Complex Example
| Chapter 12. The DropDown Widget |

## 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.

Figure 12.4. 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));
      factory->signal_unbind().connect(
        sigc::mem_fun(*this, &ExampleWindow::on_unbind_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);
    }

Examples with a Search Entry |  | Chapter 13. Combo Boxes