anchor.diff:      ++ optional screenSaverSupport libXScrnSaver
       ++ optional lameSupport lame
       ++ optional vdpauSupport libvdpau
  -    ++ optional speexSupport speex;
  +    ++ optional speexSupport speex
  +    ++ optional libpngSupport libpng
  +    ;
   
     buildNativeInputs = [ yasm ];
   
  
positive.code: assert x264Support -> x264 != null;
  assert jackaudioSupport -> jackaudio != null;
  assert pulseSupport -> pulseaudio != null;
  
  
  let
  
  
negative.code: , x264Support ? false, x264 ? null
  , jackaudioSupport ? false, jackaudio ? null
  , pulseSupport ? false, pulseaudio ? null
  # For screenshots
  , libpngSupport ? true, libpng ? null
  }:
  
  assert x11Support -> (libX11 != null && libXext != null && mesa != null);
  