W3C home > Mailing lists > Public > public-html-a11y@w3.org > March 2012

Re: Review of Ian's changes for path

From: Ian Hickson <ian@hixie.ch>
Date: Wed, 21 Mar 2012 23:21:28 +0000 (UTC)
To: Richard Schwerdtfeger <schwer@us.ibm.com>
cc: public-html-a11y@w3.org
Message-ID: <Pine.LNX.4.64.1203212313580.22654@ps20323.dreamhostps.com>
On Tue, 20 Mar 2012, Richard Schwerdtfeger wrote:
> 2. When I was at TPAC a Google developer showed me new work he was doing 
> on a new MVC model for the Web, similar to XBL, with a new model that 
> could be bound to different rendering engines: SVG, Canvas, etc. This 
> object model is separate from the DOM and I was told that this recently 
> went into a Chrome trunk. The addHitRegion() function would allow for 
> access to a separate model in that the element parameter is not required 
> (See Ian's comments). None of the ATs, including Google Chrome make use 
> of it today so introducing this mechanism would require a comprehensive 
> accessibility effort as it is a DOM circumvention. Please read my 
> comments on addHitRegion.

There seems to be some implication here that the addHitRegion() feature 
has something to do with work that the Chrome team is doing. This is not 
the case. For the record, the Web Components model being developed in the 
public-webapps working group (which I assume is what you are referring to) 
is in fact DOM-based, and is not "a new MVC model". It is not separate 
from the DOM any more than XBL is. It has no bearing on the addHitRegion() 

The model that addHitRegion() is based on is in fact the same model that 
ATs use for applications outside of HTML, but it defers to HTML for 
anything beyond the simplest of cases (namely labeled non-interactive 
content and containers). It's intentionally not DOM based for the simple 
case, for the same reason that canvas as a whole is not a retained mode 
API -- for that use case we already have SVG -- but it is straightforward 
to map it to accessibility APIs (much more so than the DOM, in fact). It 
is misleading to characterise it as "DOM circumvention", unless one would 
also describe, say, Microsoft Word or Lotus Notes as "circumventing the 
DOM"; nor do I see any reason to believe that it would require a 
"comprehensive effort" to introduce.

It addresses the use cases that were provided, does so simply and 
straightforwardly, and with minimum impact, while fitting in with the 
canvas API design aesthetic.

I hope to have a more formal proposal to present in the near future.

Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'
Received on Wednesday, 21 March 2012 23:21:52 UTC

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