Re: RE: TTF and Unicode surrogates

From: David Goldsmith (
Date: Fri May 15 1998 - 20:46:11 EDT

Rick McGowan ( wrote:

>I think the "Unicode CMAP" is convenient for some things to some people.
>Rendering of Unicode text for display is a complex problem. To do it, you
>need one or more ordered sets of glyphs, and a means of translating from
>stream of character codes into a corresponding stream of glyph codes. Just
>having a "Unicode CMAP" doesn't get you the second piece. It will get you
>long way in the Latin script and in CJK, but it won't get you much past
>into the more complex scripts.


In Apple's model, the cmap is not the only piece of the
character-to-glyph mapping. Character-to-glyph mapping is done through
the combination of the 'cmap' table and the 'mort' table. There are two
tables rather than one for historical reasons; the 'sfnt' font format was
originally defined without thought being given to complex scripts. But
Rick is correct in that a 'cmap' table alone is insufficient to correctly
map all Unicode characters to glyphs.

David Goldsmith
International and Text Department Architect
Apple Computer, Inc.

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