glib/connect.go
func ClosureNew(f interface{}, marshalData ...interface{}) (*C.GClosure, error) {
	// Create a reflect.Value from f.  This is called when the
	// returned GClosure runs.
	rf := reflect.ValueOf(f)

	// Create closure context which points to the reflected func.
	cc := closureContext{rf: rf}

	// Closures can only be created from funcs.
	if rf.Type().Kind() != reflect.Func {
		return nil, errors.New("value is not a func")
	}

	if len(marshalData) > 0 {
		cc.userData = reflect.ValueOf(marshalData[0])
	}

	c := C._g_closure_new()

	// Associate the GClosure with rf.  rf will be looked up in this
	// map by the closure when the closure runs.
	closures.Lock()
	closures.m[c] = cc
	closures.Unlock()

	return c, nil
}
func ClosureNew(f interface{}, marshalData ...interface{}) (*C.GClosure, error) {
	// Create a reflect.Value from f.  This is called when the
	// returned GClosure runs.
	rf := reflect.ValueOf(f)

	// Create closure context which points to the reflected func.
	cc := closureContext{rf: rf}

	// Closures can only be created from funcs.
	if rf.Type().Kind() != reflect.Func {
		return nil, errors.New("value is not a func")
	}

	if len(marshalData) > 0 {
		cc.userData = reflect.ValueOf(marshalData[0])
	}

	c := C._g_closure_new()

	// Associate the GClosure with rf.  rf will be looked up in this
	// map by the closure when the closure runs.
	closures.Lock()
	closures.m[c] = cc
	closures.Unlock()

	return c, nil
}
// ClosureNew creates a new GClosure and adds its callback function
// to the internally-maintained map. It's exported for visibility to other
// gotk3 packages and shouldn't be used in application code.