Add HTML-in-Canvas APIs

[foolip]

Handwavy things that need fleshing out are marked with 👋

• [ ] At least two implementers are interested (and none opposed):
  • Chromium
  • …
• [ ] Tests are written and can be reviewed and commented upon at:
  • …
• [ ] Implementation bugs are filed:
  • Chromium: https://issues.chromium.org/u/1/hotlists/6783002
  • Gecko: …
  • WebKit: …
  • Deno (only for timers, structured clone, base64 utils, channel messaging, module resolution, web workers, and web storage): …
  • Node.js (only for timers, structured clone, base64 utils, channel messaging, and module resolution): …
• [ ] Corresponding HTML AAM & ARIA in HTML issues & PRs:
• [ ] MDN issue is filed: …
• [ ] The top of this comment includes a clear commit message to use.

(See WHATWG Working Mode: Changes for more details.)

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/canvas.html ( diff ) /index.html ( diff ) /indices.html ( diff ) /infrastructure.html ( diff ) /references.html ( diff ) /rendering.html ( diff )

[foolip]

@Kaiido thank you for the review! I've fleshed things out more, renaming to drawHTMLElement() (because drawElement() will probably not be workable in WebGL) and adding the layoutsubtree attribute.

There's still some handwaving going on of course, in particular what causes the subtree to be laid out but not painted.

[foolip]

I've fleshed this out some more now, in particular the hit testing.

[foolip]

Thanks for the review @progers! I've left two comments unresolved where I'd like more feedback.