al_enable_menu_event_source - Allegro 5 API

       Enables  a  unique  event  source for this menu.  It and all of its sub-menus will use this event source.
       (It is safe to call this multiple times on the same menu.)

       Returns the event source.

       al_enable_menu_event_source - Allegro 5 API

al_register_event_source(3alleg5),                             al_get_default_menu_event_source(3alleg5),
       al_disable_menu_event_source(3alleg5)

Allegro reference manual                                                    al_enable_menu_event_source(3alleg5)

       5.1.0

              #include <allegro5/allegro_native_dialog.h>

              ALLEGRO_EVENT_SOURCE *al_enable_menu_event_source(ALLEGRO_MENU *menu)