[webkit-dev] Proposal: Add support for focus rings in Canvas 2d

Dominic Mazzoni dmazzoni at google.com
Mon Oct 14 15:02:31 PDT 2013

On Mon, Oct 14, 2013 at 2:50 PM, Rik Cabanier <cabanier at gmail.com> wrote:

> I'm unsure if it should taint the canvas. How much information would be
> leaked that isn't already available through other means?
>>> It may, for example, leak information as to whether user's machine is in
>>> high contrast mode, which is another dimension for finger-printing user.
> Yes, maybe this should taint.  Dominic, what do you think?

If high-contrast mode on Windows was the only concern, I believe it's
already been possible to detect this - see
one example, but there are many other ways to detect it already and it
seems difficult to prevent all of those.

As to the broader discussion, I think that the future plan to add hit
testing to canvas and associating a canvas path with an element in fallback
content will be a potentially better solution. Any assistive technology
would be able to determine the boundaries of any objects within the canvas
in advance, and draw its own focus rings around any application ones if

However, in the meantime I think that drawSystemFocusRing is a great idea
that solves 90% of the common cases easily. It's useful, easy to
understand, and improves accessibility when it is used.

- Dominic
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