anchor.diff:      (loop for w in (query-tree *root*) do
            (when (and (eql (window-map-state w) :viewable)
                       (eql (window-override-redirect w) :off))
  -           (add w)))
  +           (plus w)))
   
       (setf (window-event-mask *root*) '(:substructure-notify))
   
  
positive.code:                (:map-notify
                  (window override-redirect-p)
                  (unless override-redirect-p
                    (focus (add window))))
                 (:destroy-notify
                  (window)
                  (focus (destroy window)))))
        (ungrab-button *root* (code *move*) :modifiers (state *move*))
        (ungrab-button *root* (code *resize*) :modifiers (state *resize*))
        (ungrab-button *root* (code *kill*) :modifiers (state *kill*))
  
negative.code:             ((funcall test item hd) rtl)
              (t (cons hd rtl))))))
  
  (defun minus (window)
    "House keeping when window is unmapped. Returns the window to be
  focused or nil if nothing has to be done."
    (when (member window *windows* :test #'win=)
      (setf *windows* (rrem window *windows* :test #'window-equal))
      (let (res)
  