anchor.diff:  
   ;;; Event handlers
   
  +#+NIL
   (defmethod handle-event ((sb scroll-bar-pane) (event window-repaint-event))
     (dispatch-repaint sb (sheet-region sb)))
   
  
positive.code:   (let ((call (gensym)))
      `(let ((,call (funcall (symbol-function ,callback) ,pane)))
         (when ,call
  	 (funcall ,call ,pane)))))
  
  (defmethod scroll-to-top-callback ((pane scroll-bar) client gadget-id)
    (declare (ignore client gadget-id))
  
negative.code: 	(setf (gadget-current-color pane) (gadget-highlighted-color pane)))
        (disarmed-callback pane (gadget-client pane) (gadget-id pane)))))
  
  #+NIL
  (defmethod handle-event ((pane toggle-button-pane) (event window-repaint-event))
    (dispatch-repaint pane (sheet-region pane)))
  
  (defmethod handle-repaint ((pane toggle-button-pane) region)
    (declare (ignore region))
    (with-special-choices (pane)
      (let ((region (sheet-region pane))
  