Suggest extending support for aria-expanded to radios

[36degrees]

What

Make the case for extending support for aria-expanded to elements with the radio role in the ARIA spec.

Why

The current working draft of ARIA 1.2 extends support for aria-expanded to checkboxes, but not to radios. We think there is a valid case for a radio button revealing additional content, and believe that using aria-expanded is a good way to expose this behaviour to assistive technologies.

If we can make the case for extending support to radios as well, we can then raise bug reports with assistive tech vendors to make sure the expanded state is communicated reliably.

Who needs to know about this

Developers, technical writer

Further detail

Helps resolve the following issues:
#979
#1972
#1988
#1989

Done when

• Initial case written up
• Raise as an issue in w3c/aria repo
• Any follow-up questions answered

[36degrees]

I made an initial attempt at trying to write this up back in November last year:
https://gist.github.com/36degrees/0b3a6047ad7bc2e6575b7e7cba5b659c

[36degrees]

Posted at w3c/aria#1404