anchor.diff:  let
     # Abbreviations.
     cfg = config.services.xserver;
  -  xorg = pkgs.xlibs;
  +  xorg = cfg.package;
     
     inherit (pkgs.lib) optional isInList getAttr;
     stdenv = pkgs.stdenv;
  
positive.code: in
  {
    name = "kdm";
      
    job = ''
      description "KDE Display Manager"
  
  
negative.code:   resolutions = map (res: ''"${toString res.x}x${toString res.y}"'') (cfg.resolutions);
    sessionType = cfg.sessionType;
  
    videoDriverModules = getAttr [ videoDriver ] (throw "unknown video driver: `${videoDriver}'") knownVideoDrivers;
  
    modules = 
  
  