anchor.diff:    wrap-lines
     width
     modified-p
  +  last-buffer-name
  +  last-buffer-modified-tick
     (horizontal-scroll-start 0))
   
   (defun make-screen (x y width height use-modeline)
  
positive.code:                                   (screen-modified-p screen)
                                    (not (eql (screen-left-width screen)
                                              (screen-old-left-width screen))))
                                (window-buffer window)
                                (point-charpos (window-view-point window))
                                (if focus-window-p
                                    (count-lines (window-view-point window)
  
negative.code: 
  (defun redraw-display-window (window force)
    (let ((focus-window-p (eq window (current-window)))
          (buffer (window-buffer window))
          (screen (lem::window-screen window)))
      (let ((scroll-n (when focus-window-p
                        (window-see window))))
        (when (or (not *native-scroll-support*)
                  (not (equal (screen-last-buffer-name screen) (buffer-name buffer)))
                  (not (eql (screen-last-buffer-modified-tick screen)
                            (buffer-modified-tick buffer)))
                  (and scroll-n (>= scroll-n (screen-height screen))))
          (setf scroll-n nil))
        (when scroll-n
  