anchor.diff:  , librsvg
   , lensfun
   , libspiro
  +, maxflow
   , netsurf
   , pango
   , poly2tri-c
  
positive.code:     librsvg
      lensfun
      libspiro
      netsurf.libnsgif
      pango
      poly2tri-c
  
negative.code: 
  stdenv.mkDerivation rec {
    pname = "gegl";
    version = "0.4.28";
  
    outputs = [ "out" "dev" "devdoc" ];
    outputBin = "dev";
  
    src = fetchurl {
      url = "https://download.gimp.org/pub/gegl/${lib.versions.majorMinor version}/${pname}-${version}.tar.xz";
      sha256 = "sha256-HRENhXfVTMo7NCOTFb03xXzLJ91DVWVQdKLSs/2JeQA=";
    };
  
    nativeBuildInputs = [
      pkg-config
  