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[Bug 7740] New: Authoring advice for canvas is bad for accessibility

From: <bugzilla@wiggum.w3.org>
Date: Mon, 28 Sep 2009 09:26:54 +0000
To: public-html-bugzilla@w3.org
Message-ID: <bug-7740-2486@http.www.w3.org/Bugs/Public/>
http://www.w3.org/Bugs/Public/show_bug.cgi?id=7740

           Summary: Authoring advice for canvas is bad for accessibility
           Product: HTML WG
           Version: unspecified
          Platform: PC
        OS/Version: Windows NT
            Status: NEW
          Severity: normal
          Priority: P2
         Component: HTML5 spec bugs
        AssignedTo: dave.null@w3.org
        ReportedBy: faulkner.steve@gmail.com
         QAContact: public-html-bugzilla@w3.org
                CC: ian@hixie.ch, mike@w3.org, public-html@w3.org


Currently the HTML 5 spec advises authors that it OK to place fallback content
in the canvas element:

“When authors use the canvas element, they must also provide content that, when
presented to the user, conveys essentially the same function or purpose as the
bitmap canvas. 
This content may be placed as content of the canvas element. 
The contents of the canvas element, if any, are the element's fallback
content.”
http://dev.w3.org/html5/spec/the-canvas-element.html#the-canvas-element

advsing authors to put fallback inside the canvas element is demonstrably bad
for users of canvas supporting browsers who cannot access the rendered content
of the canvas bitmap.

example:http://www.whatwg.org/issues/data.html?period=1 contains a canvas based
graph that has its fallback content (a html data table) inside the canvas
element.
No firefox/opera/safari/chrome users can access it unless they view source. The
fallback content is not even displayed to IE users.


As the canvas element is widely supported and being used, the advice in the
spec should reflect the reality of todays browser implementations.


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Received on Monday, 28 September 2009 09:27:04 UTC

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