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Re: [emacs-bidi] Hebrew characters categories
From: |
TAKAHASHI Naoto |
Subject: |
Re: [emacs-bidi] Hebrew characters categories |
Date: |
Wed, 5 Dec 2001 20:44:32 +0900 (JST) |
"Yair Friedman (Jerusalem)" writes:
>> Composition is independent of categories. You can compose characters
>> without using categories at all. Never mind those categories designed
>> for Thai and Lao; they were defined because they help composition in
>> those languages. You do not have to use them for Hebrew.
> Yes, but they *do* help in composition for Hebrew as well (this is why I
> chose them in the first place). In addition, the phonetic categories
> helps in resolving placement collision.
OK, then it is reasonable to take such an approach.
> Do you think there is a better approach? I'm sorry, but I don't know
> enough about Emacs internals to start a whole new design. The Thai
> solution did seem like a good place to start.
I'm sorry, but I don't know enough about Hebrew to start a whole new
design. :-) I will read an introductory textbook again.
>>> What is the approach taken in Arabic?
>> For positioning, no new categories are defined. Since Arabic vowel
>> signs and other marks are aligned to centre, all we have to worry is
>> whether they are placed above the base character or below. Such
>> vertical positioning is automatically done by the display engine,
>> based on the glyph information stored in the font file.
> So do you force the vowel sign to same vertical position always? Even
> in cases such as Bah Vs Tah with Fatha and possibly Shadda? What about
> Alif?
No. The vertical position changes.
> Do you use special presentation forms or somehow adjust the
> composition.
No.
> Do you have assumptions about the font structure?
Yes. If
1. the font used by our Emacs has the property
"_MULE_RELATIVE_COMPOSE" and its value is A
and
2. a glyph has a descent value B, where B < 0 and -B > A
then such a glyph is put _above_ the preceding character when
composed. In case of Arabic, FATHA is such a glyph.
We also added extra white pixels above the BAH, TAH and other glyphs
so that we can get appropriate distance between the base glyphs and
FATHA.
--
TAKAHASHI Naoto
address@hidden
http://www.m17n.org/ntakahas/
- [emacs-bidi] Hebrew characters categories, Yair Friedman (Jerusalem), 2001/12/04
- Re: [emacs-bidi] Hebrew characters categories, TAKAHASHI Naoto, 2001/12/04
- Re: [emacs-bidi] Hebrew characters categories, TAKAHASHI Naoto, 2001/12/04
- Re: [emacs-bidi] Hebrew characters categories,
TAKAHASHI Naoto <=
- Re: [emacs-bidi] Hebrew characters categories, TAKAHASHI Naoto, 2001/12/05
- Re: [emacs-bidi] Hebrew characters categories, Kenichi Handa, 2001/12/11
- Re: [emacs-bidi] Hebrew characters categories, TAKAHASHI Naoto, 2001/12/12
- Re: [emacs-bidi] Hebrew characters categories, TAKAHASHI Naoto, 2001/12/12
- Re: [emacs-bidi] Hebrew characters categories, TAKAHASHI Naoto, 2001/12/26