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ACTION: PP to Proposal on ways User Agents could use live regions.

From: Peter Parente <pparent@us.ibm.com>
Date: Thu, 26 Jul 2007 10:24:28 -0400
To: Jan Richards <jan.richards@utoronto.ca>
Cc: WAU-ua <w3c-wai-ua@w3.org>, w3c-wai-ua-request@w3.org
Message-ID: <OF1A77417C.E3E1FF29-ON85257324.00452CBD-85257324.004F20EE@us.ibm.com>

This action item concerns checkpoint 3.5: Toggle automatic content
retrieval and its application to dynamic regions within a page (e.g. AJAX).
I indicated on the wiki that user agents may be able to respect this
guideline for partial page refreshes if the page contains appropriate live
region markup.

We must answer two questions before we can decide how to rewrite this
guideline. I discuss them in detail below. At the end of the email, I take
a crack at reformulating checkpoint 3.5 under a few assumptions.

1) What "part" of the UA should we hold responsible for this guideline?

So far, it has been implied that the AT is responsible for deciding how
live regions are presented. For instance, if a screen reader is busy
reading the content of a page and an event occurs outside the point of
regard in a "rude" live region, whether that change is announced or not is
determined by the screen reader settings (e.g. "Rude regions interrupt?
[yes/no]").  However, use of live region information is not limited to ATs.
For instance, the browser could conceivably have an inherent setting that
controls whether or not changes to the DOM are allowed. Essentially, this
toggle would allow the user to make parts of the DOM "read-only" on demand.
In both cases, the granularity can range from a single live region, to live
regions with certain properties, to all live regions on a page.

We need the following information from browser developers before we know if
this technique is feasible or not.

a) Is it possible to implement a "read-only DOM" setting without breaking
existing Web apps?
b) Is the base browser the right place to implement such a setting?
c) Is it possible to implement in a browser extension?

2) Is "retrieval" what we should really be toggling?

This question is about the intention of the guideline as compared with the
language used. Relying on live region markup to block changes to the DOM is
a technique applied after content has been retrieved. In fact, it can only
be applied after content has been fetched. Beforehand, the browser has no
concept of the purpose of the fetch. For instance, some Javascript code
might send a message to the server and receive a response that is never
rendered for the user. On the other hand, the Javascript code may intend to
write the response into the DOM for the user. But until that code actually
touches the DOM API, the UA has no way of determining where in the page it
will appear (i.e. in what live region, not in a live region, not in a
visible element).

I think the true intention of this checkpoint is to "toggle automatic
content changes." In some cases, such as a full page refresh, blocking
content retrieval may be the proper technique. In the case of AJAX,
however, it is not, nor should it be implied.

If we assume that implementing read-only DOM is possible and retrieval is
more of a technique than a requirement, we might rewrite the guideline as
follows:

3.5 Toggle automatic content updates

1. Allow configuration so that the user agent only replaces existing page
content on explicit user request.

Normative inclusions and exclusions

1. When the user chooses not to update content, the user agent may ignore
that content; buffering is not required for later rendering.
2. When automatic content updates are disabled, a user agent may choose to
avoid retrieving content that it will ultimately not render. The browser
should take care not to block fetches that will not render in the UI.
3. This checkpoint only applies when the user agent, not the server,
automatically initiates a content update.

(I suggest we remove the second part of 3.5 about redirects. Why don't
these count?)

Notes

(Can stay the same.)

Techniques

(This is where notes about blocking page refreshes, blocking redirects, and
making live regions read-only can go.)

Peter Parente
pparent@us.ibm.com
Tie: 526-2346
IBM: 919-486-2346


                                                                           
             Jan Richards                                                  
             <jan.richards@uto                                             
             ronto.ca>                                                  To 
             Sent by:                  WAU-ua <w3c-wai-ua@w3.org>          
             w3c-wai-ua-reques                                          cc 
             t@w3.org                                                      
                                                                   Subject 
                                       Re: User Agent Teleconference for   
             07/12/2007 03:44          July 12 2007                        
             PM                                                            
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           





Notes from the call:

http://www.w3.org/2007/07/12-ua-minutes.html


Action items:

ACTION: JR to Expand on idea of blocking functional areas: animation,
low contrast, etc.

ACTION: PP to Proposal to combine 3.2 and 3.3

ACTION: JR to Proposal to limit "background image" to body of document

ACTION: JA to Get thoughts together about 3.4 "All executable content",
managing configuration

ACTION: JR to Proposal to have config uration not to have stripped down
user agent windoews

ACTION: PP to Proposal on ways User Agents could use live regions.

ACTION: JA to Proposal that if a live region has focus, it shouldn't
update.]


Cheers,
Jan


Jim Allan wrote:
> W3C User Agent Teleconference for July 12 2007
> -------------------------------------------------------------
> Chair: Jim Allan
> Date: Thursday, July 122007
> Time: 2:00-3:00 pm Boston Local Time, USA (19:00-20:00 UTC/GMT)
> Call-in: Zakim bridge at: +1-617-761-6200, code 8294#
> for UK use 44-117.270-6152
> IRC: sever: irc.w3.org, port: 6665, channel: #ua.
> -------------------------------------------------------------
>
> Regrets, agenda requests, or comments to the list
>
> Agenda:
>
> 1. Changing Meeting time (move meeting time ahead 1 hour)
>
> 2. Ideas for topics for Tech Plenary day
>
> 3. Wiki - review edits
>    http://www.w3.org/WAI/UA/wiki/UaagDocument
>
> Jim Allan, Webmaster & Statewide Technical Support Specialist
> Texas School for the Blind and Visually Impaired
> 1100 W. 45th St., Austin, Texas 78756
> voice 512.206.9315    fax: 512.206.9264  http://www.tsbvi.edu/
> "We shape our tools and thereafter our tools shape us." McLuhan, 1964
>

--
Jan Richards, M.Sc.
User Interface Design Specialist
Adaptive Technology Resource Centre (ATRC)
Faculty of Information Studies
University of Toronto

   Email: jan.richards@utoronto.ca
   Web:   http://jan.atrc.utoronto.ca
   Phone: 416-946-7060
   Fax:   416-971-2896








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Received on Thursday, 26 July 2007 14:24:54 GMT

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