[css-view-transitions-1] What is the size of the group pseudo for the root element?

[nt1m]

From @mattwoodrow from investigating https://bugs.webkit.org/show_bug.cgi?id=272186:

Chrome seems to be setting the size of their ::view-transition-group element to that of the snapshot containing block. That seems wrong, but visually what you’d expect to happen.

Capture the image algorithm has a special case for sizing the image when capturing the root, I suspect Update pseudo-element styles should have the equivalent wording for setting the width/height style properties.

[nt1m]

@noamr @khushalsagar @vmpstr

[noamr]

Sounds reasonable to me, will wait for Vlad/Khush to confirm. Happy to make the edit.

[khushalsagar]

That seems wrong, but visually what you’d expect to happen.

Just to confirm, the error is that we're using the border-box for the document element here. Instead it should be the snapshot containing block size similar to when we do this for the old DOM here.

SGTM. Thanks for spotting this!

[mattwoodrow]

Just to confirm, the error is that we're using the border-box for the document element here. Instead it should be the snapshot containing block size similar to when we do this for the old DOM here.

Yes, exactly. Thank you!