The spec was updated so that ::backdrop should inherit from originating element. This will allow CSS variables to work properly in ::backdrop selectors. See existing WPT for test case: https://wpt.fyi/results/html/semantics/interactive-elements/the-dialog-element/backdrop-inherits.html
https://searchfox.org/wubkat/rev/85e40ad30a15e2dfcda4ebad64ed7f41292908a4/Source/WebCore/rendering/updating/RenderTreeUpdaterGeneratedContent.cpp#203-204 Should be as easy as changing `&renderer.view().style()` to `&renderer.style()` on that line (and the related comment).
I think Keith has fix for this in his local branch: https://github.com/keithamus/WebKit/commit/09077ac5976fea157c74dd161c7e49f511157477#diff-7f18480073b63da9fd4d75c26e4e35d003a101498030d45587ab9b5241b2e2bf It just needs to be push on WebKit origin.
Yep I've got a patch. I'm first resyncing the web platform tests for dialog (see https://bugs.webkit.org/show_bug.cgi?id=263838 & https://github.com/WebKit/WebKit/pull/19682).
<rdar://problem/117949961>
Committed 270246@main (d23e04b12f79): <https://commits.webkit.org/270246@main> Reviewed commits have been landed. Closing PR #20007 and removing active labels.