anchor.diff:        "--with-system-libvpx"
         # "--with-system-png" # <-- "--with-system-png won't work because the system's libpng doesn't have APNG support"
         "--enable-startup-notification"
  -      "--enable-system-cairo"
         "--enable-system-ffi"
         "--enable-system-hunspell"
         "--enable-system-pixman"
         "--enable-system-sqlite"
  -      "--with-system-libvpx"
         "--disable-crashreporter"
         "--disable-tests"
         "--disable-necko-wifi" # maybe we want to enable this at some point
         "--disable-installer"
         "--disable-updater"
  -    ];
  +    ] ++ optional useSystemCairo "--enable-system-cairo";
   
   
     xulrunner = stdenv.mkDerivation rec {
  
positive.code: 
      enableParallelBuilding = true;
  
      patches = [
        ./system-cairo.patch # accepted upstream, probably in 22
      ];
  
      preConfigure =
        ''
  
negative.code:     enableParallelBuilding = true;
  
      buildInputs =
        [ pkgconfig gtk perl zip libIDL libjpeg zlib bzip2 python
          dbus dbus_glib pango freetype fontconfig alsaLib nspr nss libnotify
          xlibs.pixman yasm mesa sqlite file unzip pysqlite
          hunspell libevent libstartup_notification libvpx
        ] ++ optional useSystemCairo cairo;
  
      patches = [
        ./disable-reporter.patch # fixes "search box not working when built on xulrunner"
  