RE: hit testing and retained graphics

Well said Matt! I look forward to the IA2 version.

Rich Schwerdtfeger
CTO Accessibility Software Group

From:	Matt May <>
To:	Silvia Pfeiffer <>, Richard
Cc:	Charles McCathieNevile <>, Cameron McCormack
            <>, Charles Pritchard <>, Cynthia
            Shelly <>, ""
            <>, ""
            <>, "Tab Atkins Jr."
            <>, "" <>,
            "" <>,
            "" <>,
            "" <>,
Date:	06/28/2011 11:17 AM
Subject:	RE: hit testing and retained graphics
Sent by:

-----Original Message-----
From: [] On Behalf Of Silvia Pfeiffer
Sent: Tuesday, June 28, 2011 7:35 AM
Subject: Re: hit testing and retained graphics

>On Mon, Jun 27, 2011 at 10:41 PM, Richard Schwerdtfeger
<> wrote:
>> So, one of the main reasons that developers use canvas is because it is
>> close to the type of API you see in Windows GDI and has been around
>> before 1990. SVG, while having many benefits will take a long time to be
>> adopted by the development community in mass. Meanwhile, canvas will be
>> by developers. When a cross-platform 2D API was created for the Web it
>> like a boom for developers. This is what they are used to. Once the cat
>> let out of the bag you can't stop developers from using it. It is
>> in all the browsers. However, now the fact that it is attached to HTML
>> the runway is shortening to make it accessible we have the JavaScript
>> accessibility problem. It will create a huge black eye on HTML as it is
>> inaccessible. It's use will now need to be prohibited for governments
>> the same way that JavaScript was prohibited for years. The difference
>> we know how to fix it and could do something about it before the problem
>> gets worse.

>What about Adobe Flash in this area? Adobe Flash is used for many of
>the same use cases that canvas is used for. Is Flash more accessible?
>How do they do it? Is Flash prohibited because it's not accessible?

Any shape drawn the a Flash stage (or canvas) can be named, and any named
display object can have an AccessibilityProperties object associated with
it that allows it to be tagged with an accessible name and description, and
other properties including grouping of child objects (forceSimple),
keyboard shortcut, and the ability to hide it from the DOM. Reading order
is handled either explicitly or algorithmically based on x,y coordinates.

Further, any display object or sprite can have an
AccessibilityImplementation object which allows MSAA (soon IAccessible2)
roles and states to be applied and managed, and marshals events through the
accessibility API. Using the Flex SDK, application developers can build
sprites from any kind of graphics they choose, and wire them up to appear
to assistive technology in the same manner as one would expect of an
OS-level control.

The Bespin/Skywriter canvas-as-UI problem, which precipitated most of the
stress over canvas accessibility in the first place, would have been
reasonably well supported by the accessibility support found in Flash
Player 8, which was released in 2005, and at least to some extent by Flash
Player 6, from 2002. I don't think it's necessary to argue the bona fides
of Flash vs. canvas in terms of accessibility, because Flash has some and
canvas has none.

>On a side not: I'm wondering if in the majority of cases we may be
>trying to achieve the impossible. For example, you may try as hard as
>you want, but you will not achieve it that a blind user will be able
>to drive a car with nothing but machine support.

Actually, that's inaccurate. In fact, the technology is so close at hand
that the state of Nevada has approved driver-less cars on public roads. I
believe you have a business relationship with the company that's
spearheaded the effort.

It says something to me that this supposedly impossible problem is actually
being tackled while HTML struggles not to have to apply semantics to shapes
on a canvas.

>Even with the best
>technology that will communicate what is happening around them, it
>will be impossible to provide a description of the visible environment
>sufficiently timely to make it possible/safe to drive without seeing.
>What is our solution for the impossible situation?

This is not an intractable problem. This is not even close to an
intractable problem. It has been a subject of research in accessibility for
decades. The only thing missing in solving this problem is the will of
those producing these specifications to address it. Or even to listen to
some people who have been focused on this issue for a while, like Rich.


Received on Tuesday, 28 June 2011 17:16:18 UTC