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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 15:31:40 +0100
Message-Id: <A704BC97-33CD-45F2-850A-309CBE90F0BB@manchester.ac.uk>
Cc: "'UAWG list'" <w3c-wai-ua@w3.org>
To: "Jim Allan" <jimallan@tsbvi.edu>
In this case should we not think about possible scenarios for UAs to  
generate missing fallback content. Maybe a set of examples,  
principles, etc so there is at least some consistency?

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
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On 20 Aug 2009, at 15:11, Jim Allan wrote:

> PF is already on this. Interestingly, HTML5 is as much a  
> specification for
> designing a user agent as it is a language spec. Viewed in that  
> light, it
> could prove useful to UAWG as a jumping off point for filling-in
> accessibility gaps. One area to fill in would be the notion of  
> fallback
> content. The user should have access to the fallback regardless of  
> the state
> of the parent element. In other words, the user should have access  
> to the
> fallback content whether canvas scripting is on or off, or other  
> conditions.
>
> The question becomes, will UA developers actually implement these  
> items.
> Canvas will still work even if the user has no access to the fallback
> content. This is the status quo with 'objects' now (Flash, video  
> players,
> etc.). They all function, yet the user has no easy access to fallback
> content.
>
> Jim
>
>> -----Original Message-----
>> From: w3c-wai-ua-request@w3.org [mailto:w3c-wai-ua-request@w3.org] On
> Behalf
>> Of Simon Harper
>> Sent: Thursday, August 20, 2009 3:10 AM
>> To: Jim Allan
>> Cc: 'UAWG list'
>> Subject: Re: The Canvas 2D API 1.0 Specification
>>
>> 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 14:32:13 GMT

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