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Re: The Canvas 2D API 1.0 Specification

From: Simon Harper <simon.harper@manchester.ac.uk>
Date: Thu, 20 Aug 2009 09:09:48 +0100
Message-Id: <A92E78BE-FB8E-4E75-8611-9A66E0AED17B@manchester.ac.uk>
Cc: "'UAWG list'" <w3c-wai-ua@w3.org>
To: Jim Allan <jimallan@tsbvi.edu>
It seems then that the accessibility interface to canvas is the bit  
we should be working on as canvas seems like a mini-ua? We should  
start to make suggestions and give solutions to the html5 people IMO.


Cheers
Si.

=======================

Simon Harper
University of Manchester (UK)

Human Centred Web Lab: http://hcw.cs.manchester.ac.uk

My Site: http://hcw.cs.manchester.ac.uk/people/harper/

My Diary (Web): http://hcw.cs.manchester.ac.uk/people/harper/ 
phpicalendar/week.php
My Diary (Subscribe): http://hcw.cs.manchester.ac.uk/diaries/harper/ 
SimonHarper.ics





On 19 Aug 2009, at 18:53, Jim Allan wrote:

> Thanks Simon. It's a nice statement. We all know, if a developer  
> can do
> something they will.
>
> One troubling bit is
>> When authors use the canvas interface element, they must also provide
>> content that, when presented to the user, conveys essentially the
>> same function or purpose as the bitmap canvas. This content may be
>> placed as content of the canvas interface element. The contents of
>> the canvas interface element, if any, are the element's fallback
>> content.
>
> UAAG20 has
> 3.1.1 Notification of Alternative Content: Provide a global option  
> for the
> user to be notified of alternatives to rendered content (e.g.,  
> short text
> alternatives, long descriptions, captions).
>
> 3.1.2 Configurable Default Rendering: Provide the user with the global
> option to set which type of alternative to render by default. If the
> alternative content has a different height and/or width, then the  
> user agent
> will reflow the viewport. (Level A)
>
> We had similar stuff in UAAG10. However no User Agents have yet  
> implemented
> a way to easily get to the internal element "fall back content".
>
> Another troubling item is
>> In interactive visual media, if scripting is enabled for the canvas
>> interface element, the canvas interface element represents an
>> embedded element with a dynamically created image.
>
> This implies there is separate scripting for canvas. Separate from
> javascript? A different instance? How does a user (or agent) turn off
> scripting for just canvas?
>
> Jim
>
>> -----Original Message-----
>> From: w3c-wai-ua-request@w3.org [mailto:w3c-wai-ua-request@w3.org] On
> Behalf
>> Of Simon Harper
>> Sent: Wednesday, August 19, 2009 10:46 AM
>> To: UAWG list
>> Subject: The Canvas 2D API 1.0 Specification
>>
>> I was monitoring xtech and saw this going through
>>
>> http://dev.w3.org/html5/canvas-api/canvas-2d-api.html
>>
>>
>> which says..
>>
>> 5. Accessibility Considerations
>>
>> Authors should not use the canvas interface element in a document
>> when a more suitable element is available. For example, it is
>> inappropriate to use a canvas interface element to render a page
>> heading: if the desired presentation of the heading is graphically
>> intense, it should be marked up using appropriate elements (typically
>> h1) and then styled using CSS and supporting technologies such as  
>> XBL.
>>
>> When authors use the canvas interface element, they must also provide
>> content that, when presented to the user, conveys essentially the
>> same function or purpose as the bitmap canvas. This content may be
>> placed as content of the canvas interface element. The contents of
>> the canvas interface element, if any, are the element's fallback
>> content.
>>
>> In interactive visual media, if scripting is enabled for the canvas
>> interface element, the canvas interface element represents an
>> embedded element with a dynamically created image.
>>
>> In non-interactive, static, visual media, if the canvas interface
>> element has been previously painted on (e.g. if the page was viewed
>> in an interactive visual medium and is now being printed, or if some
>> script that ran during the page layout process painted on the
>> element), then the canvas interface element represents embedded
>> content with the current image and size. Otherwise, the element
>> represents its fallback content instead.
>>
>> In non-visual media, and in visual media if scripting is disabled for
>> the canvas interface element, the canvas interface element represents
>> its fallback content instead.
>>
>>
>>
>> they say...
>>
>> Techniques and additional APIs to make specific uses of canvas
>> interface elements more widely accessible are under discussion, and
>> will be reflected in this draft as progress is made.
>>
>> I wonder what these are?
>>
>>
>> Cheers
>> Si.
>>
>> =======================
>>
>> Simon Harper
>> University of Manchester (UK)
>>
>> Human Centred Web Lab: http://hcw.cs.manchester.ac.uk
>>
>> My Site: http://hcw.cs.manchester.ac.uk/people/harper/
>>
>> My Diary (Web): http://hcw.cs.manchester.ac.uk/people/harper/
>> phpicalendar/week.php
>> My Diary (Subscribe): http://hcw.cs.manchester.ac.uk/diaries/harper/
>> SimonHarper.ics
>>
>>
>>
>>
>>
>
>
>
Received on Thursday, 20 August 2009 08:10:20 GMT

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