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Re: hit testing and retained graphics

From: Charles Pritchard <chuck@jumis.com>
Date: Thu, 23 Jun 2011 18:09:40 -0700
Message-ID: <4E03E3D4.6010002@jumis.com>
To: Frank Olivier <Frank.Olivier@microsoft.com>
CC: Richard Schwerdtfeger <schwer@us.ibm.com>, "Tab Atkins Jr." <jackalmage@gmail.com>, Cameron McCormack <cam@mcc.id.au>, Cynthia Shelly <cyns@microsoft.com>, "david.bolter@gmail.com" <david.bolter@gmail.com>, "Mike@w3.org" <Mike@w3.org>, "public-canvas-api@w3.org" <public-canvas-api@w3.org>, "public-html@w3.org" <public-html@w3.org>, "public-html-a11y@w3.org" <public-html-a11y@w3.org>
I strongly object with this stance, and consider it pre-mature.

That stated: Does anybody here object to the stringification methods 
I've put forward?
They in no way "step on" the propriety of SVG -- they in fact enhance 
interoperability,
and much like drawFocusRing, they enable the use of the shadow DOM in 
managing
user events.

I've not seen a direct argument against (nor for) that part of the proposal.
Is there a direct objection?

I will continue to work with this "retained mode" confusion; but I'd 
like to see
continued progress, and I believe the stringify supplemental does not 
tread on
any territory: it embraces SVG semantics.

Cameron: I did see a minor aside from you about the arcTo command --
I'd like to remind you that SVG normalized strings took this into account
and it was decided that arcTo precision was not necessary; the curves 
handled
by SVG normalization were deemed sufficient. If they are/were not 
sufficient,
then arc would have to be included in the normalization spec.... it has 
not been,
I've not seen any technical reason why this decision should be changed.



-Charles

On 6/23/2011 4:29 PM, Frank Olivier wrote:
> Microsoft considers SVG to be the correct way to do retained mode graphics. We have no plans to add retained capabilities to the immediate mode canvas API. If SVG doesn’t address the problem then effort would be better expended on fixing that problem.
>
> Thanks
> Frank
>
>
> From: Richard Schwerdtfeger [mailto:schwer@us.ibm.com]
> Sent: Thursday, June 23, 2011 2:29 PM
> To: Tab Atkins Jr.
> Cc: Cameron McCormack; Charles Pritchard; Cynthia Shelly; david.bolter@gmail.com; Frank Olivier; Mike@w3.org; public-canvas-api@w3.org; public-html@w3.org; public-html-a11y@w3.org
> Subject: Re: hit testing and retained graphics
>
> Hi Tab,
>
> We are trying to make canvas accessible and we are trying to provide hit testing support in canvas vs. throwing out canvas for SVG. SVG has a VERY long way before it is accessible and canvas developers, who have canvas implementations, don't want to throw all their work away to get hit testing by using SVG.
>
> I have a very large IBM application in development and SVG given the state of SVG accessibility and how the application is constructed it is not a good fit. I also have a commitment to ensure HTML 5 is fully accessible, as part of the HTML accessibility task force effort, and we need to make magnifiers aware of drawing object location and dimensions in canvas.
>
> Also, there is a need to have hit testing support in canvas and I am trying to marry an accessibility feature with a mainstream feature developers need.
>
> I had suggested full retained mode graphics by creating drawing objects that would inherit the 2d Context API of canvas, however the discussion on the list was indicated that was more than people wanted. So a subset of retained mode graphics using draw paths to form the bounds of objects is where the discussion is currently. Things like font, brush, or other retained mode features would be left to the canvas context as is.
>
> Rich
>
>
> Rich Schwerdtfeger
> CTO Accessibility Software Group
>
> "Tab Atkins Jr." ---06/23/2011 03:30:32 PM---On Thu, Jun 23, 2011 at 12:56 PM, Richard Schwerdtfeger<schwer@us.ibm.com>  wrote:
>
> From: "Tab Atkins Jr."<jackalmage@gmail.com>
> To: Richard Schwerdtfeger/Austin/IBM@IBMUS
> 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: 06/23/2011 03:30 PM
> Subject: Re: hit testing and retained graphics
> ________________________________________
>
>
>
> 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 event’s x/y values.
>>> I think this proposal doesn’t 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?
>
> ~TJ
Received on Friday, 24 June 2011 01:10:19 UTC

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