I discussed concerns about HTML-in-Canvas a while back as part of this post: https://acko.net/blog/html-is-dead-long-live-html/

Since then I've actually met these two and had to conclude that:

- They didn't have any use-cases in mind that weren't cosmetic

- They don't quite understand how being part of an advertising company shapes how they build and conceive of web tech

- They react quite poorly to reactions that aren't cheerleading

The answer for curved elements was handwaving and "just approximate it with flat projective transforms" which tells you this is not a serious attempt to expose mature UI internals, but just another shiny epicycle on the creaky leviathan that is the HTML5 web api.

The list of features that "automatically work" rests on assumptions that are only valid for minor visual adjustments. The moment you try to use HTML-in-Canvas as a more basic building block, a lot of that falls away.

e.g. Suppose I render a piece of text and then use that as a mask for visual effects. If the browser now draws a text selection highlight into that mask, the text becomes unreadable.