LGTM3
On 10/28/25 1:53 p.m., Chris Harrelson wrote:
LGTM2
On Tue, Oct 28, 2025 at 10:44 AM Philip Jägenstedt
<[email protected]> wrote:
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
<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/>.
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