From: Bob_Hallissy@sil.org
Date: Wed Aug 18 2004 - 03:29:28 CDT
On 18/08/2004 07:57:32 "Doug Ewell" wrote:
>Your display looks at the joining
>type of the character and its neighbors, and chooses a glyph on that
>basis. Not a character, a glyph. Internally, you can actually use the
>Unicode value of the presentation form as a way to index the glyph,
As has been mentioned previously on this list (and I would like to see it
added to http://www.unicode.org/faq/middleeast.html):
This is not a reliable technique because not all Arabic characters have a
complete set of presentation forms encoded in Unicode. Ernst Tremel mentioned on this list in February at least a few such:
1. There are no FINAL forms for U-0692 (REH WITH SMALL V) and U-0995 (REH
WITH SMALL V BELOW)
2. There are no FINAL, INITIAL and MEDIAL forms for U-06B5 (LAM WITH SMALL
V)
3. There are no FINAL and ISOLATED forms for LAM WITH ALEF WITH SMALL V
ABOVE like in U-FEF5 and U-FEF6 ff.
4. There are no FINAL, INITIAL and MEDIAL forms for U-06CE (YEH WITH SMALL
V)
And there are many others: Presentation forms are no longer being added to
Unicode.
Modern rendering systems use additional data in the font (e.g., OpenType,
Graphite, or AAT tables) to indicate which glyph to use for a given
character in a given context, without dependence on presentation form
glyphs being "encoded" (i.e., given Unicode codepoints)
Bob
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