anchor.diff:    (when (and (variable-value 'truncate-lines :default (window-buffer window))
                (not (first-line-p (window-view-point window))))
       (let ((charpos-list))
  -      (map-wrapping-line (line-string (if (start-line-p (window-view-point window))
  +      (map-wrapping-line window
  +                         (line-string (if (start-line-p (window-view-point window))
                                             (line-offset (copy-point (window-view-point window)
                                                                      :temporary)
                                                          -1)
                                             (window-view-point window)))
  -                         (window-%width window)
                            (lambda (c)
                              (push c charpos-list)))
         (cond ((and charpos-list (start-line-p (window-view-point window)))
  
positive.code:                   (window-buffer-point window)
                    (lambda (string lastp)
                      (declare (ignore lastp))
                      (map-wrapping-line string
                                         (window-%width window)
                                         #'inc)))
        offset)))
  
  
negative.code:                (window-buffer-point window)))
    (window-scroll window (- (floor (window-%height window) 2))))
  
  (defun map-wrapping-line (window string fn)
    (loop :with start := 0
          :and width := (1- (window-width window))
          :for i := (wide-index string width :start start)
          :while i
          :do
          (funcall fn i)
          (setq start i)))
  
  (defun %scroll-down-if-wrapping (window)
    (when (variable-value 'truncate-lines :default (window-buffer window))
      (let ((view-charpos (point-charpos (window-view-point window))))
        (line-start (window-view-point window))
        (map-wrapping-line window
                           (line-string (window-view-point window))
                           (lambda (c)
                             (when (< view-charpos c)
                               (line-offset (window-view-point window) 0 c)
  