bug#58479: 29.0.50; [feature/noverlay] Displaced overlays in notmuch search buffers after refreshing

[Ihor Radchenko]

Matt Armstrong <matt@rfc20.org> writes:

> The other half of the problem is this: you can see the ellipsis and I
> cannot, even on the noverlay branch.  When I play around with the buffer
> created by the following I can see the ellipsis up until when the
> overlay has length zero, then it disappears.  This is true on master and
> the noverlay branch.
>
> (defun my-b58479 ()
>   (interactive)
>   (with-current-buffer (get-buffer-create "*b58479*")
>     (add-to-invisibility-spec (cons 'ellipsis t))
>     (goto-char (point-max))
>     (insert "Hello, World! ")
>     (let ((overlay (make-overlay (- (point) 10) (- (point) 5))))
>       (overlay-put overlay 'invisible 'ellipsis))
>     (display-buffer (current-buffer))))
>
> I am not sure why you see the issue and I do not, but the clue might be
> in what `my-dump-overlays' prints.

On my side, playing with my-b58479 yields erroneous behaviour.
Upon deleting the text under overlay, Emacs suddenly hides text _after_
the overlay. Yet, the overlay is reported to be 0-length.

What I see is:

1. M-x my-b58479
2. Hell<point>...rld!

M-x my-dump-overlays

Buffer #<buffer *b58479*> has 2 overlays.

#<overlay from 1 to 15 in *b58479*>
(window #<window 68 on *b58479*> face hl-line priority -50)

#<overlay from 5 to 10 in *b58479*>
(invisible ellipsis)

3. C-d (5 times)
4. Hell...

"rld!" disappears!

Buffer #<buffer *b58479*> has 2 overlays.

#<overlay from 1 to 10 in *b58479*>
(window #<window 68 on *b58479*> face hl-line priority -50)

#<overlay from 5 to 5 in *b58479*>
(invisible ellipsis)

Also, see the video
https://cubeatic.com/index.php/s/Dd7YinibtfjtYM9

I am at Emacs commit 65a7b5a802a15daa6274403fef822ec3c9b95469.
And I can reproduce the issue with my-b58479 from emacs -Q.

-- 
Ihor Radchenko // yantar92,
Org mode contributor,
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