Sets whether or not this node is visible in the scene.
        
        :param      state | <bool>

def setVisible( self, state ):
        """
        Sets whether or not this node is visible in the scene.
        
        :param      state | <bool>
        """
        self._visible = state
        
        super(XNode, self).setVisible(self.isVisible())
        
        self.dispatch.visibilityChanged.emit(state)
        self.setDirty()