anchor.diff:                            :y y
                             :width width
                             :height height
  -                          :buffer buffer
  +                          :%buffer buffer
                             :screen (make-screen x y width height t)
                             :vtop-linum 1
                             :vtop-charpos 0)))
  
positive.code:           (make-marker buffer (make-point 1 0)))
      window))
  
  (defun window-buffer (window)
    (%window-buffer window))
  
  (defun (setf window-buffer) (buffer window)
    (screen-modify (window-screen window))
    (setf (%window-buffer window) buffer))
  
  (defun window-point (&optional (window (current-window)))
    (marker-point (window-point-marker window)))
  
negative.code: 
  (defvar *current-window*)
  
  (define-class window () (current-window)
    x
    y
    width
    height
    %buffer
    screen
    vtop-linum
    vtop-charpos
    point-marker
    delete-hook
    parameters)
  
  (defun window-p (x)
    (typep x 'window))
  