@Nabodita: You can forget about pre-K3 devices. They don't support KF8 files, and, IIRC, the few tests I did with Doitsu a while back with custom fonts & custom freetype libs lead to mostly useless results in the case of RTL and/or complex scripts. Since Bengali appears to be both, I can pretty safely say that, nope, not gonna happen

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I was going to say "see if Doitsu looked at Bengali before", and you did, so the good news appears to be that code2000 (the fallback font w/ the widest unicode support on eInk Kindles) handles it. With KF8 handling RTL & complex script shaping (mostly? I dimly remember some weird issues w/ some complex scripts in some circumstances? Take that with a grain of salt, I might be mixing up stuff), that should mean almost zero hard work on the eInk front (provided you forget about the K1 & the K2, which you can't do anything about anyway, IMHO).