anchor.diff:  (defmethod ask-space-children ((composite composite-pane))
     (mapcar #'compose-space (sheet-children composite)))
   
  +;;; FIXME: this one shoud be removed
   (defmethod compute-space ((composite composite-pane))
     (let ((space (make-space-requirement)))
       (loop for child in (sheet-children composite)
  
positive.code:     space))
  
  (defmethod allocate-space ((box vbox-pane) width height)
    (setf (sheet-region box) (make-bounding-rectangle 0 0 width height))
    (let ((h-percent (/ width (space-requirement-width (pane-space-requirement box))))
  	(v-percent (/ height (space-requirement-height (pane-space-requirement box))))
  	(y 0))
  
negative.code:     space))
  
  (defmethod allocate-space ((box hbox-pane) width height)
    (set-width-and-height box width height)
    (let ((h-percent (/ width (space-requirement-width (pane-space-requirement box))))
  	(v-percent (/ height (space-requirement-height (pane-space-requirement box))))
  	(x 0))
  