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Re: [CSSOM] Interaction of getBoundingClientRect/getClientRects with transforms

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Tue, 31 Aug 2010 07:13:19 -0700
Message-ID: <AANLkTinFE13MUfY2EpWzvtvqfagz+9WMYo6dhWt35=a9@mail.gmail.com>
To: Anne van Kesteren <annevk@opera.com>
Cc: www-style list <www-style@w3.org>, Boris Zbarsky <bzbarsky@mit.edu>
On Tue, Aug 31, 2010 at 6:13 AM, Anne van Kesteren <annevk@opera.com> wrote:
> On Tue, 31 Aug 2010 14:57:45 +0200, Boris Zbarsky <bzbarsky@mit.edu> wrote:
>>
>> How should getBoundingClientRect/getClientRects (which assume that the
>> element they're called on decomposes into a set of axis-aligned boxes)
>> interact with transforms?
>>
>> For a simple testcase of a single transformed div with the functions
>> called on it, Gecko reports the rect the div would have if the transform
>> were not applied.  Webkit and Presto seem to report a bounding client rect
>> for the transformed div (so for the case of a 100x100 px square rotated
>> 45deg clockwise about the bottom-left corner they report 142px width and
>> height and 29px top).  See testcase at end of mail.
>>
>> The spec probably needs to say what the right behavior is here.  (And of
>> course also for offset* and whatnot, but at the moment I'm more concerned
>> about getClientRects.)
>
> Bounding box is what we do for SVG so we should do that here too. Ideally
> the definition of "border box" in CSS reflects this behavior or CSS gets a
> different kind of "border box" that reflects this behavior and CSSOM View is
> updated to use that.

Given that transforms don't affect the geometry, I'd assume that the
current non-transform-aware definition of "border box" should be the
appropriate one here.

(I'm curious about how a transformed element works when used in a
background with the -moz-element() function or the -webkit-canvas()
function, particularly with background-repeat:repeat.)

~TJ
Received on Tuesday, 31 August 2010 14:14:08 GMT

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