscores are converted to '-' to conform to SGML/XML.

To refer to an external function, e.g. a standard C function:

    <function>...</function>

To include example code:

    <example>
      <title>Using a GHashTable.</title>
      <programlisting language="C">
          ...
      </programlisting>
    </example>

or possibly this, for very short code fragments which don't need a title:

    <informalexample>
      <programlisting language="C">
      ...
      </programlisting>
    </informalexample>

In both cases, the language attribute is optional and is used as a hint to the syntax highlighting engine (pygments for html output). For the latter GTK-Doc also supports an abbreviation:

    |[<!-- language="C" -->
      ...
    ]|

To include bulleted lists:

    <itemizedlist>
      <listitem>
        <para>
          ...
        </para>
      </listitem>
      <listitem>
        <para>
          ...
        </para>
      </listitem>
    </itemizedlist>

To include a note which stands out from the text:

    <note>
      <para>
        Make sure you free the data after use.
      </para>
    </note>

To refer to a type:

    <type>unsigned char</type>

To refer to an external structure (not one described in the GTK docs):

    <structname>XFontStruct</structname>

To refer to a field of a structure:

    <structfield>len</structfield>

To refer to a class name, we could possibly use:

    <classname>GtkWidget</classname>

but you'll probably be using #GtkWidget instead (to automatically create a link to the GtkWidget page - see the abbreviations).

To emphasize text:

    <emphasis>This is important</emphasis>

For filenames use:

    <filename>/home/user/documents</filename>

To refer to keys use:

    <keycombo><keycap>Control</keycap><keycap>L</keycap></keycombo>

## Filling the extra files

There are a couple of extra files, that need to be maintained along with the inline source code comments: `<package>.types`, `<package>-docs.xml` (in the past .sgml), `<package>-sections.txt`.

### Editing the types file

If your library or application includes GObjects, you want their signals, arguments/parameters and position in the hierarchy to be shown in the documentation. All you need to do, is to list the `xxx_get_type` functions together with their include inside the `<package>.types` file.

#### Example <package>.types file

    #include <gtk/gtk.h>

    gtk_accel_label_get_type
    gtk_adjustment_get_type
    gtk_alignment_get_type
    gtk_arrow_get_type

Since GTK-Doc 1.8 gtkdoc-scan can generate this list for you. Just add "--rebuild-types" to SCAN_OPTIONS in `Makefile.am`. If you use this approach you should not dist the types file nor have it under version control.

### Editing the master document

GTK-Doc produces documentation in DocBook SGML/XML. When processing the inline source comments, the GTK-Doc tools generate one documentation page per class or module as a separate file. The master document includes them and place them in an order.

While GTK-Doc creates a template master document for you, later runs will not touch it again. This means that one can freely structure the documentation. That includes grouping pages and adding extra pages. GTK-Doc has now a test suite, where also the master-document is recreated from scratch. Its a good idea to look at this from time to time to see if there are some new goodies introduced there.

Do not create tutorials as extra documents. Just write extra chapters. The benefit of directly embedding the tutorial for your library into the API documentation is that it is easy to link for the tutorial to symbol documentation. Apart chances are higher that the tutorial gets updates along with the library.

So what are the things to change inside the master document? For a start is only a little. There are some placeholders (text in square brackets) there which you should take care of.

#### Master document header

    <bookinfo>
      <title>MODULENAME Reference Manual</title>
      <releaseinfo>
        for MODULENAME [VERSION]
        The latest version of this documentation can be found on-line at
        <ulink role="online-location" url="http://[SERVER]/MODULENAME/index.html">http://[SERVER]/MODULENAME/</ulink>.
      </releaseinfo>
    </bookinfo>

    <chapter>
      <title>[Insert title here]</title>

In addition a few option elements are created in commented form. You can review these and enable them as you like.

