There has been extensive debate (e.g. #410 and #417, plus numerous OpenUI meeting discussions) about the <popup> element proposal. That proposal got "stuck" on what appear to be some rather fundamental questions about the semantics and associated AX roles for this new element.

As a result of these issues, we've put together a fresh proposal for a new way to achieve (roughly) the same list of goals. This new proposal introduces an HTML attribute syntax that allows any element to be made into a "popup" that gets rendered on top of all other page content:

<div popup=popup>I'm rendered on top!</div>

Here, the popup attribute is set to a value of popup (other values include hint and async) to indicate "popup" behaviors should be applied. That includes:

• Rendering in the top layer
• Automatically-provided light-dismiss and one-at-a-time behavior. (These depend on the value of the popup attribute.)
• Accessible by default

Additionally, another HTML attribute, triggerpopup, can be used for declarative triggering, so that this API can be used without any JavaScript required:

<button id=picker-button triggerpopup=datepicker>Pick a date</button> 
<my-date-picker role=dialog id=datepicker popup=popup hidden>
  ...date picker implementation...
</my-date-picker>

In this case, the <my-date-picker> component starts out hidden, but when the <button> is clicked, the UA removes hidden from <my-date-picker> and the date picker is shown. As with all popups, once the user clicks outside, hits Esc, etc., the UA will light-dismiss it by adding back the hidden attribute.

Please take a look at the new proposal, and add your comments here to this issue. Pull requests for changes are also great.