anchor.diff:  
   (defmethod get-object-at ((self window) x y)
     (get-object-at (window-top self) (double x) (double y)))
  -
  -(defun screen-width  () (window.get-screen-width))
  -(defun screen-height () (window.get-screen-height))
   
   
   (defmethod register   ((self window))
  
positive.code: 
  
  (defclass interactor (object)
    ((action-command :initarg :action-command :type string   :reader interactor-action-command)
     (label          :initarg :label          :type string   :reader interactor-label)))
  
  (defmethod object-slots append ((self interactor))
    (list :action-command (interactor-action-command self)
  
negative.code:   (list :nchars (text-field-nchars self)))
  
  (defmethod initialize-instance :after ((self text-field) &key &allow-other-keys)
    (text-field.create self (text-field-nchars self))
    (setf (interactor-action-command self) (interactor-action-command self)))
  
  (defmethod text-field-text ((self text-field))
    (text-field.get-text self))
  