anchor.diff:  (defmethod handle-event ((pane top-level-sheet-pane) (event window-configuration-event))
     (let ((width (window-configuration-event-width event))
           (height (window-configuration-event-height event)))
  -    (setf (sheet-region pane) (make-bounding-rectangle 0 0 width height))
  +    ;; avoid goint into an infinite loop by not using (setf sheet-region)
  +    (setf (slot-value pane 'region) (make-bounding-rectangle 0 0 width height))
       (allocate-space pane width height)))
   
   ;; SHEET 
  
positive.code: 	(v-percent (/ height (space-requirement-height (pane-space-requirement box))))
  	(x 0))
      (loop for child in (sheet-children box)
  	for request = (pane-space-requirement child)
  	for new-width = (floor (* h-percent (space-requirement-width request)))
  	for new-height = (floor (* v-percent (space-requirement-height request)))
  	do (setf (sheet-region child)
  	     (make-bounding-rectangle x 0 (+ x new-width) new-height))
  	   (allocate-space child new-width new-height)
  	   (incf x new-width))))
  
  
  ;;; VBOX-PANE class
  
negative.code: 	 (x 0)
  	 (y 0))
      (loop for children in contents
  	  do (progn (loop for child in children
  			  do (progn (setf (sheet-region child)
  					  (make-bounding-rectangle 0 0 new-width new-height))
  				    (setf (sheet-transformation child)
  					  (make-translation-transformation x y))
  				    (allocate-space child new-width new-height)
  				    (incf x new-width)))
  		    (setf x 0)
  		    (incf y new-height)))))
  
  
  ;; SPACER PANE
  