anchor.diff:    zlibSupport ? true, zlib ? null,
     libuniqueSupport ? true, libunique ? null,
     libpngSupport ? true, libpng ? null,
  -  openglSupport ? true
  +  openglSupport ? !stdenv.isDarwin
   }:
   
   assert openexrSupport -> openexr != null;
  
positive.code:       spectrophotometry.
      '';
      license = stdenv.lib.licenses.gpl2;
      platforms = stdenv.lib.platforms.linux;
      maintainers = [ stdenv.lib.maintainers.cge ];
    };
  }
  
negative.code:   
    buildInputs = with stdenv.lib;
      [ gtk2 fftw ] ++
      optional openglSupport gnome2.gtkglext ++
      optional openexrSupport openexr ++
      optional libXmuSupport xorg.libXmu ++
      optional fitsSupport cfitsio ++
  