anchor.diff:      ++ optional stdenv.isDarwin Cocoa;
   
     buildInputs = [ libiconv ]
  +    ++ optionals (x11Support && stdenv.isDarwin) [ libXext libICE libXrandr ]
       ++ optional (!hostPlatform.isMinGW) audiofile
       ++ optionals stdenv.isDarwin [ AudioUnit CoreAudio CoreServices Kernel OpenGL ];
   
  
positive.code:     "--disable-oss"
      "--disable-video-x11-xme"
      "--enable-rpath"
    ] ++ optional (!x11Support) "--without-x"
      ++ optional alsaSupport "--with-alsa-prefix=${attrs.alsaLib.out}/lib";
  
  in
  
negative.code:   nativeBuildInputs = [ pkgconfig ];
  
    propagatedBuildInputs = [ ]
      ++ optionals (x11Support && !stdenv.isDarwin) [ libXext libICE libXrandr ]
      ++ optional stdenv.isLinux libcap
      ++ optionals openglSupport [ libGL libGLU ]
      ++ optional alsaSupport alsaLib
  