anchor.diff: -{ stdenv, fetchurl, pythonPackages, pkgconfig
  +{ stdenv, lib, fetchurl, pythonPackages, pkgconfig
   , xorg, gtk2, glib, pango, cairo, gdk_pixbuf, atk
   , makeWrapper, xkbcomp, xorgserver, getopt, xauth, utillinux, which, fontsConf, xkeyboard_config
   , ffmpeg, x264, libvpx, libwebp
  -, libfakeXinerama }:
  +, libfakeXinerama
  +, gst_all_1, pulseaudioLight, gobjectIntrospection }:
  +
  +with lib;
   
   let
     inherit (pythonPackages) python cython buildPythonApplication;
  
positive.code:       --set FONTCONFIG_FILE "${fontsConf}" \
        --set XPRA_LOG_DIR "\$HOME/.xpra" \
        --set XPRA_INSTALL_PREFIX "$out" \
        --prefix LD_LIBRARY_PATH : ${libfakeXinerama}/lib \
        --prefix PATH : ${stdenv.lib.makeBinPath [ getopt xorgserver xauth which utillinux ]}
    '';
  
    preCheck = "exit 0";
  
negative.code: 
      ffmpeg libvpx x264 libwebp
  
      gobjectIntrospection
      gst_all_1.gstreamer
      gst_all_1.gst-plugins-base
      gst_all_1.gst-plugins-good
      gst_all_1.gst-plugins-bad
      gst_all_1.gst-libav
  
      makeWrapper
    ];
  
    propagatedBuildInputs = with pythonPackages; [
      pillow pygtk pygobject2 rencode pycrypto cryptography pycups lz4 dbus-python
      netifaces numpy websockify pygobject3 gst-python
    ];
  
    preBuild = ''
  