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Re: Proposal: Canvas accessibility and a media querries approach for alternative content (Action Item 6 in the HTML Accessibility Task Force)

From: Ian Hickson <ian@hixie.ch>
Date: Wed, 20 Jan 2010 12:43:43 +0000 (UTC)
To: Maciej Stachowiak <mjs@apple.com>
Cc: public-canvas-api@w3.org, HTML WG <public-html@w3.org>
Message-ID: <Pine.LNX.4.64.1001201241200.3958@ps20323.dreamhostps.com>
On Wed, 20 Jan 2010, Maciej Stachowiak wrote:
> Furthermore, objects in a canvas need not be rectangular and in general 
> can be all sorts of funny shapes. While a rectangle might be the best 
> approximation we can do for focus purposes, it would not be appropriate 
> to force that restriction for hit testing. Not only that, but visual 
> objects in the canvas can stack, and knowing their focus rectangles 
> alone does not tell you the z-order, so even hit testing of purely 
> rectangular objects might not work right (z-order might not match 
> logical order and therefore might not be the order in which things 
> appear in the hidden/fallback/model DOM.


The focus area in canvas (as drawn by .drawFocusRing()) can be 
non-rectangular, however. It just uses the canvas path. UAs can 
approximate that to a rectangle if necessary, of course, e.g. if that is 
the platform convention or if the system doesn't support drawing 
non-rectangular focus rings.

In either case, once the method is called, there is no retention of the 
focus ring position, since this is an immediate-mode API and not a 
retained-mode API.

Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'
Received on Wednesday, 20 January 2010 12:44:11 UTC

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