Re: Arabic with LuaTeX vs. XeTeX

["Idris Samawi Hamid" <ishamid@colostate.edu>]

Hi Otared and all,

On Mon, 09 Jun 2008 03:13:06 -0600, Otared Kavian <otared@gmail.com> wrote:

> I just read the thread started by Burak Emir about "Typesetting Arabic
> today", and tried to typeset the sample sent by Idris Samawi Hamid.
> One of the Arabic or Persian fonts that I have and LuaTeX can find is
> Nadeem (working on Mac OS X 10.5.3), but what I get after typesetting
> is the following attached PDF: all the characters are typeset with
> their isolated form. However typestting the same text with XeConTeXt
> or XeTeX gives a nice result.

As Khaled and Wolfgang already intimated, the problem is that Nadeem is  
not an OpenType font, but rather AAT. XeTeX is mainly Mac-based so it's  
natural that it supports AAT.

It should not be too hard to overload GSUB and GPOS features for this  
particular font using the fea file overload feature of luatex (not sure if  
that has been fixed.)

I looked at the AAT code, and saved an fea file using FontForge: but the  
contextual analysis is not there, so I suspect that AAT fonts depend on  
something like uniscribe for certain basic features. We (=Hans) need to  
know what that is.

But at this stage of development, only pure OpenType fonts will be  
supported out of the box. For example: Traditional Arabic, which comes  
with XP, has OpenType tables but depends on Uniscribe instead of OpenType  
for, eg, making marks exceptions to the contextual analysis. Since the  
mark exception was not added to the GSUB table, voweled text appears  
unjoined in Trad. Arabic processed by luaTeX.

I suppose we (=Hans) could add some "spell-checking" to the otf analyzer,  
but that's dangerous and needs some careful thought. Maybe we can come up  
with various "spell-checking" options that could be turned on and off, so  
that old-technology (Nadeem is 1998), platform-dependent (like Nadeem and  
Trad. Ar.) fonts can be used.

In any case, we want to stay as platform-independent as possible. So for  
AAT, we may need to wait at least till someone (maybe one of you?) can  
come up with a spec so that we can implement a cross-platform solution for  
AAT.

Best wishes
Idris

-- 
Professor Idris Samawi Hamid, Editor-in-Chief
International Journal of Shi`i Studies
Department of Philosophy
Colorado State University
Fort Collins, CO 80523
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