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

[Stefan Kangas]

Lars Ingebrigtsen <larsi@gnus.org> writes:

> Eli Zaretskii <eliz@gnu.org> writes:
>
>> Mode line is drawn in C, not in Lisp.
>>
>> And if the problem is that we cannot run the display code, either,
>> then how would it help to poke the glyph?  It won't be shown on the
>> glass, because redisplay cannot run.  Right?  Or what am I missing?
>
> Redisplay can run, but we can't run any Lisp code, and the normal
> formatting of a mode line does (potentially) run lots of Lisp code,
> doesn't it?

BTW, I think one goal here should be to optionally replace the glyph
with a sequence of images/icons (preferably SVG files).