Properly link flecs library

engine/libs/flecs/examples/c/entities/fwd_declare_component/include/fwd_declare_component.h

@@ -0,0 +1,16 @@
+#ifndef FWD_DECLARE_COMPONENT_H
+#define FWD_DECLARE_COMPONENT_H
+
+/* This generated file contains includes for project dependencies */
+#include "fwd_declare_component/bake_config.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+

engine/libs/flecs/examples/c/entities/fwd_declare_component/include/fwd_declare_component/bake_config.h

@@ -0,0 +1,24 @@
+/*
+                                   )
+                                  (.)
+                                  .|.
+                                  | |
+                              _.--| |--._
+                           .-';  ;`-'& ; `&.
+                          \   &  ;    &   &_/
+                           |"""---...---"""|
+                           \ | | | | | | | /
+                            `---.|.|.|.---'
+
+ * This file is generated by bake.lang.c for your convenience. Headers of
+ * dependencies will automatically show up in this file. Include bake_config.h
+ * in your main project file. Do not edit! */
+
+#ifndef FWD_DECLARE_COMPONENT_BAKE_CONFIG_H
+#define FWD_DECLARE_COMPONENT_BAKE_CONFIG_H
+
+/* Headers of public dependencies */
+#include <flecs.h>
+
+#endif
+

engine/libs/flecs/examples/c/entities/fwd_declare_component/project.json

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+{
+    "id": "fwd_declare_component",
+    "type": "application",
+    "value": {
+        "use": [
+            "flecs"
+        ],
+        "public": false
+    }
+}

engine/libs/flecs/examples/c/entities/fwd_declare_component/src/main.c

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+#include <fwd_declare_component.h>
+#include <stdio.h>
+
+// This example shows how to use utility macro's to forward declare and use a 
+// component. The ECS_COMPONENT automatically declares a variable that holds a
+// component id, but this variable is scoped to the function only. When trying
+// to access the component from another function, this typically causes errors
+// that look like this:
+//   "FLECS_IDComponentNameID" is undefined
+//
+// Forward declaring a component will make the component id available from other
+// functions, which fixes this error.
+
+// The component type
+typedef struct {
+    double x, y;
+} Position;
+
+// The forward declaration of the component id variable. This variable will have
+// the name FLECS_IDPositionID, to ensure its name won't conflict with the type.
+ECS_COMPONENT_DECLARE(Position);
+
+// When you want forward declare a component from a header, make sure to use the
+// extern keyword to prevent multiple definitions of the same variable:
+//
+// In the header:
+//   extern ECS_COMPONENT_DECLARE(Position);
+//
+// In *one* of the source files:
+//  ECS_COMPONENT_DECLARE(Position);
+
+
+// To forward declare entities created with ECS_ENTITY, ECS_TAG or ECS_PREFAB,
+// use ECS_DECLARE.
+ECS_DECLARE(Wizard);
+
+// Regular entity handles can also be forward declared
+ecs_entity_t Platoon_1;
+
+ecs_entity_t create_npc(ecs_world_t *world) {
+    ecs_entity_t result = ecs_new(world, 0);
+    
+    // Without the forward declaration, this would have thrown a compiler error
+    ecs_set(world, result, Position, {10, 20});
+    ecs_add(world, result, Wizard);
+
+    // An entity that's not declared using the utility macro's can be added with
+    // ecs_add_id. This has the same effect, with as only difference that this
+    // function doesn't look for a variable named FLECS_EPlatoon_1
+    ecs_add_id(world, result, Platoon_1);
+
+    return result;
+}
+
+int main(int argc, char *argv[]) {
+    ecs_world_t *world = ecs_init_w_args(argc, argv);
+
+    // Register the component and assign the forward declared variable.
+    ECS_COMPONENT_DEFINE(world, Position);
+
+    // Same for the tag
+    ECS_TAG_DEFINE(world, Wizard);
+
+    // A forward declared entity can be assigned as any variable
+    Platoon_1 = ecs_new_id(world);
+
+    // Create new entity with Position
+    ecs_entity_t e = create_npc(world);
+    const Position *p = ecs_get(world, e, Position);
+    printf("{%f, %f}\n", p->x, p->y);
+
+    // To access the component id variable directly, use the ecs_id macro:
+    printf("Id of Position is %u\n", 
+        (uint32_t)ecs_id(Position)); // the cast avoids formatting warnings
+
+    return ecs_fini(world);
+
+    // Output:
+    //  {10.000000, 20.000000}
+    //  Id of Position is 497
+}