[GDExtension] Add function to register main loop callbacks

core/extension/gdextension.cpp

@@ -686,6 +686,13 @@ void GDExtension::_register_get_classes_used_callback(GDExtensionClassLibraryPtr
 #endif
 }
 
+void GDExtension::_register_main_loop_callbacks(GDExtensionClassLibraryPtr p_library, const GDExtensionMainLoopCallbacks *p_callbacks) {
+	GDExtension *self = reinterpret_cast<GDExtension *>(p_library);
+	self->startup_callback = p_callbacks->startup_func;
+	self->shutdown_callback = p_callbacks->shutdown_func;
+	self->frame_callback = p_callbacks->frame_func;
+}
+
 void GDExtension::register_interface_function(const StringName &p_function_name, GDExtensionInterfaceFunctionPtr p_function_pointer) {
 	ERR_FAIL_COND_MSG(gdextension_interface_functions.has(p_function_name), vformat("Attempt to register interface function '%s', which appears to be already registered.", p_function_name));
 	gdextension_interface_functions.insert(p_function_name, p_function_pointer);
@@ -805,6 +812,7 @@ void GDExtension::initialize_gdextensions() {
 	register_interface_function("classdb_unregister_extension_class", (GDExtensionInterfaceFunctionPtr)&GDExtension::_unregister_extension_class);
 	register_interface_function("get_library_path", (GDExtensionInterfaceFunctionPtr)&GDExtension::_get_library_path);
 	register_interface_function("editor_register_get_classes_used_callback", (GDExtensionInterfaceFunctionPtr)&GDExtension::_register_get_classes_used_callback);
+	register_interface_function("register_main_loop_callbacks", (GDExtensionInterfaceFunctionPtr)&GDExtension::_register_main_loop_callbacks);
 }
 
 void GDExtension::finalize_gdextensions() {

core/extension/gdextension.h

@@ -94,6 +94,7 @@ class GDExtension : public Resource {
 	static void _unregister_extension_class(GDExtensionClassLibraryPtr p_library, GDExtensionConstStringNamePtr p_class_name);
 	static void _get_library_path(GDExtensionClassLibraryPtr p_library, GDExtensionStringPtr r_path);
 	static void _register_get_classes_used_callback(GDExtensionClassLibraryPtr p_library, GDExtensionEditorGetClassesUsedCallback p_callback);
+	static void _register_main_loop_callbacks(GDExtensionClassLibraryPtr p_library, const GDExtensionMainLoopCallbacks *p_callbacks);
 
 	GDExtensionInitialization initialization;
 	int32_t level_initialized = -1;
@@ -115,6 +116,10 @@ class GDExtension : public Resource {
 	void clear_instance_bindings();
 #endif
 
+	GDExtensionMainLoopStartupCallback startup_callback = nullptr;
+	GDExtensionMainLoopShutdownCallback shutdown_callback = nullptr;
+	GDExtensionMainLoopFrameCallback frame_callback = nullptr;
+
 	static inline HashMap<StringName, GDExtensionInterfaceFunctionPtr> gdextension_interface_functions;
 
 protected:

core/extension/gdextension_interface.h

@@ -805,6 +805,21 @@ typedef struct {
 	const char *string; // (e.g. "Godot v3.1.4.stable.official.mono")
 } GDExtensionGodotVersion2;
 
+/* Called when starting the main loop. */
+typedef void (*GDExtensionMainLoopStartupCallback)();
+
+/* Called when shutting down the main loop. */
+typedef void (*GDExtensionMainLoopShutdownCallback)();
+
+/* Called for every frame iteration of the main loop. */
+typedef void (*GDExtensionMainLoopFrameCallback)();
+
+typedef struct {
+	GDExtensionMainLoopStartupCallback startup_func;
+	GDExtensionMainLoopShutdownCallback shutdown_func;
+	GDExtensionMainLoopFrameCallback frame_func;
+} GDExtensionMainLoopCallbacks;
+
 /**
  * @name get_godot_version
  * @since 4.1
@@ -3131,6 +3146,17 @@ typedef void (*GDExtensionsInterfaceEditorHelpLoadXmlFromUtf8CharsAndLen)(const
  */
 typedef void (*GDExtensionInterfaceEditorRegisterGetClassesUsedCallback)(GDExtensionClassLibraryPtr p_library, GDExtensionEditorGetClassesUsedCallback p_callback);
 
+/**
+ * @name register_main_loop_callbacks
+ * @since 4.5
+ *
+ * Registers callbacks to be called at different phases of the main loop.
+ *
+ * @param p_library A pointer the library received by the GDExtension's entry point function.
+ * @param p_callback A pointer to the structure that contains the callbacks.
+ */
+typedef void (*GDExtensionInterfaceRegisterMainLoopCallbacks)(GDExtensionClassLibraryPtr p_library, const GDExtensionMainLoopCallbacks *p_callbacks);
+
 #ifdef __cplusplus
 }
 #endif

core/extension/gdextension_manager.cpp

@@ -60,6 +60,14 @@ GDExtensionManager::LoadStatus GDExtensionManager::_load_extension_internal(cons
 	emit_signal("extension_loaded", p_extension);
 #endif
 
