I seen you mention about RichEdit.
do it mean component or program(like wordpad)?
if something like wordpad,I ever see some of them like this one
some of them have source code.
anyway I never browe and learn ReactOS source then I don't know detail.
I will try to do it when I have time
got some more information
Dmitry G. Gorbachev,His first commit was for Thai keyboard layout .. wow(read from news)
for some of script we can read from this info
for other country(aread) can see index on http://www.unicode.org/versions/Unicode5.0.0/
change chapter as you wish.
I think we should develop together(all of us who use unicode script).