Re: hit testing and retained graphics

Yes, the author draws the widget on the canvas based on the information in
the canvas subtree.

If you don't use the subtree it won't be in the keyboard navigation order
and you can't provide the accessibility information

>From the HTML 5 spec on canvas:
http://dev.w3.org/html5/spec/the-canvas-element.html#the-canvas-element

"When a canvas element represents embedded content, the user can still
focus descendants of the canvas element (in the fallback content). When an
element is focused, it is the target of keyboard interaction events (even
though the element itself is not visible). This allows authors to make an
interactive canvas keyboard-accessible: authors should have a one-to-one
mapping of interactive regions to focusable elements in the fallback
content. (Focus has no effect on mouse interaction events.) [DOMEVENTS]"

Attached is a basic example:


(See attached file: CanvasEditor.html)
Rich Schwerdtfeger
CTO Accessibility Software Group



From:	paniz alipour <alipourpaniz@gmail.com>
To:	Richard Schwerdtfeger/Austin/IBM@IBMUS
Cc:	chuck@jumis.com, cyns@exchange.microsoft.com,
            david.bolter@gmail.com, franko@microsoft.com, Mike@w3.org,
            public-canvas-api@w3.org, public-canvas-api-request@w3.org,
            public-html@w3.org, public-html-a11y@w3.org
Date:	07/07/2011 09:04 AM
Subject:	Re: hit testing and retained graphics
Sent by:	public-canvas-api-request@w3.org



Hi Richard,

Yes I get your purpose,except one part :

 You control the drawing  ?!


in this sentence:
If you wanted to create a canvas rendering of a checkbox in the fallback
content, on the canvas that was 70X70 you can do it. You control the
drawing

and some thing else if a developer doesn't use sub-tree in shadow DOM? what
does happen?


Thanks


On Thu, Jul 7, 2011 at 6:25 PM, Richard Schwerdtfeger <schwer@us.ibm.com>
wrote:
  Hi Paniz,

  I am not sure if I am answering your question but you could create these
  objects on canvas and create equivalents in the canvas subtree whereby
  the canvas is a rendering of the HTML element in the canvas subtree and
  you can give it any size and dimension you want. All the elements in
  canvas subtree could be placed in the keyboard navigation order. If you
  wanted to create a canvas rendering of a checkbox in the fallback
  content, on the canvas that was 70X70 you can do it. You control the
  drawing. Accessibility wise I don't yet have a way to communicate those
  bounds to the accessibility API. This is what we have been discussing. We
  have been discussing creating a drawing path on canvas that represents
  the bounds of the object, binding it to the canvas subtree element (which
  is in the keyboard navigation order). In doing so we would have the user
  agent to do hit testing on the drawing objects in canvas and pass the
  pointing event to the corresponding object in the accessibility subtree.
  The bounds of the object used for hit testing would be passed to the
  corresponding accessible object (corresponding the to the DOM element in
  the subtree). Now a magnifier would know how to zoom to the corresponding
  70x70 checkbox on the canvas.

  To be honest, this is not new. This is how desktops like Windows work.
  You have a graphic on the screen bound to a COM object which supports
  MSAA. The MSAA bounding rectangle is retrieved from the retained mode
  graphic.
  We are arguing for putting this capability into canvas.



  Rich


  Rich Schwerdtfeger
  CTO Accessibility Software Group

  Inactive hide details for paniz alipour ---07/07/2011 08:42:16 AM---Hi
  Richard, I mean for example I have an interaction UI on paniz alipour
  ---07/07/2011 08:42:16 AM---Hi Richard, I mean for example I have an
  interaction UI on canvas as like web pages,


  From: paniz alipour <alipourpaniz@gmail.com>
  To: Richard Schwerdtfeger/Austin/IBM@IBMUS
  Cc: chuck@jumis.com, cyns@exchange.microsoft.com, david.bolter@gmail.com,
  franko@microsoft.com, Mike@w3.org, public-canvas-api@w3.org,
  public-html@w3.org, public-html-a11y@w3.org
  Date: 07/07/2011 08:42 AM

  Subject: Re: hit testing and retained graphics
  Sent by: public-canvas-api-request@w3.org




  Hi Richard,

  I mean for example I have an interaction UI on canvas as like web pages,

  textbox,radiobutton ,checkbox,.... .I want to know these elements that
  are drawn or are images on canvas

  could be incredible,Of course they can but in your opinion how many
  percent it is possible(forexample checkbox with height 70 and width 70)

  Best Regards

  On Thu, Jul 7, 2011 at 6:02 PM, Richard Schwerdtfeger <schwer@us.ibm.com>
  wrote:
        Hi Paniz,

        I am not quite following you. Could you please provide more detail?

        Thanks,



        Rich


        Rich Schwerdtfeger
        CTO Accessibility Software Group

        Inactive hide details for paniz alipour ---07/07/2011 06:32:18
        AM---Hello to all, Maybe you think that this question is not rel
        paniz alipour ---07/07/2011 06:32:18 AM---Hello to all, Maybe you
        think that this question is not related to this discussion,

        From: paniz alipour <alipourpaniz@gmail.com>
        To: Richard Schwerdtfeger/Austin/IBM@IBMUS
        Cc: chuck@jumis.com, franko@microsoft.com, Mike@w3.org,
        david.bolter@gmail.com, cyns@exchange.microsoft.com,
        public-canvas-api@w3.org, public-html-a11y@w3.org,
        public-html@w3.org
        Date: 07/07/2011 06:32 AM

        Subject: Re: hit testing and retained graphics






        Hello to all,

        Maybe you think that this question is not related to this
        discussion,

        But I want to know whether the web widget that are located on
        canvas,

        are they incredible .I mean a check box with height 70,weight 70,

        or no it will design as the common web widget on websites?

        Thanks

        On Fri, Jun 17, 2011 at 11:11 PM, Richard Schwerdtfeger <
        schwer@us.ibm.com> wrote:
              Charles, Frank, Mike,

              I am back from vacation. How far do we need to go with hit
              testing? Right now I am looking at associating a closed draw
              path with a DOM object in the canvas subtree. We would then
              need to address the routing of pointing device input events
              to the DOM object. The drawing path can be used to provide
              bound information to platform accessibility API.

              Do we need to bind any other drawing properties to the canvas
              object - similar to the way device context's are handled on
              graphic subsystems like Windows?

              Mike, I am including you as before I went on vacation you
              indicated that a number of developers desired this feature
              and wanted to be involved.

              Rich


              Rich Schwerdtfeger
              CTO Accessibility Software Group




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        Paniz Alipour






  --
  Paniz Alipour





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Paniz Alipour