[Bug 28252] New: Overflow clipping should not always create stacking context

https://www.w3.org/Bugs/Public/show_bug.cgi?id=28252

            Bug ID: 28252
           Summary: Overflow clipping should not always create stacking
                    context
           Product: CSS
           Version: unspecified
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Transforms
          Assignee: smfr@me.com
          Reporter: trchen@chromium.org
        QA Contact: public-css-bugzilla@w3.org
                CC: ayg@aryeh.name, cmarrin@apple.com, dino@apple.com,
                    dschulze@adobe.com, eoconnor@apple.com, smfr@me.com

In the latest draft (as of 2015/03/21) of CSS Transform,

Section 10.1: Any overflow value other than 'visible' will force the used value
of transform-style to 'flat'.

Section 10: A value of "flat" for transform-style establishes a stacking
context, and establishes a 3D rendering context. 

Therefore it is implied that whenever an overflow clip is specified, a stacking
context must be created, breaking backward compatibility.

If I understand correctly, in latest Safari(8.0.3) setting
-webkit-transform-style:flat doesn't enforce a stacking context. In the case
that we have both overflow:hidden and -webkit-transform-style:flat, no stacking
context will be created. Flattening will still be done, but no 3D rendering
context is created on the clipping container. It works as if each of the
3D-transformed descendants create their own 3D rendering context, and flattened
individually. (i.e. No z-sorting is done, and they stack in the DOM tree
order.)

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Received on Saturday, 21 March 2015 08:38:34 UTC