Can this updatePaintNode implementation be faster/neater/more elegant?

[mxyn]

Hello, I'm trying to draw a bunch of polygons of various colors on top of video. Each polygon will NOT be filled, but the perimeter (outline) will consist of 2 colors. The 2 colors could be anything defined by the user input. This is to make sure that the polygons are visible no matter what video is on in the background.

I had tried Canvas QML at first, but it used too much CPU. Then I tried QQuickPaintedItem - paint(), and that used less CPU. And now I'm trying QQuickItem - updatePaintNode().

I have implemented an QSGNode updatePaintNode() method, and it uses less CPU than a QQuickPaintedItem. I'm just not very happy with how this code looks. I feel like it could be much shorter and elegant. And I wonder if maybe I'm not taking full advantage of this batch processing ability of the scene graph?

I would appreciate any feedback.

QSGNode *Zones::updatePaintNode(QSGNode * oldNode, UpdatePaintNodeData *)
{
 qDebug("hello");
 //QSGGeometryNode *root = static_cast<QSGGeometryNode *>(oldNode);
 QSGNode *root = static_cast<QSGNode *>(oldNode);
 if(!root) {
     root = new QSGNode;
 }

 root->removeAllChildNodes();
 int sz = m_zoneList.size();    //m_zonelist holds the 4 QPointF coords of the zone, the foreground color and the background color
 QColor fgnd;
 QColor bgnd;

 if(sz > 0)
 {
     int i = 0;
     while(i < sz)	// paint the contrast zone (bgnd color) then the normal zone (fgnd color)
     {
        //i = 0;
        QVariantList zList = m_zoneList.at(i).toList();
	QPointF xy1 = zList.at(0).toPointF();
	QPointF xy2 = zList.at(1).toPointF();
	QPointF xy3 = zList.at(2).toPointF();
	QPointF xy4 = zList.at(3).toPointF();
        fgnd.setNamedColor(zList.at(4).toString());
        bgnd.setNamedColor(zList.at(5).toString());

        QSGFlatColorMaterial *cm = new QSGFlatColorMaterial;    // get contrast color
 	cm->setColor(bgnd);

        QSGGeometry *geoCZone = new QSGGeometry(QSGGeometry::defaultAttributes_Point2D(), 4);   //create contrast zone geometry
	geoCZone->setLineWidth(6);
	geoCZone->setDrawingMode(QSGGeometry::DrawLineLoop);
	geoCZone->vertexDataAsPoint2D()[0].set(xy1.x(),xy1.y());
	geoCZone->vertexDataAsPoint2D()[1].set(xy2.x(),xy2.y());
	geoCZone->vertexDataAsPoint2D()[2].set(xy3.x(),xy3.y());
	geoCZone->vertexDataAsPoint2D()[3].set(xy4.x(),xy4.y());

        QSGGeometryNode *contrastZone = new QSGGeometryNode;    // create contrastZone node
	contrastZone->setGeometry(geoCZone);
  	contrastZone->setFlag(QSGNode::OwnsGeometry);
 	contrastZone->setFlag(QSGNode::OwnsMaterial);
 	contrastZone->setMaterial(cm); 	

        
        QSGGeometry *geoZn = new QSGGeometry(QSGGeometry::defaultAttributes_Point2D(), 4);      // create normal zone geometry
	geoZn->setLineWidth(3);
        geoZn->setDrawingMode(QSGGeometry::DrawLineLoop);
	geoZn->vertexDataAsPoint2D()[0].set(xy1.x(),xy1.y());
	geoZn->vertexDataAsPoint2D()[1].set(xy2.x(),xy2.y());
	geoZn->vertexDataAsPoint2D()[2].set(xy3.x(),xy3.y());
	geoZn->vertexDataAsPoint2D()[3].set(xy4.x(),xy4.y());
	
        QSGFlatColorMaterial *z = new QSGFlatColorMaterial;                 // create normal zone color
 	z->setColor(fgnd);

        QSGGeometryNode *zone = new QSGGeometryNode;                        // create normal zone mode
        zone->setGeometry(geoZn);   	
	zone->setFlag(QSGNode::OwnsGeometry);
        zone->setFlag(QSGNode::OwnsMaterial);
        zone->setMaterial(z);	

        contrastZone->appendChildNode(zone);                                // make sure the contrastZone is drawn below the normal zone
        root->appendChildNode(contrastZone);
	
	i++;
     }
 } 
return root;
}