anchor.diff:  (define-abstract-pane-mapping 'option-pane 'generic-option-pane)
   
   (defclass generic-option-pane (option-pane
  -                               meta-list-pane
                                  value-changed-repaint-mixin
                                  3d-border-mixin
                                  activate/deactivate-repaint-mixin
  
positive.code:                  :documentation "Number of items")
     (items-origin :initform 0 :accessor items-origin
       :documentation "Index of the first item to be rendered. This changes in
  response to scroll wheel events.")
     (visible-items :initarg :visible-items ; Clim 2.0 compatibility
                    :initform nil
                    :documentation "Maximum number of visible items in list"))
    (:default-initargs :background +white+ :foreground +black+))
  
  (defmethod initialize-instance :after ((gadget meta-list-pane) &rest rest)
  
negative.code: 
  (define-abstract-pane-mapping 'list-pane 'generic-list-pane)
  
  
  
  (defclass generic-list-pane (list-pane
                               standard-sheet-input-mixin ;; Hmm..
                               activate/deactivate-repaint-mixin
                               value-changed-repaint-mixin)
    ((highlight-ink :initform +royalblue4+
                    :initarg :highlight-ink
                    :reader list-pane-highlight-ink)
  