anchor.diff:  
     nativeBuildInputs = [ pkgconfig ];
   
  -  propagatedBuildInputs = [ ]
  +  propagatedBuildInputs = [ libiconv ]
       ++ optionals x11Support [ libXext libICE libXrandr ]
       ++ optional stdenv.isLinux libcap
       ++ optionals openglSupport [ libGL libGLU ]
  
positive.code: 
    passthru = { inherit openglSupport; };
  
    meta = with stdenv.lib; {
      description = "A cross-platform multimedia library";
      homepage    = "http://www.libsdl.org/";
  
negative.code:     ++ optional pulseaudioSupport libpulseaudio
      ++ optional stdenv.isDarwin Cocoa;
  
    buildInputs = [ ]
      ++ optional (!hostPlatform.isMinGW) audiofile
      ++ optionals stdenv.isDarwin [ AudioUnit CoreAudio CoreServices Kernel OpenGL ];
  
  