OpenGL: Go into reduced performance mode when window is obscured

src/Window.h

@@ -103,6 +103,9 @@ int Window_GetWindowState(void);
 cc_result Window_EnterFullscreen(void);
 /* Attempts to restore the window to before it entered full screen. */
 cc_result Window_ExitFullscreen(void);
+/* Returns non-zero if the window is obscured (occluded or minimised) */
+/* NOTE: Not supported by all windowing backends */
+int Window_IsObscured(void);
 
 /* Makes the window visible and focussed on screen. */
 void Window_Show(void);

src/Window_Android.c

@@ -322,6 +322,8 @@ cc_result Window_ExitFullscreen(void) {
 	return 0; 
 }
 
+int Window_IsObscured(void) { return 0; }
+
 void Window_Show(void) { } /* Window already visible */
 void Window_SetSize(int width, int height) { }
 

src/Window_Carbon.c

@@ -543,6 +543,8 @@ cc_result Window_ExitFullscreen(void) {
 	return res;
 }
 
+int Window_IsObscured(void) { return 0; }
+
 void Window_Show(void) {
 	ShowWindow(win_handle);
 	/* TODO: Do we actually need to reposition */

src/Window_SDL.c

@@ -83,6 +83,8 @@ cc_result Window_EnterFullscreen(void) {
 }
 cc_result Window_ExitFullscreen(void) { SDL_RestoreWindow(win_handle); return 0; }
 
+int Window_IsObscured(void) { return 0; }
+
 void Window_Show(void) { SDL_ShowWindow(win_handle); }
 
 void Window_SetSize(int width, int height) {

src/Window_Web.c

@@ -466,6 +466,8 @@ cc_result Window_ExitFullscreen(void) {
 	return 0;
 }
 
+int Window_IsObscured(void) { return 0; }
+
 void Window_Show(void) { }
 
 void Window_SetSize(int width, int height) {

src/Window_Win.c

@@ -447,6 +447,8 @@ cc_result Window_ExitFullscreen(void) {
 	return 0;
 }
 
+int Window_IsObscured(void) { return 0; }
+
 void Window_Show(void) {
 	ShowWindow(win_handle, SW_SHOW);
 	BringWindowToTop(win_handle);

src/Window_X11.c

@@ -433,6 +433,8 @@ cc_result Window_ExitFullscreen(void) {
 	ToggleFullscreen(_NET_WM_STATE_REMOVE); return 0;
 }
 
+int Window_IsObscured(void) { return 0; }
+
 void Window_Show(void) { XMapWindow(win_display, win_handle); }
 
 void Window_SetSize(int width, int height) {

src/_GLShared.h

@@ -276,6 +276,14 @@ void Gfx_BeginFrame(void) { frameStart = Stopwatch_Measure(); }
 void Gfx_Clear(void) { glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); }
 
 void Gfx_EndFrame(void) {
+#ifndef CC_BUILD_GLMODERN
+	if (Window_IsObscured()) {
+		TickReducedPerformance();
+	} else {
+		EndReducedPerformance();
+	}
+#endif
+
 	if (!GLContext_SwapBuffers()) Gfx_LoseContext("GLContext lost");
 	if (gfx_minFrameMs) LimitFPS();
 }

src/interop_cocoa.m

@@ -323,6 +323,8 @@ cc_result Window_ExitFullscreen(void) {
 	return 0;
 }
 
+int Window_IsObscured(void) { return 0; }
+
 void Window_Show(void) { 
 	[winHandle makeKeyAndOrderFront:appHandle];
 	RefreshWindowBounds(); // TODO: even necessary?

src/interop_ios.m

@@ -248,6 +248,7 @@ void Window_CloseKeyboard(void) {
 int Window_GetWindowState(void) { return WINDOW_STATE_NORMAL; }
 cc_result Window_EnterFullscreen(void) { return ERR_NOT_SUPPORTED; }
 cc_result Window_ExitFullscreen(void) { return ERR_NOT_SUPPORTED; }
+int Window_IsObscured(void) { return 0; }
 
 void Window_EnableRawMouse(void)  { }
 void Window_UpdateRawMouse(void)  { }