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

[Eli Zaretskii]

> Resent-Sender: help-debbugs@gnu.org
> From: Tassilo Horn <tsdh@gnu.org>
> Date: Wed, 22 Apr 2015 11:45:42 +0200
> 
> I use the settings
> 
>   (setq jit-lock-defer-time 0.0312
>         jit-lock-stealth-nice 0.117
>         jit-lock-stealth-time 0.23)
> 
> to speed up scrolling in large buffers with complex font-lock rules.
> That basically works nice.  However, quite often I'm faced with buffers
> that are not fontified before I do something, e.g., move point.
> 
> This frequently happens when installing/upgrading packages with the
> package manager.  That shows the buffer containing the byte-compliation
> messages with fontified warnings and errors.  Every second time or so,
> I'm faced with a completely unfontified buffer that gets fontified only
> after selecting the window showing the buffer.
> 
> Another and even reproducible case is `report-emacs-bug'.  It goes like
> this:
> 
>   1. emacs -Q
>   2. eval my above settings in *scratch*
>   3. M-x report-emacs-bug
> 
> The new message buffer is completely unfontified initially.  As soon as
> you move point, font-lock kicks in and the header lines get their proper
> fontification.  Or maybe it's the other way round, i.e., the buffer is
> created, then redisplayed, then the fontification takes place but no
> redisplay is performed thereafter.

Sounds like the idle timer that is started by jit-lock-defer-time
never runs after the buffer is displayed.  Could it be that it already
ran before the display?