#### Optional part in the master document

      <!-- enable this when you use gobject introspection annotations
      <xi:include href="xml/annotation-glossary.xml"><xi:fallback /></xi:include>
      -->

Finally you need to add new section whenever you introduce one. The gtkdoc-check tool will remind you of newly generated xml files that are not yet included into the doc.

#### Including generated sections

      <chapter>
        <title>my library</title>
          <xi:include href="xml/object.xml"/>
          ...

### Editing the section file

The section file is used to organise the documentation output by GTK-Doc. Here one specifies which symbol belongs to which module or class and control the visibility (public or private).

The section file is a plain text file with tags delimiting sections. Blank lines are ignored and lines starting with a '#' are treated as comment lines.

While the tags make the file look like xml, it is not. Please do not close tags like <SUBSECTION>.

#### Including generated sections

    <INCLUDE>libmeep/meep.h</INCLUDE>

    <SECTION>
    <FILE>meepapp</FILE>
    <TITLE>MeepApp</TITLE>
    MeepApp
    <SUBSECTION Standard>
    MEEP_APP
    ...
    MeepAppClass
    meep_app_get_type
    </SECTION>

The <FILE> ... </FILE> tag is used to specify the file name, without any suffix. For example, using '<FILE>gnome-config</FILE>' will result in the section declarations being output in the template file `tmpl/gnome-config.sgml`, which will be converted into the DocBook XML file `xml/gnome-config.sgml` or the DocBook XML file `xml/gnome-config.xml`. (The name of the HTML file is based on the module name and the section title, or for GObjects it is based on the GObjects class name converted to lower case).

The <TITLE> ... </TITLE> tag is used to specify the title of the section. It is only useful before the templates (if used) are initially created, since the title set in the template file overrides this. Also if one uses SECTION comment in the sources, this is obsolete.

You can group items in the section by using the <SUBSECTION> tag. Currently it outputs a blank line between subsections in the synopsis section. You can also use <SUBSECTION Standard> for standard GObject declarations (e.g. the functions like g_object_get_type and macros like G_OBJECT(), G_IS_OBJECT() etc.). Currently these are left out of the documentation. You can also use <SUBSECTION Private> for private declarations which will not be output (it is a handy way to avoid warning messages about unused declarations). If your library contains private types which you don't want to appear in the object hierarchy and the list of implemented or required interfaces, add them to a Private subsection. Whether you would place GObject and GObjectClass like structs in public or Standard section depends if they have public entries (variables, vmethods).

You can also use <INCLUDE> ... </INCLUDE> to specify the #include files which are shown in the synopsis sections. It contains a comma-separate list of #include files, without the angle brackets. If you set it outside of any sections, it acts for all sections until the end of the file. If you set it within a section, it only applies to that section.

## Controlling the result

A GTK-Doc run generates report files inside the documentation directory. The generated files are named: `<package>-undocumented.txt`, `<package>-undeclared.txt` and `<package>-unused.txt`. All those are plain text files that can be viewed and postprocessed easily.

The `<package>-undocumented.txt` file starts with the documentation coverage summary. Below are two sections divided by blank lines. The first section lists undocumented or incomplete symbols. The second section does the same for section docs. Incomplete entries are those, which have documentation, but where e.g. a new parameter has been added.

The `<package>-undeclared.txt` file lists symbols given in the `<package>-sections.txt` but not found in the sources. Check if they have been removed or if they are misspelled.

The `<package>-unused.txt` file lists symbol names, where the GTK-Doc scanner has found documentation, but does not know where to put it. This means that the symbol has not yet been added to the `<package>-sections.txt` file.

Enable or add the `TESTS=$(GTKDOC_CHECK)` line in Makefile.am. If at least GTK-Doc 1.9 is installed, this will run sanity checks during `make check` run.

One can also look at the files produced by the source code scanner: `<package>-decl-list.txt` and `<package>-decl.txt`. The first one can be compared with the section file if that is manually maintained. The second lists all declarations from the headers. If a symbol is missing one could check if this file contains it.

