Help: Callback arguments

[Johan Levin <nivel zigzegv ml org>]

I'm a gtk newbie, and I'd need some help...

How do I know how many arguments a certain callback-function should take?

When attaching to window-"delete_event" I get three (widget, event, data).
When attaching to button-"clicked" I get two (widget, data).
When attaching to window-"destroy I get two (widget, data).

It seems the return types vary too. Sometimes I should return void other
times gint.

Is there some simple rule?
My code gets pretty unstable when I do this wrong...

/Johan Levin