bug#51490: Show an indicator when Emacs is busy somewhere in the Emacs window

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: Gregory Heytings <gregory@heytings.org>,  stefan@marxist.se,
>   51490@debbugs.gnu.org
> Date: Thu, 22 Sep 2022 12:54:41 +0200
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> Aren't they the simplest graphical element drawn by Emacs, a simple 
> >> black-and-white bitmap?
> >
> > No, they aren't.  They are certainly not black-and-white: they use
> > faces.
> 
> They use faces to get at the colours, but nothing beyond that, I think?

Yes, only the colors.  But accessing the faces means you cannot do
that while the Lisp machine is doing something.