Properly link flecs library

engine/libs/flecs/examples/cpp/observers/yield_existing/include/yield_existing.h

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

engine/libs/flecs/examples/cpp/observers/yield_existing/include/yield_existing/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 YIELD_EXISTING_BAKE_CONFIG_H
+#define YIELD_EXISTING_BAKE_CONFIG_H
+
+/* Headers of public dependencies */
+#include <flecs.h>
+
+#endif
+

engine/libs/flecs/examples/cpp/observers/yield_existing/project.json

@@ -0,0 +1,11 @@
+{
+    "id": "yield_existing",
+    "type": "application",
+    "value": {
+        "use": [
+            "flecs"
+        ],
+        "language": "c++",
+        "public": false
+    }
+}

engine/libs/flecs/examples/cpp/observers/yield_existing/src/main.cpp

@@ -0,0 +1,36 @@
+#include <yield_existing.h>
+#include <iostream>
+
+// Observers can enable a "yield_existing" feature that upon creation of the
+// observer produces events for all entities that match the observer query. The
+// feature is only implemented for the builtin EcsOnAdd and EcsOnSet events.
+//
+// Custom events can also implement behavior for yield_existing by adding the
+// Iterable component to the event (see EcsIterable for more details).
+
+struct Position {
+    double x, y;
+};
+
+int main(int, char *[]) {
+    flecs::world ecs;
+
+    // Create existing entities with Position component
+    ecs.entity("e1").set<Position>({10, 20});
+    ecs.entity("e2").set<Position>({20, 30});
+
+    // Create an observer for three events
+    ecs.observer<Position>()
+        .event(flecs::OnSet)
+        .yield_existing() // Trigger for existing matching entities
+        .each([](flecs::iter& it, size_t i, Position& p) {
+            std::cout << " - " << it.event().name() << ": " 
+                << it.event_id().str() << ": "
+                << it.entity(i).name() 
+                << ": {" << p.x << ", " << p.y << "}\n";
+        });
+
+    // Output
+    //   - OnSet: Position: e1: {10, 20}
+    //   - OnSet: Position: e2: {20, 30}
+}