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Re: control of presentation for conditional content, in particular backgrounds [was: Re: Notes from W3C User Agent Teleconference for 13 July 2006]

From: Jan Richards <jan.richards@utoronto.ca>
Date: Tue, 18 Jul 2006 09:36:58 -0400
Message-ID: <44BCE3FA.4070309@utoronto.ca>
To: Al Gilman <Alfred.S.Gilman@IEEE.org>
CC: WAU-ua <w3c-wai-ua@w3.org>

Al,

Thanks for this. I think you are right and this paragraph sums things up 
well:

"The point is that if the function of the image is as an expendable
background, and replacing the background with a uniform background of
a suitably contrasting color will enhance the perceptibility of the
foreground, information-bearing shapes, then the user needs to be
able to suppress the rendering of the background."


-Jan

Al Gilman wrote:
> 
> Regarding your discussion of "Toggle background images (P1)"
> 
> You went back and forth about whether this is a UA or a content
> requirement.  Also whether 3.1 applies to whole-page or page-part
> backgrounds.  I would take the position that it applies to backgrounds
> of page parts as well as to whole pages.  The toggle control could
> affect all backgrounds identifiable as such in the page, though.  Or
> it could be scoped to a current object.
> 
> As far as player vs. content requirements, there are some of each.
> 
> This relates to my comment to WCAG 2.0 in the area of
> "Distinguish two interfaces"
> 
> http://lists.w3.org/Archives/Public/public-comments-wcag20/2006Jun/att-0192/WCAG2comment-AG-2interfaces.html 
> 
> 
> The point is that if the function of the image is as an expendable
> background, and replacing the background with a uniform background of
> a suitably contrasting color will enhance the perceptibility of the
> foreground, information-bearing shapes, then the user needs to be
> able to suppress the rendering of the background.
> 
> This applies whether the author's suggested presentation has one
> background for the whole page or for some sub-element in the page.
> 
> That is the requirement at the user interface, that the user can
> suppress backgrounds; where a background is something inessential
> which has the potential to interfere with processing the foreground,
> and the foreground is sufficient to convey the essential core of the
> information.
> 
> Deeper down, there are allocated requirements to the format, the
> browser, and the author.
> 
> The format has to provide ways to separate the data that communicates
> the foreground from the data that communicates the background, and to
> identify which is which.
> 
> The player has to afford the user the capability to choose whether to
> display the background with the foreground or the foreground alone,
> without the background.
> 
> And the author has to respect the semantic distinction between
> background and foreground. That is to say, the information that is
> being communicated to the user needs to be complete as represented in
> the foreground data, or the 'background' format is being abused. If
> you cannot recognize the right information from the display of the
> foreground alone, then the thing communicated in the background
> syntax is not a semantic background and the author's responsibility
> has not been fulfilled.
> 
> This goes for audio and visual content alike.
> 
> That's a quick dump as I understand how it should work.
> 
> The format should include support for backgrounds but define
> these as conditional content.  The UA should implement user
> control over the rendering decision for such conditional content.
> 
> The author should a) use the background feature in the format
> to enable user control of rendering, and b) make sure that the
> conditional content is indeed inessential, that the presentation
> works with the background suppressed.
> 
> Al
> 
> 
> 

-- 
Jan Richards, M.Sc.
User Interface Design Specialist
Adaptive Technology Resource Centre (ATRC)
Faculty of Information Studies
University of Toronto

   Email: jan.richards@utoronto.ca
   Web:   http://jan.atrc.utoronto.ca
   Phone: 416-946-7060
   Fax:   416-971-2896
Received on Tuesday, 18 July 2006 13:43:47 GMT

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