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

From: Tassilo Horn <[email-masked]>
Date: Wed, 22 Apr 2015 22:10:21 +0200

Stefan Monnier <[email-masked]> writes:

> [ OFFTOPIC: the bug report is not about performance but about
>   a functional bug in jit-lock-defer.  ]
>
>> There's a solution (or, depending on your point of view, a workaround)
>> for this.  You're using Emacs-25, so set fast-but-imprecise-scrolling to
>> t, or customize it (it's in customisation group "scrolling").
>
> FWIW, on my machine, this doesn't make much difference: a single
> "font-lock one screen's worth" takes much too long, so after that one
> screen is displayed, Emacs takes a while catching up (with no display
> at all in the mean time).

Setting `fast-but-imprecise-scrolling' to t works quite nicely for me.
Scrolling is indeed a bit bumpy but there are no noticeable hangs.  And
it's nice that the text scrolls by fontified.

> So I recommend you try jit-lock-defer-time set to 0 instead of using
> fast-but-imprecise-scrolling, and see if you like the resulting
> behavior.

This doesn't work for me.  I get the same display freezes as with
`jit-lock-defer-time' set to nil.  I guess that's not how it's indended
to be.  Maybe keyboard events don't count as pending input?

Bye,
Tassilo