Note: This feature is a bit unusual in that it was implemented behind a flag but not advertised on blink-dev with an I2P or dev trial announcement. I picked it up after initial implementation, got clarity on some open spec issues, and adjusted the implementation to match CSSWG resolutions.
Contact emails [email protected]<mailto:[email protected]> Explainer https://github.com/MicrosoftEdge/MSEdgeExplainers/blob/main/AtRuleFeatureDetection/explainer.md Specification https://drafts.csswg.org/css-conditional-5/#support-definition-at-rules Summary This feature adds an `at-rule()` function to CSS `@supports` which enables authors to feature-detect support for CSS at-rules. Blink component Blink>CSS<https://issues.chromium.org/issues?q=customfield1222907:%22Blink%3ECSS%22> Web Feature ID supports-at-rule<https://webstatus.dev/features/supports-at-rule> Motivation Feature detection is a W3C TAG design principle and a tool that Web authors rely on for graceful degradation of their pages. Currently, the only way for web developers to detect support for CSS at-rules is to use JavaScript. This feature allows at-rule support to be detected using the same `@supports` feature used to detect support for CSS properties. Initial public proposal https://github.com/w3c/csswg-drafts/issues/2463 TAG review https://github.com/w3ctag/design-reviews/issues/1176 TAG review status Issues addressed Goals for experimentation None Risks Interoperability and Compatibility Minimal risks; this feature is purely additive. Gecko: No signal (https://github.com/mozilla/standards-positions/issues/1310) WebKit: No signal (https://github.com/WebKit/standards-positions/issues/565) Web developers: Positive There have been several requests for this feature; some examples: https://github.com/w3c/csswg-drafts/issues/9743 https://ruhr.social/@nilsbinder/112721678680237204 https://mastodon.social/@xro/113106213499516093 https://bsky.app/profile/badrihippo.fosstodon.org.ap.brid.gy/post/3m6vupwqhbkk2 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? N/A Debuggability Exposure in Dev Tools is the same as for existing `@supports` rules. 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/js/supports-at-rule.html?label=experimental&label=master&aligned Flag name on about://flags enable-experimental-web-platform-features Finch feature name CSSSupportsAtRuleFunction Rollout plan Will ship enabled for all users Requires code in //chrome? False Tracking bug https://issues.chromium.org/issues/40211832 Estimated milestones Shipping on desktop 148 DevTrial on desktop 143 Shipping on Android 148 DevTrial on Android 143 Shipping on WebView 148 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 known open issues on `@supports at-rule()` itself. There were some expansions to the feature discussed to test for certain descriptors or context, but the CSSWG resolved to separate these more detailed queries out to a separate feature `@supports-condition`; see discussion at https://github.com/w3c/csswg-drafts/issues/12622. Link to entry on the Chrome Platform Status https://chromestatus.com/feature/5110744177836032?gate=4696535686316032 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/CH4PR00MB2495314F25A2D84629348CC0C047A%40CH4PR00MB2495.namprd00.prod.outlook.com.
