Re: Please vote on the canvas accessibility proposal

trimmed CC list


Hi Sylvia,

if the content of the canvas sub tree is exposed to AT and focusable
elements are included in the tab order, by default, then regardless of what
browser an AT user has they will get get this content. Regardless of what
relationship any interactive content has to the canvas content, keyboard
only users will be able to tab into and interact with focusable elements.

So for example if I am a keyboard only user and encounter  a canvas element
that includes a link or 2 links or many that are not associated with the
displayed canvas, because they are "fallback" then focus will be lost to the
users,  end result= confusion

or  I am an AT user accessing the page *using* Firefox, I encounter the
message "your browser does not support canvas get Firefox" end
result=confusion.

regards
stevef


On 23 February 2010 14:59, Silvia Pfeiffer <silviapfeiffer1@gmail.com>wrote:

>  On Wed, Feb 24, 2010 at 12:41 AM, Steven Faulkner
> <faulkner.steve@gmail.com> wrote:
> > Hi Sylvia,
> >>  - ATs will read content like 'please upgrade your browser' instead of
> >> useful text.
> >
> >>Where does that come from? Wouldn't they just see the canvas element
> >>and try to do something useful with it?
> >
> > This is an example of the sort of content  developers are already
> including
> > inside the canvas element. I looked at www.canvasdemos.com I could not
> > find ANY with fallback (most provided zero fallback) that would be useful
> > for AT users:
> >
> >
> > http://concentriclivers.com/slippymap.html
> > <canvas id="map" width="500"
> height="500"  onmousedown="mouseDown(event);"
> > onmousemove="mouseMove(event);"   onmouseup="mouseUp();"
> > onmouseout="mouseOut();">Your  browser doesn't support canvas
> > elements.</canvas>
> > http://labs.jam3.ca/wp-content/uploads/2010/02/canvasVoxels.html
> >
> > <canvas id="myCanvas" width="100" height="100">
> >               Your browser does not support the canvas
> >       </canvas>
> >       <audio src="houseofcards.mp3" autoplay="autoplay" loop="2000">
> >               Your browser does not support the audio element.
> >       </audio>
> >
> > http://www.snappymaria.com/canvas/FunctionPlotter.html
> > <canvas onmouseout="releaseCanvas();" onmouseup="releaseCanvas();"
> > onmousemove="slideCanvas(event);" onmousedown="clickCanvas(event);"
> > height="480" width="640" id="mainCanvas">
> > It looks like your browser does not support Canvas.
> > Try FireFox, Chrome, Opera, or Safari instead.
> > </canvas>
> >
> > regards
> > stevef
> >
>
> OK, but that is fallback content for browsers who do not support the
> elements at all. There is no need to create accessibility information
> for data that the browser cannot display anyway. The text inside is
> the same text for anyone running an old or unsupported browser and it
> would be part of the normal text on a page, so read out by AT,
> wouldn't it?
>
> Regards,
> Silvia.
>



-- 
with regards

Steve Faulkner
Technical Director - TPG Europe
Director - Web Accessibility Tools Consortium

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