Skip rendering on low-end devices

Source/diablo.cpp

@@ -841,7 +841,7 @@ void RunGameLoop(interface_mode uMsg)
 
 		bool drawGame = true;
 		bool processInput = true;
-		bool runGameLoop = demo::IsRunning() ? demo::GetRunGameLoop(drawGame, processInput) : nthread_has_500ms_passed();
+		bool runGameLoop = demo::IsRunning() ? demo::GetRunGameLoop(drawGame, processInput) : nthread_has_500ms_passed(&drawGame);
 		if (demo::IsRecording())
 			demo::RecordGameLoopResult(runGameLoop);
 

Source/nthread.cpp

@@ -212,7 +212,7 @@ void nthread_ignore_mutex(bool bStart)
 	sgbThreadIsRunning = bStart;
 }
 
-bool nthread_has_500ms_passed()
+bool nthread_has_500ms_passed(bool *drawGame /*= nullptr*/)
 {
 	int currentTickCount = SDL_GetTicks();
 	int ticksElapsed = currentTickCount - last_tick;
@@ -234,6 +234,13 @@ bool nthread_has_500ms_passed()
 			ticksElapsed = 0;
 		}
 	}
+	if (drawGame != nullptr) {
+		// Check if we missed a game tick.
+		// This can happen when we run a low-end device that can't render fast enough (typically 20fps).
+		// If this happens, try to speed-up the game by skipping the rendering.
+		// This avoids desyncs and hourglasses when running multiplayer and slowdowns in singleplayer.
+		*drawGame = ticksElapsed <= gnTickDelay;
+	}
 	return ticksElapsed >= 0;
 }
 

Source/nthread.h

@@ -32,7 +32,7 @@ void nthread_ignore_mutex(bool bStart);
  * @brief Checks if it's time for the logic to advance
  * @return True if the engine should tick
  */
-bool nthread_has_500ms_passed();
+bool nthread_has_500ms_passed(bool *drawGame = nullptr);
 /**
  * @brief Updates the progress in time to the next game tick
  */