+	if (startup_callback_called) {
+		// Extension is loading after the startup callback has already been called,
+		// so we call it now for this extension to make sure it doesn't miss it.
+		if (p_extension->startup_callback) {
+			p_extension->startup_callback();
+		}
+	}
+
 	return LOAD_STATUS_OK;
 }
 
@@ -76,10 +84,24 @@ GDExtensionManager::LoadStatus GDExtensionManager::_unload_extension_internal(co
 		}
 	}
 
+	if (!shutdown_callback_called) {
+		// Extension is unloading before the shutdown callback has been called,
+		// which means the engine hasn't shutdown yet but we want to make sure
+		// to call the shutdown callback so it doesn't miss it.
+		if (p_extension->shutdown_callback) {
+			p_extension->shutdown_callback();
+		}
+	}
+
 	for (const KeyValue<String, String> &kv : p_extension->class_icon_paths) {
 		gdextension_class_icon_paths.erase(kv.key);
 	}
 
+	// Clear main loop callbacks.
+	p_extension->startup_callback = nullptr;
+	p_extension->shutdown_callback = nullptr;
+	p_extension->frame_callback = nullptr;
+
 	return LOAD_STATUS_OK;
 }
 
@@ -387,6 +409,37 @@ bool GDExtensionManager::ensure_extensions_loaded(const HashSet<String> &p_exten
 	return needs_restart;
 }
 
+void GDExtensionManager::startup() {
+	startup_callback_called = true;
+
+	for (const KeyValue<String, Ref<GDExtension>> &E : gdextension_map) {
+		const Ref<GDExtension> &extension = E.value;
+		if (extension->startup_callback) {
+			extension->startup_callback();
+		}
+	}
+}
+
+void GDExtensionManager::shutdown() {
+	shutdown_callback_called = true;
+
+	for (const KeyValue<String, Ref<GDExtension>> &E : gdextension_map) {
+		const Ref<GDExtension> &extension = E.value;
+		if (extension->shutdown_callback) {
+			extension->shutdown_callback();
+		}
+	}
+}
+
+void GDExtensionManager::frame() {
+	for (const KeyValue<String, Ref<GDExtension>> &E : gdextension_map) {
+		const Ref<GDExtension> &extension = E.value;
+		if (extension->frame_callback) {
+			extension->frame_callback();
+		}
+	}
+}
+
 GDExtensionManager *GDExtensionManager::get_singleton() {
 	return singleton;
 }

core/extension/gdextension_manager.h

@@ -39,6 +39,9 @@ class GDExtensionManager : public Object {
 	HashMap<String, Ref<GDExtension>> gdextension_map;
 	HashMap<String, String> gdextension_class_icon_paths;
 
+	bool startup_callback_called = false;
+	bool shutdown_callback_called = false;
+
 	static void _bind_methods();
 
 	static inline GDExtensionManager *singleton = nullptr;
@@ -86,6 +89,10 @@ public:
 	void reload_extensions();
 	bool ensure_extensions_loaded(const HashSet<String> &p_extensions);
 
+	void startup();
+	void shutdown();
+	void frame();
+
 	GDExtensionManager();
 	~GDExtensionManager();
 };

main/main.cpp

@@ -4562,6 +4562,8 @@ int Main::start() {
 		movie_writer->begin(DisplayServer::get_singleton()->window_get_size(), fixed_fps, Engine::get_singleton()->get_write_movie_path());
 	}
 
+	GDExtensionManager::get_singleton()->startup();
+
 	if (minimum_time_msec) {
 		uint64_t minimum_time = 1000 * minimum_time_msec;
 		uint64_t elapsed_time = OS::get_singleton()->get_ticks_usec();
@@ -4767,6 +4769,8 @@ bool Main::iteration() {
 	process_max = MAX(process_ticks, process_max);
 	uint64_t frame_time = OS::get_singleton()->get_ticks_usec() - ticks;
 
+	GDExtensionManager::get_singleton()->frame();
+
 	for (int i = 0; i < ScriptServer::get_language_count(); i++) {
 		ScriptServer::get_language(i)->frame();
 	}
@@ -4887,6 +4891,8 @@ void Main::cleanup(bool p_force) {
 	}
 #endif
 
+	GDExtensionManager::get_singleton()->shutdown();
+
 	for (int i = 0; i < TextServerManager::get_singleton()->get_interface_count(); i++) {
 		TextServerManager::get_singleton()->get_interface(i)->cleanup();
 	}