Examples with a Search Entry
| Chapter 12. The DropDown Widget |

## 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

Figure 12.2. 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.

Figure 12.3. 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);
    }

Simple String Example |  | Complex Example