Re: How to temporarily show an image in an Emacs buffer?

[Marcin Borkowski]

On 2023-03-08, at 05:53, Marcin Borkowski <mbork@mbork.pl> wrote:

> Alternatively, it _may_ change the buffer contents but in a way that is
> not recorded in `buffer-undo-list'.  Is that possible?

I did some experimenting, and this

(defvar no-undo-marker (make-marker))
(defun no-undo-insert ()
  "Test undo."
  (save-excursion
    (let ((buffer-undo-list))
      (set-marker no-undo-marker (point))
      (insert "this can't be undone\n"))))

(defun no-undo-uninsert ()
  (save-excursion
    (goto-char no-undo-marker)
    (let ((buffer-undo-list))
      (when (looking-at-p "this can't be undone\n")
        (delete-char 21)))))

seems to do the trick, but depending on the order of typing and calling
these functions, the undo list becomes corrupted (I get "primitive-undo:
Changes to be undone are outside visible portion of buffer").

Any hints?

-- 
Marcin Borkowski
http://mbork.pl