bug#45898: 27.1; wedged in redisplay again

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: Emacs-hacker2018@jovi.net,  45898@debbugs.gnu.org
> Date: Thu, 09 Jun 2022 13:04:14 +0200
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Then there's a problem of determining which window is the problematic
> > one.
> 
> Idea: Perhaps our "redisplay is wedged" function should basically be
> "switch to a *warning* buffer".  I.e., if we can determine that Window
> Foo is the problem, then switch the buffer in that window to a buffer
> that reads "Redisplay was hanging in buffer *foo*".  If we can't
> determine the window that's handing, then just switch all windows (in
> all frames) to that warning buffer.

That might be something to do after ending _this_ redisplay cycle, but
we first need to end _this_ cycle, and end it in a way that Emacs
won't immediately re-enter redisplay and try to redraw that same
window.