anchor.diff:  , runCommandCC, runCommand, vapoursynth, writeText, patchelf, buildEnv
   , zimg, libass, python3, libiconv
   , ApplicationServices
  -, ocrSupport ? false, tesseract
  -, imwriSupport ? true, imagemagick
   }:
   
   with lib;
  
positive.code:   postInstall = ''
      wrapProgram $out/bin/vspipe \
          --prefix PYTHONPATH : $out/${python3.sitePackages}
    '';
  
    meta = with lib; {
  
negative.code:   buildInputs = [
      zimg libass
      (python3.withPackages (ps: with ps; [ sphinx cython ]))
    ] ++ optionals stdenv.isDarwin [ libiconv ApplicationServices ];
  
    enableParallelBuilding = true;
  
  