anchor.diff:                                (buffer buffer))
     "Set the active buffer for the active window."
     (let ((window-active (window-active interface)))
  -    (setf (active-buffer window-active) buffer)
  -    (window-set-active-buffer interface window-active buffer)))
  +    (window-set-active-buffer interface window-active buffer)
  +    (setf (active-buffer window-active) buffer)))
  
positive.code:       "window.set.active.buffer" (id window) (id buffer))
       :host host :port port :url url)
      (setf (active-buffer window) buffer)))
  
  (defmethod window-active-buffer ((interface remote-interface) window)
    "Return the active buffer for a given window."
  
negative.code:   ;;TODO
    )
  
  (defmethod %window-set-active-buffer ((interface remote-interface)
                                       (window window)
                                       (buffer buffer))
    (with-slots (host port url) interface
  