anchor.diff:    (webkit:webkit-web-view-go-to-back-forward-list-item
      (gtk-object buffer)
      (webkit-history-entry-gtk-object history-entry)))
  -
  -(defun set-renderer ()
  -  (define-user-class window (gtk-window))
  -  (define-user-class buffer (gtk-buffer))
  -  (define-user-class browser (gtk-browser)))
  -
  -(set-renderer)
  
positive.code:   (:export-class-name-p t)
    (:export-accessor-names-p t)
    (:accessor-name-transformer #'class*:name-identity))
  
  (defmethod web-context ((browser gtk-browser))
    (or (slot-value *browser* 'web-context)
  
negative.code:   (:export-class-name-p t)
    (:export-accessor-names-p t)
    (:accessor-name-transformer #'class*:name-identity))
  (define-user-class window (gtk-window))
  
  (define-class gtk-buffer ()
    ((gtk-object)
  