code: func (v *Window) SetIconFromFile(file string) error {
  	cstr := C.CString(file)
  	defer C.free(unsafe.Pointer(cstr))
  	var err *C.GError = nil
  	res := C.gtk_window_set_icon_from_file(v.native(), (*C.gchar)(cstr), &err)
  	if res == 0 {
  		defer C.g_error_free(err)
  		return errors.New(C.GoString((*C.char)(err.message)))
  	}
  	return nil
  }
docs: // SetIconFromFile is a wrapper around gtk_window_set_icon_from_file().