From: Markus Scherer (markus.scherer@jtcsv.com)
Date: Fri Oct 11 2002 - 13:02:25 EDT
Doug Ewell wrote:
> What is the correct IBM GCGID value for U+03B8 GREEK SMALL LETTER THETA?
> Is it GT610000 or GT610002?
I have an internal document that shows
GT610000 Theta Small - (see GT610001, GT610002) U00003B8 GREEK SMALL LETTER THETA
GT610001 Theta Small (Open Form) - (resembles SA50) U00003D1 GREEK THETA SYMBOL
GT610002 Theta Small (Closed Form)
SA500000 Curly Theta Symbol - (resembles GT610001)
The last digit in the GCGID is 0 for the generic GCGID for which any glyph can be chosen. A non-zero digit selects a specific, registered glyph - quite similar to the Ideographic Variation Selectors.
Generally, the first four characters in the GCGID define the abstract character, and the other four (if present) specify appearance.
(No, I am not an expert in GCGIDs; I am looking this definition up in the Character Data Representation Architecture (CDRA) Reference. See http://www6.software.ibm.com/devcon/devcon/docs/cdrovr00.htm)
> The Unicode 1.1 lists (UNICHP6B.TXT and UNICHP6C.TXT) are inconsistent
> in this regard. Some entries, even within the same file, show GT610000
> while others show GT610002. The tables printed in Unicode 1.0 book are
> the same.
For both GT610000 and GT610002 the first internal document shows a glyph like the one for U+03b8 in the Unicode 3.0 book.
For GT610001 and SA500000 it shows a glyph like TUS 3.0 for U+03d1.
> IBM has a Web page containing many PDF charts of code pages, and they
> have the same problem: some show one GCGID for U+03B8, others show the
> other one.
>
> I suppose this might have had something to do with confusion over U+03D1
> GREEK THETA SYMBOL, but that character (a glyph variant of U+03B8) has
> been in Unicode since 1.0. Was there some dispute at that time over the
> preferred glyphs for U+03B8 and U+03D1? I remember that they were
> swapped in Unicode at one point. Was the inconsistency in GCGID a
> precursor to the decision to swap glyphs?
Well, these GCGIDs are just glyph variants, too.
> Any ideas? (It's probably best not to ask why I am paying attention to
> GCGIDs in the first place.)
I hope this helps - best regards,
markus
-- Opinions expressed here may not reflect my company's positions unless otherwise noted.
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