[Popup spec] Specify hide event sequence

[melanierichards]

On MicrosoftEdge/MSEdgeExplainers#450, @JanMiksovsky said:

I think it'd be helpful to add an example describing the sequence of events raised for the hide operation, in the same way the KeyboardEvent sequence documents the result of a key press. The event sequence could indicate:

• Relative ordering of blur and hide events. For popups that can have the focus, I assume they'd see blur occur first, then hide?
• Relative ordering of events across a stack of popups being dismissed. I assume the topmost popup gets the (non-bubbling?) hide event first, then the next one, up the hierarchy.
• Relative ordering of hide events and the actual removal of the popup from view: do all popups being hidden get the hide event, then the popups disappear?

On this topic, I notice that HTMLDialogElement doesn't define a show event, but that doesn't mean one wouldn't be useful. Document, for example, defines events like load and visibilitychange that can be used when a document is opened, so I thought some consideration could be given to defining a show event for popups.

[github-actions]

There hasn't been any discussion on this issue for a while, so we're marking it as stale. If you choose to kick off the discussion again, we'll remove the 'stale' label.

[mfreed7]

I believe this issue has been handled via the landed popover spec. I'd like to close it. If you disagree, please feel free to re-open with a comment about what's still missing.