anchor.diff:  (defclass bboard-pane (composite-pane) ())
   
   (defmethod compose-space ((bboard bboard-pane))
  -  (make-space-requirement :width 300 :max-width 300 :min-width 300
  -			  :height 300 :max-height 300 :min-height 300))
  +  (make-space-requirement :width 300 :height 300))
   
   ;;; VIEWPORT
   
  
positive.code: 
  ;;; PANES
  
  (defconstant +fill+ :fill)
  
  (defclass space-requirement ()
    ((width :initform 1
  
negative.code: 
  (defmethod compose-space ((pane pane))
    (make-space-requirement :width 200
  			  :height 200))
  
  (defmethod compose-space :around ((pane pane))
    (with-slots (sr-width sr-height sr-max-width
  