- From: Doug Schepers <schepers@w3.org>
- Date: Thu, 07 Jul 2011 12:51:20 -0400
- To: Charles Pritchard <chuck@jumis.com>
- CC: Karl Dubost <karld@opera.com>, "Tab Atkins Jr." <jackalmage@gmail.com>, Charles McCathieNevile <chaals@opera.com>, Henri Sivonen <hsivonen@iki.fi>, "public-canvas-api@w3.org" <public-canvas-api@w3.org>, "public-html@w3.org" <public-html@w3.org>, "public-html-a11y@w3.org" <public-html-a11y@w3.org>
Hi, Charles- Charles Pritchard wrote (on 7/6/11 3:07 PM): > Adobe has released several canvas export tools; accessibility is part > of authoring tool guidelines. Adobe has also released several SVG export tools, and I would like to see them release more. > Unfortunately many browser vendors have been underserved by their > teams and/motivations: they are pushing back against supporting a11y > for canvas content. Please stop using rhetoric like this. It is incorrect and perhaps even disingenuous. It makes people defensive and is a barrier to reasoned discussion. Browser vendors have not pushed back on "supporting a11y for canvas content", they have pushed back against adding a retained-mode component to the Canvas 2D API, for obvious reasons: the Canvas 2D API is intended for *immediate-mode* graphics, and we already have a 2D graphics standard for the Open Web Platform: SVG. > Vendors of authoring tools are not even able to > expose the accessibility information that might otherwise be shared. > Many browser vendors are indeed discouraging it with a vague promise > of future specs. Again, this seems to be rhetoric. I haven't heard any browser vendor offering any future work in this area. I have proposed what seems to me like a reasonable solution, which is an API that allows the two 2D graphics APIs (Canvas and SVG) available in all major browsers to be used together. You have claimed this is "overkill", but have not stated why. I find it frustrating that we have a point on which the browsers seem to agree (that SVG is the retained-mode graphics option), but rather than building on that foundation, you persist in pursuing a redundant approach that the browser vendors have already rejected. Is this NIH syndrome on your part, or do you have some specific technical reason for rejecting my proposal? If so, please state your objection clearly, without hand-waving. I have serious reservations *from an accessibility point of view* about extending the Canvas 2D API toward retained-mode or subtree logical structures further than it has already been pushed. To wit: * Issues that have been solved in SVG around the scaled viewport, around rich object structure, around smooth scaling (for crisp displays at all sizes), around shapes which move and change size or shape, and so on, are still problems that accessibility in the Canvas 2D API has yet to pose, much less to solve. * Your proposed solution of adding an element to the canvas subtree which carries shape, size, and location information seems to be simple, but only because you haven't carried it to its logical extreme, which will ultimately be to reinvent SVG (perhaps slightly differently, so that it's not even compatible). Where does it stop? When is accessibility potential of Canvas complete, and not only available, but either encouraged or mandatory, with your approach? * Your approach either either requires the user to maintain the position it themselves, in which case Cameron's aria-region suggestion [1] seems better and is already reasonably defined as a starting point, or would be done automatically, in which case SVG would be better and is already defined (though admittedly, how it works precisely with SVG would also need to be defined, implemented, and tested). [1] http://lists.w3.org/Archives/Public/public-canvas-api/2011JulSep/0067.html Regards- -Doug Schepers W3C Staff Contact, SVG, WebApps, Web Events, and Audio WGs
Received on Thursday, 7 July 2011 16:51:39 UTC