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Re: Draft Revisions to Canvas 2D Context API

From: David Bolter <david.bolter@gmail.com>
Date: Thu, 29 Apr 2010 13:07:26 -0400
Message-ID: <4BD9BCCE.5000309@gmail.com>
To: Richard Schwerdtfeger <schwer@us.ibm.com>
CC: Frank Olivier <franko@microsoft.com>, Janina Sajka <janina@rednote.net>, "public-canvas-api@w3.org" <public-canvas-api@w3.org>, Steven Faulkner <faulkner.steve@gmail.com>, public-html-a11y@w3.org
Hi Rich,

I'm sorry this email got lost in my stack! I've replied to the part 
directed at me below:

On 11/04/10 7:49 PM, Richard Schwerdtfeger wrote:
> Sorry it took so long for me  to get this draft out. Too much traveling
> going on. Please take a look and provide feedback.
> The edits reflect:
> - Separate caret/selection from drawFocusRing
> http://lists.w3.org/Archives/Public/public-html/2010Mar/0502.html. The Mac
> does not support caret tracking during selection so this needed to be
> allotted for.
> - Expose the caret blink rate via 2D canvas API. Frank indicated Windows
> has a 500 millisecond defult blink rate a. Carl Carlson (Apple) indicated a
> default blink rate of 560 milliseconds. I provided information for authors
> regarding average default blink rates should the value returned be negative
> 1.
> - Change the name of canDrawCustom and clean up its definiton which
> according to Maciej is "want to draw custom unless Special Focus Ring
> Setting is in Effect"
> http://lists.w3.org/Archives/Public/public-html/2010Mar/0363.html
> David Bolter: From the Firefox perspective we still need to see that the
> caret/selection location can be properly mapped to the accessibility API as
> is. Currently, the caret position is a logical one in IA2 and I believe the
> caret pixel position is calculated from the character font offset and the
> bounding rectangle of the text. We may need to move the system caret. I am
> trying to find the old Windows API for that.

On Windows FF updates the system caret when focus changes or when the 
caret offset changes. We call such Windows functions as:

I hope that helps. I didn't test this via AT.


> Frank: Please see if we can map the pixel position accurately, when
> provided, from the accessibility API. Windows used to have an MSAA
> notification for driving a  magnifier based on screen position. I don't
> know if this is still used when using UIA Express.
> Maciej or James: Same question for Mac regarding the caret/selection
> position.
> (See attached file: 2dcontext10-Apr-11.html)
> Rich Schwerdtfeger
> CTO Accessibility Software Group
Received on Thursday, 29 April 2010 17:08:08 UTC

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