If the project is GObject based, one can also look into the files produced by the object scanner: `<package>.args.txt`, `<package>.hierarchy.txt`, `<package>.interfaces.txt`, `<package>.prerequisites.txt` and `<package>.signals.txt`. If there are missing symbols in any of those, one can ask GTK-Doc to keep the intermediate scanner file for further analysis, by running it as `GTK_DOC_KEEP_INTERMEDIATE=1 make`.

## Modernizing the documentation

GTK-Doc has been around for quite some time. In this section we list new features together with the version since when it is available.

### GTK-Doc 1.9

When using xml instead of sgml, one can actually name the master document `<package>-docs.xml`.

This version supports `SCAN_OPTIONS=--rebuild-sections` in `Makefile.am`. When this is enabled, the `<package>-sections.txt` is autogenerated and can be removed from the vcs. This only works nicely for projects that have a very regular structure (e.g. each .{c,h} pair will create new section). If one organize a project close to that updating a manually maintained section file can be as simple as running `meld <package>-decl-list.txt <package>-sections.txt`.

Version 1.8 already introduced the syntax for documenting sections in the sources instead of the separate files under `tmpl`. This version adds options to switch the whole doc module to not use the extra tmpl build step at all, by using `--flavour no-tmpl` in `configure.ac`. If you don't have a `tmpl` checked into your source control system and haven't yet switched, just add the flag to `configure.ac` and you are done.

### GTK-Doc 1.10

This version supports `SCAN_OPTIONS=--rebuild-types` in `Makefile.am`. When this is enabled, the `<package>.types` is autogenerated and can be removed from the vcs. When using this feature it is important to also setup the `IGNORE_HFILES` in `Makefile.am` for code that is build conditionally.

### GTK-Doc 1.16

This version includes a new tool called gtkdoc-check. This tool can run a set of sanity checks on your documentation. It is enabled by adding these lines to the end of `Makefile.am`.

#### Enable gtkdoc-check

    if ENABLE_GTK_DOC
    TESTS_ENVIRONMENT = \
      DOC_MODULE=$(DOC_MODULE) DOC_MAIN_SGML_FILE=$(DOC_MAIN_SGML_FILE) \
      SRCDIR=$(abs_srcdir) BUILDDIR=$(abs_builddir)
    TESTS = $(GTKDOC_CHECK)
    endif

### GTK-Doc 1.20

Version 1.18 brought some initial markdown support. Using markdown in doc comments is less intrusive than writing docbook xml. This version improves a lot on this and add a lot more styles. The section that explains the comment syntax has all the details.

### GTK-Doc 1.25

The makefiles shipped with this version generate an entity file at `xml/gtkdocentities.ent`, containing entities for e.g. package_name and package_version. You can use this e.g. in the main xml file to avoid hardcoding the version number. Below is an example that shows how the entity file is included in the master template and how the entities are used. The entities can also be used in all generated files, GTK-Doc will use the same xml header in generated xml files.

#### Use pre-generated entities

    <?xml version="1.0"?>
    <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN"
                   "http://www.oasis-open.org/docbook/xml/4.3/docbookx.dtd"
    [
      <!ENTITY % local.common.attrib "xmlns:xi  CDATA  #FIXED 'http://www.w3.org/2003/XInclude'">
      <!ENTITY % gtkdocentities SYSTEM "xml/gtkdocentities.ent">
      %gtkdocentities;
    ]>
    <book id="index" xmlns:xi="http://www.w3.org/2003/XInclude">
      <bookinfo>
        <title>&package_name; Reference Manual</title>
        <releaseinfo>
          for &package_string;.
          The latest version of this documentation can be found on-line at
          <ulink role="online-location" url="http://[SERVER]/&package_name;/index.html">http://[SERVER]/&package_name;/</ulink>.
        </releaseinfo>
      </bookinfo>

## Documentando outras interfaces

So far we have been using GTK-Doc to document the API of code. The next sections contain suggestions how the tools can be used to document other interfaces too.

