1al_init_user_event_source(3)Library Functions Manualal_init_user_event_source(3)
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6 al_init_user_event_source
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9 #include <allegro5/allegro.h>
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11 void al_init_user_event_source(ALLEGRO_EVENT_SOURCE *src)
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14 Initialise an event source for emitting user events. The space for the
15 event source must already have been allocated.
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17 One possible way of creating custom event sources is to derive other
18 structures with ALLEGRO_EVENT_SOURCE at the head, e.g.
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20 typedef struct THING THING;
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22 struct THING {
23 ALLEGRO_EVENT_SOURCE event_source;
24 int field1;
25 int field2;
26 /* etc. */
27 };
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29 THING *create_thing(void)
30 {
31 THING *thing = malloc(sizeof(THING));
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33 if (thing) {
34 al_init_user_event_source(&thing->event_source);
35 thing->field1 = 0;
36 thing->field2 = 0;
37 }
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39 return thing;
40 }
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42 The advantage here is that the THING pointer will be the same as the
43 ALLEGRO_EVENT_SOURCE pointer. Events emitted by the event source will
44 have the event source pointer as the source field, from which you can
45 get a pointer to a THING by a simple cast (after ensuring checking the
46 event is of the correct type).
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48 However, it is only one technique and you are not obliged to use it.
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50 The user event source will never be destroyed automatically. You must
51 destroy it manually with al_destroy_user_event_source(3).
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54 ALLEGRO_EVENT_SOURCE(3), al_emit_user_event(3),
55 al_destroy_user_event_source(3)
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59Allegro reference manual al_init_user_event_source(3)