fix fullscreen getting "stuck"

stepmania/src/RageDisplay.cpp

@@ -274,6 +274,18 @@ bool RageDisplay::SetVideoMode( bool windowed, int width, int height, int bpp, i
 	return need_reload;
 }
 
+void RageDisplay::ResolutionChanged(int width, int height)
+{
+	g_CurrentWidth = width;
+	g_CurrentHeight = height;
+
+	SetViewport(0,0);
+
+	/* Clear any junk that's in the framebuffer. */
+	Clear();
+	Flip();
+}
+
 void RageDisplay::SetViewport(int shift_left, int shift_down)
 {
 	/* left and down are on a 0..SCREEN_WIDTH, 0..SCREEN_HEIGHT scale.

stepmania/src/RageDisplay.h

@@ -30,6 +30,9 @@ public:
 
 	bool SetVideoMode( bool windowed, int width, int height, int bpp, int rate, bool vsync );
 
+	/* Call this when the resolution has been changed externally: */
+	void ResolutionChanged(int width, int height);
+
 	void Clear();
 	void Flip();
 	bool IsWindowed() const;

stepmania/src/StepMania.cpp

@@ -410,9 +410,7 @@ static void GameLoop()
 			case SDL_QUIT:
 				return; /* exit the main loop */
 			case SDL_VIDEORESIZE:
-				PREFSMAN->m_iDisplayWidth = event.resize.w;
-				PREFSMAN->m_iDisplayHeight = event.resize.h;
-				ApplyGraphicOptions();
+				DISPLAY->ResolutionChanged(event.resize.w, event.resize.h);
 				break;
 			}
 		}