def cbar_value_cb(self, cbar, value, event):
        """
        This method is called when the user moves the mouse over the
        ColorBar.  It displays the value of the mouse position in the
        ColorBar in the Readout (if any).
        """
        if self.cursor_obj is not None:
            readout = self.cursor_obj.readout
            if readout is not None:
                maxv = readout.maxv
                text = "Value: %-*.*s" % (maxv, maxv, value)
                readout.set_text(text)
This method is called when the user moves the mouse over the
        ColorBar.  It displays the value of the mouse position in the
        ColorBar in the Readout (if any).