- From: Phill Jenkins <pjenkins@us.ibm.com>
- Date: Mon, 3 Dec 2001 15:47:40 -0600
- To: w3c-wai-ig@w3.org
- Cc: "Mike Scott" <mscott@msfw.com>
Mike, Charles, and others the "presentation modes" Charles referred to in the CSS spec are referring to "media types". Screen readers today are reading the "visual" media type [CSS+HTML]. If the author marked the "visual" information as hidden, the screen reader should respect that attribute. The "Aural" media type, if ever supported by screen readers, does not tell the screen reader what to do with interpreting the "Visual media" attributes. I do not agree with the private interpretations that somehow suggest that media types are referring to presentation instructions for screen readers. Even if a "self voicing browser" [not a screen reader] supported all the media types, the spec does not define what to do other than the assertion that the user agent itself decides which media types it supports. For example, Home Page Reader supports the media group "visual", so it must honor the visibility: hidden attribute. This should be something discussed further in WCAG 2.0, the Device independent working group, or a new working group for screen reader developers. Media types are explained in CSS at http://www.w3.org/TR/REC-CSS2/media.html The difference I understand between display: none and visibility: hidden is what I call "white space". Display: none creates no white space, no formatting space or box, [nothing is there], while visibility:hidden creates a space, but it is empty. Not sure if there is any difference when it comes to a screen reader. Mike wrote: > "Skip Navigation" links are perfect examples of items that we might want > hidden but definitely should be read by a screen reader. (Instead of the > current work arounds like invisible images or text set to the same color > as the background.) There is a design debate about "definitely" as in definitely hiding the "Skip navigation" link. It could be just some small text that is visible. But the reason we recommend the "current work around" [alt text on invisible images] is because it works! And it has to when CSS it turned off! Visibility: hidden wouldn't work with CSS off. > Also, there could be cases where dynamically hidden > elements (such as pop-up or expanding/collapsing menus) also should be > read. This is exactly why screen readers should NOT read text that is hidden by JavaScript. By honoring the visibility properties affected by JavaScript, the JavaScript page can be made directly accessible and - more importantly - usable. For example, web applications "hide" content when it is not pertinent to the user's profile. Blind users should not be forced to read all the hidden content, usually out of order and context, when the sighted users doesn't have to. Regards, Phill
Received on Monday, 3 December 2001 16:47:58 UTC