[csswg-drafts] [css-transforms-2][css-overflow-3] overflow: clip and 3d transforms (#6374)

frivoal has just created a new issue for https://github.com/w3c/csswg-drafts:

== [css-transforms-2][css-overflow-3] overflow: clip and 3d transforms ==
This is a follow up from #6202, where a discussion of paint containment and 3d transforms uncovered a similar point about `overflow: clip`.

On the one hand it seemed desirable that `overflow: clip` would, unlike `overflow: visible` and like every other value of `overflow`, be listed among grouping properties and cause flattening of a `preserve-3d` scene. On the other hand, it might not be that simple:
* all the other things listed in "grouping properties" are things that create a stacking context, but `overflow:clip doesn't`
* combining `overflow: clip` in one axis with `overflow: visible` in the other is possible, but being a grouping property isn't a thing that can happen on one axis only.

The second one can easily be solved by saying that if either `overflow-x` or `overflow-y` is `clip`, then we flatten. Feels a bit like a hack to me, but maybe it's fine.

For the stacking context problem, someone with a deeper understanding than me (@dbaron?) should probably comment.

Ultimately, I don't think that we absolutely have to make `clip` cause flattening, as we theoretically could clip within the 3d scene, but @smfr has been clear that he'd rather avoid that, and others seemed to agree.

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/6374 using your GitHub account


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Received on Thursday, 10 June 2021 02:33:43 UTC