How do I make markdown or org mode hide formatting characters until I edit?

Question

I'd like to hide markdown / org-mode markup characters when viewing a file, so I set org-hide-emphasis-markers and markdown-hide-markup to t. However, when editing a section of text, I'd like to see the characters. A function like markdown-toggle-markup-hiding will change the setting for the entire buffer.

Is there an easy way to apply the hiding to the entire buffer except the current line (or paragraph)? That way most of the buffer will be in "view" mode but when I move the cursor to edit something, that line will let me see the formatting characters.

Answer 1

I have a quick & dirty proof of concept for markdown-mode. Idea: keep track of the current line (similar to hl-line-mode). Use a font-lock rule to remove the markup hiding for the current line (markdown-mode seems to use display and invisible text properties, so remove those). Re-fontify the local area when moving from one line to another.

(defvar my/current-line '(0 . 0)
  "(start . end) of current line in current buffer")
(make-variable-buffer-local 'my/current-line)

(defun my/unhide-current-line (limit)
  "Font-lock function"
  (let ((start (max (point) (car my/current-line)))
        (end (min limit (cdr my/current-line))))
    (when (< start end)
      (remove-text-properties start end 
                      '(invisible t display "" composition ""))
      (goto-char limit)
      t)))

(defun my/refontify-on-linemove ()
  "Post-command-hook"
  (let* ((start (line-beginning-position))
         (end (line-beginning-position 2))
         (needs-update (not (equal start (car my/current-line)))))
    (setq my/current-line (cons start end))
    (when needs-update
      (font-lock-fontify-block 3))))

(defun my/markdown-unhighlight ()
  "Install"
  (markdown-toggle-markup-hiding 1)
  (font-lock-add-keywords nil '((my/unhide-current-line)) t)
  (add-hook 'post-command-hook #'my/refontify-on-linemove nil t))

(add-hook 'markdown-mode-hook #'my/markdown-unhighlight)

I don't know if this is the best way to do it. I'm seeing some occasional errors in the message area but it seems to be working ok so far.

Edit: also works in org mode with (add-hook 'org-mode-hook #'my/markdown-unhighlight)