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Re: [SVGMobile12] uDOM attribute normalization on color values

From: Chris Lilley <chris@w3.org>
Date: Fri, 9 Jun 2006 16:01:08 +0200
Message-ID: <4641987.20060609160108@w3.org>
To: www-svg@w3.org
Cc: Anne van Kesteren <fora@annevankesteren.nl>

Hello www-svg,

Anne van Kesteren <fora@annevankesteren.nl> wrote:
> In
> <http://www.w3.org/TR/2005/WD-SVGMobile12-20051207/svgudom.html#Attribute_Normalization>
> it is defined what viewers may return for attribute values. The color
> normalization part does not define in enough detail what exactly may be
> returned for sRGB values

The intent is not to standardize a lexical form. If people want access
to the color values without doing their own microparsing, they already
have trait access which gives the color values directly:

interface SVGRGBColor
        attribute unsigned long red;
        attribute unsigned long green;
        attribute unsigned long blue;

>  as described in
> <http://www.w3.org/TR/2005/WD-SVGMobile12-20051207/painting.html#colorSyntax>.
> What is the normalized value of "rgb(100,      30,32,123)"?

Well, that particular one is an unsupported value so would be ignored
anyway :)

> The section also doesn't address the problem. It is still unclear what you get
> back when you retrieve such a value. When using getAttributeNS that is what you
> can expect, but when using traits it should be more clear.

Trait access looks very clear.

> I suggest that the SVG WG defines color normalization in a way similar to
> <http://whatwg.org/specs/web-apps/current-work/#fillstyle> (dropping the rgba()
> bit that doesn't apply to SVG).

That would not work well. It tries to standardize a single lexical form
(which still has to be parsed) and fails to pick the most precise lexical
form so will always produce round-off error even if normalization is not

> In addition, I suggest that the SVG WG contacts the CSS WG about this
> to discuss normalization of these property/attribute values together
> so a common syntax can be agreed upon and used.

SVG, like CSS 2.1, states that the computed value is the specified
color. CSS does not address color normalization at all.

 Chris Lilley                    mailto:chris@w3.org
 Interaction Domain Leader
 Co-Chair, W3C SVG Working Group
 W3C Graphics Activity Lead
 Co-Chair, W3C Hypertext CG
Received on Friday, 9 June 2006 14:01:30 UTC

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