Properly link flecs library

engine/libs/flecs/examples/cpp/systems/mutate_entity_handle/include/mutate_entity_handle.h

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

engine/libs/flecs/examples/cpp/systems/mutate_entity_handle/include/mutate_entity_handle/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 MUTATE_ENTITY_HANDLE_BAKE_CONFIG_H
+#define MUTATE_ENTITY_HANDLE_BAKE_CONFIG_H
+
+/* Headers of public dependencies */
+#include <flecs.h>
+
+#endif
+

engine/libs/flecs/examples/cpp/systems/mutate_entity_handle/project.json

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

engine/libs/flecs/examples/cpp/systems/mutate_entity_handle/src/main.cpp

@@ -0,0 +1,88 @@
+#include <mutate_entity_handle.h>
+#include <iostream>
+#include <iomanip>
+
+// This example is the same as the mutate_entity example, but instead stores the
+// handle of the to be deleted entity in a component.
+
+struct Timeout { 
+    flecs::entity to_delete;
+    double value;
+};
+
+struct Tag { };
+
+int main(int, char *[]) {
+    flecs::world ecs;
+
+    ecs.system<Timeout>()
+        .each([](flecs::iter& it, size_t, Timeout& t) {
+            t.value -= static_cast<double>(it.delta_time());
+            if (t.value <= 0) {
+                // Delete the entity
+
+                // To make sure the delete operation is enqueued (see 
+                // mutate_entity example for more details) we need to provide it
+                // with a mutable context (stage) using the mut() function. If
+                // we don't provide a mutable context, the operation will be
+                // attempted on the context stored in the flecs::entity object,
+                // which would throw a readonly error.
+
+                // To catch these errors at compile time, replace the type of
+                // to_delete with flecs::entity_view. This class does not have 
+                // any methods for mutating the entity, which forces the code to
+                // first call mut().
+
+                // The it.world() function can be used to provide the context:
+                //   t.to_delete.mut(it.world()).destruct();
+                // 
+                // The current entity can also be used to provide context. This 
+                // is useful for functions that accept a flecs::entity:
+                //   t.to_delete.mut(it.entity(index)).destruct();
+                //
+                // A shortcut is to use the iterator directly:
+                t.to_delete.mut(it).destruct();
+                std::cout << "Expire: " << t.to_delete.name() << " deleted!\n";
+            }
+        });
+
+    ecs.system<const Timeout>()
+        .each([](const Timeout& t) {
+            std::cout << "PrintExpire: " << t.to_delete.name() << " has " 
+                << std::fixed << std::setprecision(2) << t.value 
+                << " seconds left\n";
+        });
+
+    ecs.observer<Tag>()
+        .event(flecs::OnRemove)
+        .each([](flecs::entity e, Tag) {
+            std::cout << "Expired: " << e.name() << " actually deleted\n";
+        });
+
+    // Add Tag so we can get notified when entity is actually deleted
+    flecs::entity to_delete = ecs.entity("ToDelete")
+        .add<Tag>();
+
+    ecs.entity("MyEntity")
+        .set<Timeout>({to_delete, 3.0});
+
+    ecs.set_target_fps(1);
+
+    while (ecs.progress()) {
+        // If entity is no longer alive, exit
+        if (!to_delete.is_alive()) {
+            break;
+        }
+
+        std::cout << "Tick...\n";
+    }
+
+    // Output
+    //  PrintExpire: ToDelete has 2.00 seconds left
+    //  Tick...
+    //  PrintExpire: ToDelete has 0.98 seconds left
+    //  Tick...
+    //  Expire: ToDelete deleted!
+    //  PrintExpire: ToDelete has -0.03 seconds left
+    //  Expired: ToDelete actually deleted
+}