Sets the central widget for this overlay to the inputed widget.

        :param      widget | <QtGui.QWidget>

def setCentralWidget(self, widget):
        """
        Sets the central widget for this overlay to the inputed widget.

        :param      widget | <QtGui.QWidget>
        """
        self._centralWidget = widget

        if widget is not None:
            widget.setParent(self)

            widget.installEventFilter(self)

            # create the drop shadow effect
            effect = QtGui.QGraphicsDropShadowEffect(self)
            effect.setColor(QtGui.QColor('black'))
            effect.setBlurRadius(80)
            effect.setOffset(0, 0)
            widget.setGraphicsEffect(effect)