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Accessibility in SVG (was: Set circle radius using CSS)

From: Doug Schepers <doug@schepers.cc>
Date: Fri, 16 Sep 2005 17:39:05 -0400
To: "'David Woolley'" <david@djwhome.demon.co.uk>, <www-svg@w3.org>
Message-Id: <20050916213906.DC2B412DA0A@pilfer.dreamhost.com>

Hi, David-

Thank you for reminding me of a very serious issue.

| > Moreover, I would personally discourage you from using CSS 
| with SVG at 
| > all, if you can help it. CSS is not required for an implementation, 
| > it's not used
| My impression is that CSS support was originally proposed as 
| part of the token compliance to W3C accessibility 
| requirements; 

That may have been part of the reason. I think the major reason, however,
was to play nice with other W3C Specs, and build upon existing work.
However, I don't feel that the CSS WG has made any efforts at all to make
CSS generically work with other markup languages than HTML, so the fit with
SVG is rather poor.

| it allows the user some ability to make pages 
| more easily readable when they have colour and other visiou 
| defects, but currently there doesn't seem any serious 
| interest in accessibilty.

In principle, I think this is a reasonable idea, and may work for some
limited use cases with SVG. However, I think that the primary benefits that
can be obtained using HTML+CSS in this regard (for instance, changing
background colors, increasing font size, etc.) are not really applicable to
SVG's semantics. For example, there is no background color that can be
contrasted with unless one designates an arbitrary rectangle to fit that
role. Font size can be increased by zooming in.

In short, I think that the accessibility solutions CSS offers simply don't
work with SVG. That is not to say that the goal should be abandoned.
Jonathan Chetwynd, myself, and several others have offered numerous
suggestions for accessibility on subjects ranging from vision problems
(color insensitivity, contrast problems, blindness) to navigation and
mobility concerns. The WG has generally entertained such suggestions and
taken several of the more pragmatic ones to heart.

However, these are not easy problems to solve. It is very easy to criticize
without offering solutions. Do you have a way in which accessibility in SVG
could be made better? My own ideas are that a better color description
language should be offered, with a method to establish which areas (or
elements) should contrast with which others. I'm still doing experiments
with this, and will publish something in the next couple of months. This
would help out with color contrast problems. But there are numerous other
vision issues, and untold issues that don't have anything to do with vision,
that also need to be addressed. I'm sure that the SVG WG would welcome your

If you can show a real-worl use-case where CSS helps SVG's accessibility, I
would be very eager to see that.


doug . schepers  @ vectoreal.com
www.vectoreal.com ...for scalable solutions.
Received on Friday, 16 September 2005 21:39:22 UTC

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