Table of Contents
Dialogs are used as secondary windows, to provide specific information or to ask questions. Gtk::Dialog windows contain a few pre-packed widgets to ensure consistency, and a run() method which blocks until the user dismisses the dialog.
There are several derived dialog classes which you might find useful. For instance, you will probably use Gtk::MessageDialog for most simple notifications. But at other times you might need to derive your own dialog class to provide more complex functionality.
To pack widgets into a custom dialog, you should pack them into the Gtk::VBox, available via get_vbox(). To just add a button to the bottom of the dialog, you could use the add_button() method.
The run() method returns an int. This may be a value from the Gtk::ResponseType if the user closed the button by clicking a standard button, or it could be the custom response value that you specified when using add_button().
This is a convenience class, used to create simple, standard message dialogs, with a message, an icon, and buttons for user response. You can specify the type of message and the text in the constructor, as well as specifying standard buttons via ORed Gtk::ButtonsType values.
File: examplewindow.h
#ifndef GTKMM_EXAMPLEWINDOW_H
#define GTKMM_EXAMPLEWINDOW_H
#include <gtkmm.h>
class ExampleWindow : public Gtk::Window
{
public:
  ExampleWindow();
  virtual ~ExampleWindow();
protected:
  //Signal handlers:
  virtual void on_button_info_clicked();
  virtual void on_button_question_clicked();
  //Child widgets:
  Gtk::VButtonBox m_ButtonBox;
  Gtk::Button m_Button_Info, m_Button_Question;
};
#endif //GTKMM_EXAMPLEWINDOW_H
File: examplewindow.cc
#include "examplewindow.h"
#include <gtkmm/dialog.h>
#include <iostream>
ExampleWindow::ExampleWindow()
: m_Button_Info("Show Info MessageDialog"),
  m_Button_Question("Show Question MessageDialog")
{
  set_title("Gtk::MessageDialog example");
  add(m_ButtonBox);
  
  m_ButtonBox.pack_start(m_Button_Info);
  m_Button_Info.signal_clicked().connect( sigc::mem_fun(*this, &ExampleWindow::on_button_info_clicked) );
  m_ButtonBox.pack_start(m_Button_Question);
  m_Button_Question.signal_clicked().connect( sigc::mem_fun(*this, &ExampleWindow::on_button_question_clicked) );
  show_all_children();
}
ExampleWindow::~ExampleWindow()
{
}
void ExampleWindow::on_button_info_clicked()
{
  Gtk::MessageDialog dialog(*this, "This is an INFO MessageDialog");
  dialog.run();
}
void ExampleWindow::on_button_question_clicked()
{
  Gtk::MessageDialog dialog(*this, "This is a QUESTION MessageDialog", false /* use_markup */, Gtk::MESSAGE_QUESTION, (Gtk::ButtonsType)(Gtk::BUTTONS_OK | Gtk::BUTTONS_CANCEL));
  int result = dialog.run();
  //Handle the response:
  switch(result)
  {
    case(Gtk::RESPONSE_OK):
    {
      std::cout << "OK clicked." << std::endl;
      break;
    }
    case(Gtk::RESPONSE_CANCEL):
    {
      std::cout << "Cancel clicked." << std::endl;
      break;
    }
    default:
    {
      std::cout << "Unexpected button clicked." << std::endl;
      break;
    }
  }
  
}
File: main.cc
#include <gtkmm/main.h>
#include "examplewindow.h"
int main(int argc, char *argv[])
{
  Gtk::Main kit(argc, argv);
  ExampleWindow window;
  Gtk::Main::run(window); //Shows the window and returns when it is closed.
  return 0;
}