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

[Lars Ingebrigtsen]

Eli Zaretskii <eliz@gnu.org> writes:

>> Would binding `inhibit-redisplay' there help?
>
> Maybe it will, but how can we do that?  It would break any pre- and
> post-command hooks that do need to trigger redisplay.

Do they need to while in this hard-narrow mode?  Hm... probably.

I'm not quite understanding why we're narrowing here in the first place.
Point is not in a long line in this test case -- there's just a long
line (hidden under a display property) earlier in the buffer.