how to make custom combining diacritical marks for arabic letters? should only font drivers and programs support it, or should also unicode support it, for example, have special area for them?
as i know, private use area can be used to make combining diacritical marks for latin script without problems. but when i tried, several years ago, to make that for arabic script, with fontforge, i had to use right to left override mark, and manually insert beginning, middle, ending forms of arabic letters, and even then, my custom marks were not located very properly above letters.