LGTM1 There is some discussion in https://github.com/mozilla/standards-positions/issues/1302 about whether this feature triggers more layouts, which it does not IIUC. But if there is more feedback from Mozilla on this and some changes are needed for Gecko to avoid extra layout work, we should adjust the spec and implementation as needed.
On Thu, Oct 23, 2025 at 8:16 AM Morten Stenshorne <[email protected]> wrote: > *Contact emails* > [email protected] > > *Explainer* > *No information provided* > > *Specification* > https://drafts.csswg.org/css-anchor-position-1/#anchor-position-size > > *Summary* > When an anchor-positioned element is tethered against an anchor that has a > transform (or is contained by something with a transform), resolve anchor() > and anchor-size() functions against the bounding box of the transformed > anchor. > > *Blink component* > Blink>Layout > <https://issues.chromium.org/issues?q=customfield1222907:%22Blink%3ELayout%22> > > *Web Feature ID* > anchor-positioning <https://webstatus.dev/features/anchor-positioning> > > *Motivation* > https://drafts.csswg.org/css-anchor-position-1/#anchor-position-size says > that transform effects on an anchor should affect the anchor box, so that > anchor-positioned elements may be positioned with regards to where an > anchor is on screen. This chimes well with how scroll offsets are also > taken into account. https://drafts.csswg.org/css-anchor-position-1/#scroll > This > behavior is crucial for creating sophisticated UI effects where elements > need to remain logically connected while one of them is being transformed. > Consider a tooltip that points to a button. If the button rotates or scales > on hover, you want the tooltip to move along with it, maintaining its > relative position. > > *Initial public proposal* > *No information provided* > > *TAG review* > *No information provided* > > *TAG review status* > Pending > > *Risks* > > > *Interoperability and Compatibility* > *No information provided* > > *Gecko*: No signal ( > https://github.com/mozilla/standards-positions/issues/1302) > > *WebKit*: No signal ( > https://github.com/WebKit/standards-positions/issues/558) > > *Web developers*: No signals > > *Other signals*: > > *WebView application risks* > > Does this intent deprecate or change behavior of existing APIs, such that > it has potentially high risk for Android WebView-based applications? > *No information provided* > > > *Debuggability* > *No information provided* > > *Will this feature be supported on all six Blink platforms (Windows, Mac, > Linux, ChromeOS, Android, and Android WebView)?* > Yes > > *Is this feature fully tested by web-platform-tests > <https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md>?* > Yes > > https://wpt.fyi/results/css/css-anchor-position?label=master&label=experimental&aligned > > *Flag name on about://flags* > *No information provided* > > *Finch feature name* > CSSAnchorWithTransforms > > *Rollout plan* > Will ship enabled for all users > > *Requires code in //chrome?* > False > > *Tracking bug* > https://issues.chromium.org/issues/382294252 > > *Estimated milestones* > Shipping on desktop 144 > Shipping on Android 144 > Shipping on WebView 144 > > *Anticipated spec changes* > > Open questions about a feature may be a source of future web compat or > interop issues. Please list open issues (e.g. links to known github issues > in the project for the feature specification) whose resolution may > introduce web compat/interop risk (e.g., changing to naming or structure of > the API in a non-backward-compatible way). > *No information provided* > > *Link to entry on the Chrome Platform Status* > https://chromestatus.com/feature/5201048700583936?gate=5152239350054912 > > *Links to previous Intent discussions* > Intent to Prototype: > https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAKWZFm6cenwaNiH0YEpJae2n%3DfWz7O553%3D9fKSukBL_KhvUK0A%40mail.gmail.com > > > This intent message was generated by Chrome Platform Status > <https://chromestatus.com/>. > > -- > You received this message because you are subscribed to the Google Groups > "blink-dev" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion visit > https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAKWZFm7qjp6xQ2TX2jSFaXszEZnyBSKA-DSddU4B2P4mKLU4GQ%40mail.gmail.com > <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAKWZFm7qjp6xQ2TX2jSFaXszEZnyBSKA-DSddU4B2P4mKLU4GQ%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "blink-dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAARdPYdb6iroDcWtbBDUNPoTF8aPQ24%3D8tex2_L%3DUPJVMDBhLg%40mail.gmail.com.
