Github Source

I recently stumbled upon a small bash script that calls feh --bg-fill in a loop over an array of PNG files to animate the desktop background. The performance was fairly poor. Cumulative CPU usage was close to 40% on my X230.

As an alternative, I discovered SDL2 can provide a generic interface to create a window from a pixel array, including the base root X11 window used by desktop wallpaper setters. That is to say, X11 windows can be coerced into a void pointer and passed to SDL2 and directly accessed via an SDL renderer:

Display* x11d = XOpenDisplay(NULL);
Window x11w = RootWindow(x11d, DefaultScreen(x11d));
SDL_Window* window = SDL_CreateWindowFrom((void*) x11w);
SDL_Renderer* renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC);

From here:

1) Bitmaps are loaded into RAM with SDL2:

SDL_Surface* surface = SDL_LoadBMP("frame.bmp");

2) The bitmaps are moved from RAM to the GPU:

SDL_Texture* texture = SDL_CreateTextureFromSurface(renderer, surface);

3) The bitmaps, now residing in GPU memory, are copied to the desktop wallpaper:

SDL_RenderCopy(renderer, texture, NULL, NULL);

The two NULL arguments signal the renderer to stretch fill the background wallpaper. A picture does not do an animated wallpaper any justice, so check it out on youtube.

Also, try giving the source a read. A single file (main.c) in less than 150 lines yields a high performance animated desktop wallpaper at 60 frames per second. The name paperview stems from pre-Netflix era video services dubbed Pay-Per-View and the idea of viewing wallpapers in an animated fashion. My X230 uses an integrated Intel video chipset, and fortunately Arch provides a nice GPU metric tool; running the following at 1920x1080 (via the VGA port to an external monitor at 60 Hz):

intel_gpu_time ./paperview scenes/castle 5
user: 1.904135s, sys: 0.357277s, elapsed: 100.458648s, CPU: 2.3%, GPU: 11.7%