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Fwd: Re[2]: Your comments on WCAG 2.0 Last Call Draft of April 2006

From: Loretta Guarino Reid <lorettaguarino@google.com>
Date: Tue, 29 May 2007 06:20:18 -0700
Message-ID: <824e742c0705290620t2ed19a20j424f5968102485a5@mail.gmail.com>
To: public-comments-WCAG20@w3.org

---------- Forwarded message ----------
From: Loretta Guarino Reid <lorettaguarino@google.com>
Date: May 28, 2007 6:43 AM
Subject: Re: Re[2]: Your comments on WCAG 2.0 Last Call Draft of April 2006
To: Marco Bertoni <m.bertoni@webprofession.com>
Cc: Gregg Vanderheiden <gv@trace.wisc.edu>

Thanks for the additional explanation, Marco.

The working group spent a lot of time discussing such options; in
fact, some of our initial proposals  looked very much like your
suggestions. However, we discovered several problems.

As text is scaled larger and larger, it becomes impossible to prevent
loss of content or functionality. In the limit, as text becomes large
enough, wrapping algorithms turn the text into a vertical column of
words, possibly clipped if the word itself is too large to fit into
the available horizontal space on screen.

Arbitrary resizing also introduces problems with testing. How does an
author know when he has satisfied the success criterion, particularly
for more sophisticated web pages that may change their layout  based
on the text size to produce more readable results. An example would be
a page that switches between single and multiple column text so that
line widths stay within the ~16 word range recommended for some
cognitive, learning, and language disabilities.

So we felt that some choice of explicit values was necessary to make
these success criteria testable. 200% was chosen after experimenting
with various web pages that the working group felt were well designed,
to see when scaling started to introduce problems. We also looked at
the scaling supported directly by popular browsers. (IE's largest text
scaling factor is only about  180%). And we looked at the support
provided by screen magnifiers. For older screen magnifiers, 200% was
the smallest scale factor that could be chosen.

We believe that there is a range of  visual disabilities that can best
be addressed directly and a range where the most effective solutions
rely on assistive technology such as screen magnifiers. Other success
criteria ensure that assistive technology can access the content
successfully. These new success criteria identify the author's
responsibility when supporting users where direct access is more

Note, by the way, that the success criteria don't require just scaling
to 200% and 50%, but to all the values between. Our expectation is
that solutions that work across that range will continue to work "as
well as possible" beyond those limits.


On 5/28/07, Marco Bertoni <m.bertoni@webprofession.com> wrote:
> Hello Gregg and Loretta,
> a more generic solution may be something like this:
> Level AA: Visually rendered text can be resized without assistive technology and without loss of content or functionality.
> Level AAA: Visually rendered text can be resized without assistive technology and without loss of content or functionality and in a way that does not require the user to scroll horizontally.
> If we impose to make text scalable *without loss of content or functionality* only at one specific increment value (200 percent) the danger is that people that need more than a 200 percent increment may notice loss of content or functionality.
> On the contrary, avoiding to impose explicit values (like 200 percent) we force the designer to make text scalable *without loss of content or functionality* at every scale increment (200 percent, 300 percent... or IE 6 "Larger", IE 6 "Largest" etc.).
> Also this generic solution have his own problems: it's hard for a designer to guarantee virtually infinite text increments (or decrements) without loss of content or functionality. But this depends on the designer professionalism. Moreover, the common sense will probably tell a good designer that if there is a bit of  loss of content or functionality at a certain really big text increment (or decrement) level, this is not a major accessibility issue. But, obviously, this is all debatable.
> IMHO, only one thing is certain: it is wrong to impose a specific increment value without making full usability tests with partially sighted users. Especially because low vision is complex (e.g. central field loss, multiple field loss, tunnel vision, contrast loss and glare problems etc.) so partially sighted users may have quite different levels of sight and, accordingly, quite different requirements.
> At last, I think that the lesser of two evils is to avoid to mention specific values.
> Have a nice day,
> Marco
> Sunday, May 27, 2007, 5:09:37 AM, you wrote:
> > Hi Marco,
> >   Thank you for your comment.  Can you tell us more about what you meant by
> >> However, I think that to impose
> >> explicit values (like 200 percent and so on) may be
> >> dangerous. How about a more generic solution?
> > Thanks
> > Gregg
> >  -- ------------------------------
> > Gregg C Vanderheiden Ph.D.
> --
> Best regards,
> Marco Bertoni
> International Webmasters Association / The HTML Writers Guild
> http://www.iwanet.org
Received on Tuesday, 29 May 2007 13:20:50 UTC

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