Add ToggleEvent.source

[josepharhar]

This adds a new Element attribute to ToggleEvent called source. The ToggleEvent's source attribute is set to the element which invoked the element which the ToggleEvent is being fired on. Sources can be set up as a parameter passed to element.showPopover(), an element with the popovertarget attribute, or an element with the commandfor attribute.

Fixes #9111

• At least two implementers are interested (and none opposed):
  • Chromium
  • Gecko: ToggleEvent source attribute mozilla/standards-positions#1220
  • WebKit: ToggleEvent source attribute WebKit/standards-positions#494
• Tests are written and can be reviewed and commented upon at:
  • Implement ToggleEvent.source web-platform-tests/wpt#52589
• Implementation bugs are filed:
  • Chromium: https://issues.chromium.org/issues/408018828
  • Gecko: https://bugzilla.mozilla.org/show_bug.cgi?id=1968987
  • WebKit: https://bugs.webkit.org/show_bug.cgi?id=293686
• Corresponding HTML AAM & ARIA in HTML issues & PRs: I don't think this needs any ARIA/AAM stuff.
• MDN issue is filed: ToggleEvent.source mdn/content#39723
• The top of this comment includes a clear commit message to use.

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

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/form-control-infrastructure.html ( diff )
/form-elements.html ( diff )
/infrastructure.html ( diff )
/interaction.html ( diff )
/interactive-elements.html ( diff )
/popover.html ( diff )

[domenic]

I haven't kept up with all the command discussions, but didn't we decide never to use the word "invoker" in the public APIs? (I've been a bit disappointed to see it popping up in documentation given that decision, but that's a separate thing...)

I thought we settled on source in CommandEvent.

[nt1m]

source is also what's used for the imperative API: showPopover({source: ...})

[josepharhar]

Thank you both! I renamed it from invoker to source.

[keithamus]

Generally this looks good, and I think it is well motivated. I've done what I'll call a "pseudo editorial review pass" and by my eyes this has no editorial issues.

Some meta commentary that's perhaps worth pointing out: details elements toggling, and dialog.show()/showModal(), all dispatch toggle events where the source will be null. I think that's a little odd, and maybe worth discussing, but I don't see it as problematic to change in a follow-up, or possibly never. For example it might be nice to later add {source} as an argument to show()/showModal().

[josepharhar]

Thanks Keith!

If command invokers make it possible to declaratively toggle a details element in the future, we could make the command attribute invoker element get set as the source of the toggle event. We could also use the summary element as Luke mentioned in the issue thread if that seems valuable, hopefully that's not too hard to spec.

Adding a source argument to show()/showModal() makes sense, but since that argument already does more for popovers I'm not sure that this change alone justifies adding that as a parameter to those methods. If an invoker/source argument is ever added though, we should add it as the source of the toggle event.

[domenic]

Generally looks good, but I think we can do the events betterNope, we can't, I was wrong.

Also, I haven't yet done a final check that all updated algorithms match all their call sites. It looks likely that you got them all, but if you want to double-check that could save us some time.

[josepharhar]

Also, I haven't yet done a final check that all updated algorithms match all their call sites. It looks likely that you got them all, but if you want to double-check that could save us some time.

I just double checked and fixed two of them