Re: Questions about throw-on-input

[yyoncho <yyoncho@gmail.com>]

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Hi Eli,

Out of curiosity, do you think that having a function
(process-events) which will process all keyboard(?) events
and resume the current invocation can be implemented easily?
AFAIK a lot of gui toolkits have that kind of function, e. g.
https://docs.microsoft.com/en-us/dotnet/api/system.windows.forms.application.doevents?view=netcore-3.1

IMO it will be very useful for certain cases.

Thanks,
Ivan

On Thu, May 7, 2020 at 3:37 PM Eli Zaretskii <eliz@gnu.org> wrote:

> > From: Ivan Yonchovski <yyoncho@gmail.com>
> > Date: Thu, 07 May 2020 10:31:23 +0300
> >
> >
> > 1. In the following example:
> >
> > (dotimes (_ 10)
> >   (message "Length %s"
> >            (length
> >             (let (result)
> >               (catch t
> >                 (let ((throw-on-input t))
> >                   (dotimes (counter 10000000)
> >                     (push (number-to-string counter) result))))
> >               result))))
> >
> > .. after I execute the following block each of the 10 computations will
> be
> > canceled after pressing C-n for example, how do I force the handling of
> > the command to be processed? I tried redisplay but it does not help.
>
> Invoking redisplay won't help because the commands which interrupted
> the inner loop (C-n) were not yet executed.  Emacs will process them
> only after the outer loop ends, because that outer loop is the last
> command, and it is still being executed.  Emacs doesn't perform
> commands in the middle of another command.
>
> > (message "Length %s"
> >          (length
> >           (let (result)
> >             (catch t
> >               (let ((throw-on-input t))
> >                 (dotimes (counter 10000000)
> >                   (push (number-to-string counter) result))))
> >             result)))
> >
> >
> > (run-with-idle-timer
> >  0.0
> >  nil
> >  (lambda ()
> >    (message "Length %s"
> >             (length
> >              (let (result)
> >                (catch t
> >                  (let ((throw-on-input t))
> >                    (dotimes (counter 10000000)
> >                      (push (number-to-string counter) result))))
> >                result)))))
> >
> > The issue is with the second block, it seems like throw-on-input is
> > disregarded when used in run-with-idle-timer. Can anyone confirm if this
> > is a bug/desired behavior or I should use something else if I want to
> > run cancelable tasks in on-idle?
>
> When the time function is run, Emacs binds inhibit-quit to t (so that
> the user's C-g would not interrupt the timer function, for example).
> And throw-on-input uses quitting to do its job.
>
> Why do you need to interrupt an idle timer like that?  The usual way
> of doing this is not to call expensive functions in an idle timer, and
> if you have a lot of processing, divide them into small enough chunks
> and do it piecemeal.  That's what jit-stealth font-lock does, for
> example.
>

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