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Re: Type in SVG: final form only?

From: Leonard Rosenthol <leonardr@lazerware.com>
Date: Tue, 12 Sep 2000 14:38:38 -0400
Message-Id: <a04310108b5e42731b309@[207.29.200.50]>
To: "Eric Muller" <emuller@Adobe.COM>, www-svg@w3.org
At 10:37 AM -0700 9/12/00, Eric Muller wrote:
>A bit of background for the question: In my (personal) opinion, one
>needs to distinguish very strongly between "text" and "positioned
>glyphs".

	Agreed.


>When dealing with documents that will eventually include type in their
>presentation, there has to be a layout engine at some point. In the
>case of HTML, it is in the HTML viewer, and one can argue that HTML
>supports only text. In the case of PDF, it is not in the PDF viewer,
>i.e. PDF supports only positioned glyphs.

	Actually, PDF supports both positioned glyphs and text, since 
you can choose to use a PDF operator that simply says draw this text 
starting here "(this is some text) Tj" as opposed to explicit 
individual glyph positioning.

	And because of that, a given PDF rendering engine can choose 
to do things like subpixel positioning (for improved anti-aliasing), 
or deal with font (and/or glyph substitution issues).


>It is clear from the SVG requirements and recommendation that SVG
>supports positioned glyphs. The question is: does SVG support text?

	Yes, exactly like PDF does, in that you can have both.  Also, 
since SVG supports text decorations (underline, overline, strikeout) 
and text alignment (left, right, center), those definitely are more 
"text" than "glyph"


>Does the SVG recommendation essentially implies that every SVG viewer
>include a text layout engine? I carefully read the SVG recommendation
>and could not conclusively conclude one way or the other.

	I don't know that it implies it, but in practice I suspect 
you need one.  HOWEVER, it can be a very simplistic one since you 
don't have to worry (in standard SVG) about things like line wrap. 
But since you do have to worry about alignment and such, you do need 
one.


>Another way to ask: when an SVG viewer sees <text>act</text>, can it
>decide to render the characters "c" and "t" using a ligature glyph
>"ct" if there is one in the font? Can it determine the position of
>this glyph by doing optical kerning with the "a" glyph?
>
	I don't see why not.


Leonard
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Leonard Rosenthol      			Internet:       leonardr@lazerware.com
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Received on Tuesday, 12 September 2000 14:36:01 GMT

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