Re: Unfreezing the display during auto-repeated scrolling. Simpler approach.

[Eli Zaretskii <eliz@gnu.org>]

> Date: Wed, 29 Oct 2014 14:52:11 +0000
> Cc: Stefan Monnier <monnier@iro.umontreal.ca>, emacs-devel@gnu.org
> From: Alan Mackenzie <acm@muc.de>
> 
> On Wed, Oct 29, 2014 at 04:14:12PM +0200, Eli Zaretskii wrote:
> > > From: Stefan Monnier <monnier@iro.umontreal.ca>
> > > Date: Tue, 28 Oct 2014 20:57:16 -0400
> > > Cc: Eli Zaretskii <eliz@gnu.org>, emacs-devel@gnu.org
> 
> > > I'm beginning to like your C-level hack.
> 
> > And I still dislike it.
> 
> Just to be absolutely clear, we're talking about my _simpler_ hack, the
> one that binds fontification-functions to nil during scrolling.

I didn't realize that, thanks for clarifying.

Yes, that's better.

> ONLY when the user option (precise mechanism not yet worked out)
> use-default-face-for-fast-scrolling is non-nil.

As long as CC Mode doesn't set that by default, I can live with that.

> By suggesting the use of jit-lock-defer, somehow, to speed up scrolling,
> the principle that scrolled over buffer regions MUST be fontified has
> been given up.

That wasn't my reasoning, it was the opposite: _if_ we are willing to
accept that the scrolled-over parts be unfontified, _then_ we already
have an optional feature which does precisely that.

> I'm guessing you still accept that the problem (frozen screen during and
> after auto-repeated scrolling) needs to be solved.

Yes, but (a) it is IMO not a very important use case, and (b) the best
way to solve it is where it is caused, i.e. in CC Mode.  Otherwise, we
are on a slippery slope: here is the mode that succeeds in wedging
redisplay, and we are "solving" it by disabling important parts of the
display engine.  No offense, but that's tail wagging the dog.  Next
time another mode will come up with the same problem, what do we say
to ask the author/maintainer to get their act together?

> What do you think?

Given that no one is willing to do (what I think is) TRT, I guess your
suggestion is something we can live with, as long as that variable is
off by default.