anchor.diff:  
   ;;; PANES
   
  -(defconstant +fill+ :fill)
  +(defconstant +fill+ most-positive-fixnum)
   
   (defclass space-requirement ()
     ((width :initform 1
  
positive.code:   (dispatch-repaint pane (sheet-region pane)))
  
  (defmethod compose-space ((pane clim-stream-pane))
    (make-space-requirement :width 300 :height 300
  			  :max-width 300 :max-height 300))
  
  (defmethod dispatch-repaint ((pane clim-stream-pane) region)
    (repaint-sheet pane region))
  
negative.code:     (print-unreadable-object (space stream :type t :identity t)
        (format stream "width: ~S height: ~S" width height))))
  
  (defun make-space-requirement (&key (width 1) (height 1)
  				    (min-width 0) (min-height 0)
  				    (max-width +fill+) (max-height +fill+))
    (assert (<= 0 min-width width max-width) (min-width width max-width))
    (assert (<= 0 min-height height max-height) (min-height height max-height))
    (make-instance 'space-requirement
      :width width
      :max-width max-width
  