set SDL_VIDEODRIVER so SDL doesn't try to fire up aalib, etc

stepmania/src/arch/LowLevelWindow/LowLevelWindow_SDL.cpp

@@ -64,6 +64,25 @@ CString LowLevelWindow_SDL::TryVideoMode( RageDisplay::VideoModeParams p, bool &
 		EventEnabled[i] = mySDL_EventState( (Uint8) i, SDL_QUERY );
 
 	SDL_QuitSubSystem(SDL_INIT_VIDEO);
+
+#if defined(LINUX)
+	static bool bSetVideoDriver = false;
+	if( !bSetVideoDriver )
+	{
+		bSetVideoDriver = true;
+
+		/* Most people don't have this set.  SDL has a habit of trying to
+		 * fall back on other drivers (svgalib, aalib), so set it to "x11". */
+		const char *sVideoDriver = getenv("SDL_VIDEODRIVER");
+		if( sVideoDriver == NULL )
+		{
+			static char env[] = "SDL_VIDEODRIVER=x11";
+			putenv( env );
+		} else if( strcmp( sVideoDriver, "x11" ) )
+			LOG->Info( "SDL_VIDEODRIVER has been set to %s", sVideoDriver );
+	}
+#endif
+
 	if( SDL_InitSubSystem(SDL_INIT_VIDEO) == -1 )
 		RageException::Throw( "SDL_INIT_VIDEO failed: %s", mySDL_GetError().c_str() );