al_register_event_source - Allegro 5 API

       Register  the  event  source  with the event queue specified.  An event source may be registered with any
       number of event queues simultaneously, or none.  Trying to register an event source with the  same  event
       queue more than once does nothing.

       al_register_event_source - Allegro 5 API

al_unregister_event_source(3alleg5), ALLEGRO_EVENT_SOURCE(3alleg5)

Allegro reference manual                                                       al_register_event_source(3alleg5)

              #include <allegro5/allegro.h>

              void al_register_event_source(ALLEGRO_EVENT_QUEUE *queue,
                 ALLEGRO_EVENT_SOURCE *source)