Contact emails
kbabb...@microsoft.com<mailto:kbabb...@microsoft.com>

Specification
https://www.w3.org/TR/css-color-5/#resolving-rcs

Design docs
https://docs.google.com/document/d/1568wVjrIRbrU9_O37gPu10cj0CDWRiAc6ZMk9t0JpXs/edit

Summary
Allow relative colors in CSS (using the 'from' keyword) to use 'currentcolor' 
as a base. This will make it easy for web developers to set complementary 
colors, based on an element's text color, for that element's borders, shadows, 
backgrounds, etc.

Blink component
Blink>CSS<https://bugs.chromium.org/p/chromium/issues/list?q=component:Blink%3ECSS>

TAG review

https://github.com/w3ctag/design-reviews/issues/894
TAG review status

Satisfied. The link above is for Relative Color Syntax in general. Tests for 
currentcolor cases were added as part of the discussion before the TAG signed 
off on the review; I interpret that to mean that they're satisfied with this 
use case.


Risks

Interoperability and Compatibility
Interoperability: Relative Color Syntax is a focus area for Interop 2024, and 
inclusion of currentcolor is well covered by existing WPTs, so the risk of 
other engines not converging on an interoperable implementation is low.

Compatibility: The only risk here is that enabling currentcolor support will 
"light up" color declarations that are being rejected at present. Total usage 
of Relative Color Syntax on the Web (including currentcolor or otherwise) is 
~0.09% of page loads as of May 1, 2024[1]. I haven't done an analysis of 
currentcolor in RCS, but given that no major engine supported it as of that 
date, I would expect it to be a tiny fraction of those. [1] 
https://chromestatus.com/metrics/feature/timeline/popularity/4632


Gecko: Positive (https://github.com/mozilla/standards-positions/issues/841) 
Implementation bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1893966

WebKit: Shipped/Shipping (https://bugs.webkit.org/show_bug.cgi?id=245970) 
Changes landed May 13.

Web developers: Positive 
(https://github.com/web-platform-tests/interop/issues/426) This feature is part 
of Interop 2024.

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?
None


Debuggability
Covered by existing DevTools support for debugging CSS properties.


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-color?label=master&label=experimental&aligned&view=interop&q=label%3Ainterop-2024-relative-color


Flag name on chrome://flags
None

Finch feature name
CSSRelativeColorSupportsCurrentcolor

Requires code in //chrome?
False

Tracking bug
https://issues.chromium.org/issues/325309578


Estimated milestones
Shipping on desktop
129

Shipping on Android
129

Shipping on WebView
129


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).
None

Link to entry on the Chrome Platform Status
https://chromestatus.com/feature/5307971793059840?gate=6194544847880192

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

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