W3C home > Mailing lists > Public > public-canvas-api@w3.org > April to June 2011

Re: hit testing and retained graphics

From: Charles Pritchard <chuck@jumis.com>
Date: Thu, 23 Jun 2011 13:56:51 -0700
Message-ID: <4E03A893.1000107@jumis.com>
To: "Tab Atkins Jr." <jackalmage@gmail.com>
CC: Richard Schwerdtfeger <schwer@us.ibm.com>, Cameron McCormack <cam@mcc.id.au>, Cynthia Shelly <cyns@microsoft.com>, david.bolter@gmail.com, Frank Olivier <Frank.Olivier@microsoft.com>, Mike@w3.org, public-canvas-api@w3.org, public-html@w3.org, public-html-a11y@w3.org
On 6/23/2011 1:28 PM, Tab Atkins Jr. wrote:
> On Thu, Jun 23, 2011 at 12:56 PM, Richard Schwerdtfeger
> <schwer@us.ibm.com>  wrote:
>>> So normally, I imagine, hit testing would be done either by using
>>> isPointInPath() or by custom code looking at a mouse event’s x/y values.
>>> I think this proposal doesn’t work with isPointInPath(), though, is that
>>> right?
>>>
>> I think it would but we would need to incorporate Z order and a notion of
>> the last drawn element to compute which element is on top. The user agent
>> would need to manage this.
> You are attempting to recreate a retained-mode API in an
> immediate-mode API.  Why is "use SVG" not sufficient for this?
>
> ~TJ
Tab, we've been through this one before.

"use SVG" is not a relevant statement -- we're trying to make Canvas 
accessible.

Assistive technology products create their own retained-modes; we are 
focused on
exposing sufficient information for those products to operate -- at the 
same time, we're trying
to make things a little easier on developers, using those same methods. 
This is the "stalking horse" technique
that Ian Hickson often puts forward as a reason for updating specifications.

Retained-mode semantics are not exclusionary to immediate-mode APIs; 
OpenGL is a good example,
as mentioned by Wikipedia.  We're restricting the "retained mode" to 
items which are in the DOM,
The shadow DOM is acting as the retained mode API, just as it should.
Canvas is still in an immediate mode.

( wikipedia link: http://en.wikipedia.org/wiki/Retained_mode )

I'd appreciate it, Tab, if you'd add something to the conversation, 
instead of condescending
developers like me by repeating the same comment over and over.

-Charles
Received on Thursday, 23 June 2011 20:57:34 UTC

This archive was generated by hypermail 2.4.0 : Friday, 17 January 2020 19:10:30 UTC