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

From: Lars Ingebrigtsen <[email-masked]>
Date: Sun, 21 Aug 2022 15:37:02 +0200

Gregory Heytings <[email-masked]> 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.