Re: [css-transforms] Clarifying backface-visibility

The statement that blink and webkit create a stacking contexts is
incorrect. Blink and WebKit paint atomically which seems like a painting
bug, but they do not actually create a stacking context. Example:
http://jsbin.com/buloti

On Thu, Feb 25, 2016 at 6:50 PM, Philip Rogers <pdr@chromium.org> wrote:

> We're working on implementing backface-visibility in Blink's new paint
> architecture and have hit inconsistencies between implementations and the
> spec:
> https://drafts.csswg.org/css-transforms/#backface-visibility-property
>
> Should backface-visibility create a stacking context?
> Testcase: https://pr.gg/backfaceVisibilityStackingContextTest.html
> Blink: yes, if backface-visibility: hidden.
> WebKit: yes, if backface-visibility: hidden.
> Gecko: no
> Edge: no
> Because WebKit and Blink have unfortunately had this behavior for a long
> time, it is likely that content now depends on the stacking context
> behavior.
>
> Which descendants does backface-visibility affect?
> Testcase: https://pr.gg/backfaceVisibilityDescendantTest.html
> We've outlined some proposals below, although this is not exhaustive.
> Proposal A is our favorite but has issues such as the "3D plane" concept
> being poorly defined.
> Proposal A: backface-visibility only works on elements that create a 3D
> plane and applies to that plane.
> Proposal B: backface-visibility only works on flattening elements (i.e.,
> elements that create a sub 3D rendering context) and applies to every plane
> within that context.
> Proposal C: backface-visibility only works on elements that create
> stacking contexts, and affects the normal-flow descendants.
> Proposal D (as in the current spec): backface-visibility works on all
> individual elements, similar to how visibility works but with the used
> value determined by face orientation.
>
> How does backface-visibility interact with isolated groups as in
> compositing/blending?
> https://drafts.fxtf.org/compositing
> Blending with a transparent rect is different from not blending at all so
> we’re wondering whether hidden implies transparency or not drawing at all.
>
> Philip/pdr@chromium.org & Tien-Ren/trchen@chromium.org
>