+(defun hexl-follow-ascii (&optional arg)
+ "Toggle following ASCII in Hexl buffers.
+With prefix ARG, turn on following if and only if ARG is positive.
+When following is enabled, the ASCII character corresponding to the
+element under the point is highlighted.
+Customize the variable `hexl-follow-ascii' to disable this feature."
+ (interactive "P")
+ (let ((on-p (if arg
+ (> (prefix-numeric-value arg) 0)
+ (not hexl-ascii-overlay))))
+
+ (make-local-hook 'post-command-hook)
+
+ (if on-p
+ ;; turn it on
+ (if (not hexl-ascii-overlay)
+ (progn
+ (setq hexl-ascii-overlay (make-overlay 1 1)
+ hexl-follow-ascii t)
+ (overlay-put hexl-ascii-overlay 'face 'highlight)
+ (add-hook 'post-command-hook 'hexl-follow-ascii-find nil t)))
+ ;; turn it off
+ (if hexl-ascii-overlay
+ (progn
+ (delete-overlay hexl-ascii-overlay)
+ (setq hexl-ascii-overlay nil
+ hexl-follow-ascii nil)
+ (remove-hook 'post-command-hook 'hexl-follow-ascii-find t)
+ )))))
+
+(defun hexl-follow-ascii-find ()
+ "Find and highlight the ASCII element corresponding to current point."
+ (let ((pos (+ 51
+ (- (point) (current-column))
+ (mod (hexl-current-address) 16))))
+ (move-overlay hexl-ascii-overlay pos (1+ pos))
+ ))
+