QML Clip Custom Item - qt

Question

I made my own QQuickItem, which I draw using the updatePaintNode method (using the scenegraph). In a qml File I add this item as a child to a Rectangle:
Rectangle {
anchors.centerIn: parent
width: parent.width/2.
height: parent.height/2.
border.color: "#000000"
clip: true
MyItem {
id: myitem
anchors.centerIn: parent
width: parent.width
height: parent.height
MouseArea {
anchors.fill: parent
onWheel: {
if (wheel.modifiers & Qt.ControlModifier) {
parent.scale = parent.scale+ 0.2 * wheel.angleDelta.y / 120;
if (parent.scale < 1)
parent.scale = 1;
}
}
}
}
}
As you can see, I added a zoom function and set
clip: True
for the rectangle. However, when I zoom, my item is not clipped at the Rectangle but extends beyond it. What would be the correct way to do clipping?
Edit: Here is the content of the cpp file for MyItem
MyItem::MyItem(QQuickItem *parent): QQuickItem(parent)
{
setFlag(QQuickItem::ItemHasContents,true);
// code to initialize xdata, ydata, xmax, ymax
}
QSGNode *MyItem::updatePaintNode(QSGNode *oldNode, UpdatePaintNodeData *) {
QSGGeometryNode *mypath = static_cast<QSGGeometryNode*>(oldNode);
if(!mypath) {
mypath = new QSGGeometryNode;
mypath->setFlag(QSGNode::OwnsMaterial,true);
mypath->setFlag(QSGNode::OwnsGeometry,true);
}
QSGGeometry *geometry = new QSGGeometry(QSGGeometry::defaultAttributes_Point2D(),_xdata.size());
QSGGeometry::Point2D *points = geometry->vertexDataAsPoint2D();
for(int i=0;i<_xdata.size();i++) {
points[i].x = _xdata[i]/_xmax*width();
points[i].y = _ydata[i]/_ymax*height();
}
geometry->setLineWidth(2);
geometry->setDrawingMode(GL_LINE_STRIP);
mypath->setGeometry(geometry);
QSGFlatColorMaterial *material = new QSGFlatColorMaterial;
material->setColor(Qt::blue);
mypath->setMaterial(material);
return mypath;
}
and here is the header file:
#include <QQuickItem>
#include <vector>
class MyItem : public QQuickItem
{
Q_OBJECT
public:
MyItem(QQuickItem *parent = 0);
private:
std::vector<double> _xdata;
std::vector<double> _ydata;
double _xmax;
double _ymax;
signals:
public slots:
protected:
QSGNode * updatePaintNode(QSGNode *oldNode, UpdatePaintNodeData *data) override;
};