Properly link flecs library

engine/libs/flecs/examples/c/prefabs/variant/src/main.c

@@ -0,0 +1,101 @@
+#include <variant.h>
+#include <stdio.h>
+
+/* Prefabs can inherit from each other, which creates prefab variants. With
+ * variants applications can reuse a commmon set of components and specialize it
+ * by adding or overriding components on the variant. */
+
+typedef struct { double value; } Attack;
+typedef struct { double value; } Defense;
+typedef struct { double value; } FreightCapacity;
+typedef struct { double value; } ImpulseSpeed;
+
+typedef struct {
+    double x; 
+    double y; 
+} Position;
+
+int main(int argc, char *argv[]) {
+    ecs_world_t *ecs = ecs_init_w_args(argc, argv);
+
+    ECS_COMPONENT(ecs, Position);
+    ECS_COMPONENT(ecs, Attack);
+    ECS_COMPONENT(ecs, Defense);
+    ECS_COMPONENT(ecs, FreightCapacity);
+    ECS_COMPONENT(ecs, ImpulseSpeed);
+
+    // Create a base prefab for SpaceShips.
+    ecs_entity_t SpaceShip = ecs_new_prefab(ecs, "SpaceShip");
+    ecs_set(ecs, SpaceShip, ImpulseSpeed, {50});
+    ecs_set(ecs, SpaceShip, Defense, {25});
+
+        // Create a Freighter variant which inherits from SpaceShip
+        ecs_entity_t Freighter = ecs_new_prefab(ecs, "Freighter");
+        ecs_add_pair(ecs, Freighter, EcsIsA, SpaceShip);
+        ecs_set(ecs, Freighter, FreightCapacity, {100});
+        ecs_set(ecs, Freighter, Defense, {50});
+
+            // Create a MammothFreighter variant which inherits from Freighter
+            ecs_entity_t MammothFreighter = ecs_new_prefab(ecs, "MammothFreighter");
+            ecs_add_pair(ecs, MammothFreighter, EcsIsA, Freighter);
+            ecs_set(ecs, MammothFreighter, FreightCapacity, {500});
+
+        // Create a Frigate variant which inherits from SpaceShip
+        ecs_entity_t Frigate = ecs_new_prefab(ecs, "Frigate");
+        ecs_add_pair(ecs, Frigate, EcsIsA, SpaceShip);
+        ecs_set(ecs, Frigate, Attack, {100});
+        ecs_set(ecs, Frigate, Defense, {75});
+        ecs_set(ecs, Frigate, ImpulseSpeed, {125});
+
+
+    // Create an instance of the MammothFreighter. This entity will inherit the
+    // ImpulseSpeed from SpaceShip, Defense from Freighter and FreightCapacity
+    // from MammothFreighter.
+    ecs_entity_t inst = ecs_new_entity(ecs, "my_freighter");
+    ecs_add_pair(ecs, inst, EcsIsA, MammothFreighter);
+
+    // Add a private Position component.
+    ecs_set(ecs, inst, Position, {10, 20});
+
+    // Instances can override inherited components to give them a private copy
+    // of the component. This freighter got an armor upgrade:
+    ecs_set(ecs, inst, Defense, {100});
+
+    // Queries can match components from multiple levels of inheritance
+    ecs_query_t *q = ecs_query(ecs, {
+        .filter.terms = {
+            { .id = ecs_id(Position) },
+            { .id = ecs_id(ImpulseSpeed) }, 
+            { .id = ecs_id(Defense) }, 
+            { .id = ecs_id(FreightCapacity) }
+        }
+    });
+
+    ecs_iter_t it = ecs_query_iter(ecs, q);
+    while (ecs_query_next(&it)) {
+        Position  *p = ecs_field(&it, Position, 1);
+        ImpulseSpeed *s = ecs_field(&it, ImpulseSpeed, 2);
+        Defense *d = ecs_field(&it, Defense, 3);
+        FreightCapacity *c = ecs_field(&it, FreightCapacity, 4);
+
+        for (int i = 0; i < it.count; i ++) {
+            printf("%s:\n", ecs_get_name(ecs, it.entities[i]));
+            printf(" - position: %f, %f\n", p[i].x, p[i].y);
+            printf(" - impulse speed: %f\n", s[i].value);
+            printf(" - defense: %f\n", d[i].value);
+            printf(" - capacity: %f\n", c[i].value);
+        }
+    }
+
+    // Note that when matching tables with shared components, entities are
+    // returned one by one. See the queries/instancing example for more details.
+
+    // Output:
+    //  my_freighter:
+    //   - position: 10.000000, 20.000000
+    //   - impulse speed: 50.000000
+    //   - defense: 100.000000
+    //   - capacity: 500.000000
+
+    return ecs_fini(ecs);
+}