Re: master 7362554: Widen around c-font-lock-fontify-region. This fixes bug #38049.

[Eli Zaretskii <eliz@gnu.org>]

> Cc: monnier@iro.umontreal.ca, acm@muc.de, emacs-devel@gnu.org
> From: Dmitry Gutov <dgutov@yandex.ru>
> Date: Thu, 14 Nov 2019 16:35:14 +0200
> 
> On 14.11.2019 16:29, Eli Zaretskii wrote:
> >> From: Dmitry Gutov <dgutov@yandex.ru>
> >> Date: Thu, 14 Nov 2019 16:05:13 +0200
> >> Cc: Alan Mackenzie <acm@muc.de>, emacs-devel@gnu.org
> >>
> >> The hope is that calling vertical-motion (or font-lock-ensure directly)
> >> inside narrowing is a rare occasion
> > 
> > Why do we need to have such hopes?
> 
> For starters, because it's the current expectation of mmm-mode. :-)

It's an unrealistic expectation.  Code that narrows a buffer and then
invokes something that calls vertical-motion is not special in any
case, and could happen anywhere.

> > The reality could be different,
> > and I'd like us to support those different conditions.  It doesn't
> > sound like it's much harder.
> 
> There are options, sure. But I think all of them will require explicit 
> support from major modes.

I don't think so.  All we need to make sure is that the narrowing
doesn't conceal portions of the embedded fragment.