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        STATUS.connect("metric-mode-changed", lambda w, d: self.mode_changed(d))
        STATUS.connect('state-off', lambda w: self.w.pushbutton_metric.setEnabled(False))
        STATUS.connect('state-estop', lambda w: self.w.pushbutton_metric.setEnabled(False))
        STATUS.connect('interp-idle', lambda w: self.w.pushbutton_metric.setEnabled(self.homed_on_test()))
        STATUS.connect('interp-run', lambda w: self.w.pushbutton_metric.setEnabled(False))
        STATUS.connect('all-homed', lambda w: self.w.pushbutton_metric.setEnabled(True))
        STATUS.connect('not-all-homed', lambda w, data: self.w.pushbutton_metric.setEnabled(False))
        self._block_signal = False

        self.w.pushbutton_metric.clicked[bool].connect(self.change_mode)

    #####################
    # general functions #
    #####################

    def mode_changed(self,data):
        self._block_signal = True
        self.w.pushbutton_metric.setChecked(data)
        # if using state labels option update the labels
        if self.w.pushbutton_metric._state_text:
           self.w.pushbutton_metric.setText(None)
        self._block_signal = False

    def change_mode(self, data):
        if self._block_signal: return
        if data:
            ACTION.CALL_MDI('G21')
        else:
            ACTION.CALL_MDI('G20')

    def homed_on_test(self):
        return (STATUS.machine_is_on()
            and (STATUS.is_all_homed() or INFO.NO_HOME_REQUIRED))