Merge bac9bf93bc into 03672ed8eb

The game loop must run with the game lock held.

src/engine_gui.cpp

@@ -84,7 +84,7 @@ struct EnginePreviewWindow : Window {
 
 		/* Get size of engine sprite, on loan from depot_gui.cpp */
 		EngineID engine = static_cast<EngineID>(this->window_number);
-		EngineImageType image_type = EIT_PURCHASE;
+		EngineImageType image_type = EIT_PREVIEW;
 		uint x, y;
 		int x_offs, y_offs;
 

src/video/null_v.cpp

@@ -50,8 +50,11 @@ void VideoDriver_Null::MainLoop()
 {
 	uint i;
 
-	for (i = 0; i < this->ticks; i++) {
-		::GameLoop();
+	for (i = 0; i < this->ticks && ! _exit_game; i++) {
+		{
+			std::lock_guard<std::mutex> lock(this->game_state_mutex);
+			::GameLoop();
+		}
 		::InputLoop();
 		::UpdateWindows();
 	}