In typical Persian fonts which are True Type, there is a historical problem with yeh and kafs.
These fonts are created for Windows 98, which didn't include full Persian support, and now, we have 2 kind of Kafs: Keheh(0x6a9, ک), and Arabic Kaf(0x643, ك), and 2 kind of Yehs: Farsi Yeh(0x6cc, ی), and Arabic Yeh(0x64a, ي). Old fonts use Arabic ones, but the standard keyboard for Persian uses the Persian ones of course.
Is it possible to edit and fix these fonts? I've made many attempts to replace these characters with FontLab Studio, which I failed. Any suggestions?