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Re: hit testing and retained graphics

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Wed, 29 Jun 2011 00:35:20 +1000
Message-ID: <BANLkTi=3okTjC=pXKJpxdVR9KEj2-Epayg@mail.gmail.com>
To: Richard Schwerdtfeger <schwer@us.ibm.com>
Cc: Charles McCathieNevile <chaals@opera.com>, Cameron McCormack <cam@mcc.id.au>, Charles Pritchard <chuck@jumis.com>, Cynthia Shelly <cyns@microsoft.com>, david.bolter@gmail.com, Frank Olivier <Frank.Olivier@microsoft.com>, "Tab Atkins Jr." <jackalmage@gmail.com>, Mike@w3.org, public-canvas-api@w3.org, public-html@w3.org, public-html-a11y@w3.org, public-html-a11y-request@w3.org
On Mon, Jun 27, 2011 at 10:41 PM, Richard Schwerdtfeger
<schwer@us.ibm.com> wrote:
> Rich Schwerdtfeger
> CTO Accessibility Software Group
> public-html-a11y-request@w3.org wrote on 06/27/2011 06:20:44 AM:
>> From: "Charles McCathieNevile" <chaals@opera.com>
>> To: Richard Schwerdtfeger/Austin/IBM@IBMUS, "Tab Atkins Jr."
>> <jackalmage@gmail.com>
>> Cc: "Cameron McCormack" <cam@mcc.id.au>, "Charles Pritchard"
>> <chuck@jumis.com>, "Cynthia Shelly" <cyns@microsoft.com>,
>> david.bolter@gmail.com, "Frank Olivier"
>> <Frank.Olivier@microsoft.com>, Mike@w3.org, public-canvas-
>> api@w3.org, public-html@w3.org, public-html-a11y@w3.org
>> Date: 06/27/2011 06:22 AM
>> Subject: Re: hit testing and retained graphics
>> Sent by: public-html-a11y-request@w3.org
>> On Thu, 23 Jun 2011 22:28:32 +0200, Tab Atkins Jr. <jackalmage@gmail.com>
>> wrote:
>> > On Thu, Jun 23, 2011 at 12:56 PM, Richard Schwerdtfeger
>> > <schwer@us.ibm.com> wrote:
>> >>> So normally, I imagine, hit testing would be done either by using
>> >>> isPointInPath() or by custom code looking at a mouse eventís x/y
>> >>> values.
>> >>> I think this proposal doesnít work with isPointInPath(), though, is
>> >>> that
>> >>> right?
>> >>>
>> >> I think it would but we would need to incorporate Z order and a notion
>> >> of the last drawn element to compute which element is on top. The user
>> >> agent would need to manage this.
>> >
>> > You are attempting to recreate a retained-mode API in an
>> > immediate-mode API. Why is "use SVG" not sufficient for this?
>> Because people don't - they use canvas instead. If that were not the case,
>> the whole effort to specify canvas would be solving a theoretical problem.
> 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 since
> 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 used
> by developers. When a cross-platform 2D API was created for the Web it was
> like a boom for developers. This is what they are used to. Once the cat is
> let out of the bag you can't stop developers from using it. It is supported
> in all the browsers. However, now the fact that it is attached to HTML and
> 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 much
> the same way that JavaScript was prohibited for years. The difference being
> 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?

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. 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?

Received on Tuesday, 28 June 2011 14:36:08 UTC

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