Pause rendering when the window is minimized

OpenRA.Game/Game.cs

@@ -828,8 +828,7 @@ namespace OpenRA
 
 					var haveSomeTimeUntilNextLogic = now < nextLogic;
 					var isTimeToRender = now >= nextRender;
-
-					if ((isTimeToRender && haveSomeTimeUntilNextLogic) || forceRender)
+					if (!Renderer.WindowIsSuspended && ((isTimeToRender && haveSomeTimeUntilNextLogic) || forceRender))
 					{
 						nextRender = now + renderInterval;
 
@@ -844,6 +843,19 @@ namespace OpenRA
 						RenderTick();
 						renderBeforeNextTick = false;
 					}
+
+					// Simulate a render tick if it was time to render but we skip actually rendering
+					if (Renderer.WindowIsSuspended && isTimeToRender)
+					{
+						// Make sure that nextUpdate is set to a proper minimum interval
+						nextRender = now + renderInterval;
+
+						// Still process SDL events to allow a restore to come through
+						Renderer.Window.PumpInput(new NullInputHandler());
+
+						// Ensure that we still logic tick despite not rendering
+						renderBeforeNextTick = false;
+					}
 				}
 				else
 					Thread.Sleep((int)(nextUpdate - now));

OpenRA.Game/Graphics/PlatformInterfaces.cs

@@ -59,6 +59,7 @@ namespace OpenRA
 		int DisplayCount { get; }
 		int CurrentDisplay { get; }
 		bool HasInputFocus { get; }
+		bool IsSuspended { get; }
 
 		event Action<float, float, float, float> OnWindowScaleChanged;
 

OpenRA.Game/Renderer.cs

@@ -33,6 +33,7 @@ namespace OpenRA
 		public RgbaSpriteRenderer RgbaSpriteRenderer { get; private set; }
 
 		public bool WindowHasInputFocus => Window.HasInputFocus;
+		public bool WindowIsSuspended => Window.IsSuspended;
 
 		public IReadOnlyDictionary<string, SpriteFont> Fonts;
 

OpenRA.Platforms.Default/Sdl2Input.cs

@@ -94,6 +94,18 @@ namespace OpenRA.Platforms.Default
 								case SDL.SDL_WindowEventID.SDL_WINDOWEVENT_SIZE_CHANGED:
 									device.WindowSizeChanged();
 									break;
+
+								case SDL.SDL_WindowEventID.SDL_WINDOWEVENT_HIDDEN:
+								case SDL.SDL_WindowEventID.SDL_WINDOWEVENT_MINIMIZED:
+									device.IsSuspended = true;
+									break;
+
+								case SDL.SDL_WindowEventID.SDL_WINDOWEVENT_EXPOSED:
+								case SDL.SDL_WindowEventID.SDL_WINDOWEVENT_SHOWN:
+								case SDL.SDL_WindowEventID.SDL_WINDOWEVENT_MAXIMIZED:
+								case SDL.SDL_WindowEventID.SDL_WINDOWEVENT_RESTORED:
+									device.IsSuspended = false;
+									break;
 							}
 
 							break;

OpenRA.Platforms.Default/Sdl2PlatformWindow.cs

@@ -99,6 +99,8 @@ namespace OpenRA.Platforms.Default
 
 		public bool HasInputFocus { get; internal set; }
 
+		public bool IsSuspended { get; internal set; }
+
 		public GLProfile GLProfile
 		{
 			get