Is it possible to make only parts of a buffer read-only?

Say I have set two marks or line-numbers in the buffer and I would like to make everything between those two marks or line-numbers as read-only.

The function (read-only-mode) applies to the entire buffer but not to parts of it.

Also, if possible, I would like the read-only parts of a buffer marked with a different background color say light beige.

2 Answers 2

(defface my-read-only '((default . (:background "beige")))
  "Face for `my-read-only-region'")

(defun my-read-only-region (begin end)
  "Make the marked region read-only.  See also `my-writeable-region'.

Read-only text is given the face `my-read-only'."
  (interactive "r")
  (let ((inhibit-read-only t))
      (add-text-properties begin end '(read-only t))
      (let ((overlay (make-overlay begin end)))
        (overlay-put overlay 'my-type 'read-only)
        (overlay-put overlay 'face 'my-read-only)))))

(defun my-writeable-region (begin end)
  "Make the marked region writeable.  See also `my-read-only-region'."
  (interactive "r")
  (let ((inhibit-read-only t))
      (remove-text-properties begin end '(read-only t))
      (remove-overlays begin end 'my-type 'read-only))))
  • I'm curious: why overlays and text-properties?
    – rpluim
    Nov 19, 2018 at 9:55
  • AFAIU adding faces via overlays is less susceptible to font-lock conflicts than using text-properties, and it seemed to Do The Right Thing in all my tests. It's not something I use a lot, though, and I'd be happy to be shown a more unified method. I'd then have done it all with the overlay, except there's no 'read-only' overlay property; so I believe that part needs to be a text-property.
    – phils
    Nov 19, 2018 at 11:01

@phils said how to deal with the problem programmatically.

Here is how to deal with it interactively:

  • Select the region
  • Menu Edit -> Text Properties -> Special Properties -> Read-Only

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