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Fw: Draft Revisions to Canvas 2D Context API to drive magnification

From: Richard Schwerdtfeger <schwer@us.ibm.com>
Date: Thu, 29 Apr 2010 15:25:26 -0600
To: Maciej Stachowiak <mjs@apple.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, david.bolter@gmail.com
Message-ID: <OFB3FFDD52.3A753999-ON86257714.0074F3F2-86257714.0075AFDF@us.ibm.com>

Hi Maciej,

I have not heard back from Apple on this proposal. Please take a look at
the proposal (attached HTML file) and let me know if this will work for the
Mac. I think I addressed your issues and would like your feedback.

We have an MSAA API call on Windows which we can call to set the Caret
Position so that a magnifier can can follow it which can be used by IE and

I don't know if you have a similar API for the Mac where the selection
position could drive the magnifier.



Rich Schwerdtfeger
CTO Accessibility Software Group
----- Forwarded by Richard Schwerdtfeger/Austin/IBM on 04/29/2010 04:17 PM
             tin/IBM@IBMUS                                              To 
             Sent by:                  Frank Olivier                       
             public-canvas-api         <franko@microsoft.com>, Janina      
             -request@w3.org           Sajka <janina@rednote.net>,         
                                       <public-canvas-api@w3.org>, Steven  
             04/11/2010 06:49          Faulkner                            
             PM                        <faulkner.steve@gmail.com>,         
                                       Draft Revisions to Canvas 2D        
                                       Context API                         

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
- 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"

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.

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

(See attached file: 2dcontext10-Apr-11.html)

Rich Schwerdtfeger
CTO Accessibility Software Group(See attached file:

(image/gif attachment: pic12933.gif)

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Received on Thursday, 29 April 2010 21:26:27 UTC

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