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

[Eli Zaretskii]

> Cc: address@hidden, address@hidden, address@hidden
> From: Dmitry Gutov <address@hidden>
> Date: Thu, 14 Nov 2019 16:35:14 +0200
> 
> On 14.11.2019 16:29, Eli Zaretskii wrote:
> >> From: Dmitry Gutov <address@hidden>
> >> Date: Thu, 14 Nov 2019 16:05:13 +0200
> >> Cc: Alan Mackenzie <address@hidden>, address@hidden
> >>
> >> 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.