GNU bug report logs - #35400
27.0.50; Timers repeated after waking from suspend

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From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: Eli Zaretskii <eliz <at> gnu.org>, 35400 <at> debbugs.gnu.org
Subject: bug#35400: 27.0.50; Timers repeated after waking from suspend
Date: Wed, 03 Feb 2021 19:42:29 +0100

Stefan Monnier <monnier <at> iro.umontreal.ca> writes:

>> So maybe this should be a property of the timer itself?

Yeah, that sounds like a good idea.

> I think for the case where we missed some timer repetitions, the best
> thing we can do is not to call that timer repeatedly but instead to call
> it once and pass it the number of times it has fired since the last time
> we ran it (so it can then freely decide to repeat its operation N times
> or not).
>
> A related issue is that for many timers, rather than "repeat every
> N seconds" we'd rather want "wait N seconds between invocations" (so if
> the execution of the timer terminates M seconds after the time T it was
> supposed to start running, the next execution should not be scheduled
> for T+N but T+M+N).

That's true.  I think the current way code deals with this is to ask
Emacs to repeat once, and then the function itself computes the next
delay, and then runs `run-at-time' itself (see for instance
`image-animate-timeout').

Having `run-at-time' compute this would be an improvement -- not at
least because it would be one single timer function, and you could
inspect it from `list-timers', which you can't really do today in this
scenario (because it's a new timer on every update).

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

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