W3C home > Mailing lists > Public > www-style@w3.org > November 2014

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

From: Robert O'Callahan <robert@ocallahan.org>
Date: Thu, 20 Nov 2014 18:53:42 +1300
Message-ID: <CAOp6jLZmHpSy8T30_E_8i3nh3JuFDTmOnO5wek_x_Rxbqsd5xA@mail.gmail.com>
To: Chris Harrelson <chrishtr@google.com>
Cc: Greg Whitworth <gwhit@microsoft.com>, www-style list <www-style@w3.org>
On Thu, Nov 20, 2014 at 5:48 PM, Chris Harrelson <chrishtr@google.com>
wrote:

> Apologies for not knowing the full background of this decision, but could
> someone point me at documentation for why it's bad for position:fixed to be
> a stacking context? There are definitely performance & simplicity
> advantages to Blink making it so.
>

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?

Rob
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Received on Thursday, 20 November 2014 05:54:17 UTC

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