GClosure questions

[Robert Nikander <nikander mindspring com>]

Hi,
I am trying to understand GClosures. I think I am getting most of it, 
but can someone tell me or point me to some docs about...

1. What is the purpose of the _C_ Closure stuct and gcclosure_new, 
etc?  For example, when does the 'cb' in

   closure = g_cclosure_new( cb, data, notify )

get called?

2. What is the 'meta marshal' function.  I set it and it got called 
just like a 'marshal' function.

Thanks,

Rob