anchor.diff:  
   (define-abstract-pane-mapping 'list-pane 'generic-list-pane)
   
  -(defclass meta-list-pane ()
  -  ((mode        :initarg :mode
  -                :initform :exclusive
  -                :reader list-pane-mode
  -                :type (member :one-of :some-of :exclusive :nonexclusive))
  -   (items       :initarg :items
  -                :initform nil
  -                :reader list-pane-items
  -                :type sequence)
  -   (name-key    :initarg :name-key
  -                :initform #'princ-to-string
  -                :reader list-pane-name-key
  -                :documentation "A function to be applied to items to gain a printable representation")
  -   (value-key   :initarg :value-key
  -                :initform #'identity
  -                :reader list-pane-value-key
  -                :documentation "A function to be applied to items to gain its value
  -                                for the purpose of GADGET-VALUE.")
  -   (presentation-type-key :initarg :presentation-type-key
  -                          :initform (constantly nil)
  -                          :reader list-pane-presentation-type-key
  -                          :documentation "A function to be applied to items to find the presentation types for their values, or NIL.")
  -   (test        :initarg :test
  -                :initform #'eql
  -                :reader list-pane-test
  -                :documentation "A function to compare two items for equality.")))
  -
  -(defclass generic-list-pane (list-pane meta-list-pane
  -                                       standard-sheet-input-mixin ;; Hmm..
  -                                       activate/deactivate-repaint-mixin
  -                                       value-changed-repaint-mixin)
  +
  +
  +(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)
  
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 'option-pane 'generic-option-pane)
  
  (defclass generic-option-pane (option-pane
                                 value-changed-repaint-mixin
                                 3d-border-mixin
                                 activate/deactivate-repaint-mixin
  