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Re: [AnimationRequestFrame] Initial editor's draft of AnimationRequestFrame spec available

From: Robert O'Callahan <robert@ocallahan.org>
Date: Wed, 4 May 2011 09:36:06 +1200
Message-ID: <BANLkTimpX9yU5DWenaszECnZb7QHnLVngA@mail.gmail.com>
To: James Robinson <jamesr@google.com>
Cc: Boris Zbarsky <bzbarsky@mit.edu>, public-web-perf@w3.org
On Wed, May 4, 2011 at 9:05 AM, James Robinson <jamesr@google.com> wrote:

> This can help in some cases, but does not improve the worst case (for
> example http://webstuff.nfshost.com/raf-make-visible.html where each
> callback changes the visibility of another element by toggling the
> style.display property between "blank" and "").
>

Yes of course.

I think we can accommodate both your proposed algorithm and the current
> WebKit implementation by defining the visibility requirement sufficiently
> loosely so that the user agent can use potentially stale style+information
> to decide that an element might be visible, so long as it ensures that no
> callbacks are left pending with definitely visible elements at the end of
> the algorithm.
>

Indeed.

The drawback of leaving this loose is that the order of callback invocation
> will change depending on the details of the algorithm.  For example, in
> http://webstuff.nfshost.com/raf-visible-ordering.html the callbacks run in
> the order A, B, C in WebKit currently, but would run in the order A, C, B in
> Robert's proposed algorithm.  This has a chance of tripping up some authors.
>

Potentially. Experience will tell, and we can tighten the specification up
later if that proves necessary.

Rob
-- 
"Now the Bereans were of more noble character than the Thessalonians, for
they received the message with great eagerness and examined the Scriptures
every day to see if what Paul said was true." [Acts 17:11]
Received on Tuesday, 3 May 2011 21:36:34 GMT

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