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Type in SVG: final form only?

From: Eric Muller <emuller@Adobe.COM>
Date: Tue, 12 Sep 2000 10:37:38 -0700
Message-ID: <39BE69E2.3CD167E0@adobe.com>
To: www-svg@w3.org
A bit of background for the question: In my (personal) opinion, one
needs to distinguish very strongly between "text" and "positioned
glyphs". Positioned glyphs are the choice of specific glyphs of a
specific font to be displayed at specific positions. Most often,
positioned glyphs are obtained by feeding text in a layout engine.
Text is a sequence of characters, which by itself does not imply a
specific representation, i.e. can be laid out into many sets of
positioned glyphs. Of course, text presented to a layout engine will
often be supplemented with formatting directives, such as font
specification, point size, tracking, etc. It is perfectly possible
that two different layout engines would produce different positioned
glyphs from the same text and directives: e.g. one could use the
kerning data in the font, the other could do optical kerning; one
could do automatic optical size selection, the other could stick to
one optical size.

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.

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

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?


Thanks,
Eric.

PS: The views expressed here are my own only and do not reflect
Adobe's position.
Received on Tuesday, 12 September 2000 13:36:43 GMT

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