anchor.diff:  let
   
     cfg = config.services.random-background;
  +
  +  flags = lib.concatStringsSep " " (
  +    [ "--randomize" "--bg-${cfg.display}" ]
  +    ++ lib.optional (!cfg.enableXinerama) "--no-xinerama"
  +  );
   
   in
   
  
positive.code:           as a duration understood by systemd.
          '';
        };
      };
    };
  
  
negative.code: 
            Service = {
              Type = "oneshot";
              ExecStart = "${pkgs.feh}/bin/feh ${flags} ${cfg.imageDirectory}";
              IOSchedulingClass = "idle";
            };
  
  