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al_init_user_event_source(3)                      al_init_user_event_source(3)

NAME
       al_init_user_event_source - Allegro 5 API

SYNOPSIS

              #include <allegro5/allegro.h>

              void al_init_user_event_source(ALLEGRO_EVENT_SOURCE *src)

DESCRIPTION
       Initialise an event source for emitting user events.  The space for the
       event source must already have been allocated.

       One possible way of creating custom event sources is to derive other
       structures with ALLEGRO_EVENT_SOURCE at the head, e.g.

              typedef struct THING THING;

              struct THING {
                  ALLEGRO_EVENT_SOURCE event_source;
                  int field1;
                  int field2;
                  /* etc. */
              };

              THING *create_thing(void)
              {
                  THING *thing = malloc(sizeof(THING));

                  if (thing) {
                      al_init_user_event_source(&thing->event_source);
                      thing->field1 = 0;
                      thing->field2 = 0;
                  }

                  return thing;
              }

       The advantage here is that the THING pointer will be the same as the
       ALLEGRO_EVENT_SOURCE pointer.  Events emitted by the event source will
       have the event source pointer as the source field, from which you can
       get a pointer to a THING by a simple cast (after ensuring checking the
       event is of the correct type).

       However, it is only one technique and you are not obliged to use it.

       The user event source will never be destroyed automatically.  You must
       destroy it manually with al_destroy_user_event_source(3).

SEE ALSO
       ALLEGRO_EVENT_SOURCE(3), al_destroy_user_event_source(3),
       al_emit_user_event(3), ALLEGRO_USER_EVENT(3)

Allegro reference manual                          al_init_user_event_source(3)