gtk/print.go
func (ps *PrintSettings) ForEach(cb PrintSettingsCallback, userData uintptr) {
	printSettingsCallbackRegistry.Lock()
	id := printSettingsCallbackRegistry.next
	printSettingsCallbackRegistry.next++
	printSettingsCallbackRegistry.m[id] =
		printSettingsCallbackData{fn: cb, userData: userData}
	printSettingsCallbackRegistry.Unlock()

	C._gtk_print_settings_foreach(ps.native(), C.gpointer(uintptr(id)))
}
func (ps *PrintSettings) ForEach(cb PrintSettingsCallback, userData uintptr) {
	printSettingsCallbackRegistry.Lock()
	id := printSettingsCallbackRegistry.next
	printSettingsCallbackRegistry.next++
	printSettingsCallbackRegistry.m[id] =
		printSettingsCallbackData{fn: cb, userData: userData}
	printSettingsCallbackRegistry.Unlock()

	C._gtk_print_settings_foreach(ps.native(), C.gpointer(uintptr(id)))
}
// Foreach() is a wrapper around gtk_print_settings_foreach().