Properly link flecs library

engine/libs/flecs/examples/cpp/game_mechanics/scene_management/include/scene_management.h

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

engine/libs/flecs/examples/cpp/game_mechanics/scene_management/include/scene_management/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 SCENE_MANAGEMENT_BAKE_CONFIG_H
+#define SCENE_MANAGEMENT_BAKE_CONFIG_H
+
+/* Headers of public dependencies */
+#include <flecs.h>
+
+#endif
+

engine/libs/flecs/examples/cpp/game_mechanics/scene_management/project.json

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

engine/libs/flecs/examples/cpp/game_mechanics/scene_management/src/main.cpp

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+#include <scene_management.h>
+#include <iostream>
+#include <string>
+
+// This example shows one possible way to implement scene management
+// using pipelines.
+
+// Scene relationships/tags
+struct ActiveScene { }; // Represents the current scene
+struct SceneRoot { }; // Parent for all entities unique to the scene
+
+// Scenes
+using Pipeline = flecs::entity;
+struct MenuScene { Pipeline pip; };
+struct GameScene { Pipeline pip; };
+
+// Components for Example
+struct Position { float x, y; };
+struct Button { std::string text; };
+struct Character { bool alive; };
+struct Health { int amount; };
+
+// Removes all entities who are children of
+// the current scene root.
+// (NOTE: should use defer_begin() / defer_end())
+void reset_scene(flecs::world& ecs) {
+    ecs.delete_with(flecs::ChildOf, ecs.entity<SceneRoot>());
+}
+
+void menu_scene(flecs::iter& it, size_t, ActiveScene) {
+    std::cout << "\n>> ActiveScene has changed to `MenuScene`\n\n";
+
+    flecs::world ecs = it.world();
+    flecs::entity scene = ecs.component<SceneRoot>();
+    
+    reset_scene(ecs);
+
+    // Creates a start menu button
+    // when we enter the menu scene.
+    ecs.entity("Start Button")
+        .set(Button{ "Play the Game!" })
+        .set(Position{ 50, 50 })
+        .child_of(scene);
+
+    ecs.set_pipeline(ecs.get<MenuScene>()->pip);
+}
+
+void game_scene(flecs::iter& it, size_t, ActiveScene) {
+    std::cout << "\n>> ActiveScene has changed to `GameScene`\n\n";
+
+    flecs::world ecs = it.world();
+    flecs::entity scene = ecs.component<SceneRoot>();
+    
+    reset_scene(ecs);
+
+    // Creates a player character
+    // when we enter the game scene.
+    ecs.entity("Player")
+        .set(Character{ })
+        .set(Health{ 2 })
+        .set(Position{ 0, 0 })
+        .child_of(scene);
+
+    ecs.set_pipeline(ecs.get<GameScene>()->pip);
+}
+
+void init_scenes(flecs::world& ecs) {
+    // Can only have one active scene
+    // in a game at a time.
+    ecs.component<ActiveScene>()
+        .add(flecs::Exclusive);
+
+    // Each scene gets a pipeline that
+    // runs the associated systems plus
+    // all other scene-agnostic systems.
+    flecs::entity menu = ecs.pipeline()
+            .with(flecs::System)
+            .without<GameScene>() // Use "without()" of the other scenes
+                                  // so that we can run every system that
+                                  // doesn't have a scene attached to it.
+            .build();
+
+    flecs::entity game = ecs.pipeline()
+            .with(flecs::System)
+            .without<MenuScene>()
+            .build();
+
+    // Set pipeline entities on the scenes
+    // to easily find them later with get().
+    ecs.set<MenuScene>({ menu });
+    ecs.set<GameScene>({ game });
+
+    // Observer to call scene change logic for
+    // MenuScene when added to the ActiveScene.
+    ecs.observer<ActiveScene>("Scene Change to Menu")
+        .event(flecs::OnAdd)
+        .second<MenuScene>()
+        .each(menu_scene);
+
+    // Observer to call scene change logic for
+    // GameScene when added to the ActiveScene.
+    ecs.observer<ActiveScene>("Scene Change to Game")
+        .event(flecs::OnAdd)
+        .second<GameScene>()
+        .each(game_scene);
+}
+
+void init_systems(flecs::world& ecs) {
+    // Will run every time regardless of the
+    // current scene we're in.
+    ecs.system<const Position>("Print Position")
+        .each([](flecs::entity e, const Position& p) {
+            // Prints out the position of the
+            // entity.
+            std::cout << e.name() << ": {" << p.x << ", " << p.y << "}\n";
+        });
+
+    // Will only run when the game scene is
+    // currently active.
+    ecs.system<Health>("Characters Lose Health")
+        .kind<GameScene>()
+        .each([](Health& h) {
+            // Prints out the character's health
+            // and then decrements it by one.
+            std::cout << h.amount << " health remaining\n";
+            h.amount--;
+        });
+
+    // Will only run when the menu scene is
+    // currently active.
+    ecs.system<const Button>("Print Menu Button Text")
+        .kind<MenuScene>()
+        .each([](const Button& b) {
+            // Prints out the text of the menu
+            // button.
+            std::cout << "Button says \"" << b.text << "\"\n";
+        });
+}
+
+int main(int, char *[]) {
+    flecs::world ecs;
+
+    init_scenes(ecs);
+    init_systems(ecs);
+
+    ecs.add<ActiveScene, MenuScene>();
+    ecs.progress();
+
+    ecs.add<ActiveScene, GameScene>();
+    ecs.progress();
+    ecs.progress();
+    ecs.progress();
+
+    ecs.add<ActiveScene, MenuScene>();
+    ecs.progress();
+
+    ecs.add<ActiveScene, GameScene>();
+    ecs.progress();
+    ecs.progress();
+    ecs.progress();
+
+    // Output
+    // >> ActiveScene has changed to `MenuScene`
+
+    // Start Button: {50, 50}
+    // Button says "Play the Game!"
+
+    // >> ActiveScene has changed to `GameScene`
+
+    // Player: {0, 0}
+    // 2 health remaining
+    // Player: {0, 0}
+    // 1 health remaining
+    // Player: {0, 0}
+    // 0 health remaining
+
+    // >> ActiveScene has changed to `MenuScene`
+
+    // Start Button: {50, 50}
+    // Button says "Play the Game!"
+
+    // >> ActiveScene has changed to `GameScene`
+
+    // Player: {0, 0}
+    // 2 health remaining
+    // Player: {0, 0}
+    // 1 health remaining
+    // Player: {0, 0}
+    // 0 health remaining
+}