### Command line options and man pages

As one can generate man pages for a docbook refentry as well, it sounds like a good idea to use it for that purpose. This way the interface is part of the reference and one gets the man-page for free.

#### Documente a ferramenta

Create one refentry file per tool. Following our example we would call it `meep/docs/reference/meeper/meep.xml`. For the xml tags that should be used and can look at generated file in the xml subdirectory as well as examples e.g. in glib.

#### Adding the extra configure check

##### Extra configure checks

    AC_ARG_ENABLE(man,
                  [AC_HELP_STRING([--enable-man],
                                  [regenerate man pages from Docbook [default=no]])],enable_man=yes,
                  enable_man=no)

    AC_PATH_PROG([XSLTPROC], [xsltproc])
    AM_CONDITIONAL(ENABLE_MAN, test x$enable_man != xno)

#### Adding the extra makefile rules

##### Extra configure checks

    man_MANS = \
           meeper.1

    if ENABLE_GTK_DOC
    if ENABLE_MAN

    %.1 : %.xml
            @XSLTPROC@ -nonet http://docbook.sourceforge.net/release/xsl/current/manpages/docbook.xsl $<

    endif
    endif

    BUILT_EXTRA_DIST = $(man_MANS)
    EXTRA_DIST += meep.xml

### Intefaces de DBus

(FIXME: http://hal.freedesktop.org/docs/DeviceKit/DeviceKit.html, http://cgit.freedesktop.org/DeviceKit/DeviceKit/tree/doc/dbus)

## Preguntas frecuentes

Pregunta
Resposta
Non hai herdanza de clases.
The objects `xxx_get_type()` function has not been entered into the `<package>.types` file.
Aínda non hai herdanza de clases.
Missing or wrong naming in `<package>-sections.txt` file (see explanation).
Redemo, aínda non hai herdanza de clase.
Is the object name (name of the instance struct, e.g. GtkWidget) part of the normal section (don't put this into Standard or Private subsections).
No symbol index.
Does the `<package>-docs.{xml,sgml}` contain a index that xi:includes the generated index?
Symbols are not linked to their doc-section.
Is the doc-comment using the correct markup (added #,% or ())? Check if the gtkdoc-fixxref warns about unresolvable xrefs.
A new class does not appear in the docs.
Is the new page xi:included from `<package>-docs.{xml,sgml}`.
A new symbol does not appear in the docs.
Is the doc-comment properly formatted. Check for spelling mistakes in the begin of the comment. Check if the gtkdoc-fixxref warns about unresolvable xrefs. Check if the symbol is correctly listed in the `<package>-sections.txt` in a public subsection.
A type is missing from the class hierarchy.
If the type is listed in `<package>.hierarchy` but not in `xml/tree_index.sgml` then double check that the type is correctly placed in the `<package>-sections.txt`. If the type instance (e.g. GtkWidget) is not listed or incidentally marked private it will not be shown.
I get foldoc links for all gobject annotations.
Check that `xml/annotation-glossary.xml` is xi:included from `<package>-docs.{xml,sgml}`.
Parameter described in source code comment block but does not exist
Check if the prototype in the header has different parameter names as in the source.
multiple "IDs" for constraint linkend: XYZ
Symbol XYZ appears twice in `<package>-sections.txt` file.
Element typename in namespace '' encountered in para, but no template matches.

## Tools related to gtk-doc

GtkDocPlugin - a Trac GTK-Doc integration plugin, that adds API docs to a trac site and integrates with the trac search.

Gtkdoc-depscan - a tool (part of gtk-doc) to check used API against since tags in the API to determine the minimum required version.

Version 1.1, March 2000
2000
Free Software Foundation, Inc.

