https://github.com/web-platform-tests/wpt/blob/master/css/css-will-change/will-change-fixpos-cb-contain-1.html
This is possibly already done in https://bugs.webkit.org/show_bug.cgi?id=224742 but I am fine if this bug covers it (and in fact my change may only be a subset of this bug).
<rdar://problem/77958378>
Rob, I'm tentatively assigning this to you. Relevant code is here: https://webkit-search.igalia.com/webkit/rev/7c76a6e054902182b30fd3ce7f3a08f507dc1f1f/Source/WebCore/rendering/style/WillChangeData.cpp#63-78 Adding the property here will cause it to create a containing block for both position: fixed & position: absolute cases. Please let me know if you have any questions.
Created attachment 428784 [details] Patch
Created attachment 428789 [details] Patch
Created attachment 428803 [details] Patch
Comment on attachment 428803 [details] Patch View in context: https://bugs.webkit.org/attachment.cgi?id=428803&action=review > Source/WebCore/ChangeLog:3 > + will-change: contain should create a containing block I think the CSS stacking context change is important to mention in the main message and in LayoutTests/ChangeLog as well. > LayoutTests/TestExpectations:4926 > +webkit.org/b/208988 imported/w3c/web-platform-tests/webxr/xrWebGLLayer_opaque_framebuffer_stencil.https.html [ Skip ] nit: unrelated change
You'll probably need to rebase on top of bug 225443 btw (sorry for the conflict!).
Created attachment 428820 [details] Patch
Comment on attachment 428803 [details] Patch View in context: https://bugs.webkit.org/attachment.cgi?id=428803&action=review >> Source/WebCore/ChangeLog:3 >> + will-change: contain should create a containing block > > I think the CSS stacking context change is important to mention in the main message and in LayoutTests/ChangeLog as well. Done. >> LayoutTests/TestExpectations:4926 >> +webkit.org/b/208988 imported/w3c/web-platform-tests/webxr/xrWebGLLayer_opaque_framebuffer_stencil.https.html [ Skip ] > > nit: unrelated change This is a vi(m) setting problem that comes up from time to time, I think I figured it out. Done!
Committed r277580 (237807@main): <https://commits.webkit.org/237807@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 428820 [details].
(In reply to Rob Buis from comment #10) > Comment on attachment 428803 [details] > Patch > > View in context: > https://bugs.webkit.org/attachment.cgi?id=428803&action=review > > >> Source/WebCore/ChangeLog:3 > >> + will-change: contain should create a containing block > > > > I think the CSS stacking context change is important to mention in the main message and in LayoutTests/ChangeLog as well. > > Done. It doesn't matter too much since things are in the details, but that part wasn't done. The main commit message should have been "will-change: contain should create a containing block & a stacking context". Anyway, I'll rename this bug for clarity.