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Re: hit testing and retained graphics

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Tue, 28 Jun 2011 16:40:31 -0700
Message-ID: <BANLkTinK1Tmho-HKCz8HiksJ1tW1kQUcxZ8p5MDVYjkdJSfRgQ@mail.gmail.com>
To: John Foliot <jfoliot@stanford.edu>
Cc: Charles Pritchard <chuck@jumis.com>, Charles McCathieNevile <chaals@opera.com>, 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 Tue, Jun 28, 2011 at 2:32 PM, John Foliot <jfoliot@stanford.edu> wrote:
> Tab Atkins Jr. wrote:
>> The WHATWG wiki pages for Video Caption and Modal Dialog use cases
>> exemplify what is meant by compiling clear use-cases:
>> *
>> <http://wiki.whatwg.org/wiki/Use_cases_for_timed_tracks_rendered_over_v
>> ideo_by_the_UA>
>>
>> They examine existing usage to discover what features are important,
>> and give several examples of each.  This way we can tell directly
>> whether the solutions we're crafting are adequate, by attempting to
>> recreate the examples with the proposed solution.
>
> And right there, you've identified the disconnect. Those "use cases" for
> video captioning are, frankly, bollocks, as they do not address a
> significant amount of accessibility concerns.
>
> Tab I must tell you that most folk I know scoffed at that WHATWG wiki page
> of anime examples and other screen-captures, as they barely scratched the
> surface in terms of identifying use-cases, or rather *user-requirements*.
> How could they? They are pictures, with no examination of what is actually
> trying to be solved, or even a clear understanding of what the problems
> are - at best those pictures illustrate some visual design requirements.
> That wiki page accurately exemplifies the slap-dash WHATWG approach to
> addressing any accessibility problem on the web - the "close enough, we can
> fix it later" approach.
>
> Contrast that collection of incomplete pictures with the detailed User
> Requirements that the media sub-team created, and you will quickly see that
> the incomplete "use-case" exercise that the WHATWG folks undertook was
> woefully inadequate.
> (http://www.w3.org/WAI/PF/HTML/wiki/Media_Accessibility_User_Requirements)

The WHATWG wiki page answers the question "What are authors doing with
captions in other technologies?".  Knowing the answer to that helps us
know what a new technology needs to enable, which helps us craft a
solution.

The WAI wiki page also endeavors to answer that question, in addition
to answering "What caption-specific types of accessibility problems
may exist?", which is also valuable.  (Separately, the WAI wiki page
also has several problems, where requirements on different targets
(authoring API vs browser UX) are intermixed, and some requirements
don't appear to have adequate justification.)

> Now today we have a <canvas> element that took the first approach (rather
> than the second one), and so we are in a situation where <canvas> is
> woefully inaccessible - in part because when it was being designed it wasn't
> examined and thought through w.r.t. accessibility, once again it was "close
> enough, we can fix it later". (I don't mean to pick on Ben Galbraith or Dion
> Almaer, but Bespin epitomized this:
> http://benzilla.galbraiths.org/2009/02/18/bespin-and-canvas-part-2/)
>
> Well, "later" is *now*.

I agree.  Did you think I was defending the current <canvas> API?  My
argument is simply that I don't think the approach taken in this
thread of defining a minimally-invasive API atop the 2d context is
good.  "Minimally-invasive" fixes usually result in bad solutions.  We
should instead be starting from a list of problems to be solved, so we
can determine if the best solution is to patch the 2d context, create
a new canvas context that better solves the problems, or use a
different technology entirely like SVG.

~TJ
Received on Tuesday, 28 June 2011 23:41:20 GMT

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