Trigger types on areas

src/dusk/rpg/overworld/maparea.c

@@ -8,6 +8,7 @@
 #include "maparea.h"
 #include "assert/assert.h"
 #include "util/math.h"
+#include "util/memory.h"
 #include "rpg/overworld/map.h"
 
 maparea_t MAP_AREAS[MAP_AREA_COUNT_MAX];
@@ -17,7 +18,8 @@ void mapAreaInit(
   const worldpos_t min,
   const worldpos_t max,
   const mapareacallback_t callback,
-  const mapareanotify_t notify
+  const uint8_t notify,
+  const uint8_t trigger
 ) {
   assertNotNull(area, "Map area pointer cannot be NULL");
   assertNotNull(callback, "Map area callback cannot be NULL");
@@ -32,6 +34,9 @@ void mapAreaInit(
 
   area->callback = callback;
   area->notify = notify;
+  area->trigger = trigger;
+
+  memorySet(area->entities, 0, sizeof(area->entities));
 }
 
 bool_t mapAreaIsInside(const maparea_t *area, const worldpos_t position) {
@@ -94,11 +99,12 @@ uint8_t mapAreaAdd(
   const worldpos_t min,
   const worldpos_t max,
   const mapareacallback_t callback,
-  const mapareanotify_t notify
+  const uint8_t notify,
+  const uint8_t trigger
 ) {
   for(uint8_t i = 0; i < MAP_AREA_COUNT_MAX; i++) {
     if(MAP_AREAS[i].callback != NULL) continue;
-    mapAreaInit(&MAP_AREAS[i], min, max, callback, notify);
+    mapAreaInit(&MAP_AREAS[i], min, max, callback, notify, trigger);
     return i;
   }
 
@@ -117,8 +123,23 @@ void mapAreaCheckEntity(entity_t *entity) {
   for(uint8_t i = 0; i < MAP_AREA_COUNT_MAX; i++) {
     maparea_t *area = &MAP_AREAS[i];
     if(area->callback == NULL) continue;
-    if(!mapAreaIsInside(area, entity->position)) continue;
     if(!mapAreaShouldNotify(area, entity)) continue;
-    area->callback(entity);
+
+    bool_t wasInside = area->entities[entity->id] != 0;
+    bool_t isInside = mapAreaIsInside(area, entity->position);
+    uint8_t trigger = 0;
+
+    if(isInside && !wasInside) {
+      area->entities[entity->id] = 1;
+      trigger = MAP_TRIGGER_ENTER;
+    } else if(isInside && wasInside) {
+      trigger = MAP_TRIGGER_STEP;
+    } else if(!isInside && wasInside) {
+      area->entities[entity->id] = 0;
+      trigger = MAP_TRIGGER_EXIT;
+    }
+
+    if(trigger == 0 || !(area->trigger & trigger)) continue;
+    area->callback(entity, trigger);
   }
 }

src/dusk/rpg/overworld/maparea.h

@@ -7,39 +7,44 @@
 
 #pragma once
 #include "worldpos.h"
+#include "rpg/entity/entity.h"
 
 typedef struct chunk_s chunk_t;
-typedef struct entity_s entity_t;
 typedef struct maparea_s maparea_t;
 
 #define MAP_AREA_COUNT_MAX 32
 
-typedef uint8_t mapareanotify_t;
+#define MAP_AREA_NOTIFY_PLAYER (1 << 0)
+#define MAP_AREA_NOTIFY_NPC (1 << 1)
+#define MAP_AREA_NOTIFY_ALL (MAP_AREA_NOTIFY_PLAYER | MAP_AREA_NOTIFY_NPC)
 
-#define MAP_AREA_NOTIFY_PLAYER ((mapareanotify_t)(1 << 0))
+#define MAP_TRIGGER_STEP  (1 << 0)
-#define MAP_AREA_NOTIFY_NPC    ((mapareanotify_t)(1 << 1))
+#define MAP_TRIGGER_ENTER (1 << 1)
-#define MAP_AREA_NOTIFY_ALL    ((mapareanotify_t)( \
+#define MAP_TRIGGER_EXIT  (1 << 2)
-  MAP_AREA_NOTIFY_PLAYER | MAP_AREA_NOTIFY_NPC \
+#define MAP_TRIGGER_ALL   (MAP_TRIGGER_STEP | MAP_TRIGGER_ENTER | MAP_TRIGGER_EXIT)
-))
 
