Re: [css-transforms] Should transform-style: preserve-3d create containing block for positioned descendants?

On Fri, Dec 12, 2014 at 7:47 AM, Simon Fraser <smfr@me.com> wrote:

> There is disagreement among implementations about whether
> "transform-style: preserve-3d” creates containing block for positions
> descendants.
>
> The working draft[1] says in the prose:
>
> A 3D rendering context is established by a a transformable element whose
> computed value for transform-style is preserve-3d, and which itself is not
> part of a 3D rendering context. Note that such an element is always a
> containing block.
>
>
> but we don't explicitly call this out under the transform-style property.
> The new spec text doesn't require that preserve-3d create containing block,
> and logically I see no reason why it should. (I’m also not sure why
> perspective has to create a containing block.)
>
> WebKit/Blink have this behavior because of a bug[2]. Firefox has this
> behavior too, possibly because they copied WebKit behavior, or went by the
> spec prose. IE 11 does not have this behavior.
>

I think it's simpler if it does. If we don't make it a containing block,
then abs-pos children can escape from a preserve-3d parent and it's unclear
whether and how the parent's preserve-3d would apply to them.

Rob
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