Intent to Ship: CSS anchor positioning with transforms

[Morten Stenshorne]

Contact emails

mste...@chromium.org

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

Web Feature ID

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?

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.