[webkit-dev] Adding high resolution platform timestamp to DOM events

[Robert Flack]

FWIW, I don't plan to have it enabled by default on any platforms until
we're sure what we want. The discussion with Anne about reusing timestamp
was before she found out that timestamp calls for a 1970 based time by spec
(http://lists.w3.org/Archives/Public/www-dom/2012OctDec/0022.html). I think
we need a new property for this and systemTime has some consensus (as per
the post from Anne), but I will of course not expose it to the public until
we've reached a consensus and a proposed standard.


On Thu, Oct 25, 2012 at 12:59 PM, Ryosuke Niwa <rniwa at webkit.org> wrote:

> As Elliott pointed out, this property doesn't seem to be on any working
> draft or editor's draft yet. And it doesn't seem like either thread on
> www-dom or www-perf reached a consensus.
>
> I'd appreciate if you waited until either thread reached a rough consensus
> about the feature. Namely, www-dom thread discussion leads me to believe
> that some people think we can simply modify timeStamp IDL attribute instead
> of adding new one.
>
> - Ryosuke
>
> On Wed, Oct 24, 2012 at 6:17 PM, Robert Flack <flackr at chromium.org> wrote:
>
>> Hi webkit-dev,
>>
>> I would like to add platform timestamps to DOM events as the systemTime
>> property. I have a patch implementing the feature:
>> https://bugs.webkit.org/show_bug.cgi?id=94987. This will let us know the
>> time at which the system received an event to be able to accurately handle
>> it, whereas the timestamp property gives the time the DOM event was created
>> in an inaccurate milliseconds since 1970 form. This has been discussed on
>> www-dom (http://lists.w3.org/Archives/Public/www-dom/2012OctDec/0028.html)
>> and www-perf (
>> http://lists.w3.org/Archives/Public/public-web-perf/2012Oct/0046.html)
>> and use cases for this have been discussed (
>> http://lists.w3.org/Archives/Public/www-dom/2012AprJun/0092.html).
>>
>> The platform timestamp comes in as a monotonic timestamp. Since the DOM
>> Event spec requires that timeStamp() be a 1970-epoch based timestamp it is
>> not sufficient for a high resolution precise time delta on event delivery.
>> Instead, we add a systemTime property which uses the Performance API spec (
>> http://dvcs.w3.org/hg/webperf/raw-file/tip/specs/HighResolutionTime/Overview.html)
>> for high res timestamps (time since document load timestamp to avoid user
>> fingerprinting) and provide the platform's high resolution timestamp to
>> ECMAScript.
>>
>> Let me know if you have any suggestions. I look forward to everyone's
>> feedback, cheers!
>> - Rob
>>
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>>
>>
>
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