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RE: [CSS2.1] Fixed z-index interop issue

From: Rossen Atanassov <Rossen.Atanassov@microsoft.com>
Date: Thu, 20 Nov 2014 19:03:44 +0000
To: "robert@ocallahan.org" <robert@ocallahan.org>, Chris Harrelson <chrishtr@google.com>
CC: Greg Whitworth <gwhit@microsoft.com>, www-style list <www-style@w3.org>
Message-ID: <640e82274b1341d0b2e76db91be9f8a1@BY2PR03MB192.namprd03.prod.outlook.com>
> -----Original Message-----
> From: rocallahan@gmail.com [mailto:rocallahan@gmail.com] On Behalf Of
> Robert O'Callahan
> Sent: Wednesday, November 19, 2014 9:54 PM
> 
> It broke some existing content (most of which has probably been fixed by
> now, but maybe not all). It makes position:fixed less consistent with
> position:absolute. Prior to Webkit changing behavior, we had interop across
> all browsers. Other browsers didn't have an implementation need to change
> behavior (and apparently still don't). You have to solve most of the
> architectural issues anyway if you want async scrolling of arbitrary scrollable
> elements, since a position:absolute child of a scrollable non-positioned
> element has very similar z-ordering problems to position:fixed. In Gecko,
> forcing position:fixed elements to be stacking contexts wouldn't help us
> much at this point. So my point of view is, why change the spec?

I recall this telcon [1] discussing where the issue was raised and we requested compat data (especially for desktop). I don't remember if we resolved on it later on but if we did it was probably in Tucson? The fact is that now the mobile content relies on this behavior so whatever decision we make now, there will be compat issues to deal with.

As far as the perf benefits of this change are concerned, I'm still not convinced we'll benefits much from it in our architecture.

Thanks,
Rossen

[1] http://lists.w3.org/Archives/Public/www-style/2012Oct/0115.html 
Received on Thursday, 20 November 2014 19:04:16 UTC

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