Tracks whether or not this item is being hovered.
        
        :param      event | <QEvent>

def hoverMoveEvent( self, event ):
        """
        Tracks whether or not this item is being hovered.
        
        :param      event | <QEvent>
        """
        point = event.pos()
        
        found_key = ''
        found = None
        for key, value, subpath in self._subpaths:
            if subpath.contains(point):
                found = subpath
                found_key = key
                break
        
        if found:
            # update the tooltip
            tip    = self.keyToolTip(found_key)
            if ( tip ):
                widget = self.scene().chartWidget()
                anchor = XPopupWidget.Anchor.RightCenter
                
                # show the popup widget
                XPopupWidget.showToolTip(tip, 
                                         anchor = anchor,
                                         parent = widget,
                                         foreground = self.color().darker(120),
                                         background = self.alternateColor())
            
            if ( found != self._hoveredPath ):
                self._hoveredPath = found
                self.update()