Re: Questions about throw-on-input

[yyoncho <yyoncho@gmail.com>]

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Hi Stefan,

Thank you for your reply! Can you elaborate on "won't have the desired
semantics"? I would suggest something crazier - using inhibit-quit to

Thanks,
Ivan

On Fri, May 8, 2020 at 4:59 AM Stefan Monnier <monnier@iro.umontreal.ca>
wrote:

> > 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?
>
> It can be implemented, but it won't have the desired semantics.
> If you want something robust you have 2 options:
>
> - write in an event-driven style (or CPS style) so that you can easily
>   stop at various points in the program and stash the rest of the
>   computation for later.
>
> - use a thread (which will basically do the same, but transparently,
>   i.e. without the awkward programming style.)
>
>
>         Stefan
>
>
> > 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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