bug#57207: 29.0.50; Fontification is slow after e7b5912b23 (Improvements to long lines handling)

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: Eli Zaretskii <eliz@gnu.org>,  57207@debbugs.gnu.org,  yantar92@gmail.com
> Date: Sun, 21 Aug 2022 15:37:02 +0200
> 
> Gregory Heytings <gregory@heytings.org> writes:
> 
> >>  (flyspell-mode)
> >>  (insert "\n\n"
> >>      (propertize (make-string 20000 ?x) 'display "foo")
> >>      "\n\nbar\nzot\n")
> >>  (goto-char (point-min)))
> >>
> >> Then type `d'.  Everything after "foo" disappears.
> >>
> >
> > It doesn't, here :(  Strange...
> 
> Does flyspell-mode actually work for you, then?  Try `M-x flyspell-mode'
> in "emacs -Q" and see what happens.

On my system, I need to toggle flyspell-mode twice in the foo.txt
buffer, before I can see the issue, because the original invocation of
it, as part of the recipe, errors out, and the post-command-hook isn't
installed.