anchor.diff:    (values curx cury y))
   
   (defun screen-display-lines (screen redraw-flag buffer start-charpos start-linum pos-x pos-y)
  -  (when redraw-flag
  -    (charms/ll:werase (screen-%scrwin screen)))
  +  ;; (when redraw-flag
  +  ;;   (charms/ll:werase (screen-%scrwin screen)))
     (disp-reset-lines screen buffer start-linum)
     (let ((curx 0)
           (cury (- pos-y start-linum))
  
positive.code:          (if (buffer-truncate-lines buffer)
               #'disp-line-wrapping
               #'disp-line)))
      (let ((wrap-lines (screen-wrap-lines screen)))
        (setf (screen-wrap-lines screen) nil)
        (loop
          :with y := 0
          :for i :from 0
          :for str :across (screen-lines screen)
          :while (< y (screen-height screen))
          :do
          (cond ((and (not redraw-flag)
                      (aref (screen-old-lines screen) i)
                      str
                      (fat-equalp str (aref (screen-old-lines screen) i))
                      (/= (- pos-y start-linum) i))
                 (setf (aref (screen-old-lines screen) i) str)
                 (let ((n (count i wrap-lines)))
                   (when (and (< 0 n) (<= y cury))
                     (incf cury n))
                   (incf y (1+ n))
                   (dotimes (_ n)
                     (push i (screen-wrap-lines screen)))))
                (str
                 (when (zerop (fat-length str))
                   (charms/ll:wmove (screen-%scrwin screen) y 0)
  
negative.code:                  (multiple-value-setq (curx cury y2)
                                        (funcall disp-line-fun
                                                 screen start-charpos curx cury pos-x y str))
                   (when (buffer-truncate-lines buffer)
                     (charms/ll:wclrtoeol (screen-%scrwin screen))
                     (let ((offset (- y2 y)))
                       (cond ((< 0 offset)
                              (setq redraw-flag t)
                              (dotimes (_ offset)
                                (push i (screen-wrap-lines screen))))
                             ((and (= offset 0) (find i wrap-lines))
                              (setq redraw-flag t))))
                     (setf y y2))))
                (t
                 (fill (screen-old-lines screen) nil :start i)
                 (charms/ll:wmove (screen-%scrwin screen) y 0)
  