Return the main brush for this node.
        
        :return     <QBrush>

def disabledBrush( self ):
        """
        Return the main brush for this node.
        
        :return     <QBrush>
        """
        # create the background brush
        grad = QLinearGradient()
        rect = self.rect()
        
        grad.setStart(QPointF(0, rect.y()))
        grad.setFinalStop(QPointF(0, rect.bottom()))
        
        grad.setColorAt(0, self.disabledColor())
        grad.setColorAt(1, self.disabledAlternateColor())
            
        return QBrush(grad)