anchor.diff:      optionalString
       splitString;
   
  +  version = "13.0.0";
  +
     # this is the default search path for DRI drivers
     driverSearchPath = "/run/opengl-driver-${stdenv.targetSystem}";
   in
   stdenv.mkDerivation rec {
     name = "mesa-noglu-${version}";
  -  version = "12.0.3";
   
     src =  fetchurl {
       urls = [
  +      "https://mesa.freedesktop.org/archive/${version}/mesa-${version}.tar.xz"
         "ftp://ftp.freedesktop.org/pub/mesa/${version}/mesa-${version}.tar.xz"
         # Tarballs for old releases are moved to another directory
  -      ("ftp://ftp.freedesktop.org/pub/mesa/older-versions/"
  +      ("https://mesa.freedesktop.org/archive/older-versions/"
           + head (splitString "." version)
           + ".x/${version}/mesa-${version}.tar.xz")
       ];
  -    multihash = "QmT7WzMaNSBaMWDVJhPiqgfe7cpA1QwsWdyZvJjWGpsQwY";
  +    multihash = "QmVqR8KfVh8V5PN6R8gNHZd9hhaGZAKpTAr86XSrHDanyt";
       hashOutput = false;  # Provided by upstream directly
  -    sha256 = "1dc86dd9b51272eee1fad3df65e18cda2e556ef1bc0b6e07cd750b9757f493b1";
  +    sha256 = "94edb4ebff82066a68be79d9c2627f15995e1fe10f67ab3fc63deb842027d727";
     };
   
     nativeBuildInputs = [
  
positive.code:     "--with-dri-driverdir=$(drivers)/lib/dri"
      "--with-dri-searchpath=${driverSearchPath}/lib/dri"
      "--with-dri-drivers=i915,i965,nouveau,radeon,r200,swrast"
      "--with-vulkan-drivers=intel"
      #"--with-vulkan-icddir=DIR"
      #osmesa-bits=8
      #"--with-clang-libdir=${llvm}/lib"
  
negative.code: #, libva
  , libvdpau
  , llvm
  , lm-sensors
  , openssl
  , wayland
  , xorg
  
  