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

[Lars Ingebrigtsen]

Eli Zaretskii <eliz@gnu.org> writes:

>> Could the reason you're not seeing this be because flyspell-mode doesn't
>> trigger for you?
>
> What do you mean by "does not trigger"?

That flyspell-mode doesn't work.

> Didn't you say the reproduction recipe doesn't work in "emacs -Q",
> only in some session of yours?  If so, maybe what you have in that
> session explains why you see it and I don't?

No, I can reproduce it from "emacs -Q" fine, both on Linux and Macos.

Eval this:

(progn
  (pop-to-buffer "foo.txt")
  (flyspell-mode)
  (insert (propertize (make-string 20000 ?x) 'display "foo")
          "\n\n"))
 
Then type "d".  [Narrow] is shown in the mode line.