Re: Questions about throw-on-input

[Eli Zaretskii <eliz@gnu.org>]

> From: Ivan Yonchovski <yyoncho@gmail.com>
> Cc: emacs-devel@gnu.org
> Date: Fri, 08 May 2020 14:23:34 +0300
> 
> (defun process-events ()
>   (when (input-pending-p)
>     (run-with-timer 0.01 nil (lambda () (throw 'exit nil)))
>     (recursive-edit)))
> 
> (dotimes (counter 1000)
>   (sleep-for 0.01) ;; simulate execution of N tasks
>   (message "%s" counter)
>   (process-events))
> 
> This code is able to handle C-n but obviously it will break if someone
> starts another recursive-edit or for complex keybindings, e. g. `C-x b`.

I think you will indeed find that this is very fragile.

> Are you aware of something doing something similar? Do you think it
> makes sense if you want to process something slow on the background
> without blocking emacs?

I think this is why we added threads to Emacs.  Why not try doing this
in a thread?

> > AFAIU, such facilities need to have a separate event loop that
> > generally runs in a separate thread.
> 
> In the C# case it all happens on the UI thread. DoEvents means handle
> mouse clicks, repaint controls, etc(the stuff from the event loop) and
> then continue with current execution.

When display is as intimately connected to the global state as it is
in Emacs, I don't think such separation can fly.