Wotcher TAG!

I'm requesting a TAG review of the baseline-source CSS property.

The baseline-source property allows web developers to specify if an inline-level box should use the first or last baseline for alignment within an line-box.

Today the default behaviour is confusing for web developers. Consider:

test <div style="display: inline-block;">line1<br>line2</div>
test <div style="display: inline-flex;">line1<br>line2</div>

The "inline-block" will align to the last baseline, and the "inline-flex" will align to the first baseline.

baseline-source: auto is the existing (confusing) behaviour.

Web developers can specify baseline-source: first or baseline-source: last to directly determine how they want these boxes to align within a line-box.

See demo here: https://twitter.com/bfgeek/status/1612518098611089408

• Explainer¹ (minimally containing user needs and example code): [url] See above
• Specification URL: [spec url]
• Tests: [wpt folder(s), if available]
• User research: [url to public summary/results of research]
• Security and Privacy self-review²: [url]
• GitHub repo (if you prefer feedback filed there): [url]
• Primary contacts (and their relationship to the specification):
  • @bfgeek (Implemetor) , @fantasai (Spec Editor)
• Organization(s)/project(s) driving the specification: Google
• 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/5730575560736768

Further details:

• I have reviewed the TAG's Web Platform Design Principles
• Relevant time constraints or deadlines: Implementation complete.
• The group where the work on this specification is currently being done: CSSWG
• The group where standardization of this work is intended to be done (if current group is a community group or other incubation venue): CSSWG
• Major unresolved issues with or opposition to this specification: No major issues.
• This work is being funded by: Blink implementation is being done by Google.

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