Upadte file name label.

def update_fname_label(self):
        """Upadte file name label."""
        filename = to_text_string(self.get_current_filename())
        if len(filename) > 100:
            shorten_filename = u'...' + filename[-100:]
        else:
            shorten_filename = filename
        self.fname_label.setText(shorten_filename)