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On Sun, 22 Feb 2009 13:54:51 -0700, Khaled Hosny
http://www.microsoft.com/typography/otfntdev/arabicot/features.htm
:-)
watch the "The standard order for applying Arabic features encoded in OpenType fonts" ... an earlier mkiv otf handler did this but then we found out that it violates the otf 'any order possible' rule so now we do just the order as we encounter it (and even then it took us a while to figure out where/how to avoid interferences); so ... it's up to the font designer (or technician)
IIRC, the 'ccmp' should be applied before any other lookup, the rest are applied as they are ordered in the font, at least this makes sense more.
It is not the order of the features, but the order of the lookups that really counts here. So, more precisely, the lookups in ccmp should be defined in the font before all other lookups. See also http://www.microsoft.com/typography/otfntdev/arabicot/shaping.htm http://www.microsoft.com/typography/otfntdev/arabicot/default.htm
now, having init, medi, fina, isol, rlig enabled might be the default, but for instance arabtype output looks much better when instead of rlig we use calt/clig etc so, in that case the defaults would bot be the best choice; again an argument for a database approach
Arabic Typesetting is a quit a special case font, though I believe that 'calt' and 'clig' should be on by default for any font.
That's just it, there are so many exceptional cases it's not trivial to define a rule. Again, Scheherazade seems appropriate as a place to start... I will try to find some time in the next month to work on this, or someone can start and Hans and I can complete the module.
there are even fonts out there that have the right gsub/gpos info but lack the feature being listed in the script/lang dictionary which is complicating live even more; maybe we should assume that the renderers of ms and adobe have some additional built in heuristics of using specific fonts
Any links to such fonts? Looks interesting.
Hans may be referring to hybrids like Traditional Arabic.... 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