Undo custom command without moving the point

Question

I would like to have a command that inserts some text at a distance, while keeping the point in place during its own execution and while being undone.

To illustrate the point, consider following example:

(save-excursion (goto-char (point-at-eol)) (insert "test"))

As I was writing this, I found a solution through making an invisible change at the original position, at the beginning and at the end of execution. This will ensure that original position is the last position visited by point during undo or redo.

Following solution works, however I would like to apply more conventional approach if one exists:

(atomic-change-group (insert " ") (delete-char -1)
                     (save-excursion (goto-char (point-at-eol))
                                     (insert "test"))
                     (insert " ") (delete-char -1))

Answer 1

The undo log normally doesn't keep track of point motion (tho it does try to put point back to where it was before a change, it does so under the assumption that point was only moved as a side effect of the changes and doesn't try to handle pointmotions that happened before the buffer modification).

So you'll have to explicitly add an undo entry to put point back to where it was, e.g.:

(save-excursion (if (listp buffer-undo-list)
                    (push (point) buffer-undo-list))
                (goto-char (point-at-eol))
                (insert "test"))

Answer 2

(save-excursion (undo-boundary) (goto-char (point-at-eol)) (insert "test"))

IOW, tell undo what you want it to do. One way to do that is to use undo-boundary.

If you want more info about what you are calling an "atomic [undo] group", see the Elisp manual, node Undo.