Reduce the FPS when the window is unfocused (#8837)

builtin/settingtypes.txt

@@ -606,8 +606,8 @@ arm_inertia (Arm inertia) bool true
 #    to not waste CPU power for no benefit.
 fps_max (Maximum FPS) int 60 1
 
-#    Maximum FPS when game is paused.
-pause_fps_max (FPS in pause menu) int 20 1
+#    Maximum FPS when the window is not focused, or when the game is paused.
+fps_max_unfocused (FPS when unfocused or paused) int 20 1
 
 #    Open the pause menu when the window's focus is lost. Does not pause if a formspec is
 #    open.

src/client/game.cpp

@@ -3996,9 +3996,10 @@ inline void Game::limitFps(FpsControl *fps_timings, f32 *dtime)
 	else
 		fps_timings->busy_time = 0;
 
-	u32 frametime_min = 1000 / (g_menumgr.pausesGame()
-			? g_settings->getFloat("pause_fps_max")
-			: g_settings->getFloat("fps_max"));
+	u32 frametime_min = 1000 / (
+		device->isWindowFocused() && !g_menumgr.pausesGame()
+			? g_settings->getFloat("fps_max")
+			: g_settings->getFloat("fps_max_unfocused"));
 
 	if (fps_timings->busy_time < frametime_min) {
 		fps_timings->sleep_time = frametime_min - fps_timings->busy_time;

src/defaultsettings.cpp

@@ -165,7 +165,7 @@ void set_default_settings(Settings *settings)
 	settings->setDefault("tooltip_show_delay", "400");
 	settings->setDefault("tooltip_append_itemname", "false");
 	settings->setDefault("fps_max", "60");
-	settings->setDefault("pause_fps_max", "20");
+	settings->setDefault("fps_max_unfocused", "20");
 	settings->setDefault("viewing_range", "100");
 #if ENABLE_GLES
 	settings->setDefault("near_plane", "0.1");
@@ -477,7 +477,7 @@ void set_default_settings(Settings *settings)
 	settings->setDefault("max_block_generate_distance", "5");
 	settings->setDefault("enable_3d_clouds", "false");
 	settings->setDefault("fps_max", "30");
-	settings->setDefault("pause_fps_max", "10");
+	settings->setDefault("fps_max_unfocused", "10");
 	settings->setDefault("max_objects_per_block", "20");
 	settings->setDefault("sqlite_synchronous", "1");
 	settings->setDefault("server_map_save_interval", "15");

src/gui/guiEngine.cpp

@@ -297,10 +297,14 @@ void GUIEngine::run()
 
 		driver->endScene();
 
+		IrrlichtDevice *device = RenderingEngine::get_raw_device();
+		u32 frametime_min = 1000 / (device->isWindowFocused()
+			? g_settings->getFloat("fps_max")
+			: g_settings->getFloat("fps_max_unfocused"));
 		if (m_clouds_enabled)
-			cloudPostProcess();
+			cloudPostProcess(frametime_min, device);
 		else
-			sleep_ms(25);
+			sleep_ms(frametime_min);
 
 		m_script->step();
 
@@ -367,9 +371,8 @@ void GUIEngine::cloudPreProcess()
 }
 
 /******************************************************************************/
-void GUIEngine::cloudPostProcess()
+void GUIEngine::cloudPostProcess(u32 frametime_min, IrrlichtDevice *device)
 {
-	float fps_max = g_settings->getFloat("pause_fps_max");
 	// Time of frame without fps limit
 	u32 busytime_u32;
 
@@ -380,12 +383,10 @@ void GUIEngine::cloudPostProcess()
 	else
 		busytime_u32 = 0;
 
-	// FPS limiter
-	u32 frametime_min = 1000./fps_max;
-
+	// FPS limit
 	if (busytime_u32 < frametime_min) {
 		u32 sleeptime = frametime_min - busytime_u32;
-		RenderingEngine::get_raw_device()->sleep(sleeptime);
+		device->sleep(sleeptime);
 	}
 }
 

src/gui/guiEngine.h

@@ -277,7 +277,7 @@ private:
 	/** do preprocessing for cloud subsystem */
 	void cloudPreProcess();
 	/** do postprocessing for cloud subsystem */
-	void cloudPostProcess();
+	void cloudPostProcess(u32 frametime_min, IrrlichtDevice *device);
 
 	/** internam data required for drawing clouds */
 	struct clouddata {