Fix launching Atlas from the main menu

This was SVN commit r8491.

source/ps/GameSetup/GameSetup.cpp

@@ -659,6 +659,8 @@ void Shutdown(int UNUSED(flags))
 	ShutdownSDL();
 	TIMER_END(L"shutdown SDL");
 
+	g_VideoMode.Shutdown();
+
 	TIMER_BEGIN(L"shutdown ScriptingHost");
 	delete &g_ScriptingHost;
 	TIMER_END(L"shutdown ScriptingHost");

source/ps/VideoMode.cpp

@@ -198,6 +198,13 @@ bool CVideoMode::InitNonSDL()
 	return true;
 }
 
+void CVideoMode::Shutdown()
+{
+	debug_assert(m_IsInitialised);
+
+	m_IsInitialised = false;
+}
+
 void CVideoMode::EnableS3TC()
 {
 	// On Linux we have to try hard to get S3TC compressed texture support.

source/ps/VideoMode.h

@@ -35,6 +35,11 @@ public:
 	 */
 	bool InitNonSDL();
 
+	/**
+	 * Shut down after InitSDL/InitNonSDL, so that they can be used again.
+	 */
+	void Shutdown();
+
 	/**
 	 * Resize the SDL window and associated graphics stuff to the new size.
 	 */
@@ -67,6 +72,11 @@ private:
 	bool SetVideoMode(int w, int h, int bpp, bool fullscreen);
 	void EnableS3TC();
 
+	/**
+	 * Remember whether Init has been called. (This isn't used for anything
+	 * important, just for verifying that the callers call our methods in
+	 * the right order.)
+	 */
 	bool m_IsInitialised;
 
 	// Initial desktop settings