Subject: Re: bug#20404: 25.0.50; Sometimes no fontification with jit-lock-defer-time

From: Eli Zaretskii <[email-masked]>
Date: Thu, 23 Apr 2015 20:34:44 +0300

> From: Stefan Monnier <[email-masked]>
> Cc: [email-masked],  [email-masked],  [email-masked]
> Date: Thu, 23 Apr 2015 13:27:20 -0400
> 
> > FWIW, when I set jit-lock-defer-time to zero and lean on the PageDown
> > key, I see somewhat clunky scrolling with no fontifications, until I
> > release the key.
> > But fontification inside the scrolling code itself still happens, I
> > think.
> 
> Hmm... while I guess it's still possible, it normally shouldn't happen:
> if the fontification takes place during the scrolling itself, then the
> next redisplay should not be skipped

How does this work?

By "fontification inside scrolling" I mean fontification triggered by
calling move_it_* functions, which simulate display.  They will only
fontify those parts of text over which they iterate, which might be
much less than the window.

> (and hence you should see fontified text rather than unfontified
> text, tho, some of the displayed text may still be unfontified,
> because it was marked as "fontified=defer" in the previous
> redisplay).

It's hard to say, but I'm almost sure I sometimes indeed see a small
part of the scrolling window, near its beginning, fontified.  Or maybe
I'm just imagining things.