*Contact emails*
[email protected]

*Explainer*
https://github.com/w3c/csswg-drafts/blob/main/css-conditional-5/named-feature-explainer.md

*Specification*
https://drafts.csswg.org/css-conditional-5/#typedef-supports-named-feature-fn

*Summary*
The named-feature() function allows CSS @supports rules to query for a
small set of specific named features that are not possible to test for
using other @supports mechanisms but which are considered highly valuable
to test for.

*Blink component*
Blink>CSS
<https://issues.chromium.org/issues?q=customfield1222907:%22Blink%3ECSS%22>

*Web Feature ID*
Missing feature

*Motivation*
Sometimes we add new features to CSS where two things are simultaneously
true: first, that CSS authors see high value in writing conditional styles
for whether the feature is supported using @supports, and second, that the
existing mechanisms in @supports don't provide a useful way to test for the
feature.

This provides a way for us to give names to a small number of high-value
features so that CSS authors can test for them in their style sheets.

We will ship initially with a single supported feature, identified by the
anchor-position-follows-transforms keyword.

*Initial public proposal*
https://github.com/w3c/csswg-drafts/issues/3559#issuecomment-1868169502

*TAG review*
https://github.com/w3ctag/design-reviews/issues/1186

*TAG review status*
Issues addressed

*Goals for experimentation*
None

*Risks*


*Interoperability and Compatibility*
*No information provided*

*Gecko*: No signal (
https://github.com/mozilla/standards-positions/issues/1340)

*WebKit*: No signal (
https://github.com/WebKit/standards-positions/issues/600)

*Web developers*: Positive (https://github.com/w3c/csswg-drafts/issues/3559) In
various forums developers have asked questions about how to feature-detect
things in CSS that we couldn't previously offer feature detection for.
While some developers have asked for more powerful feature detection (that
would be difficult for us to provide), this provides a simple solution for
something developers have been asking for.

*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-conditional/at-supports-named-feature-001.html

*Flag name on about://flags*
*No information provided*

*Finch feature name*
CSSSupportsNamedFeatureFunction

*Rollout plan*
Will ship enabled for all users

*Requires code in //chrome?*
False

*Tracking bug*
https://issues.chromium.org/353715317

*Availability expectation*
Hoping that other engines will implement soon after launch in Chrome,
although we haven't seen concrete signs of this yet.

*Adoption expectation*
I'd expect that once this is available it will be quickly become a best
practice for feature detection of future new features that are given
feature names as they roll out to developers.

*Adoption plan*
Adoption is really tied to the adoption of the other features that this is
used to feature-detect.

*Estimated milestones*
Shipping on desktop 150
DevTrial on desktop 146
Shipping on Android 150
DevTrial on Android 146
Shipping on WebView 150

*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/5153932394102784?gate=4891886507261952

*Links to previous Intent discussions*
Intent to Prototype:
https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAG0MU3ih_y_Z1CVCKHCzK1Sq08HxAc3cvqwpPZrc6%3DB%3DPacz6A%40mail.gmail.com


This intent message was generated by Chrome Platform Status
<https://chromestatus.com/>.

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