Fixed bug 3519 - SDL_GetDisplayMode fails to report mode.format when using Wayland backend

Ryan C. Gordon

Kristian says you can't do it with Wayland, and that going forward, it'll just handle whatever you throw at it anyhow.

https://twitter.com/hoegsberg/status/816148272402165761

So I say we mark it SDL_PIXELFORMAT_RGB888, which is what my X11 display currently reports, and leave it at that.

src/video/wayland/SDL_waylandvideo.c

@@ -221,6 +221,7 @@ display_handle_mode(void *data,
     SDL_DisplayMode mode;
 
     SDL_zero(mode);
+    mode.format = SDL_PIXELFORMAT_RGB888;
     mode.w = width;
     mode.h = height;
     mode.refresh_rate = refresh / 1000; // mHz to Hz