scim and transliteration

[François Patte]

Bonjour,

I would like to know if there is an input method in scim which could
provide roman transliteration letters: I need vowel with macron,
consonnant with upper and underdot etc.

I have found "latin pre" and "latin post" virtual keyboard but they do
not provide all composed letters I need. Is it possible to add some
composed letters?

There is also an "unicode" and "utf-8" keyboard: is there a
configuration method of scim which could allow to define keyboard short
cuts giving the letter corresponding to a code; for example, I define
"Alt a" short cut with u+0101 and get a lowercase a-macron, "Alt A" will
give uppercase a macron, and so on.

Thank you for attention and (I hope) answer.
-- 
François Patte
UFR de mathématiques et informatique
Université René Descartes
http://www.math-info.univ-paris5.fr/~patte