anchor.diff:      chmod a+x $out/opt/Pencil/libffmpeg.so
   
       # fix missing libudev
  -    ln -s ${udev}/lib/systemd/libsystemd-shared.so $out/opt/Pencil/libudev.so.1
  +    ln -s ${systemd.lib}/lib/libudev.so.1 $out/opt/Pencil/libudev.so.1
       wrapProgram $out/opt/Pencil/pencil \
         --prefix LD_LIBRARY_PATH : $out/opt/Pencil
     '';
  
positive.code:     ar p "$src" data.tar.xz | tar xJ
    '';
  
    buildPhase = ":";
  
    nativeBuildInputs = [ makeWrapper ];
  
  
negative.code:   # build dependencies
    alsaLib, atk, cairo, cups, dbus, expat, fontconfig,
    freetype, gdk_pixbuf, glib, gnome2, nspr, nss, xorg,
    glibc, systemd
  }:
  
  stdenv.mkDerivation rec {
  