wiiu/render: Add a prevent swap window flag

This makes it possible to present TV/DRC-only windows without swapping the scanbuffers and thus preventing a v-sync.

Author: GaryOderNichts

include/SDL_video.h

@@ -126,6 +126,7 @@ typedef enum
     SDL_WINDOW_KEYBOARD_GRABBED = 0x00100000,   /**< window has grabbed keyboard input */
     SDL_WINDOW_WIIU_GAMEPAD_ONLY = 0x01000000,      /**< Wii U: window must be drawn only on the Gamepad */
     SDL_WINDOW_WIIU_TV_ONLY      = 0x02000000,      /**< Wii U: window must be drawn only on the TV */
+    SDL_WINDOW_WIIU_PREVENT_SWAP = 0x04000000,      /**< Wii U: window will not swap scanbuffers on present */
     SDL_WINDOW_VULKAN           = 0x10000000,   /**< window usable for Vulkan surface */
     SDL_WINDOW_METAL            = 0x20000000,   /**< window usable for Metal view */
 

src/render/wiiu/SDL_rpresent_wiiu.c

@@ -75,8 +75,11 @@ int WIIU_SDL_RenderPresent(SDL_Renderer * renderer)
         GX2CopyColorBufferToScanBuffer(&tdata->cbuf, GX2_SCAN_TARGET_DRC);
     }
 
-    /* Swap buffers */
-    GX2SwapScanBuffers();
+    /* Swap buffers if the window doesn't prevent it */
+    if (!(flags & SDL_WINDOW_WIIU_PREVENT_SWAP)) {
+        GX2SwapScanBuffers();
+    }
+
     GX2Flush();
 
     /* Restore SDL context state */

src/video/SDL_video.c

@@ -1517,7 +1517,7 @@ static int SDL_UpdateFullscreenMode(SDL_Window *window, SDL_bool fullscreen)
 }
 
 #define CREATE_FLAGS \
-    (SDL_WINDOW_OPENGL | SDL_WINDOW_BORDERLESS | SDL_WINDOW_RESIZABLE | SDL_WINDOW_ALLOW_HIGHDPI | SDL_WINDOW_ALWAYS_ON_TOP | SDL_WINDOW_SKIP_TASKBAR | SDL_WINDOW_POPUP_MENU | SDL_WINDOW_UTILITY | SDL_WINDOW_TOOLTIP | SDL_WINDOW_VULKAN | SDL_WINDOW_MINIMIZED | SDL_WINDOW_METAL | SDL_WINDOW_WIIU_GAMEPAD_ONLY | SDL_WINDOW_WIIU_TV_ONLY)
+    (SDL_WINDOW_OPENGL | SDL_WINDOW_BORDERLESS | SDL_WINDOW_RESIZABLE | SDL_WINDOW_ALLOW_HIGHDPI | SDL_WINDOW_ALWAYS_ON_TOP | SDL_WINDOW_SKIP_TASKBAR | SDL_WINDOW_POPUP_MENU | SDL_WINDOW_UTILITY | SDL_WINDOW_TOOLTIP | SDL_WINDOW_VULKAN | SDL_WINDOW_MINIMIZED | SDL_WINDOW_METAL | SDL_WINDOW_WIIU_GAMEPAD_ONLY | SDL_WINDOW_WIIU_TV_ONLY | SDL_WINDOW_WIIU_PREVENT_SWAP)
 
 static SDL_INLINE SDL_bool IsAcceptingDragAndDrop(void)
 {