As I understand it, WPF does not use Uniscribe, but its own text handler should produce the same results as Uniscribe. I will bring this discussion to the attention of Uniscribe and WPF engineers.

WPF implements complete OpenType layout format specification. It is not using Unisribe and does not share code with it. There are may be bugs in it. Although we spent lots of time testing it and endure it produces the same results as Uniscribe, it is relatively new product and less people outside Microsoft had a chance to test it with various fonts and scripts.

You may want to provide more details about what is not working for you, so we can invesigate. Does it happen with all or only particular Arabic fonts? What is special about the string you are shaping?

Thanks,
Sergey

Sergey, I've confirmed this bug in WPF Arabic handling. If you enter the characters لَاِ within WPF both marks are positioned relative to the left letter (alif) of the ligature, rather than the first, above marks being positioned relative to the right letter (lam). I tested this with a randomly selected Linotype Arabic font and also with Microsoft's own Arabic Typesetting font. It appears that WPF is failing to correctly enumerate ligature components.

I guess ZARNEGAR (old+new version) is the Middle east version of WPF.ME
http://www.sinasoft.com/ZARNEGAR/index.asp
It is the most powerful Arabic Typesetting system ever developed.
Version 6 can now handle M$OTFs besides its own OTFs.