Add an example disclosure widget without the definition list

[DavidMacDonald]

There are times when a definition list may not be the best semantics. Consider a simple example with a

<button aria-expanded="false">[Trigger title]</button>
<p style="display:none;">Content</p>

Is aria-controls really necessary when the content immediately follows the trigger? It causes additional complexity and burden on the author of choosing unique ids ...

The other example I see a lot of in the wild is for a heading to be expandable.

<h3><button aria-expanded="false">[Trigger title]</button></h3>
<p style="display:none;">Content</p>

[mcking65]

@DavidMacDonald,

Is there anything about the example page that implies you can't simply remove the dl and have asingle, free-standing button? I'd be happy to modify the description or accessibility notes if there is anything that implies the dl is essential.

I think we cover the collapsable heading approach in the accordion pattern, which I should list in similar examples. BTW, the accordion is going to be re-built without dl (see #815).

About aria-controls ... It's purpose, effects, and requirements are being discussed in a variety of places, e.g., w3c/aria#531. The disclosure will certainly work for screen reader users without aria-controls. However, I think we will wait until we have more clarity at the spec level before deciding whether or not to change anything in the examples that use it.

Personally, I see 1 existing benefit and several potential benefits to using aria-controls. Today, it can be helpful to automated testing, such as the regression testing we are implementing for the APG. I would also love to have simple and user friendly exploitation of it by screen readers. For instance, when reading the expanded content, I'd love to be able to easily jump the reading cursor back to the controlling button from any point in the controlled container with a general purpose undo/go-back type of quick key. I definitely would not want a key dedicated to that purpose, however. My brain already has too many thousands of key commands taking up space that would be better used for other things.