Julian:
>I have just finished the implememntion of Arabic (06XX range) and the
>customer has now told me I need to get the joined arabic (FEXX) working.
Generally, you don't want to use the Arabic Presentation Forms blocks (FBxx
and FExx). Definitely, you don't want to encode data using them. As Marco
has pointed out, start by reading Chapter 8, which does give some
discussion of Arabic glyph shaping.
Somewhere in the rendering process, you need an algorithm that does the
necessary transformations. One way to do this is to do transformations on
characters, mapping sequences in the 06xx block into the FBxx and FExx
blocks. This may not do what you need, though. In particular, the Arabic
Presentation Forms blocks do not contain all of the ligatures that might be
needed (and apparently several that are unattested in actual use).
Another way to do this is to do transformations on glyphs, i.e. it all
happens at the font level. Generally, this is preferable: it becomes an
issue for the type designer, who really is the one that needs to determine
exactly what shapes are needed for correct display. To give you an idea of
how one technology does that, check out
http://www.microsoft.com/typography/OTSPEC/arabicot/summ.htm.
Depending upon the context you're working in, this may already be
available. Some operating environments already provide the necessary
support for Arabic; you just need to start using what's already there. You
didn't give any details in that regard. Perhaps you should say something
about that.
- Peter
---------------------------------------------------------------------------
Peter Constable
Non-Roman Script Initiative, SIL International
7500 W. Camp Wisdom Rd., Dallas, TX 75236, USA
Tel: +1 972 708 7485
E-mail: <peter_constable@sil.org>
This archive was generated by hypermail 2.1.2 : Fri Jul 06 2001 - 00:17:18 EDT