Re: Reasons of using Canvas for UI design

Rich Schwerdtfeger
CTO Accessibility Software Group

public-canvas-api-request@w3.org wrote on 08/15/2011 11:41:20 AM:

> From: David Singer <singer@apple.com>
> To: Richard Schwerdtfeger/Austin/IBM@IBMUS
> Cc: paniz alipour <alipourpaniz@gmail.com>, Cynthia Shelly
> <cyns@microsoft.com>, Steve Faulkner <faulkner.steve@gmail.com>,
> Frank Olivier <Frank.Olivier@microsoft.com>, Canvas
<public-canvas-api@w3.org>
> Date: 08/15/2011 11:42 AM
> Subject: Re: Reasons of using Canvas for UI design
> Sent by: public-canvas-api-request@w3.org
>
> On Jul 29, 2011, at 16:04 , Richard Schwerdtfeger wrote:
>
> 2. Now the we have these objects a screen reader or screen magnifier
> needs to know there location and bounds on the drawing surface.
> Unlike HTML, as a default, that information is not provided.
> And you are assuming it always exists; I am not sure it does,
> particularly in the cases where people use canvas to do 'new' UIs.
> - By mapping a path to a fallback element the browser can use the
> information to fill the bounds of the object to the accessibility
> API bounds. The browser has all the path transformation information
> to do the job
> All true -- if the assumption holds.

I am not sure what is missing. Are you concerned about a coding error? That
can always happen.

> With the basic plumbing in place now we can have the discussion on
> how you make something accessible and there are multiple strategies
> that apply. The solution depends on the problem and like in HTML
> content (this is not limited to canvas) the author may need to
> provide an alternative rendering based on the persons ability. So,
> spending our time defining different use cases is a bit of a red
> herring in that we can go through an exhaustive list of these and
> still come back to the basic plumbing problem we are trying to address
here.
> No, I disagree, I think. I think it quite possible you'll "miss",
> possibly by only a little.  But a miss is as good as a mile, as they say.

Being able to support the basic accessibility APIs is essential. Right now
we do not have that. The need to indicate where an object is on the drawing
surface is an essential requirement.

I agree that going beyond what is there today is a good thing and I agree
we will in fact miss things but that is for an entirely separate and
lengthy research project. We have already begun that in IBM, for example,
as we have lots of complex visualizations used in information management.
We pushed much of this to ARIA 2.0 for SVG as it is a big project.

What we need to avoid here is the statement that "well you have not fully
boiled the ocean so you can't do anything." We do know that the very basic
need to identify where objects are must be met. Tieing them to hit testing
as we have done on every OS to date is a logical step to having the author
avoid additional work. All GUI OS platforms today provide for this basic
capability and this was done without boiling the ocean.

I am more than happy to work with you and the SVG team on digging the
entire complex drawing accessibility effort and have already started
looking at SVG accessibility with Doug Schepers.

Rich
>
> David Singer
> Multimedia and Software Standards, Apple Inc.