Re: feedback requested: Canvas change for improved hit testing that also facilitates accessibility

Hello,

Finally we can say that accessibility problem of canvas is completely has
been solved?

Thanks

On Thu, Jun 23, 2011 at 11:40 PM, Richard Schwerdtfeger
<schwer@us.ibm.com>wrote:

> We need to able to bind a path to hit testing functionality. It is not
> enough just to be able to define and save a path. Clearly, people are
> wanting hit testing support.
>
>
>
> Rich Schwerdtfeger
> CTO Accessibility Software Group
>
> [image: Inactive hide details for Charles Pritchard ---04/01/2011 05:00:51
> PM---With VoiceOver, I have to use a bunch of ugly hacks. Th]Charles
> Pritchard ---04/01/2011 05:00:51 PM---With VoiceOver, I have to use a bunch
> of ugly hacks. That happens in compatibility work.
>
>
> From: Charles Pritchard <chuck@jumis.com>
> To: Richard Schwerdtfeger/Austin/IBM@IBMUS
> Cc: Boris Zbarsky <bzbarsky@mit.edu>, "cyns@exchange.microsoft.com" <
> cyns@exchange.microsoft.com>, "david.bolter@gmail.com" <
> david.bolter@gmail.com>, "faulkner.steve@gmail.com" <
> faulkner.steve@gmail.com>, "franko@microsoft.com" <franko@microsoft.com>,
> Oliver Hunt <oliver@apple.com>, "public-canvas-api@w3.org" <
> public-canvas-api@w3.org>, "public-canvas-api-request@w3.org" <
> public-canvas-api-request@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" <public-html-request@w3.org>
> Date: 04/01/2011 05:00 PM
>
> Subject: Re: feedback requested: Canvas change for improved hit testing
> that also facilitates accessibility
> ------------------------------
>
>
>
> With VoiceOver, I have to use a bunch of ugly hacks. That happens in
> compatibility work.
> Hopefully my attendance to the standards mailing list, and promotion of bug
> reports, will
> reduce the need to use such hacks in the future.
>
> On the thread-- sharing path data in the context of a11y.
>
> Once we start keeping paths around, we're going to encounter push-back to
> the next version of canvas.
> The existing canvas spec allows-for the recording of all paths, but no
> implementers are doing it.
>
> I'm still struggling for a solution which implementers might approach in
> this version.
> I'm trying to round up some ideas from other canvas-users.
>
> These are the ones I have:
>
> Using CSS pointer-events would be an appropriate way to -enable- slower
> code paths.
>
> pointer-events: stroke would work fine with strokeText and stroke(),
> and when enabled, may stash pixels in a 1-bit bitmap, and/or a character
> buffer.
>
> When pointer-events are set the implementation would expose the current
> path
> to the dom or canvas2d api.
>
> These are steps towards a long-term solution.
>
> They both help canvas authors, pointer-events really help with DOM
> management and speed-up hit testing [by memory trade-off],
> and grabbing a DOMString of the path makes debugging easier.
>
> It's reasonable to expect an AT to calculate the extents of a DOMString,
> normalized SVG Path.
>
> Those two items provide a foundation for a a few simple methods
> to notify the AT that pointer/coordinate focus should be associated with
> fallback content.
>
> I'd like to see if they have any support.
>
> -Charles
>
>
> On 3/30/2011 1:54 PM, Richard Schwerdtfeger wrote:
>
>
>    Charles, right now the fallback content in canvas is a black hole in
>    webkit and thus Safari. So, VoiceOver can't read anything in canvas without
>    a Ouija board. (sorry, a little humor is due)
>
>
>    Rich Schwerdtfeger
>    CTO Accessibility Software Group
>
>    [image: Inactive hide details for Charles Pritchard ---03/30/2011
>    02:24:58 PM---Oliver, What's your take on the VoiceOver integration w]Charles
>    Pritchard ---03/30/2011 02:24:58 PM---Oliver, What's your take on the
>    VoiceOver integration with canvas?
>
>    From: Charles Pritchard *<chuck@jumis.com>* <chuck@jumis.com>
>    To: Oliver Hunt *<oliver@apple.com>* <oliver@apple.com>
>    Cc: Richard Schwerdtfeger/Austin/IBM@IBMUS, Boris Zbarsky *
>    <bzbarsky@mit.edu>* <bzbarsky@mit.edu>, *"cyns@exchange.microsoft.com"*<cyns@exchange.microsoft.com>
>    *<cyns@exchange.microsoft.com>* <cyns@exchange.microsoft.com>, *
>    "david.bolter@gmail.com"* <david.bolter@gmail.com> *
>    <david.bolter@gmail.com>* <david.bolter@gmail.com>, *
>    "faulkner.steve@gmail.com"* <faulkner.steve@gmail.com> *
>    <faulkner.steve@gmail.com>* <faulkner.steve@gmail.com>, *
>    "franko@microsoft.com"* <franko@microsoft.com> *<franko@microsoft.com>*<franko@microsoft.com>,
>    *"public-canvas-api@w3.org"* <public-canvas-api@w3.org> *
>    <public-canvas-api@w3.org>* <public-canvas-api@w3.org>, *
>    "public-canvas-api-request@w3.org"* <public-canvas-api-request@w3.org>
>    *<public-canvas-api-request@w3.org>* <public-canvas-api-request@w3.org>,
>    *"public-html@w3.org"* <public-html@w3.org> *<public-html@w3.org>*<public-html@w3.org>,
>    *"public-html-a11y@w3.org"* <public-html-a11y@w3.org> *
>    <public-html-a11y@w3.org>* <public-html-a11y@w3.org>, *
>    "public-html-request@w3.org"* <public-html-request@w3.org> *
>    <public-html-request@w3.org>* <public-html-request@w3.org>
>    Date: 03/30/2011 02:24 PM
>    Subject: Re: feedback requested: Canvas change for improved hit testing
>    that also facilitates accessibility
>
>    ------------------------------
>
>
>
>    Oliver,
>
>    What's your take on the VoiceOver integration with canvas?
>    First and foremost, we're looking to enable authors to provide more
>    information to accessibility software.
>
>    This is a brainstorming thread.
>
>    Ideas welcome.
>
>    On Mar 30, 2011, at 12:20 PM, Oliver Hunt <*oliver@apple.com*<oliver@apple.com>>
