Rebuilds the dependency path for this item.

def rebuild( self ):
        """
        Rebuilds the dependency path for this item.
        """
        scene      = self.scene()
        if ( not scene ):
            return
        
        sourcePos  = self.sourceItem().viewItem().pos()
        sourceRect = self.sourceItem().viewItem().rect()
        
        targetPos  = self.targetItem().viewItem().pos()
        targetRect = self.targetItem().viewItem().rect()
        
        cellWidth  = scene.ganttWidget().cellWidth()
        
        startX = sourcePos.x() + sourceRect.width() - (cellWidth / 2.0)
        startY = sourcePos.y() + (sourceRect.height() / 2.0)
        
        endX   = targetPos.x() - 2
        endY   = targetPos.y() + (targetRect.height() / 2.0)
        
        path = QPainterPath()
        path.moveTo(startX, startY)
        path.lineTo(startX, endY)
        path.lineTo(endX, endY)
        
        a = QPointF(endX - 10, endY - 3)
        b = QPointF(endX, endY)
        c = QPointF(endX - 10, endY + 3)
        
        self._polygon = QPolygonF([a, b, c, a])
        
        path.addPolygon(self._polygon)
        
        self.setPath(path)