[Vala] SourceFunc with parameters?

[JM <interflug1 gmx net>]

Hi all
I'm just trying to make some Idle and Source callback functions and I
would really love to hand over some function parameters to these
SourceFuncs. 
Is there a sane way to do it? Maybe something better than just writing
params to class variables and then picking them up from the idle
callback, while hoping these have not changed in the meantime?
Regards
Jörn