bool al_emit_user_event(ALLEGRO_EVENT_SOURCE *src,
ALLEGRO_EVENT *event, void (*dtor)(ALLEGRO_USER_EVENT *))
Emit an event from a user event source. The event source must have been initialised with al_init_user_event_source(3alleg5). Returns false if the event source isn't registered with any queues, hence the event wouldn't have been delivered into any queues.
Events are copied in and out of event queues, so after this function returns the memory pointed to by event may be freed or reused. Some fields of the event being passed in may be modified by the function.
Reference counting will be performed if dtor is not NULL. Whenever a copy of the event is made, the reference count increases. You need to call al_unref_user_event(3alleg5) to decrease the reference count once you are done with a user event that you have received from al_get_next_event(3alleg5), al_peek_next_event(3alleg5), al_wait_for_event(3alleg5), etc.
Once the reference count drops to zero dtor will be called with a copy of the event as an argument. It should free the resources associated with the event, but not the event itself (since it is just a copy).
If dtor is NULL then reference counting will not be performed. It is safe, but unnecessary, to call al_unref_user_event(3alleg5) on non-reference counted user events.
You can use al_emit_user_event to emit both user and non-user events from your user event source. Note that emitting input events will not update the corresponding input device states. For example, you may emit an event of type ALLEGRO_EVENT_KEY_DOWN(3alleg5), but it will not update the ALLEGRO_KEYBOARD_STATE(3alleg5) returned by al_get_keyboard_state(3alleg5).