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Re: [HighResolutionTime] performance.now() value depends on the document, which can cause problems

From: Jonas Sicking <jonas@sicking.cc>
Date: Mon, 14 May 2012 12:23:01 -0700
Message-ID: <CA+c2ei996obLjuAr8czAGKBfvRKDGVhVVkh72HgNUa=7=LGEQA@mail.gmail.com>
To: Boris Zbarsky <bzbarsky@mit.edu>
Cc: public-web-perf@w3.org
On Mon, May 14, 2012 at 11:07 AM, Boris Zbarsky <bzbarsky@mit.edu> wrote:
> Right now, the value returned by performance.now() depends on the Window the
> performance object came from.  This means that any code working with
> multiple subframes and trying to use performance.now() has to be extremely
> careful: the value will differ in different subframes depending on when they
> were last loaded.  This behavior has already bitten the editor of the
> requestAnimationFrame spec, and I expect it to bite web authors.
>
> The bad news is that I'm not sure how to fix this problem.  :(  One option
> is to walk up the window.parent chain as long as the ancestors are
> same-origin, but that would make the .now() method a lot slower...

You'd only need to do that the first time.now() is accessed. So
performance doesn't seem like a problem.

/ Jonas
Received on Monday, 14 May 2012 19:24:01 UTC

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