WAI-ARIA listbox and custom component support

[RobertBColton]

The clipboard API in its current form is largely designed around raw text clipboard actions. I have actually found that it does not scale well for custom components.

Take, for example, the WAI-ARIA listbox example: https://www.w3.org/TR/wai-aria-practices/examples/listbox/listbox.html

If we attempt to implement clipboard events on such a component they will not work with the current drag and drop API. The reason for this is because some browsers like Chrome add user-select: none; to elements with draggable="true" to prevent the text from being selected. Sometimes it's not the browser doing it, but the CSS author, as it can be desirable to disable text selection when dragging certain kinds of content. The ambiguity of the clipboard API doesn't clarify whether the list should still receive clipboard events.

https://bugs.chromium.org/p/chromium/issues/detail?id=754593

Perhaps the spec could be expanded to include support for such functionality?