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#45898
27.1; wedged in redisplay again
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Message #23 received at 45898 <at> debbugs.gnu.org (full text, mbox):
> Cc: Emacs-hacker2018 <at> jovi.net, 45898 <at> debbugs.gnu.org
> Date: Wed, 08 Jun 2022 17:08:56 +0300
> From: Eli Zaretskii <eliz <at> gnu.org>
>
> > From: Lars Ingebrigtsen <larsi <at> gnus.org>
> > Cc: Emacs-hacker2018 <at> jovi.net, 45898 <at> debbugs.gnu.org
> > Date: Wed, 08 Jun 2022 13:47:28 +0200
> >
> > But if we had this facility (i.e., a way to make Emacs call some
> > function after `C-g'-ing a lot during redisplay), then we can start
> > experimenting -- and users can, too. So I think having a
> > `break-during-redisplay-function' variable that specifies something to
> > be called in these situations would allow some possible progress in this
> > area.
>
> One problem with this is that we already have the "emergency exit"
> feature, which is triggered by 2 or more C-g's. This only works
> reliably on TTY frames, but it's still a feature we don't want to
> lose.
>
> The other problem is that I don't know how to do this safely.
Btw, this says "redisplay", but that's somewhat misleading: in many
cases I've seen, at least half of the time, and sometimes most of it,
is spent in the move_it_* functions, which are called both from the
display engine (to make layout decisions), and more-or-less directly
from Lisp, like via posn-at-point, vertical-motion, and scrolling
commands. These are not "redisplay", strictly speaking, although they
reuse a lot of the display code.
So one challenge is to detect the "during redisplay" situation,
including the fact that it's "still the same redisplay cycle".
As for the C-g idea, I think a better and cleaner idea would be to use
atimers to detect signs of potentially a very long redisplay cycle,
and then do...something. Not unlike what we already do with the
hourglass-cursor feature.
Other clever ideas are welcome.
This bug report was last modified 2 years and 356 days ago.
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