 /**
  * Callback invoked for a map area.
  *
  * @param entity Pointer to the entity associated with the callback.
+ * @param trigger Which MAP_TRIGGER_* condition invoked the callback.
  */
-typedef void (*mapareacallback_t)(entity_t *entity);
+typedef void (*mapareacallback_t)(entity_t *entity, const uint8_t trigger);
 
 typedef struct maparea_s {
   worldpos_t min;
   worldpos_t max;
   mapareacallback_t callback;
-  mapareanotify_t notify;
+  uint8_t notify;
+  uint8_t trigger;
+  uint8_t entities[ENTITY_COUNT];
 } maparea_t;
 
 extern maparea_t MAP_AREAS[MAP_AREA_COUNT_MAX];
 
 /**
- * Initializes a map area with the given bounds, callback and notify flags.
+ * Initializes a map area with the given bounds, callback, notify flags
+ * and trigger flags.
  *
  * @param area Pointer to the map area to initialize.
  * @param min The minimum world position of the area.
@@ -47,13 +52,16 @@ extern maparea_t MAP_AREAS[MAP_AREA_COUNT_MAX];
  * @param callback The callback to invoke for this area. Must not be NULL.
  * @param notify Bitwise MAP_AREA_NOTIFY_* flags for which entity types
  *   should trigger the callback.
+ * @param trigger Bitwise MAP_TRIGGER_* flags for which conditions should
+ *   invoke the callback.
  */
 void mapAreaInit(
   maparea_t *area,
   const worldpos_t min,
   const worldpos_t max,
   const mapareacallback_t callback,
-  const mapareanotify_t notify
+  const uint8_t notify,
+  const uint8_t trigger
 );
 
 /**
@@ -106,13 +114,16 @@ bool_t mapAreaShouldNotify(const maparea_t *area, const entity_t *entity);
  * @param callback The callback to invoke for this area. Must not be NULL.
  * @param notify Bitwise MAP_AREA_NOTIFY_* flags for which entity types
  *   should trigger the callback.
+ * @param trigger Bitwise MAP_TRIGGER_* flags for which conditions should
+ *   invoke the callback.
  * @returns The ID of the newly added map area.
  */
 uint8_t mapAreaAdd(
   const worldpos_t min,
   const worldpos_t max,
   const mapareacallback_t callback,
-  const mapareanotify_t notify
+  const uint8_t notify,
+  const uint8_t trigger
 );
 
 /**
@@ -125,8 +136,10 @@ void mapAreaRemove(const uint8_t id);
 
 /**
  * Checks every active map area against an entity's current position,
- * invoking each matching area's callback if the entity is inside it and
+ * for areas whose notify flags include the entity's type. Invokes the
- * its type is included in that area's notify flags.
+ * area's callback with MAP_TRIGGER_ENTER the frame the entity first
+ * becomes inside, MAP_TRIGGER_STEP on every subsequent frame it remains
+ * inside, and MAP_TRIGGER_EXIT the frame it leaves.
  *
  * @param entity Pointer to the entity to check.
  */

src/dusk/rpg/rpg.c

@@ -20,8 +20,8 @@
 #include "assert/assert.h"
 #include "console/console.h"
 
-void rpgTestAreaCallback(entity_t *entity) {
+void rpgTestAreaCallback(entity_t *entity, const uint8_t trigger) {
-  consolePrint("rpgTestAreaCallback");
+  consolePrint("rpgTestAreaCallback: trigger=%u", trigger);
 }
 
 errorret_t rpgInit(void) {
@@ -53,7 +53,8 @@ errorret_t rpgInit(void) {
     (worldpos_t){ 11, 3, 0 },
     (worldpos_t){ 16, 9, 10 },
     rpgTestAreaCallback,
-    MAP_AREA_NOTIFY_ALL
+    MAP_AREA_NOTIFY_ALL,
+    MAP_TRIGGER_ENTER | MAP_TRIGGER_EXIT
   );
   assertTrue(areaIndex != 0xFF, "No available map area slots!.");