// bool on_button_press_event (GdkEventButton*);
// bool on_button_release_event (GdkEventButton*);
bool on_scroll_event (GdkEventScroll* ev);
// bool on_button_press_event (GdkEventButton*);
// bool on_button_release_event (GdkEventButton*);
bool on_scroll_event (GdkEventScroll* ev);