anchor.diff:                  :reader list-pane-test
                   :documentation "A function to compare two items for equality.")))
   
  -(defclass generic-list-pane (meta-list-pane value-changed-repaint-mixin mouse-wheel-scroll-mixin)
  +(defclass generic-list-pane (list-pane meta-list-pane
  +                                       value-changed-repaint-mixin
  +                                       mouse-wheel-scroll-mixin)
     ((highlight-ink :initform +royalblue4+
                     :initarg :highlight-ink
                     :reader list-pane-highlight-ink)
  
positive.code: ;;; Common colors:
  
  (defmethod gadget-highlight-background ((gadget basic-gadget))
    (compose-over (compose-in +paleturquoise+ (make-opacity .5))
                  (pane-background gadget)))
  
  (defmethod effective-gadget-foreground ((gadget basic-gadget))
  
negative.code:                (draw-circle* pane x y 7.0
                               :filled nil :ink +white+
                               :start-angle (* 0.25 pi)
                               :end-angle   (* 1.25 pi))
                 (draw-circle* pane x y 7.0
                               :filled nil :ink +black+
                               :start-angle (* 1.25 pi)
  