W3C home > Mailing lists > Public > www-svg@w3.org > November 2002

Re: svg textLength issue (and a little thing about use...)

From: Chris Lilley <chris@w3.org>
Date: Wed, 13 Nov 2002 12:19:36 +0100
Message-ID: <15663032281.20021113121936@w3.org>
To: www-svg@w3.org, "Jim Ley" <jim@jibbering.com>

Hello Jim, www-svg,

You said

[two things, one about circular references that was cleared up by the
mention from the 1.1 spec "URI references that directly or indirectly
reference themselves are treated as invalid circular references."
andone about textLength, legibility and making text bigger. This email
is about that part.]

You said

> The textLength attribute on SVG's textLength causes accesibility
> problems for users who use their own stylesheets to overide author
> selections.

This is incorrect. There are several related but distinct things here:

- users often need the text to be bigger so they can see it

- in system that use textflow, such as HTML, this is often done by
increasing the font size

- if people do that in SVG, there is no reflow but the text gets
bigger and ovderlaps other stuff, decreasing legibility

- SVG allows zooming as a mechanism to make the text bigger

- variations in font metrics between platforms can result in slightly
overlaping text, a problem that textLength takes care of

> Consider:
>    <text font-size="20px" textLength="38px"
> lengthAdjust="spacingAndGlyphs">Hello</text>
> Which will work fine if the font-size is close to the 20px, the
> adjustments whilst making the font slightly less clear shouldn't have too
> much effect on legibility.

Yes - in fact, if there are other graphics or text nearby, they will
increase legibility.

> However if the user takes advantage of CSS2 to increase the font-size to
> something they find legible, the resulting narrow letters will likely be
> unreadable for them.

Yes. And if there was no textLength specified, they would also get a
decrease in legibility because of overlap with other text or graphics.

They should not do that, but should use zoom instead.

> I do not see any mechanism for a user to override the textLength
> property in their user stylesheet, yet a user would need this
> ability to adjust font-size.

No, that would not help at all. It would just move the problem around.

Systems that do not do reflow cannot use the font-size property to
make text larger for increased legibility. They need other methods
that prevent overlap, such as zoom.

 Chris                          mailto:chris@w3.org
Received on Wednesday, 13 November 2002 06:19:35 UTC

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