Interactive accessible canvas with multiple controls

Attached is a quick and dirty mockup of an interactive accessible canvas with multiple UI controls (Tested in Safari, not in other browsers yet)

It is not an inordinate amount of work to hook up the focus, blur and click events for each UI control (keeping mouse and keyboard interactions in sync); if browsers support the 'Shadow DOM' concept natively, it would be easy for authors to have accessible custom canvas controls.

Thanks
Frank Olivier