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

[Eli Zaretskii]

> Date: Tue, 16 Aug 2022 16:58:15 +0300
> Cc: 56682@debbugs.gnu.org, gregory@heytings.org
> From: Dmitry Gutov <dgutov@yandex.ru>
> 
> On 16.08.2022 16:09, Eli Zaretskii wrote:
> >> From: Stefan Monnier<monnier@iro.umontreal.ca>
> >> Cc: Eli Zaretskii<eliz@gnu.org>,56682@debbugs.gnu.org,dgutov@yandex.ru
> >> Date: Tue, 16 Aug 2022 09:07:59 -0400
> >>
> >>> The way I see this is that Emacs is doing efforts to solve editing 
> >>> slowdowns
> >>> as best as possible, but that there is a "last mile" that cannot be solved
> >>> without the collaboration from major and minor modes.
> >> The locked narrowing prevents that "last mile", sadly.
> > Nonsense, it doesn't prevent any such things.
> > 
> > Let's not exaggerate when we try to make a point, okay?
> 
> Why nonsense?

Because it takes no effort to override it and then try changes in any
major mode.