283295 2024-11-18 04:01:33 -0800 [css-anchor-position-1] Trigger evaluation of default anchor when it's used for anchor-center 2025-02-18 09:43:29 -0800 1 1 1 Unclassified WebKit CSS WebKit Nightly Build Unspecified Unspecified RESOLVED FIXED InRadar P2 Normal --- 1 plampe koivisto bfulgham kiet.ho koivisto simon.fraser webkit-bug-importer zalan oldest_to_newest 2075800 0 plampe 2024-11-18 04:01:33 -0800 While working on anchor-center I've discovered that in some cases the resolution of anchoring is not done and therefore the anchored elements are not being linked to anchors. In other words, in some cases it's impossible to fetch default anchor element (https://drafts.csswg.org/css-anchor-position-1/#default-anchor-element) of given element. Example 1: In case of https://github.com/web-platform-tests/wpt/blob/master/css/css-anchor-position/anchor-center-offset-change.html the position-anchor is set to --anchor (that is a valid anchor) and the left is set to anchor(--unknown right, 0px) - in this case the anchor resolution should succeed and the internal anchoring-related data structures should store the relation between anchor and the anchor target. Example 2: In case of https://github.com/web-platform-tests/wpt/blob/master/css/css-anchor-position/anchor-center-scroll.html the position-anchor is set to --anchor (that is a valid anchor) and yet no inset properties are using anchor() function. In this case the anchor resolution should still succeed and the internal anchoring-related data structures should store the relation between anchor and the anchor target. 2075840 1 webkit-bug-importer 2024-11-18 08:35:10 -0800 <rdar://problem/140124449> 2086703 2 kiet.ho 2025-01-13 02:15:18 -0800 I haven't dived into this, so some speculation: We gather: * all anchor references - anchor name used in anchor() or anchor-size(), or elements with anchor-center * all anchors - elements with anchor-name specified. Then we attempt to resolve the anchor references, using the gathered list of anchors. I think the code right now only looks for anchor references in anchor() and anchor-size(). If an element uses anchor-center and not anchor()/anchor-size(), then the reference isn't caught, even though anchor-center refers to the default anchor. 2089205 3 plampe 2025-01-23 00:05:36 -0800 That's correct. IMO we should store all the anchor-references used (along with position-anchor) or at least the default one. 2090000 4 kiet.ho 2025-01-27 10:42:11 -0800 Pull request: https://github.com/WebKit/WebKit/pull/39599 2095432 5 koivisto 2025-02-18 02:55:46 -0800 Pull request: https://github.com/WebKit/WebKit/pull/40758 2095479 6 ews-feeder 2025-02-18 09:43:27 -0800 Committed 290534@main (aa6b7858fefa): <https://commits.webkit.org/290534@main> Reviewed commits have been landed. Closing PR #40758 and removing active labels.