Re: Why is jit-lock-stealth-time nil by default?

[Eli Zaretskii <eliz@gnu.org>]

> Date: Thu, 17 Feb 2022 06:26:31 +0000
> From:  emacsq via Users list for the GNU Emacs text editor <help-gnu-emacs@gnu.org>
> 
> I use commands which can show unvisited parts of a buffer and I find it
> annoying when those parts are not fontified.

That shouldn't happen.  Emacs uses a JIT fontification feature, which
is turned on by default, and which should make sure any part of the
buffer is always fontified before it is displayed.  So please report
these cases as bugs, preferably with a reproduction recipe that starts
from "emacs -Q".

> I looked into it and found stealth font locking which performs fontification
> of those parts when the user is idle.
> 
> But jit-lock-stealth-time is nil by default. Is there a reason for this? It's a useful
> feature and today's computers have plenty of idle time, so why is not enabled
> out of the box?

It isn't the default because not many people like or use it.  (I do
like it and always use it, FWIW.)  One problem with this is that it
will cause Emacs to use CPU resources when Emacs is idle, which could
drain the batteries in laptops.