anchor.diff:  	for (nil . child) in (if (>= size sum) maxs mins)
   	and box-size = sum then (- box-size (get-pane-height child))
   	for tmp = (round (/ (* size (get-pane-height child)) box-size))
  -	for new-size = (do-in tmp (sr-min-height child) (sr-max-height child))
  +	for new-size = (clamp tmp (sr-min-height child) (sr-max-height child))
   	for new-sum = new-size then (+ new-sum new-size)
   	do (decf size new-size)
   	   (setf (slot-value child 'new-height) new-size)
  
positive.code: 	and x = 0 then (+ x nw)
  	and nh = (/ (* height (get-pane-height child)) (get-pane-height box))
          do (move-sheet child x 0)
  	   (setf nh (do-in nh (sr-min-height child) (sr-max-height child)))
  	   (allocate-space child nw (round nh))))
  
  ;;; VBOX-PANE
  
negative.code: 	 (margin-width (- (sr-width spacing) (sr-width child)))
  	 (margin-height (- (sr-height spacing) (sr-height child))))
      (setf margin-width
  	  (clamp (round (/ (* width margin-width) (get-pane-width spacing)))
  		 (slot-value spacing 'margin-min-width)
  		 (slot-value spacing 'margin-max-width))
  	  margin-height
  	  (clamp (round (/ (* height margin-height) (get-pane-height spacing)))
  		 (slot-value spacing 'margin-min-height)
  		 (slot-value spacing 'margin-max-height))
  	  (sheet-transformation child)
  