anchor.diff:  let
     xcfg = config.services.xserver;
     dmcfg = xcfg.displayManager;
  -  cfg = xcfg.slim;
  +  cfg = dmcfg.slim;
  +
  +  inherit (pkgs.lib) mkIf;
   
     slimConfig = pkgs.writeText "slim.cfg" ''
       xauth_path ${dmcfg.xauthBin}
  
positive.code: let
    inherit (pkgs.lib) mkOption;
  
    options = { services = { xserver = {
  
      slim = {
  
        theme = mkOption {
          default = null;
          example = pkgs.fetchurl {
            url = http://download.berlios.de/slim/slim-wave.tar.gz;
            sha256 = "0ndr419i5myzcylvxb89m9grl2xyq6fbnyc3lkd711mzlmnnfxdy";
          };
          description = "
            The theme for the SLiM login manager.  If not specified, SLiM's
            default theme is used.  See <link
            xlink:href='http://slim.berlios.de/themes01.php'/> for a
            collection of themes.
          ";
        };
  
        defaultUser = mkOption {
          default = "";
          example = "login";
          description = "
            The default user to load. If you put a username here you
            get it automatically loaded into the username field, and
            the focus is placed on the password.
          ";
        };
  
        hideCursor = mkOption {
          default = false;
          example = true;
          description = "
            Hide the mouse cursor on the login screen.
          ";
        };
      };
  
    }; /* xserver */ }; /* services */ };
  
negative.code: 
  in
  
  mkIf cfg.enable {
    require = [
      options
      copyOldOptions
    ];
  
    services = {
  