Support multi-threaded rendering with OpenGL on Android

Author: dsnopek

platform/android/display_server_android.cpp

@@ -484,20 +484,13 @@ int64_t DisplayServerAndroid::window_get_native_handle(HandleType p_handle_type,
 		}
 #ifdef GLES3_ENABLED
 		case DISPLAY_HANDLE: {
-			if (rendering_driver == "opengl3") {
-				return reinterpret_cast<int64_t>(eglGetCurrentDisplay());
-			}
-			return 0;
+			return reinterpret_cast<int64_t>(egl_display);
 		}
 		case OPENGL_CONTEXT: {
-			if (rendering_driver == "opengl3") {
-				return reinterpret_cast<int64_t>(eglGetCurrentContext());
-			}
-			return 0;
+			return reinterpret_cast<int64_t>(egl_context);
 		}
 		case EGL_DISPLAY: {
-			// @todo Find a way to get this from the Java side.
-			return 0;
+			return reinterpret_cast<int64_t>(egl_display);
 		}
 		case EGL_CONFIG: {
 			// @todo Find a way to get this from the Java side.
@@ -792,6 +785,13 @@ DisplayServerAndroid::DisplayServerAndroid(const String &p_rendering_driver, Dis
 #if defined(GLES3_ENABLED)
 	if (rendering_driver == "opengl3") {
 		RasterizerGLES3::make_current(false);
+		swap_own_buffers = OS::get_singleton()->is_separate_thread_rendering_enabled();
+		// These will have been set via eglMakeCurrent() on the Java side. It would be nice to explicitly pass
+		// them from Java, but there's no way to get the native handles with javax.microedition.khronos.egl;
+		// we'd need to switch to android.opengl.
+		egl_display = eglGetCurrentDisplay();
+		egl_surface = eglGetCurrentSurface(EGL_DRAW);
+		egl_context = eglGetCurrentContext();
 	}
 #endif
 
@@ -963,6 +963,28 @@ bool DisplayServerAndroid::should_swap_buffers() const {
 
 void DisplayServerAndroid::swap_buffers() {
 	swap_buffers_flag = true;
+
+#ifdef GLES3_ENABLED
+	if (swap_own_buffers) {
+		eglSwapBuffers(egl_display, egl_surface);
+	}
+#endif
+}
+
+void DisplayServerAndroid::gl_window_make_current(DisplayServer::WindowID p_window_id) {
+#ifdef GLES3_ENABLED
+	if (swap_own_buffers && egl_display && p_window_id == DisplayServer::MAIN_WINDOW_ID) {
+		eglMakeCurrent(egl_display, egl_surface, egl_surface, egl_context);
+	}
+#endif
+}
+
+void DisplayServerAndroid::release_rendering_thread() {
+#ifdef GLES3_ENABLED
+	if (swap_own_buffers && egl_display) {
+		eglMakeCurrent(egl_display, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
+	}
+#endif
 }
 
 void DisplayServerAndroid::set_native_icon(const String &p_filename) {

platform/android/display_server_android.h

@@ -72,13 +72,21 @@ class DisplayServerAndroid : public DisplayServer {
 
 	bool keep_screen_on;
 	bool swap_buffers_flag;
+	bool swap_own_buffers = false;
 
 	CursorShape cursor_shape = CursorShape::CURSOR_ARROW;
 
 #if defined(RD_ENABLED)
 	RenderingContextDriver *rendering_context = nullptr;
 	RenderingDevice *rendering_device = nullptr;
 #endif
+
+#ifdef GLES3_ENABLED
+	void *egl_display = nullptr;
+	void *egl_surface = nullptr;
+	void *egl_context = nullptr;
+#endif
+
 	NativeMenu *native_menu = nullptr;
 
 	ObjectID window_attached_instance_id;
@@ -193,6 +201,7 @@ class DisplayServerAndroid : public DisplayServer {
 
 	virtual void window_set_max_size(const Size2i p_size, WindowID p_window = MAIN_WINDOW_ID) override;
 	virtual Size2i window_get_max_size(WindowID p_window = MAIN_WINDOW_ID) const override;
+	virtual void gl_window_make_current(DisplayServer::WindowID p_window_id) override;
 
 	virtual void window_set_min_size(const Size2i p_size, WindowID p_window = MAIN_WINDOW_ID) override;
 	virtual Size2i window_get_min_size(WindowID p_window = MAIN_WINDOW_ID) const override;
@@ -251,7 +260,9 @@ class DisplayServerAndroid : public DisplayServer {
 
 	void reset_swap_buffers_flag();
 	bool should_swap_buffers() const;
+	inline bool get_swap_own_buffers() const { return swap_own_buffers; }
 	virtual void swap_buffers() override;
+	virtual void release_rendering_thread() override;
 
 	virtual void set_native_icon(const String &p_filename) override;
 	virtual void set_icon(const Ref<Image> &p_icon) override;

platform/android/java_godot_lib_jni.cpp

@@ -267,7 +267,7 @@ JNIEXPORT jboolean JNICALL Java_org_godotengine_godot_GodotLib_step(JNIEnv *env,
 		Main::setup2(false); // The logo is shown in the next frame otherwise we run into rendering issues
 		input_handler = new AndroidInputHandler();
 		step.increment();
-		return true;
+		return !DisplayServerAndroid::get_singleton()->get_swap_own_buffers();
 	}
 
 	if (step.get() == STEP_SHOW_LOGO) {
@@ -286,12 +286,12 @@ JNIEXPORT jboolean JNICALL Java_org_godotengine_godot_GodotLib_step(JNIEnv *env,
 		}
 
 		step.increment();
-		return true;
+		return !DisplayServerAndroid::get_singleton()->get_swap_own_buffers();
 	}
 
 	if (step.get() == STEP_STARTED) {
 		if (Main::start() != EXIT_SUCCESS) {
-			return true; // should exit instead and print the error
+			return !DisplayServerAndroid::get_singleton()->get_swap_own_buffers(); // should exit instead and print the error
 		}
 
 		godot_java->on_godot_setup_completed(env);
@@ -305,12 +305,13 @@ JNIEXPORT jboolean JNICALL Java_org_godotengine_godot_GodotLib_step(JNIEnv *env,
 	DisplayServerAndroid::get_singleton()->process_magnetometer(magnetometer);
 	DisplayServerAndroid::get_singleton()->process_gyroscope(gyroscope);
 
+	bool swap_own_buffers = DisplayServerAndroid::get_singleton()->get_swap_own_buffers();
 	bool should_swap_buffers = false;
 	if (os_android->main_loop_iterate(&should_swap_buffers)) {
 		_terminate(env, false);
 	}
 
-	return should_swap_buffers;
+	return !swap_own_buffers && should_swap_buffers;
 }
 
 // Called on the UI thread