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

[Rik Cabanier]

On Mon, Oct 14, 2013 at 2:38 PM, Ryosuke Niwa <rniwa at webkit.org> wrote:

> 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.
>>
>
True. That sounds like bad design though.
Wouldn't you have the same problem with focusable content in an
"overflow:hidden" element that just fits its child?


>
>> 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.
>>
>
Yes, maybe this should taint.  Dominic, what do you think?
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