Customizable select element

[josepharhar]

こんにちは TAG-さん!

I'm requesting a TAG review of customizable select element.

Customizable select is an HTML parser change and a CSS property to make the select element render additional content and be fully stylable. Here is a basic example:

<select>
  <button>
    <selectedoption></selectedoption>
  </button>
  <option><img src="...">Orange</option>
  <option><img src="...">Banana</option>
</select>
<style>
select, ::picker(select) {
  appearance: base-select;
}
</style>

• Explainer¹: https://open-ui.org/components/customizableselect/
• Specification: List of spec PRs in the issue description here: Customizable <select> element whatwg/html#9799
• WPT Tests: https://wpt.fyi/results/html/semantics/forms/the-select-element/customizable-select
• User research:
• Security and Privacy self-review²: TODO
• GitHub repo:
  • https://github.com/whatwg/html
  • https://github.com/w3c/csswg-drafts
  • https://github.com/openui/open-ui
• Primary contacts:
  • Joey Arhar (@josepharhar) Google
• Organization/project driving the specification: Google, Microsoft, OpenUI community group
• Multi-stakeholder support³:
  • Chromium comments: Yes
  • Mozilla comments: Customizable select element mozilla/standards-positions#1060
  • WebKit comments: Customizable select element WebKit/standards-positions#386
  • Feedback from developers is present in most of the OpenUI issues about this project: https://github.com/openui/open-ui/issues?q=is%3Aissue+label%3Aselect
• Status/issue trackers for implementations⁴: https://chromestatus.com/feature/5737365999976448

Further details:

• I have reviewed the TAG's Web Platform Design Principles
• Relevant time constraints or deadlines:
• The group where the work on this specification is currently being done: WHATWG, CSSWG, and OpenUI CG
• The group where standardization of this work is intended to be done (if different from the current group): WHATWG and CSSWG
• Major unresolved issues with or opposition to this specification:
• This work is being funded by: Google