anchor.diff:        (with-output-as-gadget (stream)
           gadget))))
   
  -(defun %standard-value-changed-callback (query-identifier)
  -  (lambda (pane item)
  +(defun %standard-value-changed-callback (query-identifier &optional value-transform)
  +  ;; Return a function to be used as value-changed-callback of a
  +  ;; gadget.  The returned function changes the value of the query
  +  ;; associated with the gadget inside a dialog. The query is
  +  ;; identified by QUERY-IDENTIFIER.  If VALUE-TRANSFORM is NIL the
  +  ;; new value of the query will be the value of the gadget, otherwise
  +  ;; the VALUE-TRANSFORM function will be called with the value of the
  +  ;; gadget as argument and the returned value will be the new value
  +  ;; of the query.
  +  (lambda (pane value)
       (declare (ignore pane))
  -    (throw-object-ptype `(com-change-query ,query-identifier ,item)
  -                        '(command :command-table accept-values))))
  +    (let ((new-value (if value-transform
  +                         (funcall value-transform value)
  +                         value)))
  +      (throw-object-ptype `(com-change-query ,query-identifier ,new-value)
  +                          '(command :command-table accept-values)))))
   
   ;;; Use textual-dialog-view as default for Views not implemented
   
  
positive.code:                                   :choices buttons
                                    :current-selection selection
                                    :value-changed-callback
                                    (lambda (pane item)
                                      (declare (ignore pane))
                                      (%standard-value-changed-callback
                                       (map 'list #'gadget-id item))))))
  
  ;;; option-pane-view
  
  
negative.code:                                   :choices buttons
                                    :current-selection selection
                                    :value-changed-callback
                                    (%standard-value-changed-callback
                                     query-identifier #'gadget-id))))
  
  ;;; check-box-view
  
  