anchor.diff:  	for (nil . child) in (if (>= size sum) maxs mins)
   	and box-size = sum then (- box-size (get-pane-width child))
   	for tmp = (round (/ (* size (get-pane-width child)) box-size))
  -	for new-size = (do-in tmp (sr-min-width child) (sr-max-width child))
  +	for new-size = (clamp tmp (sr-min-width child) (sr-max-width child))
   	for new-sum = new-size then (+ new-sum new-size)
   	do (decf size new-size)
   	   (setf (slot-value child 'new-width) new-size)
  
positive.code:   (:documentation ""))
  
  (defmethod compose-space ((rack hrack-pane))
    (mapc #'compose-space (sheet-children rack))
    (loop with space = (make-space-requirement
  		      :max-height (sr-max-height (car (sheet-children rack))))
  	for child in (sheet-children rack)
  	for request = (pane-space-requirement child)
  	sum (get-pane-width child) into sum-width
  	do (incf (space-requirement-width space)
  		 (space-requirement-width request))
  	   (incf (space-requirement-max-width space)
  		 (space-requirement-max-width request))
  	   (incf (space-requirement-min-width space)
  		 (space-requirement-min-width request))
  	   (setf (space-requirement-height space)
  		 (max (space-requirement-height space)
  		      (space-requirement-height request)))
  	   (setf (space-requirement-max-height space)
  		 (min (space-requirement-max-height space)
  		      (space-requirement-max-height request)))
  	   (setf (space-requirement-min-height space)
  		 (max (space-requirement-min-height space)
  		      (space-requirement-min-height request)))
  	finally (progn
  		  (setf (slot-value rack 'sum-width) sum-width)
  		  (return space))))
  
  (defmethod compute-extremum ((rack hrack-pane))
    (make-extremums-children-ratio-width rack (sheet-children rack)))
  
negative.code:   (when (first (sheet-children pane))
      (allocate-space 
          (first (sheet-children pane))
  	(clamp width (sr-min-width pane) (sr-max-width pane))
  	(clamp height (sr-min-height pane) (sr-max-height pane)))))
  
  (defmethod dispatch-event ((pane top-level-sheet-pane) event)
    (handle-event pane event))
  