Creates a new closure which invokes the function found at the offset struct_offset in the class structure of the interface or classed type identified by itype.
the #GType identifier of an interface or classed type
the offset of the member function of itype's class structure which is to be invoked by the new closure
a floating reference to a new #GCClosure
Creates a new closure which invokes the function found at the offset struct_offset in the class structure of the interface or classed type identified by itype.