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Re: canvas API changes to drive magnification

From: Steven Faulkner <faulkner.steve@gmail.com>
Date: Wed, 10 Mar 2010 14:46:11 +0000
Message-ID: <55687cf81003100646j3ab8a6b4tde79447905194def@mail.gmail.com>
To: Richard Schwerdtfeger <schwer@us.ibm.com>
Cc: David Bolter <david.bolter@gmail.com>, Charles McCathieNevile <chaals@opera.com>, cooper@w3.org, cyns@exchange.microsoft.com, Frank Olivier <franko@microsoft.com>, janina@rednote.net, jcraig@apple.com, "public-canvas-api@w3.org" <public-canvas-api@w3.org>
Hi Rich,
>Are you thinking that the browser uses the area map coordinates to draw the
rectangle on the canvas?

I would expect that image maps work the same way as on images; the focus
outline (dotted line) is displayed when an area receives focus.

I admit it is unclear to me for reading the current spec,

>4. If the user has requested the use of particular focus rings (e.g.
high-contrast focus rings), or if the canDrawCustom argument is absent or
false, then draw a >focus ring of the appropriate style along the path,
following platform conventions, return false, and abort these steps.
source: http://www.w3.org/TR/2dcontext/#dom-context-2d-drawfocusring

but step 4 appears to indicate that a focus ring is drawn by the browser
rather than the author unless '*canDrawCustom' is true.*
**
*regards*
*stevef*



On 9 March 2010 19:01, Richard Schwerdtfeger <schwer@us.ibm.com> wrote:

