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

From: Eli Zaretskii <[email-masked]>
Date: Fri, 19 Aug 2022 20:51:34 +0300

> From: Lars Ingebrigtsen <[email-masked]>
> Cc: [email-masked],  [email-masked]
> Date: Fri, 19 Aug 2022 19:25:24 +0200
> 
> Eli Zaretskii <[email-masked]> writes:
> 
> > I types "s".  Does it matter what you type?
> 
> Nope.

Ah, I know what's causing this: flyspell calls redisplay (via sit-for)
inside its post-command-hook.

So I think this basically means we cannot narrow the buffer while
calling pre- and post-command-hooks, because any of them can trigger
redisplay, and that will show "Narrow" on the mode line.

(I also understand why I didn't see the problem on my system: it's
because the recipe signals an error here, and flyspell-mode isn't
completely enabled.)