>    wrote:
>
>       On Mar 30, 2011, at 12:06 PM, Richard Schwerdtfeger wrote:
>
>          Oliver,
>
>          It is an attempt to simplify hit testing in canvas while at the
>          same time providing a vehicle to tell an assistive technology the bounds of
>          the corresponding UI object being drawn on canvas as represented in fallback
>          content. Currently there is no mapping. These bounds are needed by screen
>          magnifiers for zooming and screen readers for Braille support (earlier
>          post).
>
>          Now the canvas author has to manage all the hit testing. This is
>          a canvas deficiency that should have been in place to start - so grafting
>          seems like an inappropriate response. Consequently, I am also seeing canvas
>          applications that create the equivalent of visio by creating separate canvas
>          elements overlayed on top of another canvas to represent drawing objects.
>          This is very inefficient and will get worse unless something is done.
>
>       This is not a canvas deficiency -- canvas is an immediate mode
>       renderer, one of the things you have to handle yourself when dealing with
>       _any_ immediate mode renderer is hit detection. This is true of Canvas, GDI,
>       CG, raw component painting in Java, etc, etc
>
>       If you want hit detection to be done for you, you want a retained
>       mode renderer, such as SVG.
>
>       --Oliver
>
>
>
>          Rich Schwerdtfeger
>          CTO Accessibility Software Group
>
>          <graycol.gif>Oliver Hunt ---03/30/2011 12:11:53 PM---This feels
>          like an attempt to graft retained mode rendering on to canvas, what am i
>          missing? --Olive
>
>          From: Oliver Hunt <*oliver@apple.com* <oliver@apple.com>>
>          To: Richard Schwerdtfeger/Austin/IBM@IBMUS
>          Cc: Boris Zbarsky <*bzbarsky@mit.edu* <bzbarsky@mit.edu>>, *
>          chuck@jumis.com* <chuck@jumis.com>, *cyns@exchange.microsoft.com*<cyns@exchange.microsoft.com>,
>          *david.bolter@gmail.com* <david.bolter@gmail.com>, *
>          faulkner.steve@gmail.com* <faulkner.steve@gmail.com>, *
>          franko@microsoft.com* <franko@microsoft.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* <public-html-request@w3.org>
>          Date: 03/30/2011 12:11 PM
>          Subject: Re: feedback requested: Canvas change for improved hit
>          testing that also facilitates accessibility
>          Sent by: *public-canvas-api-request@w3.org*<public-canvas-api-request@w3.org>
>          ------------------------------
>
>
>
>          This feels like an attempt to graft retained mode rendering on to
>          canvas, what am i missing?
>
>          --Oliver
>
>          On Mar 30, 2011, at 8:39 AM, Richard Schwerdtfeger wrote:
>
>             Thanks Boris. Sorry for being a pest but I really want
>             developers to work through the issues.
>
>             So, you would do the following:
>
>             - Assign the a closed draw path to an element in fallback
>             content: setClickableRegion(element). This immediately makes the association
>             and places it at the bottom of the list.
>             - Any time you draw the element it moves it to the top of the
>             list.
>             - If the fallback element is removed the association would
>             need to go away. I did not address that so I will need to add that to the
>             proposal
>             - When a pointer event (click, etc.) goes to the fallback
>             element the normal capture/bubbling event processing would apply
>
>             Rich
>
>
>             Rich Schwerdtfeger
>             CTO Accessibility Software Group
>
>             <graycol.gif>Boris Zbarsky ---03/30/2011 10:05:48 AM---On
>             3/30/11 10:55 AM, Richard Schwerdtfeger wrote: > Seeing as nobody has
>             commented can we assume tha
>
>             From: Boris Zbarsky <*bzbarsky@mit.edu* <bzbarsky@mit.edu>>
>             To: Richard Schwerdtfeger/Austin/IBM@IBMUS
>             Cc: *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* <public-html-request@w3.org>, *
>             chuck@jumis.com* <chuck@jumis.com>, *
>             cyns@exchange.microsoft.com* <cyns@exchange.microsoft.com>, *
>             david.bolter@gmail.com* <david.bolter@gmail.com>, *
>             faulkner.steve@gmail.com* <faulkner.steve@gmail.com>, *
>             franko@microsoft.com* <franko@microsoft.com>
>             Date: 03/30/2011 10:05 AM
>             Subject: Re: feedback requested: Canvas change for improved
>             hit testing that also facilitates accessibility
>
>             ------------------------------
>
>
>
>             On 3/30/11 10:55 AM, Richard Schwerdtfeger wrote:
>             > Seeing as nobody has commented can we assume that developers
>             have no
>             > problem with our totally changing the canvas 2D API to
>             support clickable
>             > regions?
>
>             It might just mean that people don't read their mailing list
>             spam every
>             few hours.
>
>             >From reading over your proposal, I'm not sure I follow how it
>             would
>             behave in the face of DOM mutations (e.g. elements being
>             removed from
>             the fallback content).
>
>             Or put another way, once you draw, you're permanently
>             attaching some
>             element to the canvas, right? Or is that not the proposal?
>
>             -Boris
>
>
>
>


-- 
Paniz Alipour