How do I query a password from a calendar backend?

Hi,

I am having difficulties using e_passwords_ask_password() from with my
calendar backend. I am trying to query the password from within the
open_sync() method. 

I have tried wrapping the e_passwords_ask_password() in
gdk_threads_enter()/gdk_threads_leave() but that will only result in
Evolution freezing when invoking e_passwords_ask_password().

Not doing the gdk_threads_enter()/gdk_threads_leave() wrapping will make
Xlib complain about an unexpected async call.

I can not simply put "auth=1" in the gconf source as that would force a
password dialog to open even if I didn't want one to open. So I need a
way to query a password from the user when a password is really needed.

So, what can I do except from launching an external helper application?
In Camel I could use camel_session_get_password(). Is there anything
like that from within a calendar backend?


Thanks a lot in advance,
  jules