anchor.diff:  
     propagatedBuildInputs = [ x11 inputproto libXi freeglut ];
   
  -  nativeBuildInputs = [ pkgconfig ];
  +  enableParallelBilding = true;
  +
  +  nativeBuildInputs = [
  +    pkgconfig
  +    automake autoconf libtool # only required because of patch
  +  ];
   
     flags =
       # this could be tidied up (?).. eg why does it require freeglut without glSupport?
  
positive.code: { composableDerivation, fetchurl, pkgconfig, x11, inputproto, libXi
  , freeglut, mesa, libjpeg, zlib, libXinerama, libXft, libpng }:
  
  let inherit (composableDerivation) edf; in
  
  
negative.code:     description = "A C++ cross-platform light-weight GUI library binding";
      homepage = http://www.fltk.org;
    };
  
    patches = [
      # https://bugs.archlinux.org/task/36186
      (fetchurl {
      url = "https://bugs.archlinux.org/task/36186?getfile=10750";
      sha256 = "1hpb1i87nc3zw6mgpgf3bfv557ci930bsn6rwlhaif51nlqd2wbj";
    }) ];
  }
  