>  canDrawFocus is specific to <canvas>. The areamap would not be rendered
> if it were used as the shadow DOM for canvas. Are you thinking that the
> browser uses the area map coordinates to draw the rectangle on the canvas?
>
>
> Rich
>
>
> Rich Schwerdtfeger
> Distinguished Engineer, SWG Accessibility Architect/Strategist
>
> [image: Inactive hide details for David Bolter ---03/09/2010 12:33:21
> PM---The typical image map is an image element with the usemap at]David
> Bolter ---03/09/2010 12:33:21 PM---The typical image map is an image element
> with the usemap attribute
>
>
>      *David Bolter <david.bolter@gmail.com>*
>             Sent by: public-canvas-api-request@w3.org
>
>             03/09/2010 12:29 PM
>
>
> To
>
> Richard Schwerdtfeger/Austin/IBM@IBMUS
>
> cc
>
> Charles McCathieNevile <chaals@opera.com>, cooper@w3.org,
> cyns@exchange.microsoft.com, Steven Faulkner <faulkner.steve@gmail.com>,
> Frank Olivier <franko@microsoft.com>, janina@rednote.net, jcraig@apple.com,
> "public-canvas-api@w3.org" <public-canvas-api@w3.org>,
> public-canvas-api-request@w3.org
>
> Subject
>
> Re: canvas API changes to drive magnification
>
> The typical image map is an image element with the usemap attribute
> pointing to a map of elements that specify their shape and coordinates.
> With image maps the browser is responsible for drawing focus. I was
> thinking if we wanted to support this, the canDrawCustom might be
> relevant? But really I don't know what is intended.
>
> cheers,
> David
>
> On 09/03/10 12:29 PM, Richard Schwerdtfeger wrote:
> > I am still confused. In the usemap appraoch we would have DOM elements in
> > the area map which would act as elements. This is no different than if we
> > created a navsubtree. So, now we have an element to reference in either
> > scenario.
> >
> > To draw a caret. the element has to either be focused or child descendant
> > of the focused element. The caret is drawn on the canvas itself.
> >
> > Steve, can you provide more clarification behind canDrawCustom? Hixie's
> > wording was unclear to David and me.
> >
> > BTW - I am trying to integrate areamap and navsubtree with Charles on a
> > single proposal.
> >
> > Rich
> >
> > Rich Schwerdtfeger
> > Distinguished Engineer, SWG Accessibility Architect/Strategist
> >
> >
> >
> >               David Bolter
> >               <david.bolter@gma
> >               il.com>
>   To
> >               Sent by:                  Richard
> >               public-canvas-api         Schwerdtfeger/Austin/IBM@IBMUS
> >               -request@w3.org
>  cc
> >                                         Charles McCathieNevile
> >                                         <chaals@opera.com>,
> cooper@w3.org,
> >               03/09/2010 10:00          cyns@exchange.microsoft.com,
> Steven
> >               AM                        Faulkner
> >                                         <faulkner.steve@gmail.com>,
> Frank
> >                                         Olivier<franko@microsoft.com>,
> >                                         janina@rednote.net,
> >                                         jcraig@apple.com,
> >                                         "public-canvas-api@w3.org"
> >                                         <public-canvas-api@w3.org>
> >
> Subject
> >                                         Re: canvas API changes to drive
> >                                         magnification
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > Hi Rich,
> >
> > I don't know if I am against the canDrawCustom attribute, I just want to
> > understand it better. Perhaps it is useful for interop with the usemap
> > approach?
> >
> > cheers,
> > David
> > On 09/03/10 9:56 AM, Richard Schwerdtfeger wrote:
> >
> >> David,
> >>
> >> Good pickup. I believe the author should be responsible for drawing the
> >> caret. The canDrawCustom argument is left over from Hixie's proposal and
> >>
> > I
> >
> >> agree that is a bit confusing. I have not seen a convention whereby the
> >> system draws the caret - has anyone else? I left it in. Do you think it
> >>
> > is
> >
> >> possible for the browser to draw a default caret?  I can see a focus
> ring
> >> being doable but for caret I have my doubts.
> >>
> >> Rich
> >>
> >> Rich Schwerdtfeger
> >> Distinguished Engineer, SWG Accessibility Architect/Strategist
> >>
> >>
> >>
> >>                David Bolter
> >>                <david.bolter@gma
> >>                il.com>
> >>
> > To
> >
> >>                                          Richard
> >>                03/09/2010 08:34          Schwerdtfeger/Austin/IBM@IBMUS
> >>                AM
> >>
> > cc
> >
> >>                                          cooper@w3.org,
> >>
> > janina@rednote.net,
> >
> >>                                          Charles McCathieNevile
> >>                                          <chaals@opera.com>,
> >>                                          cyns@exchange.microsoft.com,
> >>
> > Steven
> >
> >>                                          Faulkner
> >>                                          <faulkner.steve@gmail.com>,
> Frank
> >>                                          Olivier<franko@microsoft.com>,
> >>                                          jcraig@apple.com,
> >>                                          "public-canvas-api@w3.org"
> >>                                          <public-canvas-api@w3.org>
> >>
> >>
> > Subject
> >
> >>                                          Re: canvas API changes to drive
> >>                                          magnification
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >> Hi Rich, all,
> >>
> >> I just read the proposal at
> >> http://www.w3.org/html/wg/wiki/ChangeProposals/canvasaccessibility,
> >>
> >> I don't feel like I fully understand the proposal. Take the case for
> >>
> > canvas
> >
> >> drawn text. Each time the user presses the right arrow, does the author
> >> catch that event and call e.g. drawFocusRing(myTextBox, 10, 5, true,
> >>
> > true)?
> >
> >> I want to understand who is responsible for drawing the caret or focus
> >>
> > ring
> >
> >> in various examples.
> >>
> >> http://www.paciellogroup.com/blog/misc/canvas/2dcontext-caret.html is
> >> really hard to understand (maybe because of typos). For example I don't
> >> understand how to parse this sentence: " If the given element is focused
> >>
> > or
> >
> >> is a descendant of the focus element, and isCaret is true, canDrawCustom
> >> argument is true draws a caret following the platform conventions for
> >> carets." -- Who draws?
> >>
> >> cheers,
> >> David
> >>
> >> On 08/03/10 7:17 PM, Richard Schwerdtfeger wrote:
> >>
> >>
> >>         I would like to have people review Steve and my proposal to the
> >>         canvas
> >>         accessibility API to address focus and caret tracking for the
> next
> >>         canvas
> >>         meeting on the 15th so that we can take this to the task force
> for
> >>         approval. David, Frank, Cynthia, James, and Charles I would very
> >>
> > much
> >
> >>         like
> >>         your feedback by the next call.
> >>
> >>
> http://www.w3.org/html/wg/wiki/ChangeProposals/canvasaccessibility
> >>
> >>         Thanks,
> >>         Rich
> >>
> >>         Rich Schwerdtfeger
> >>         Distinguished Engineer, SWG Accessibility Architect/Strategist
> >>
> >>
> >>
> >>
> >
> >
> >
>
>
>
>


-- 
with regards

Steve Faulkner
Technical Director - TPG Europe
Director - Web Accessibility Tools Consortium

www.paciellogroup.com | www.wat-c.org
Web Accessibility Toolbar -
http://www.paciellogroup.com/resources/wat-ie-about.html


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Received on Wednesday, 10 March 2010 14:47:05 UTC

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