On Thu, Oct 10, 2013 at 6:08 PM, Ryosuke Niwa <rn...@webkit.org> wrote:
> On Thu, Oct 10, 2013 at 1:35 PM, Rik Cabanier <caban...@gmail.com> wrote: >> >> Support (behind runtime flags) has landed in: >>>> - Firefox: https://bugzilla.mozilla.org/show_bug.cgi?id=540456 >>>> - chrome: https://code.google.com/p/chromium/issues/detail?id=261998 >>>> >>>> Focus rings associate elements that are in a canvas tag with areas of >>>> the canvas. >>>> If the user tabs into the hidden element or the accessibility software >>>> selects them, these methods will draw or let the author draw the focus >>>> rings. >>>> >>> >>> How does this API address this use case? It seems like each Web app >>> needs to explicitly opt-in and manually draw focus ring? >>> >> >> That is correct. This is code that the canvas developer needs to >> implement. >> >> I'm not sure if that's a good accessibility API given that many authors >>> don't even use most basic accessibility feature such as ARIA roles. >>> >> >> There's not much we can do about this. However, for authors that DO want >> to provide this, there's is currently no way to provide accessibility for >> canvas. >> >> >>> >>> e.g. why can't UA automatically draw focus ring on top of the canvas? >>> >> >> The problem is that the UA doesn't know what part of the canvas area >> corresponds with the hidden element. This API is designed to make that >> association >> > > Why can't authors provide that information by placing elements at the area > it should be displayed instead? > Place invisible elements on top with absolute positioning? That seems error prone + you'd constantly have to change the DOM Also, the focus area is not always rectangular. For an example see http://dmazzoni-google.github.io/canvas-focus-ring-demo/ (You will need chorme canary or latest firefox nightly with focusrings turned on) > > >> Also, the spec seems to indicate that the physical (rendered) position >>> of an element can change dynamically without UA being notified. >>> How are ATs supposed to inform users of the ordering of those focusable >>> elements? >>> >> >> I'm unsure I follow. Can you elaborate? >> > > How are ATs supposed to know the visual ordering of elements if authors > are only updating elements' positions by calling drawSystemFocusRing when > they are focused is my question. To put it another way, ATs need to know > where elements appear in order to let user move the focus onto those > elements. > What is an AT? :-) You don't call drawSystemFocusRing when an element is focused. You *always* call it and if it is focused, a ring will be drawn. In all cases, the accessibility software is notified of the area.
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