Handle Quit event more gracefully

PortabilityLayer/AppEventHandler.h

@@ -0,0 +1,19 @@
+#pragma once
+
+namespace PortabilityLayer
+{
+	struct IAppEventHandler
+	{
+		virtual void OnQuit() = 0;
+	};
+
+	class AppEventHandler
+	{
+	public:
+		static IAppEventHandler *GetInstance();
+		static void SetInstance(IAppEventHandler *instance);
+
+	private:
+		static IAppEventHandler *ms_instance;
+	};
+}