[css-contain] Position in painting order

[frivoal]

layout and paint containment cause the element to establish a stacking context. Where in the painting order does that go?

I believe the normative description for this is https://www.w3.org/TR/CSS22/zindex.html, and that seems to say that the element stays wherever it would otherwise be: just becoming a stacking context doesn't change its place in the painting order, it only affects the painting order of its descendants.

However, I believe that that was written when the only thing that could create stacking contexts was positioned elements, so there may be some shortcuts taken in that description, and maybe the intent would be that all things which create a stacking context, including elements with containment, get the same position in painting order as if they were positioned elements with z-index: auto.

I don't think I understand stacking contexts well enough to answer than myself.

[tabatkins]

I think this is actually a duplicate of #2717

[frivoal]

Yes, it is. I had the feeling I'd seen this before, but I my searchfu was weak today and I couldn't find that issue.