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ComboBox

Reference

9.1.1. The model

The model for a ComboBox can be defined and filled exactly as for a TreeView. For instance, you might derive a ComboBox class with one integer and one text columns, like so: 

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;

After appending rows to this model, you should provide the model to the ComboBox with the set_model() method. Then use the pack_start() or pack_end() methods to specify what methods will be displayed in the ComboBox. As with the TreeView you may either use the default cell renderer by passing the TreeModelColumn to the pack methods, or you may instantiate a specific CellRenderer and specify a particular mapping with either add_attribute() or set_cell_data_func(). Note that these methods are in the CellLayout base class.

9.1.2. The chosen item

To discover what item, if any, the user has chosen from the ComboBox, call ComboBox::get_active(). This returns a TreeModel::iterator that you can dereference to a Row in order to read the values in your columns. 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 Combo. For instance: 

Gtk::TreeModel::iterator iter = m_Combo.get_active();
if(iter)
{
  Gtk::TreeModel::Row row = *iter;

  //Get the data for the selected row, using our knowledge
  //of the tree model:
  int id = row[m_Columns.m_col_id];
  set_something_id_chosen(id); //Your own function.
}
else
  set_nothing_chosen(); //Your own function.

9.1.3. Responding to changes

You might need to react to every change of selection in the ComboBox, for instance to update other widgets. To do so, you should handle the "changed" signal. For instance: 

m_combo.signal_changed().connect( sigc::mem_fun(*this,
      &ExampleWindow::on_combo_changed) );

9.1.4. Full Example

Figure 9-1 ComboBox

Source Code

File: examplewindow.h (For use with gtkmm 2, not gtkmm 3) 

#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:  
  //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); }

    Gtk::TreeModelColumn<int> m_col_id;
    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 2, not gtkmm 3) 

#include "examplewindow.h"
#include <gtkmm/stock.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:
  Gtk::TreeModel::Row row = *(m_refTreeModel->append());
  row[m_Columns.m_col_id] = 1;
  row[m_Columns.m_col_name] = "Billy Bob";
  /*
  Gtk::TreeModel::Row 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:
  m_Combo.pack_start(m_Columns.m_col_id);
  m_Combo.pack_start(m_Columns.m_col_name);

  //Add the ComboBox to the window.
  add(m_Combo);

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

  show_all_children();
}

ExampleWindow::~ExampleWindow()
{
}

void ExampleWindow::on_combo_changed()
{
  Gtk::TreeModel::iterator iter = m_Combo.get_active();
  if(iter)
  {
    Gtk::TreeModel::Row 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 2, not gtkmm 3) 

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

int main(int argc, char *argv[])
{
  Gtk::Main kit(argc, argv);

  ExampleWindow window;
  //Shows the window and returns when it is closed.
  Gtk::Main::run(window);

  return 0;
}

9.1.5. Simple Text Example

Figure 9-2 ComboBox

Source Code

File: examplewindow.h (For use with gtkmm 2, not gtkmm 3) 

#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 2, not gtkmm 3) 

#include "examplewindow.h"
#include <gtkmm/stock.h>
#include <iostream>

ExampleWindow::ExampleWindow()
{
  set_title("ComboBoxText example");

  //Fill the combo:
  m_Combo.append_text("something");
  m_Combo.append_text("something else");
  m_Combo.append_text("something or other");

  add(m_Combo);

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

  show_all_children();
}

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 2, not gtkmm 3) 

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

int main(int argc, char *argv[])
{
  Gtk::Main kit(argc, argv);

  ExampleWindow window;
  //Shows the window and returns when it is closed.
  Gtk::Main::run(window);

  return 0;
}
ComboBox ComboBoxEntry

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