    Free Software Foundation, Inc. 51 Franklin Street,
            Suite 330, Boston, MA
            02110-1301  USA

Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.

## GNU Free Documentation License

### 0. PREAMBLE

The purpose of this License is to make a manual, textbook, or other written document free in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.

This License is a kind of copyleft, which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.

We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.

### 1. APPLICABILITY AND DEFINITIONS

This License applies to any manual or other work that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. The Document, below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as you.

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The Invariant Sections are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License.

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### 2. VERBATIM COPYING

You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3.

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### 3. COPIANDO EN CANTIDADE

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### 4. MODIFICACIÓNS

You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version:

- #### A

  Use in the Title Page (and on the covers, if any) a title distinct from that of the Document, and from those of previous versions (which should, if there were any, be listed in the History section of the Document). You may use the same title as a previous version if the original publisher of that version gives permission.

- #### B

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- #### C

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- #### D

  Preserve all the copyright notices of the Document.

- #### E

  Add an appropriate copyright notice for your modifications adjacent to the other copyright notices.

- #### F

  Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the Addendum below.

- #### G

  Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document's license notice.

- #### H

  Include an unaltered copy of this License.

- #### I

  Preserve the section entitled History, and its title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page. If there is no section entitled History in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence.

- #### J

  Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document for previous versions it was based on. These may be placed in the History section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to gives permission.

- #### K

  In any section entitled Acknowledgements or Dedications, preserve the section's title, and preserve in the section all the substance and tone of each of the contributor acknowledgements and/or dedications given therein.

- #### L

  Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles. Section numbers or the equivalent are not considered part of the section titles.

- #### M

  Delete any section entitled Endorsements. Such a section may not be included in the Modified Version.

- #### N

  Do not retitle any existing section as Endorsements or to conflict in title with any Invariant Section.

If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document, you may at your option designate some or all of these sections as invariant. To do this, add their titles to the list of Invariant Sections in the Modified Version's license notice. These titles must be distinct from any other section titles.

You may add a section entitled Endorsements, provided it contains nothing but endorsements of your Modified Version by various parties--for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.

You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.

The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version .

### 5. COMBINING DOCUMENTS

You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice.

The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work.

In the combination, you must combine any sections entitled History in the various original documents, forming one section entitled History; likewise combine any sections entitled Acknowledgements, and any sections entitled Dedications. You must delete all sections entitled Endorsements.

### 6. COLLECTIONS OF DOCUMENTS

You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.

You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.

### 7. AGGREGATION WITH INDEPENDENT WORKS

A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, does not as a whole count as a Modified Version of the Document, provided no compilation copyright is claimed for the compilation. Such a compilation is called an aggregate, and this License does not apply to the other self-contained works thus compiled with the Document , on account of their being thus compiled, if they are not themselves derivative works of the Document. If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one quarter of the entire aggregate, the Document's Cover Texts may be placed on covers that surround only the Document within the aggregate. Otherwise they must appear on covers around the whole aggregate.

### 8. TRANSLATION

Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License provided that you also include the original English version of this License. In case of a disagreement between the translation and the original English version of this License, the original English version will prevail.

### 9. TERMINATION

You may not copy, modify, sublicense, or distribute the Document except as expressly provided for under this License. Any other attempt to copy, modify, sublicense or distribute the Document is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.

### 10. FUTURE REVISIONS OF THIS LICENSE

The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See http://www.gnu.org/copyleft/.

Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License or any later version applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation.

### Addendum

To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:

> Copyright YEAR YOUR NAME.

> Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with the Invariant Sections being LIST THEIR TITLES, with the Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST. A copy of the license is included in the section entitled GNU Free Documentation License.

If you have no Invariant Sections, write with no Invariant Sections instead of saying which ones are invariant. If you have no Front-Cover Texts, write no Front-Cover Texts instead of Front-Cover Texts being LIST; likewise for Back-Cover Texts.

If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.