W3C home > Mailing lists > Public > www-style@w3.org > February 2009

Re: Proposal for overflow painting order

From: Robert O'Callahan <robert@ocallahan.org>
Date: Thu, 5 Feb 2009 12:48:38 +1300
Message-ID: <11e306600902041548x6039a03dv30664f62e2cda5@mail.gmail.com>
To: David Hyatt <hyatt@apple.com>
Cc: "www-style@w3.org List" <www-style@w3.org>
On Thu, Feb 5, 2009 at 11:55 AM, David Hyatt <hyatt@apple.com> wrote:

> I'd prefer to see overflow special-cased such that it does not interleave
> with other normal flow content by default.  I don't think there is any real
> benefit to be gained by allowing such interleaving. It is also more
> difficult to encapsulate the painting of the overflow (e.g., if you wanted
> to optimize it for accelerated compositing) if the overflow block has to
> break up its painting because of surrounding normal flow content.

I'm not really sure what the last sentence means. In Gecko, we do quite a
bit of analysis to figure out if blitting is possible; for example, we
disallow blitting if the scrollable element is transparent and the content
behind it is not a single solid color, and we disallow blitting if there's
other content (e.g., text) positioned over it. Given the infrastructure we
have for that analysis, making the overflowing element a stacking context
doesn't actually simplify anything for us. And with 3 out of 4 of the latest
versions of the major engines obeying the current spec, a spec change seems
like a hard sell.

Having said that, I don't really care about this issue one way or another,
as long as browsers converge on a consistent rendering. I'd be happy to
implement a spec change since the work would be trivial.

"He was pierced for our transgressions, he was crushed for our iniquities;
the punishment that brought us peace was upon him, and by his wounds we are
healed. We all, like sheep, have gone astray, each of us has turned to his
own way; and the LORD has laid on him the iniquity of us all." [Isaiah
Received on Wednesday, 4 February 2009 23:49:15 UTC

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