Review request for CSS Variables

[svgeesus]

Braw mornin' TAG!

I'm requesting a TAG review of CSS Custom Properties for Cascading Variables Module Level 1, (a precise but unwieldy title for what everyone calls CSS Variables). This is a very widely implemented and used specification.

This module introduces cascading variables as a new primitive value type that is accepted by all CSS properties, and custom properties for defining them.

• Explainer¹ (minimally containing user needs and example code): https://developer.mozilla.org/en-US/docs/Web/CSS/Using_CSS_custom_properties
• Specification URL: https://drafts.csswg.org/css-variables/
• Tests: https://wpt.fyi/results/css/css-variables?label=experimental&label=master&aligned
• Security and Privacy self-review²: https://github.com/w3c/csswg-drafts/issues/6808
  • https://drafts.csswg.org/css-variables/#privacy
  • https://drafts.csswg.org/css-variables/#security
• GitHub repo (if you prefer feedback filed there): https://github.com/w3c/csswg-drafts
• Primary contacts (and their relationship to the specification):
  • Tab Atkins, @tabatkins Editor
  • Chris Lilley, @svgeesus Team Contact
• Organization(s)/project(s) driving the specification: all browsers
• Key pieces of existing multi-stakeholder review or discussion of this specification:
• External status/issue trackers for this specification (publicly visible, e.g. Chrome Status):
  • https://chromestatus.com/feature/6401356696911872
  • https://caniuse.com/css-variables

Further details:

• [x] I have reviewed the TAG's Web Platform Design Principles
• Relevant time constraints or deadlines: No particular rush, being readied for a new CR Snapshot
• The group where the work on this specification is currently being done: CSSWG
• Major unresolved issues with or opposition to this specification: 4 open, 47 closed issues:
  • https://github.com/w3c/csswg-drafts/issues/6871
  • https://github.com/w3c/csswg-drafts/issues/6253
  • https://github.com/w3c/csswg-drafts/issues/2515

You should also know that...

This is widely implemented in all browsers (WPT wall of green) and has been for some time. We want to complete a final wide review before the specification (which has been in CR since 2015) advances to Proposed Recommendation.

We'd prefer the TAG provide feedback as (please delete all but the desired option):

🐛 open issues in our GitHub repo for each point of feedback

[LeaVerou]

We looked at this during a breakout today and all looks good to us and we do not see any architectural concerns with the changes since the 2015 CR. Thank you for flying TAG!