text: #ifndef GTKMM_EXAMPLE_HELLOWORLD_H
  #define GTKMM_EXAMPLE_HELLOWORLD_H
  
  #include <gtkmm/box.h>
  #include <gtkmm/button.h>
  #include <gtkmm/window.h>
  
  class HelloWorld : public Gtk::Window
  {
  public:
    HelloWorld();
    virtual ~HelloWorld();
  
  protected:
  
    // Signal handlers:
    // Our new improved on_button_clicked(). (see below)
    void on_button_clicked(Glib::ustring data);
  
    // Child widgets:
    Gtk::HBox m_box1;
    Gtk::Button m_button1, m_button2;
  };
  
  #endif // GTKMM_EXAMPLE_HELLOWORLD_H
  