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

[Ryosuke Niwa]

Sorry, the original email had lots of typos. I've fixed them below:

On Mon, Oct 14, 2013 at 2:35 PM, Ryosuke Niwa <rniwa at webkit.org> wrote:

> On Mon, Oct 14, 2013 at 2:28 PM, Rik Cabanier <cabanier at gmail.com> wrote:
>
>> On Mon, Oct 14, 2013 at 1:31 PM, Timothy Hatcher <timothy at apple.com>wrote:
>>
>>> On Oct 14, 2013, at 12:43 PM, Rik Cabanier <cabanier at gmail.com> wrote:
>>>
>>> Also, how would your suggestion tell the UA about what areas are
>>> associated with the elements? What happens if an element is no longer
>>> focused? The ring is drawn into the canvas bitmap so those pixels have to
>>> be regenerated.
>>>
>>>
>>> Focus rings are usually larger than the control they surround. How is
>>> the developer suppose to know the pixel padding needed for each platform's
>>> focus ring? Guess and hope for the best?
>>>
>>
>> Why would he need to know this? Is it for the path that describes the
>> ring?
>>
>
> Isn't focus ring drawn on the canvas?  If so, it's important that the
> focus ring fits within the canvas. e.g. consider focusing an element of
> 100px by 100px inside a canvas of the same size.  If the focus ring were to
> be drawn around the element that currently has focus, then the entire focus
> ring would be drawn outside of the visible region.
>
> Would drawing the system focus ring taint the canvas pixels? (Drawing form
>>> controls into canvas via SVG images and <foreignObject> has been considered
>>> taint worthy because it could leak the user's UI theme.)
>>>
>>
>> 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.
>
> - R. Niwa
>
>
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