anchor.diff:  		   (incf last-x dx)
   		   (incf last-y dy)))
   		((= last-button (code *resize*))
  -		 (move window :width delta-x :height delta-y))))
  +		 (move window :width delta-x :height delta-y))
  +		((= last-button (code *center-resize*))
  +		 (move window :x (- (first last-center) (truncate delta-x 2))
  +			      :y (- (second last-center) (truncate delta-y 2))
  +			      :width delta-x :height delta-y))))
   	(setf last-motion time)))))
   
   (defhandler :button-release () (ungrab-mouse))
  
positive.code: (defun grab-all ()
    "Grab prefix and mouse buttons on root."
    (grab-it *prefix*)
    (dolist (b (list *move* *resize* *close*))
      (grab-it b)))
  
  (defun ungrab-all ()
    (dolist (b (list *move* *resize* *close*))
      (grab-it b :inverse-p t))
    (grab-it *prefix* :inverse-p t))
  
  
negative.code:             (t
               (cond ((sc= *move* state code)
                      (setf last-x x last-y y))
                     ((or (sc= *resize* state code)
  			(sc= *center-resize* state code))
  		    (let ((x (xlib:drawable-x window))
  			  (y (xlib:drawable-y window))
  			  (width (xlib:drawable-width window))
  			  (height (xlib:drawable-height window)))
  		      ;; here i use [last-x; last-y] as the [x; y]
  		      ;; position of the current window
  		      (setf last-x x last-y y
  			    last-center (window-center window))
  		      (xlib:warp-pointer window width height))))
               (setf last-button code)
               (focus window)
  