Fix play mode runtime scene replacement

engine/include/XCEngine/Scene/RuntimeLoop.h

@@ -22,6 +22,7 @@ public:
 
     void Start(Scene* scene);
     void Stop();
+    void ReplaceScene(Scene* scene);
 
     void Tick(float deltaTime);
     void Pause();

engine/include/XCEngine/Scene/SceneRuntime.h

@@ -34,6 +34,7 @@ public:
 
     void Start(Scene* scene);
     void Stop();
+    void ReplaceScene(Scene* scene);
 
     void FixedUpdate(float fixedDeltaTime);
     void Update(float deltaTime);

engine/include/XCEngine/Scripting/ScriptEngine.h

@@ -28,6 +28,7 @@ public:
 
     void OnRuntimeStart(Components::Scene* scene);
     void OnRuntimeStop();
+    void OnRuntimeSceneReplaced(Components::Scene* scene);
 
     void OnFixedUpdate(float fixedDeltaTime);
     void OnUpdate(float deltaTime);

engine/src/Scene/RuntimeLoop.cpp

@@ -44,6 +44,12 @@ void RuntimeLoop::Stop() {
     m_stepRequested = false;
 }
 
+void RuntimeLoop::ReplaceScene(Scene* scene) {
+    m_sceneRuntime.ReplaceScene(scene);
+    m_fixedAccumulator = 0.0f;
+    m_stepRequested = false;
+}
+
 void RuntimeLoop::Tick(float deltaTime) {
     if (!IsRunning()) {
         return;

engine/src/Scene/SceneRuntime.cpp

@@ -46,6 +46,18 @@ void SceneRuntime::Stop() {
     m_scene = nullptr;
 }
 
+void SceneRuntime::ReplaceScene(Scene* scene) {
+    if (!m_running) {
+        m_scene = scene;
+        m_uiRuntime->Reset();
+        return;
+    }
+
+    m_scene = scene;
+    m_uiRuntime->Reset();
+    Scripting::ScriptEngine::Get().OnRuntimeSceneReplaced(scene);
+}
+
 void SceneRuntime::FixedUpdate(float fixedDeltaTime) {
     if (!m_running || !m_scene || !m_scene->IsActive()) {
         return;

engine/src/Scripting/ScriptEngine.cpp

@@ -141,6 +141,54 @@ void ScriptEngine::OnRuntimeStop() {
     m_runtime->OnRuntimeStop(stoppedScene);
 }
 
+void ScriptEngine::OnRuntimeSceneReplaced(Components::Scene* scene) {
+    if (!m_runtimeRunning) {
+        m_runtimeScene = nullptr;
+        m_runtimeSceneCreatedSubscription = 0;
+        m_scriptStates.clear();
+        m_scriptOrder.clear();
+        return;
+    }
+
+    const float configuredFixedDeltaTime = m_runtimeFixedDeltaTime;
+    m_runtime->OnRuntimeStop(nullptr);
+    m_runtimeFixedDeltaTime = configuredFixedDeltaTime;
+
+    m_runtimeScene = scene;
+    m_runtimeSceneCreatedSubscription = 0;
+    m_scriptStates.clear();
+    m_scriptOrder.clear();
+
+    if (!m_runtimeScene) {
+        return;
+    }
+
+    m_runtime->OnRuntimeStart(m_runtimeScene);
+    m_runtimeSceneCreatedSubscription = m_runtimeScene->OnGameObjectCreated().Subscribe(
+        [this](Components::GameObject* gameObject) {
+            HandleGameObjectCreated(gameObject);
+        });
+
+    for (Components::GameObject* root : m_runtimeScene->GetRootGameObjects()) {
+        CollectScriptComponents(root);
+    }
+
+    const std::vector<ScriptInstanceKey> startupKeys = m_scriptOrder;
+    for (const ScriptInstanceKey& key : startupKeys) {
+        auto it = m_scriptStates.find(key);
+        if (it == m_scriptStates.end()) {
+            continue;
+        }
+
+        ScriptInstanceState& state = it->second;
+        if (!ShouldScriptRun(state)) {
+            continue;
+        }
+
+        EnsureScriptReady(state, true);
+    }
+}
+
 void ScriptEngine::OnFixedUpdate(float fixedDeltaTime) {
     if (!m_runtimeRunning) {
         return;