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Re: Comment on ARIA 1.0: Problematic conformance requirement for aria-hidden

From: Steve Faulkner <faulkner.steve@gmail.com>
Date: Fri, 27 Apr 2012 09:21:48 +0100
Message-ID: <CA+ri+VmUQ2jpsAZXx-jrDAo_5qrGYN4+m1LxTT2W=c+tHQ5=ug@mail.gmail.com>
To: Benjamin Hawkes-Lewis <bhawkeslewis@googlemail.com>
Cc: PFWG Public Comments <public-pfwg-comments@w3.org>, W3C WAI-XTECH <wai-xtech@w3.org>
Hi Ben,

Have not been following this discussion closely, but just wanted to provide
info about an implementation detail.

In all supporting browsers CSS display:none is applied to elements with the
hidden attribute.


On 27 April 2012 07:44, Benjamin Hawkes-Lewis

> Comment on Accessible Rich Internet Applications (WAI-ARIA) 1.0
> Comment based on Editor's Draft of 16 April 2012, archived at:
>  http://www.webcitation.org/673DWtJcY
> 6.6 defines a conformance requirement for the "aria-hidden" property:
> "Authors MUST set aria-hidden="true" on content that is not displayed,
> regardless of the mechanism used to hide it."
> This is problematic, because some host languages authors have neither
> complete control nor certain knowledge of whether content is
> displayed. For example, an author might specify the HTML5 @hidden
> attribute, and the user might expose hidden elements using a user
> stylesheet. Since user agents know whether or not they are displaying
> content, why is this an author requirement rather than a user agent
> requirement?
> The spec need to define "displayed". Does it mean the same thing as
> HTML5's "being rendered"?
>   http://dev.w3.org/html5/spec/rendering.html#being-rendered
> If so, then this conformance requirement is counter-productive, since
> it would require authors to set "aria-hidden" on <canvas> sub-DOM,
> eliminating the content from appearing as objects in the accessibility
> tree.
> The spec also says aria-hidden "Indicates that the element and all of
> its descendants are not visible or perceivable to any user as
> implemented by the author." Is an element "visible or perceivable" if
> it's acting as a backing store for <canvas>? What does the
> qualification "as implemented by the author" mean?
> One reason to use CSS mechanisms rather than semantic mechanisms like
> "hidden" is in order to show content to users who do not apply user
> agent styles. Is "as implemented by the author" meant to imply the
> application of author style suggestions, in which case aria-hidden
> must be applied? Or is it more important that the author is
> intentionally not hiding it from all users, in which case aria-hidden
> must not be applied?
> What if the author provides multiple stylesheets, and elements are
> hidden in one stylesheet but visible in another stylesheet?
> The spec includes a note that "Note: Authors are reminded that
> visibility:hidden and display:none apply to all CSS media types"
> This is erroneous. While "display" applies to all media types,
> "visibility" only applies to "visual" media types, as stated clearly
> in the CSS specification's definition of the property to which ARIA
> directly links:
> http://www.w3.org/TR/CSS21/visufx.html#visibility
> --
> Benjamin Hawkes-Lewis

with regards

Steve Faulkner
Technical Director - TPG

www.paciellogroup.com | www.HTML5accessibility.com |
HTML5: Techniques for providing useful text alternatives -
Web Accessibility Toolbar - www.paciellogroup.com/resources/wat-ie-about.html
Received on Friday, 27 April 2012 08:22:40 UTC

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