Re: C-n is very slow in Font-Lock mode

[David Kastrup <dak@gnu.org>]

"Eli Zaretskii" <eliz@gnu.org> writes:

>> Cc: emacs-devel@gnu.org
>> From: David Kastrup <dak@gnu.org>
>> Date: Wed, 27 Apr 2005 00:57:05 +0200
>> 
>> Without looking at the code, it would be my guess that it would
>> currently run immediately after redisplay, whereas my suggestion for
>> jit-lock-defer-time=0 semantics would be that it be run immediately
>> before redisplay.
>
> I'm not sure what that means.  You _are_ aware that, when you scroll
> thru text with C-n or C-v, there's almost nothing going on in Emacs
> _except_ redisplay, yes?

We are talking about the situation where the input is coming in faster
than Emacs can process it.  In that case it will refrain from updating
the display.  The question is whether it should also refrain from
fontification.

Currently it doesn't.  My proposal was to provide a special setting
for jit-lock-defer-time that would not bother with fontification
unless it was going to update the display.  That would mean that
vertical-motion could possibly work on unfontified stuff when Emacs
was not keeping up with the display.

> So when you are saying ``before redisplay'', what exactly do you
> mean?

Before material actually gets transferred to the screen.

-- 
David Kastrup, Kriemhildstr. 15, 44793 Bochum