Add popover=hint

[josepharhar]

Fixes https://github.com/whatwg/html/issues/9776

Explainer: https://open-ui.org/components/popover-hint.research.explainer/#popoverhint-behavior

• [x] At least two implementers are interested (and none opposed):
  • Chrome
  • https://github.com/WebKit/standards-positions/issues/305
  • Supportive: https://github.com/mozilla/standards-positions/issues/965
• [x] Tests are written and can be reviewed and commented upon at:
  • https://wpt.fyi/results/html/semantics/popovers/popover-types-with-hints.tentative.html
• [x] Implementation bugs are filed:
  • Chromium: Implemented
  • WebKit: https://bugs.webkit.org/show_bug.cgi?id=275048
  • Gecko: https://bugzilla.mozilla.org/show_bug.cgi?id=1867743
• [ ] MDN issue is filed: …

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

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/interactive-elements.html ( diff ) /popover.html ( diff )

[nt1m]

I would probably want https://github.com/keithamus/invoker-buttons-proposal to be worked on first before addressing this, as I think it's a building block for this and other declarative attributes.

[mfreed7]

I would probably want https://github.com/keithamus/invoker-buttons-proposal to be worked on first before addressing this, as I think it's a building block for this and other declarative attributes.

So I've significantly updated the popover=hint explainer, and there are a few sections detailing why I believe the functionality described in this PR is independent of the hover-triggering functionality described by the Invokers explainer (note that it was moved to the OpenUI repo). See this section:

• https://open-ui.org/components/popover-hint.research.explainer/#tooltip-lifecycle-behaviors

Indeed both are important bits of functionality, but I'm hoping we can tackle them independently rather than needing to put up another huge spec PR. That didn't work very well for the original Popover spec PR, at least in my opinion.

[josepharhar]

Note to self: this will require additional changes in https://chromium-review.googlesource.com/c/chromium/src/+/5229300 if the corresponding PR to be opened gets merged

[mfreed7]

Gentle ping - any chance we could get an initial review of this PR? @annevk @domenic

[mfreed7]

Conceptually looks good,

Cool, thanks for the review! Sounds like you're supportive of the PR in general? If so, mind marking that on https://github.com/mozilla/standards-positions/issues/965?

though I think the current getStackPosition behavior is not correct / what we want? I might be wrong tho.

See my comment in the review - let's discuss there. I want to understand a bit better.

[mfreed7]

This issue/PR was just discussed at the OpenUI/WHATWG/CSSWG form controls task force meeting, in the context of a more general discussion of the "tooltip" use case. The notes are located here:

https://logs.csswg.org/irc.w3.org/css/2024-07-25/#e1637392

[mfreed7]

Conceptually looks good,

Cool, thanks for the review! Sounds like you're supportive of the PR in general? If so, mind marking that on mozilla/standards-positions#965?

@emilio any thoughts on this one? I.e. adding support (or not) from Mozilla's point of view, for popover=hint?