bool on_key_release_event (GdkEventKey *);
bool on_button_press_event (GdkEventButton*);
bool on_button_release_event (GdkEventButton*);
bool on_key_release_event (GdkEventKey *);
bool on_button_press_event (GdkEventButton*);
bool on_button_release_event (GdkEventButton*);