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: Fri, 01 Jul 2022 08:14:33 -0400
> 
> >> > That's only true if max-redisplay-ticks is zero.
> >> 
> >> Why would that make a difference?
> >
> > Because if it is not zero, we won't let the entire line to be
> > fontified, we will stop that before it gets to the end of the line.
> 
> Interesting, where in the code do you do that?

In scan_sexps_forward, near the end: if too many "ticks" are counted,
update_redisplay_ticks will signal an error.  Same thing in
re_match_2_internal.