bug#56682: feature/improved-locked-narrowing 9dee6df39c: Reworked locked narrowing.

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: Gregory Heytings <gregory@heytings.org>,  akrl@sdf.org,
>   56682@debbugs.gnu.org
> Date: Thu, 09 Feb 2023 12:31:44 -0500
> 
> >> A function/macro to check that could indeed be added, its body would be:
> >> 
> >> (save-restriction (widen) (buffer-narrowed-p))
> >
> > We should add it and document it, but I'm surprised that there's no
> > easier way.  One problem with the above is that it could cause a more
> > thorough redisplay because it fiddles with buffer restrictions.
> 
> Seeing how `buffer-narrowed-p` is not used very often, I'm not
> too worried.  Even more so given that the redisplay does try to notice
> when the restriction has been modified temporarily but "reset" to its
> original value since then.

The last part is only true for Lisp that's called from redisplay
itself, not for Lisp running between redisplay cycles.