bug#56682: Fix the long lines font locking related slowdowns

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: gerd.moellmann@gmail.com,  56682@debbugs.gnu.org,  gregory@heytings.org,
>   visuweshm@gmail.com
> Date: Sun, 24 Jul 2022 11:48:35 -0400
> 
> >> Not only more intervals, but also more elements in the `plist`s of
> >> each interval.
> > Could be, if there are many different properties.  But since we are
> > talking about font-lock, there's only one we are talking about: 'face'.
> 
> `face` may be the one we care about, but there will be others
> (especially in the case you were talking about, i.e. the impact of
> non-display-related faces)

In general, sure.  But this particular discussion is about the
difference in performance between font-lock being on and off, and in
that case the only property that counts is 'face'.

If you are thinking about non-display-related properties, you are in
the wrong thread ;-)  That one was raised by João in another
discussion.