I'm trying to understand how OpenType and Uniscribe is supposed to work, specifically for the Bengali language, and I've discovered one thing I can't seem to understand. It's about the sequence Ka (09af) + Halanth (09cd) + Ra (09b0).
As the Bengali specification states, this is first reordered into Ka + Ra + Halanth by Uniscribe before it's sent to the OpenType rules, then the blwf feature is supposed to turn Ra + Halanth into the Vrama character (named bn_ra_phala in the Vrinda font), then the vatu feature will turn Ka + Vrama into the Kro character (bn_k_ra in Vrinda).
However, before these two rules are applied, the rphf feature is applied, which turns Ra + Halanth into the Reph character. So, Ka + Ra + Halanth will turn into Ka + Reph and not Kro.
But I see that Windows does manage to do this correctly anyway, so what is the problem in my reasoning?
Regards, Alexander Toresson