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Re: Thoughts towards an accessible <canvas>

From: Alasdair King <alasdairking@gmail.com>
Date: Thu, 19 Mar 2009 10:00:56 +0000
Message-ID: <7df2c90b0903190300s6004fa16tf2e18db156ee3317@mail.gmail.com>
To: Jonathan Avila <jon.avila@ssbbartgroup.com>, Jon Gunderson <jongund@illinois.edu>, John Foliot <jfoliot@stanford.edu>, richarduserite <richard@userite.com>, "John Foliot - WATS.ca" <foliot@wats.ca>, Wai-Ig <w3c-wai-ig@w3.org>, wai-xtech@w3.org, HTMLWG <public-html@w3.org>
(Sorry, I, Alasdair King, wrote about the alt="" - not John Foliot)

The alt="" assignment tells the browser that the image shouldn't be
rendered to someone who can't see it. So in your low-vision use case,
Jonathan, it should tell you (if your browser supported it) that the
picture isn't worth trying to decipher. It allows you to differentiate
between authors who have not bothered to provide any alt attribute and
authors who are telling you not to bother rendering the image.

So you could switch images off and the superfluous images with an alt
attribute of "" could disappear entirely, letting you focus on images
that you now know are of importance to understanding and using the
page. Screenreaders can ignore the images. That kind of thing.

Alasdair King

On Thu, Mar 19, 2009 at 1:01 AM, Jonathan Avila
<jon.avila@ssbbartgroup.com> wrote:
> <quote user="John Foliot">1 Could we perhaps have a way to define (e.g.
> meta tag) that the
> canvas shouldn't be rendered to some set of users, like alt="" does
> now?</quote>
> The whole idea of hiding something like alt text or some other elements
> because it's assumed that users can either see perfectly or not see is
> unfair.  What about people like myself with low vision.  Most images I can
> see but some I cannot.  I often do not use assistive technology but I am
> then forced to turn off images for a page to see the alt text or have
> images on and not be able to access the alt text.  The same would go for
> someone with cognitive impairment.  They may be able to interpret what
> some images mean but not others, yet they can't access the alternative
> text.  Most graphical pages are more visually accessible to me and a page
> with graphics stripped out with alt text would actual make using a
> page/site ineffective.  Use of the title does not fill this void as the
> title should be used for supplementary material beneficial to all users
> but not required to understand the image.
> This practice seems like it was developed by someone in the 1970s who
> decided that people fall into certain specific categories and that people
> cannot be somewhere between disabled or not disabled, blind or sighted,
> deaf and have full hearing.
> Jonathan
> -----Original Message-----
> From: w3c-wai-ig-request@w3.org [mailto:w3c-wai-ig-request@w3.org] On
> Behalf Of Alasdair King
> Sent: Wednesday, March 18, 2009 5:44 PM
> To: Jon Gunderson
> Cc: John Foliot; richarduserite; John Foliot - WATS.ca; Wai-Ig;
> wai-xtech@w3.org; HTMLWG; WebAIM Discussion List; Gawds_Discuss
> Subject: Re: Thoughts towards an accessible <canvas>
> John Foliot:
> 1 Could we perhaps have a way to define (e.g. meta tag) that the
> canvas shouldn't be rendered to some set of users, like alt="" does
> now?
> 2 The only other content is likely be be a brief text string, but this
> might be extended to a link to some equivalent data source, like a
> simplified-HTML version of the content.
> I don't think you're going to get anything else put in there, based on
> my experience of writing a web browser and looking at the contents of
> things like LONGDESC nodes.
> Jon Gunderson:
> May I pitch this to you?
> http://www.webbie.org.uk/webbiefordesigners.htm
> Another alternative is to install NVDA and try the page out in Firefox
> with your monitor turned off.
> Cheers,
> Alasdair King
> WebbIE
> http://www.webbie.org.uk
> On Wed, Mar 18, 2009 at 1:34 PM, Jon Gunderson <jongund@illinois.edu>
> wrote:
>> It would be useful if browsers had an accessibility mode that would
> allow web developers to easily view the accessibility of the content of a
> web page and at least have keyboard support for navigation to headings
> (h1-h6) and the new ARIA landmark roles.
>> Accessibility mode would have at least the following features:
>> 1. Render alternatives in place of non-text content
>> 2. Remove CSS and tables that are being used for layout
>> This would provide at least one level of visualization of the content to
> people using assistive technologies.
>> The Opera Browser does have built-in support for header navigation and
> they do make it easy to switch between many different renderings for web
> developers to view their content for many devices and users, including the
> features above.
>> Jon
>> ---- Original message ----
>>>Date: Tue, 17 Mar 2009 09:45:41 -0700 (PDT)
>>>From: "John Foliot" <jfoliot@stanford.edu>
>>>Subject: RE: Thoughts towards an accessible <canvas>
>>>To: "'richarduserite'" <richard@userite.com>, "'John Foliot - WATS.ca'"
> <foliot@wats.ca>, "'Wai-Ig'" <w3c-wai-ig@w3.org>, <wai-xtech@w3.org>,
> "'HTMLWG'" <public-html@w3.org>
>>>Cc: "'WebAIM Discussion List'" <webaim-forum@list.webaim.org>,
> "'Gawds_Discuss'" <gawds_discuss@yahoogroups.com>
>>>Richarduserite wrote:
>>>> However I am not so sure about your idea of not rendering non-
>>>> conforming content
>>>> "Finally, I propose that any instance of <canvas> that lacks at a
>>>> minimum
>>>> the 2 proposed mandatory values be non-conformant and not render on
>>>> screen."
>>>> Would you apply the same rules all non-text content such as images?
>>>Actually, yes, I have proposed this form of draconian response before
>>>It's about consequences: until such time as there are real consequences
>>>for slack developers/tools that allows content to exist that is
>>>incomplete, then there will be content that is incomplete - it's a
> simple
>>>as that.  Why would <img src="path..." /> be any more complete than <img
>>>alt="Photo of a leprechaun" />?  I mean, clearly, anyone processing that
>>>info in their user-agent will 'get' the intent of the author, right?
>  Yet
>>>today, the first example will render in the browser, the second delivers
> a
>>>'fail'.  Ergo (to me) there is a problem of inequity here that must be
>>>addressed - if it fails for some, it should fail for all.
>>>> The crucial thing is that the users software (browser, screen reader,
>>>> etc.)
>>>> is able to render the appropriate alternative (if it exists). And for
>>>> this
>>>> to happen you are right that the software developers as well as web
>>>> authors
>>>> need to be given a definitive, unambigous, set of guidelines. But I
>>>> don't
>>>> think you can ask Microsoft etc to create browser that refuse to
>>>> display any
>>>> content that is not fully accessible.
>>>I get that.  However, it does not change my thoughts, it only suggests
>>>that I will likely not get what I believe should be given.  But
> sometimes
>>>an extreme position must be articulated, if for no other reason than to
>>>set the outside bars far enough that the compromise (middle) position
>>>remains a win most of the time. Shooting for the stars will hopefully
>>>deliver the moon.
>> Jon Gunderson, Ph.D.
>> Coordinator Information Technology Accessibility
>> Disability Resources and Educational Services
>> Rehabilitation Education Center
>> Room 86
>> 1207 S. Oak Street
>> Champaign, Illinois 61821
>> Voice: (217) 244-5870
>> WWW: http://www.cita.uiuc.edu/
>> WWW: https://netfiles.uiuc.edu/jongund/www/
> --
> Alasdair King

Alasdair King
Received on Thursday, 19 March 2009 10:01:42 UTC

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