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Re: Minutes, 26 September 2009 SVG WG F2F - Day 1

From: Robert O'Callahan <robert@ocallahan.org>
Date: Mon, 28 Sep 2009 18:37:57 +1000
Message-ID: <11e306600909280137o193d2a72m844a22f8f2097bcc@mail.gmail.com>
To: Alex Danilo <alex@abbra.com>
Cc: anthony.grasso@cisra.canon.com.au, www-svg@w3.org, public-svg-wg@w3.org
On Mon, Sep 28, 2009 at 6:10 PM, Alex Danilo <alex@abbra.com> wrote:

> --Original Message--:
> >On Mon, Sep 28, 2009 at 5:45 PM, Alex Danilo <alex@abbra.com> wrote:
> >
> >--Original Message--:
> >>It's not clear to me what was resolved about SVG Fonts, in particular the
> issue of cloning vs patterns. It sounds like people want 'stroke' and 'fill'
> properties on <text> to apply to the arbitrary SVG content of a glyph? I
> honestly don't think that's possible to do in a sane way that works in
> general.
> >
> >Yes it is. Whether it's difficult in some existing implementations is an
> orthgonal issue.
> >
> >By cascading the CSS properties from <text> into the font glyph content
> and hoping that everything works out OK?
> >
> >I previously explained how that completely fails whenever the text might
> have characters that aren't covered by the SVG Font, because then you can't
> know which coordinate system will be used to interpret user units in the
> style of the <text>.
>
> I expect you meant glyphs here.


No, I mean the character.

Perhaps I wasn't clear. Suppose the author writes
<text style="stroke-width:10; font:MySVGFont 100px;">ABC</text>
Suppose MySVGFont uses the default units per em of 1000, and suppose it
includes glyphs for A and B but not C, and the A and B glyphs use <path>
elements to render the letters, with the stroke-width inherited from the
<text>. Then the stroke used for A and B will be about 1px wide, but the
stroke used for C will be 10px wide. The problem is that for characters
covered by the SVG font, stroke-width (and everything else that uses user
units) is interpreted in the font coordinate system, but for all other
characters stroke-width is interpreted in the user unit coordinate system
for the <text>.

So in practice it seems to me that this cascading is only useful when you
have a very tight relationship between the producer of the font and the
consumer of the font, and in particular the consumer of the font must be
able to restrict the characters used in the text --- for example
user-provided text is right out. But if there is such a tight relationship
between the producer and consumer, why not just put the styling in the font
glyph content directly? Are there really significant use cases where there's
value in reusing font glyph content, inheriting different styles from
different <text> elements, but the font consumer is restricted to static
text and has intimate knowledge of the font design details?

Since you've implemented it, maybe you can point us to some examples of
people using these features for real projects.

Rob
-- 
"He was pierced for our transgressions, he was crushed for our iniquities;
the punishment that brought us peace was upon him, and by his wounds we are
healed. We all, like sheep, have gone astray, each of us has turned to his
own way; and the LORD has laid on him the iniquity of us all." [Isaiah
53:5-6]
Received on Monday, 28 September 2009 08:38:44 GMT

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