bug#45898: 27.1; wedged in redisplay again

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: gerd.moellmann@gmail.com,  larsi@gnus.org,  psainty@orcon.net.nz,
>   Emacs-hacker2018@jovi.net,  45898@debbugs.gnu.org
> Date: Thu, 30 Jun 2022 13:22:29 -0400
> 
> > If so, I guess the expensive part is somewhere else.
> 
> Unsuprisingly so: none of `C-n/C-p/C-v/...` involve font-lock or
> jit-lock either during their operation or during the
> subsequent redisplay phase in the current code: the one-line is all
> fontified once and for all when you open the file and after that
> font-lock is not involved any more (until you make an edit, that is).

That's only true if max-redisplay-ticks is zero.

> > I'd install this patch regardless, because it sounds like TRT not to
> > let syntactic fontifications run amok this way.  We do similar stuff
> > in bidi.c for similar reasons.
> 
> OK, I pushed it to `master`.  The improvement is far from convincing,
> but I tend to agree that it's "The Right Thing".

Thanks.