ComboBox with an Entry

A ComboBox may contain an Entry widget for entering of arbitrary text, by specifying true for the constructor's has_entry parameter.

11.6.1. The text column

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);

When you select a choice from the drop-down menu, the value from this column will be placed in the Entry.

11.6.2. The entry

Because the user may enter arbitrary text, an active model row isn't enough to tell us what text the user has entered. Therefore, you should retrieve the Entry widget with the ComboBox::get_entry() method and call get_text() on that.

11.6.3. Responding to changes

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 and focus_out_event signals, 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) );

  entry->signal_focus_out_event().connect(sigc::mem_fun(*this,
    &ExampleWindow::on_entry_focus_out_event) );
}
The changed signals of ComboBox and Entry are both emitted for every change. It doesn't matter which one you connect to. But only Entry's focus_out_event signal is useful here.

X events are described in more detail in the X Event signals section in the appendix.

11.6.4. Full Example

Figure 11-3ComboBox with 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>

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

protected:
  //Signal handlers:
  void on_combo_changed();
  void on_entry_changed();
  void on_entry_has_focus_changed();

  //Signal connection:
  sigc::connection m_ConnectionHasFocusChanged;
  bool m_entry_had_focus {false};

  //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: 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");

  ExampleWindow window;

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

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

#include "examplewindow.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.
  add(m_Combo);

  //Connect signal handlers:
  m_Combo.signal_changed().connect(sigc::mem_fun(*this, &ExampleWindow::on_combo_changed));

  auto entry = m_Combo.get_entry();
  if (entry)
  {
    entry->signal_changed().connect(sigc::mem_fun(*this,
      &ExampleWindow::on_entry_changed) );
    m_ConnectionHasFocusChanged = entry->property_has_focus().signal_changed().
      connect(sigc::mem_fun(*this, &ExampleWindow::on_entry_has_focus_changed));
  }
  else
    std::cout << "No Entry ???" << std::endl;
}

ExampleWindow::~ExampleWindow()
{
  // The has_focus changed 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_ConnectionHasFocusChanged.disconnect();
}

void ExampleWindow::on_combo_changed()
{
  auto entry = m_Combo.get_entry();
  if (entry)
  {
    std::cout << "on_combo_changed(): Row=" << m_Combo.get_active_row_number()
      << ", ID=" << entry->get_text() << std::endl;
  }
}

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;
  }
}

void ExampleWindow::on_entry_has_focus_changed()
{
  auto entry = m_Combo.get_entry();
  if (entry)
  {
    const bool entry_has_focus = entry->has_focus();
    if (m_entry_had_focus && !entry_has_focus)
    {
      // entry->has_focus() has changed from true to false; entry has lost focus.
      std::cout << "on_entry_has_focus_changed() to not focused: Row="
        << m_Combo.get_active_row_number() << ", ID=" << entry->get_text() << std::endl;
    }
    m_entry_had_focus = entry_has_focus;
  }
}

11.6.5. Simple Text Example

Figure 11-4ComboBoxText with 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>

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

protected:
  //Signal handlers:
  void on_combo_changed();
  void on_entry_changed();
  void on_entry_has_focus_changed();

  //Signal connection:
  sigc::connection m_ConnectionHasFocusChanged;
  bool m_entry_had_focus {false};

  //Child widgets:
  Gtk::ComboBoxText m_Combo;
};

#endif //GTKMM_EXAMPLEWINDOW_H

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");

  ExampleWindow window;

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

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

#include "examplewindow.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);

  add(m_Combo);

  //Connect signal handlers:
  m_Combo.signal_changed().connect(sigc::mem_fun(*this,
    &ExampleWindow::on_combo_changed) );

  auto entry = m_Combo.get_entry();
  if (entry)
  {
    entry->signal_changed().connect(sigc::mem_fun(*this,
      &ExampleWindow::on_entry_changed));
    m_ConnectionHasFocusChanged = entry->property_has_focus().signal_changed().
      connect(sigc::mem_fun(*this, &ExampleWindow::on_entry_has_focus_changed));
  }
  else
    std::cout << "No Entry ???" << std::endl;

  m_Combo.property_has_frame() = false;
}

ExampleWindow::~ExampleWindow()
{
  // The has_focus changed 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_ConnectionHasFocusChanged.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;
}

void ExampleWindow::on_entry_changed()
{
  std::cout << "on_entry_changed(): Row=" << m_Combo.get_active_row_number()
    << ", Text=" << m_Combo.get_active_text() << std::endl;
}

void ExampleWindow::on_entry_has_focus_changed()
{
  auto entry = m_Combo.get_entry();
  if (entry)
  {
    const bool entry_has_focus = entry->has_focus();
    if (m_entry_had_focus && !entry_has_focus)
    {
      // entry->has_focus() has changed from true to false; entry has lost focus.
      std::cout << "on_entry_has_focus_changed() to not focused: Row="
        << m_Combo.get_active_row_number() << ", ID=" << entry->get_text() << std::endl;
    }
    m_entry_had_focus = entry_has_focus;
  }
}