W3C home > Mailing lists > Public > public-html@w3.org > July 2011

Re: hit testing and retained graphics

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Fri, 8 Jul 2011 11:35:44 -0700
Message-ID: <CAAWBYDBBcS43ZaVGeWfQbrCyOkNmQNxqUXeoj8YvG7aMA8hv-w@mail.gmail.com>
To: Richard Schwerdtfeger <schwer@us.ibm.com>
Cc: Doug Schepers <schepers@w3.org>, Charles McCathieNevile <chaals@opera.com>, Charles Pritchard <chuck@jumis.com>, Henri Sivonen <hsivonen@iki.fi>, Karl Dubost <karld@opera.com>, "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>, public-html-request@w3.org
On Fri, Jul 8, 2011 at 9:08 AM, Richard Schwerdtfeger <schwer@us.ibm.com> wrote:
> From: Doug Schepers <schepers@w3.org>
>> Charles Pritchard wrote (on 7/6/11 3:07 PM):
>> 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.
>
> Doug, forgive me but you make it sounds like you are concerned that if we
> add retained mode graphics to canvas that industry will not use SVG.

He's not saying that at all.  He's saying that we already have a
decent, mature retained-mode API for graphics, so it's probably a bad
idea to try to make another one unless there are very compelling
reasons why the new solution is better.


> 2. we are roughly 1 feature away from fixing
> canvas accessibility.

No we're not.  Not by a long shot.  I've given several reasons why not
in the past.


> The smoothing of shapes has nothing to do with retained mode.

Um, it has everything to do with retained mode if you want it to be
automatic.  By definition.


> What we are
> trying to do is make canvas accessible. SVG is another technology and that
> is a separate accessibility effort.

Conway's Law strikes again.


> If SVG is so wonderful why are you not
> pushing for an SVG element in HTML 5?

SVG is in HTML.  <http://whatwg.org/html#svg-0>


> Why have you not pushed to ditch
> canvas from HTML in favor of SVG?

Because that would be a stupid thing to push for, frankly.  Doug's a
smart guy.  He recognizes, like everyone else, that immediate mode
APIs have an advantage over retained mode APIs in some circumstances.


> Finally, on this point. When a developer picks a technology they do it based
> on a number of factors. Canvas already has been used my many open web
> applications. It needs to be able to support accessibility if this is the
> developers choice.

Please see Jonas's post for a well-written response to this point.  I
have also responded to this in depth in previous emails.

(One cogent reason developers choose canvas is that it's easy to use
to get pixels on the screen.  Building SVG from script is really
painful.  This is just an API problem, though - we all know that the
DOM is a *horrible* API.  If someone were to make a pretty API for SVG
that's well-designed for Javascript - something like paper.js - I
believe this situation would change drastically.)

~TJ
Received on Friday, 8 July 2011 18:36:34 UTC

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