retrieve function members types/domains <= types

retrieve function members types/domains <= types

Hi list,

I'm trying to make a rights manager that retrieve all its info from PG
tables.

I found out how to retrieve function names; but now I'm stuck after that,
as I can't find a way to retrieve types/domains used by a function in order
to "rebuild" it in my manager and be able to test/set user rights on this
function, like: 
SELECT has_function_privilege('myfun(int,domain14)', 'execute');

What queries should I issue to get such info?

-- 
Texas law forbids anyone to have a pair of pliers in his possession.