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-window w)))
  +           (add w)))
   
       (setf (window-event-mask *root*) '(:substructure-notify))
   
  
positive.code:                (:map-notify
                  (window override-redirect-p)
                  (unless override-redirect-p
                    (focus (add-window window))))
                 (:destroy-notify
                  (window)
                  (when (member window *windows* :test #'win=)
  
negative.code:                                 (string= class "Idl"))))
    "List of predicates against which windows are grouped")
  
  (defun add (window)
    "Add window to the list of managed windows. Take care of grouping
  and don't add window already in the list."
    (let ((grouper (find-if #'(lambda (f) (funcall f window)) *groupers*)))
  