anchor.diff:      ;
     buildInputs = with xorg; [
       autoreconfHook intltool expat libxml2Python llvm
  -    libXfixes glproto dri2proto libX11 libXext libxcb libXt
  +    glproto dri2proto dri3proto presentproto
  +    libX11 libXext libxcb libXt libXfixes libxshmfence
       libffi wayland libvdpau libelf
     ] ++ optionals enableExtraFeatures [ /*libXvMC*/ ]
       ++ optional stdenv.isLinux udev
  
positive.code: 
    src =  fetchurl {
      url = "ftp://ftp.freedesktop.org/pub/mesa/${version}/MesaLib-${version}.tar.bz2";
      sha256 = "0h2sq8h0l7415vsqfkb7mn1rxm62m2anpi9swlca69fbpr9bavpz";
    };
  
    prePatch = "patchShebangs .";
  
negative.code: */
  
  let
    version = "10.1.1";
    # this is the default search path for DRI drivers
    driverLink = "/run/opengl-driver" + stdenv.lib.optionalString stdenv.isi686 "-32";
  in
  