Fix HOME menu hang by forcing VSYNC on Wii U

Implement workaround for SDL bug where GX2SetSwapInterval(0) causes
black screen after returning from HOME menu. When leaving foreground,
GX2 silently restores swap interval to 1, but SDL doesn't reapply
zero-interval mode after regaining foreground, causing render thread
to stop presenting frames.

Changes:
- Force VSYNC enabled on Wii U in SetVideoMode() renderer creation
- Prevent VSYNC toggle from disabling VSYNC on Wii U in all games
- Add detailed comments explaining the SDL bug and workaround
- Only affects Wii U builds via __WIIU__ preprocessor guards

This workaround keeps GX2SetSwapInterval(1) active so the system's
reset matches what SDL expects, preventing the black screen hang.

Long-term solution: Rebuild SDL with PR devkitPro/SDL#107 which
adds proper GX2SetSwapInterval(0) reapplication in WIIU_ForegroundAcquired().

Author: strejf79

src/doom/m_crispy.c

@@ -592,7 +592,13 @@ void M_CrispyToggleVsync(int choice)
 	return;
     }
 
+#ifdef __WIIU__
+    // Prevent disabling VSYNC on Wii U to avoid HOME menu hang issue
+    // SDL bug: GX2SetSwapInterval(0) causes black screen after HOME menu
+    return;
+#else
     crispy->post_rendering_hook = M_CrispyToggleVsyncHook;
+#endif // __WIIU__
 }
 
 static int hookchoice;

src/heretic/mn_menu.c

@@ -1568,9 +1568,15 @@ static void CrispyVsyncHook(void)
 
 static boolean CrispyVsync(int option)
 {
+#ifdef __WIIU__
+    // Prevent disabling VSYNC on Wii U to avoid HOME menu hang issue
+    // SDL bug: GX2SetSwapInterval(0) causes black screen after HOME menu
+    return true;
+#else
     crispy->post_rendering_hook = CrispyVsyncHook;
 
     return true;
+#endif // __WIIU__
 }
 
 static boolean CrispyBrightmaps(int option)

src/hexen/mn_menu.c

@@ -1606,7 +1606,13 @@ static void CrispyVsyncHook(void)
 
 static void CrispyVsync(int option)
 {
+#ifdef __WIIU__
+    // Prevent disabling VSYNC on Wii U to avoid HOME menu hang issue
+    // SDL bug: GX2SetSwapInterval(0) causes black screen after HOME menu
+    return;
+#else
     crispy->post_rendering_hook = CrispyVsyncHook;
+#endif // __WIIU__
 }
 
 static void CrispyBrightmaps(int option)

src/i_video.c

@@ -1510,10 +1510,19 @@ static void SetVideoMode(void)
     // Turn on vsync if we aren't in a -timedemo
     if (!singletics && mode.refresh_rate > 0)
     {
+#ifdef __WIIU__
+        // Force VSYNC on Wii U to prevent HOME menu hang issue
+        // When leaving foreground, GX2 silently restores swap interval to 1
+        // SDL doesn't reapply zero-interval mode after regaining foreground
+        // Keeping VSYNC enabled avoids this SDL bug
+        renderer_flags |= SDL_RENDERER_PRESENTVSYNC;
+        crispy->vsync = true; // Ensure config matches
+#else
         if (crispy->vsync) // [crispy] uncapped vsync
         {
             renderer_flags |= SDL_RENDERER_PRESENTVSYNC;
         }
+#endif // __WIIU__
     }
 
     if (force_software_renderer)