[A5] simulate_keypress()?

no-reply@allegro.cc (Renato Riolino) — Wed, 20 Feb 2013 01:24:30 +0000

Quick question: How do I simulate a keypress on Allegro5 (ex: make a specific key goes into keyboard buffer so I can grab it later from keyboard event source?

Thanks.

no-reply@allegro.cc (Edgar Reynaldo) — Wed, 20 Feb 2013 02:28:31 +0000

Use al_init_user_event_source to initialize an ALLEGRO_EVENT_SOURCE which you can then register with al_register_event_source. Then you can have it emit an event to any registered queues with al_emit_user_event.

no-reply@allegro.cc (Trent Gamblin) — Wed, 20 Feb 2013 03:19:56 +0000

Will that really work though? The only way I see it working is if you have a custom event type, not ALLEGRO_EVENT_KEY_*. Which might be fine for the OP. But for user events you have to call al_unref_user_event on all of them or you'll be leaking memory.

no-reply@allegro.cc (Peter Wang) — Wed, 20 Feb 2013 04:56:53 +0000

Trent Gamblin said:

But for user events you have to call al_unref_user_event on all of them or you'll be leaking memory.

Only if it's reference counted, i.e. if you use al_emit_user_event with a non-null destructor argument.

no-reply@allegro.cc (Trent Gamblin) — Wed, 20 Feb 2013 05:00:05 +0000

Oh, good to know.

no-reply@allegro.cc (Edgar Reynaldo) — Wed, 20 Feb 2013 09:17:50 +0000

Trent Gamblin said:

Well, it depends on whether or not allegro changes any fields of an event when it is emitted. If not, then you can just set the keyboard fields of the ALLEGRO_EVENT, as an ALLEGRO_USER_EVENT is part of the event union.

Would this work?

#SelectExpand
  1ALLEGRO_EVENT_SOURCE evt_src;
  2al_init_user_event_source(evt_src);
  3ALLEGRO_EVENT_QUEUE* queue = al_create_event_queue();
  4
  5al_register_event_source(queue , &evt_src);
  6
  7// later
  8
  9// Simulate escape key press
 10ALLEGRO_EVENT ev;
 11ev.type = ALLEGRO_EVENT_KEY_DOWN;
 12ev.source = &evt_src;
 13ev.keyboard.keycode = ALLEGRO_KEY_ESCAPE;
 14ev.keyboard.display = &evt_src;
 15
 16al_emit_user_event(&evt_src , &ev , NULL);

no-reply@allegro.cc (Trent Gamblin) — Wed, 20 Feb 2013 09:31:20 +0000

That wasn't my concern, but the memory leak but Peter cleared that up.

no-reply@allegro.cc (SiegeLord) — Thu, 21 Feb 2013 01:17:14 +0000

Edgar Reynaldo said:

Would this work?

From the source of al_emit_user_event:

#SelectExpand
  1boolal_emit_user_event(ALLEGRO_EVENT_SOURCE*src,
  2ALLEGRO_EVENT*event, void(*dtor)(ALLEGRO_USER_EVENT*))  3{  4size_t num_queues;  5bool rc;  6  7ASSERT(src);  8ASSERT(event);  9   ASSERT(ALLEGRO_EVENT_TYPE_IS_USER(event->any.type));
 10 11if(dtor){ 12      ALLEGRO_USER_EVENT_DESCRIPTOR *descr =al_malloc(sizeof(*descr)); 13      descr->refcount =0; 14      descr->dtor = dtor; 15      event->user.__internal__descr = descr; 16} 17else{ 18      event->user.__internal__descr = NULL;
 19}

Firstly, there is an assertion there which will trigger in debug mode if you try to emit a non-user event. Secondly, al_emit_user_event assigns one field of the passed event. Looking at the two event types:

#SelectExpand
  1typedef struct ALLEGRO_KEYBOARD_EVENT
  2{
  3   _AL_EVENT_HEADER(struct ALLEGRO_KEYBOARD)
  4   struct ALLEGRO_DISPLAY *display; /* the window the key was pressed in */
  5   int keycode;                 /* the physical key pressed */
  6   int unichar;                 /* unicode character or negative */
  7   unsigned int modifiers;      /* bitfield */
  8   bool repeat;                 /* auto-repeated or not */
  9} ALLEGRO_KEYBOARD_EVENT;
 10
 11struct ALLEGRO_USER_EVENT
 12{
 13   _AL_EVENT_HEADER(struct ALLEGRO_EVENT_SOURCE)
 14   struct ALLEGRO_USER_EVENT_DESCRIPTOR *__internal__descr;
 15   intptr_t data1;
 16   intptr_t data2;
 17   intptr_t data3;
 18   intptr_t data4;
 19};

So that assignment clobbers the value of event.keyboard.display. It'll clobber useful values for other events too. So, in general, al_emit_user_event is for user events only. If this is a real need for emitting fake Allegro events, then such functionality remains to be implemented.