anchor.diff:    (let ((curx 0)
           (cury (- pos-y start-linum))
           (disp-line-fun
  -         #'disp-line-wrapping
  -         #+nil
            (if (buffer-truncate-lines buffer)
                #'disp-line-wrapping
                #'disp-line)))
  
positive.code:                  (setf start i))))
      (values curx cury y)))
  
  #+nil
  (defun disp-line (screen start-charpos curx cury pos-x y str)
    (declare (ignore start-charpos))
    (check-type str fatstring)
    (when (= cury y)
      (setq curx (string-width (fat-string str) 0 pos-x)))
    (let ((width (string-width (fat-string str)))
          (cols (screen-width screen))
          do-clrtoeol)
      (cond
        ((< width (screen-width screen))
         (setf do-clrtoeol t)
         nil)
        ((or (/= cury y)
             (< curx (1- cols)))
         (setf do-clrtoeol nil)
         (let ((i (wide-index (fat-string str) (1- cols))))
           (setq str
                 (if (<= cols (string-width (fat-string str) 0 i))
                     (fat-concat (fat-substring str 0 (1- i)) " $")
                     (fat-concat (fat-substring str 0 i) "$")))))
        ((< pos-x (fat-length str))
         (setf do-clrtoeol nil)
         (let* ((start (wide-index (fat-string str) (- curx cols -3)))
                (end pos-x)
                (substr (fat-substring str start end)))
           (setq curx (- cols 2))
           (if (wide-char-p (fat-char substr (- (fat-length substr) 1)))
               (progn
                 (setq str
                       (fat-concat "$"
                                   (fat-substring
                                    substr
                                    0 (1- (fat-length substr)))
                                   " $"))
                 (decf curx))
               (setq str (fat-concat "$" substr "$")))))
        (t
         (setf do-clrtoeol t)
         (let ((start (- curx cols -2)))
           (setq str
                 (fat-concat "$"
                             (fat-substring str
                                            (wide-index (fat-string str) start)))))
         (setq curx (- cols 1))))
      (disp-print-line screen y str do-clrtoeol)
      (values curx cury y)))
  
  (defun screen-display-lines (screen redraw-flag buffer start-charpos start-linum pos-x pos-y)
  
negative.code:         :while (< y (screen-height screen))
          :do
          (cond ((and ;; 表示回数を減らすための節
                      (buffer-truncate-lines buffer)
                      (not redraw-flag)                     ; 再描画フラグが偽で
                      (not (null str/attributes))           ; その行に表示する行文字列があり
                      #1=(aref (screen-old-lines screen) i) ; 以前にその行に文字列を表示しており
  