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Re: [whatwg] Proposal: Wake Lock API

From: Nils Dagsson Moskopp <nils@dieweltistgarnichtso.net>
Date: Sat, 16 Aug 2014 18:19:03 +0200
To: Jonas Sicking <jonas@sicking.cc>, Mounir Lamouri <mounir@lamouri.fr>
Message-ID: <87egwgs8zs.fsf@dieweltistgarnichtso.net>
Cc: WHAT Working Group <whatwg@lists.whatwg.org>, Marcos Caceres <w3c@marcosc.com>
Jonas Sicking <jonas@sicking.cc> writes:

> On Fri, Aug 15, 2014 at 6:14 AM, Mounir Lamouri <mounir@lamouri.fr> wrote:
>> On Thu, 14 Aug 2014, at 11:00, Jonas Sicking wrote:
>>> I am however more worried about that only having a request() and a
>>> release() function means that pages that contain multiple independent
>>> subsystems will have to make sure that they don't stomp on each
>>> other's locks. Simply counting request() calls vs. release() calls
>>> helps, but doesn't fully solve the problem. It's very easy to
>>> accidentally call release too many times, in response to some UI
>>> action for example.
>>>
>>> An alternative design would be something like
>>>
>>> x = new WakeLock("display");
>>> x.request();
>>> x.release();
>>>
>>> Extra calls of either request() or release() are ignored, but pages
>>> can create any number of WakeLocks of the same type.
>>
>> It seems that we already discussed using an object and this solution was
>> dismissed because of this model being error-prone.
>
> Where was this discussed? Why was it considered more error prone? Was
> it related to the patterns discussed at
>
> http://lists.whatwg.org/htdig.cgi/whatwg-whatwg.org/2014-August/297431.html
>
>> It's also not clear
>> how this solution is superior than the current solution [1] with regards
>> to multiple releases or requests. In [1], if you call .request() or
>> .release() multiple time, the promise reacts appropriately.
>
> The problem arises when you have several semi-independent pieces of
> code within a single page. Given that request() and release() is
> likely going to happen in response to very different UI events or IO
> events, it makes it fairly easy to accidentally have unbalanced calls.
>
> Consider for example a lock which is released either when a video
> reaches its end, when the user presses the pause button, or when the
> user close the <dialog> in which the video is rendered. It seems quite
> easy to end up with a race where if the user close the <dialog> right
> when the video ends, that release() would get called twice. Or if the
> user pause the video first and then close the <dialog> that release()
> would get called twice.

Seems to me a declarative solution (like CSS) might be appropriate.

@media screen {
    video:playing {
        wake-lock: display 15s;
    }
}

article.recipe:target {
    wake-lock: display;
}

-- 
Nils Dagsson Moskopp // erlehmann
<http://dieweltistgarnichtso.net>
Received on Saturday, 16 August 2014 16:19:33 UTC

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