Update the Qtmacs internal focus state as the result of a mouse click.

        |Args|

        * ``new`` (**QWidget**): the widget that received the focus.

        |Returns|

        * **None**

        |Raises|

        * **None**

def _qteMouseClicked(self, widgetObj):
        """
        Update the Qtmacs internal focus state as the result of a mouse click.

        |Args|

        * ``new`` (**QWidget**): the widget that received the focus.

        |Returns|

        * **None**

        |Raises|

        * **None**
        """

        # ------------------------------------------------------------
        # The following cases for widgetObj have to be distinguished:
        #   1: not part of the Qtmacs widget hierarchy
        #   2: part of the Qtmacs widget hierarchy but not registered
        #   3: registered with Qtmacs and an applet
        #   4: registered with Qtmacs and anything but an applet
        # ------------------------------------------------------------

        # Case 1: return immediately if widgetObj is not part of the
        # Qtmacs widget hierarchy; otherwise, declare the applet
        # containing the widgetObj active.
        app = qteGetAppletFromWidget(widgetObj)
        if app is None:
            return
        else:
            self._qteActiveApplet = app

        # Case 2: unregistered widgets are activated immediately.
        if not hasattr(widgetObj, '_qteAdmin'):
            self._qteActiveApplet.qteMakeWidgetActive(widgetObj)
        else:
            if app._qteAdmin.isQtmacsApplet:
                # Case 3: widgetObj is a QtmacsApplet instance; do not
                # focus any of its widgets as the focus manager will
                # take care of it.
                self._qteActiveApplet.qteMakeWidgetActive(None)
            else:
                # Case 4: widgetObj was registered with qteAddWidget
                # and can thus be focused directly.
                self._qteActiveApplet.qteMakeWidgetActive(widgetObj)

        # Trigger the focus manager.
        self._qteFocusManager()