Re: [csswg-drafts] [css-transforms-2] transform-style: flat should not create stacking context, and 3D context grouping (#1950)

I'm reviewing this, and I'm still confused. :(

As far as I can tell, there are two independent things you want to know about an element's 3d context-ness:
1. Whether its children "see" each other and interact in 3d space, or just get flattened and then CSS-layered.
2. Whether the element maintains itself and its children as a 3d entity when its doing its own 3d transforms, or just flattens its subtree into a plane and then transforms the plane.

These are indeed fully independent:

* A 1-3d (from its parent) and 2-3d (from itself) object, if overlapped with a similar sibling, will interweave its transformed descendants with those of its sibling
* A 1-3d and 2-flat object, if overlapped with a similar sibling, will just be a flat plane, but still be z-ordered according to its own transform (and possibly intersect its sibling, etc).
* A 1-flat and 2-3d object, if overlapped with a similar sibling, will project its transformed descendants away from itself appropriately, then flatten into its parent's plane and be CSS-layered with its sibling.
* A 1-falt and 2-flat object, if overlapped with a similar sibling, will run its descendants' transforms, flatten them into itself, transform itself, get flattened into its parents plane, then CSS-layer with its sibling.

In other words, 2 is about flattening *before* the element runs its own transforms (into its own plane), while 1 is about flattening *after* the element runs its own transforms (into its parent's plane).

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I still can't tell, from @mattwoodrow's descriptions, what the intended behavior of 'transform-style' and flattening properties is in these terms. The term "flattened" is thrown around without sufficient clarification for me to tell whether something is being 1-flattened or 2-flattened in any given instance.

Any help?

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Received on Wednesday, 8 May 2019 23:46:39 UTC