- From: Al Gilman <Alfred.S.Gilman@IEEE.org>
- Date: Thu, 13 Jul 2006 17:17:33 -0400
- To: WAU-ua <w3c-wai-ua@w3.org>
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
Received on Thursday, 13 July 2006 21:17:48 UTC