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Re: [whatwg] Event loop processing model, and current time

From: James Robinson <jamesr@chromium.org>
Date: Mon, 23 Feb 2015 17:26:00 -0800
Message-ID: <CAD73md+h=HBNcMigja8SCwOf2CY4hdQQUWnuB_35UMAh0qOq4Q@mail.gmail.com>
To: Simon Fraser <smfr@me.com>
Cc: whatwg <whatwg@whatwg.org>
On Mon, Feb 23, 2015 at 4:57 PM, Simon Fraser <smfr@me.com> wrote:

> https://html.spec.whatwg.org/multipage/webappapis.html#processing-model-9
> says:
>
> 1. Let now be the value that would be returned by the Performance object's
> now() method
> 2. Let docs be the list of Document objects associated with the event loop
> in question…
> ...
> 4. For each fully active Document in docs, run the resize steps for that
> Document, passing in now as the timestamp
> ...
>
> This makes no sense, as performance.now() is per-document (it’s relative
> to the document start time), so passing the same value to all documents in
> the browsing context is bogus.
>
> What may be intended is to “freeze” the performance.now() time in all
> documents before processing those documents, but give each document its own
> performance.now() time.
>

That is the intent.  The algorithm should grab a timestamp for each
document "at the same time" (which is really just a matter of grabbing one
timestamp and applying the correct offset for each document).

- James
Received on Tuesday, 24 February 2015 01:26:25 UTC

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