anchor.diff:    (space-requirement+* (space-requirement+* (compose-label-space gadget)
                                               :min-width (* 2 (pane-x-spacing gadget))
                                               :width (* 2 (pane-x-spacing gadget))
  -                                            :max-width (* 2 (pane-x-spacing gadget))
  +                                            :max-width +fill+
                                               :min-height (* 2 (pane-y-spacing gadget))
                                               :height (* 2 (pane-y-spacing gadget))
  -                                            :max-height (* 2 (pane-y-spacing gadget)))
  +                                            :max-height +fill+)
                          :min-width (* 2 *3d-border-thickness*)
                          :width (* 2 *3d-border-thickness*)
  -                       :max-width (* 2 *3d-border-thickness*)
                          :min-height (* 2 *3d-border-thickness*)
                          :height (* 2 *3d-border-thickness*)
  -                       :max-height (* 2 *3d-border-thickness*)))
  +		       ))
   
   ;;; ------------------------------------------------------------------------------------------
   ;;;  30.4.4 The concrete scroll-bar Gadget
  
positive.code:      (space-requirement+* sr
                            :min-width  (* 3 (pane-x-spacing pane))
                            :width      (* 3 (pane-x-spacing pane))
                            :max-width  (* 3 (pane-x-spacing pane))
                            :min-height (* 2 (pane-y-spacing pane))
                            :height     (* 2 (pane-y-spacing pane))
                            :max-height (* 2 (pane-y-spacing pane)))
       :min-width (space-requirement-height sr)
       :width     (space-requirement-height sr)
       :max-width (space-requirement-height sr)
       :min-height 0
       :max-height 0
       :height 0)))
  
  (defgeneric draw-toggle-button-indicator (gadget type value x1 y1 x2 y2))
  
negative.code:                             :max-width +fill+
                              :min-height total-height
                              :height total-height
                              :max-height +fill+)))
  
  (defgeneric generic-option-pane-draw-widget (pane))
  
  