text: #ifndef GTKMM_EXAMPLE_HELLO_WORLD_HPP
  #define GTKMM_EXAMPLE_HELLO_WORLD_HPP
  
  #include <gtkmm/button.h>
  #include <gtkmm/window.h>
  
  class HelloWorld : public Gtk::Window
  {
  
  public:
    HelloWorld();
  
  protected:
    // Signal handlers:
    void on_button_clicked();
  
    // Member widgets:
    Gtk::Button m_button;
  };
  
  #endif// GTKMM_EXAMPLE_HELLO_WORLD_HPP
  