bool button_press_handler_1 (ArdourCanvas::Item *, GdkEvent *, ItemType);
bool button_press_handler_2 (ArdourCanvas::Item *, GdkEvent *, ItemType);
bool button_release_handler (ArdourCanvas::Item*, GdkEvent*, ItemType);
bool button_press_handler_1 (ArdourCanvas::Item *, GdkEvent *, ItemType);
bool button_press_handler_2 (ArdourCanvas::Item *, GdkEvent *, ItemType);
bool button_release_handler (ArdourCanvas::Item*, GdkEvent*, ItemType);