NEW304551
CSS anchor positioning with a fixed-positioned anchored element works incorrectly in the top layer 
https://bugs.webkit.org/show_bug.cgi?id=304551
Summary CSS anchor positioning with a fixed-positioned anchored element works incorre...
Pavel Pomerantsev
Reported 2025-12-20 11:26:42 PST
Created attachment 477806 [details] Chrome (correct) and Safari (incorrect) layouts side by side An element is positioned incorrectly if all of the following are true: * It's anchor-positioned (has a `position-anchor` set to an existing element). * It has `position: fixed`. * Both the element and its anchor are in the top layer. See example with a modal dialog and a fullscreen element (both examples of top layer usage): https://codepen.io/pavelp/pen/ByzBKrE Compare layout in latest Chrome (appears to be correct) vs latest Safari TP (appears incorrect). Note: this may or may not be a duplicate of https://bugs.webkit.org/show_bug.cgi?id=289743. Top layer is mentioned there, but it looks like currently all the top-layer tests in https://wpt.fyi/results/css/css-anchor-position?label=experimental&label=master&aligned are passing in Safari TP, so this might be a case for which a web platform test doesn't exist yet.
Attachments
Chrome (correct) and Safari (incorrect) layouts side by side (410.18 KB, image/png)
2025-12-20 11:26 PST, Pavel Pomerantsev 		no flags
Details
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Radar WebKit Bug Importer
Comment 1 2025-12-27 11:27:12 PST
<rdar://problem/167239379>
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