How to rotate diamond on 2D view using C++?

void MainWindow::on_drawDiamondbtn_clicked()
{
     if (isDimond_Drawn)
        {
            //  *****  8Facet  *****

            // Draw a circle in the center of the QGraphicsView
            int centerX = ui->CameraGraphicsView->width() / 2;
            int centerY = ui->CameraGraphicsView->height() / 2;

            double RectSize = Rect_size;
            double PixelFact = (1.00 * userenterMM) / RectSize;
            double diaMMtoPX = dia_meter * 1.00 / PixelFact;
            double TablePX = tbl / 100.00 * (diaMMtoPX);

            // Set the circle's properties
            int circleRadius = diaMMtoPX;  // Set your desired radius

            QGraphicsItemGroup *diamondGroup = new QGraphicsItemGroup;

            QGraphicsEllipseItem *circle = new QGraphicsEllipseItem
                 (centerX - circleRadius, centerY - circleRadius, 2 * 
                  circleRadius, 2 * circleRadius);
            circle->setPen(QPen(Qt::green));  // Set the pen color
            scene->addItem(circle);
            diamondGroup->addToGroup(circle);

            // Set the button color to green
            ui->drawDiamondbtn->setStyleSheet
                      ("background-color: green;");

            // Draw lines inside the circle
            QPen linePen(Qt::green);  // Set the line color
            linePen.setWidth(1);

            int lineLength = TablePX;  // Set your desired line length
            int numLines = 8;          // Number of lines to draw

            // Declare variables for line coordinates
            double x1, y1, x2, y2;
            double x3, y3, x4, y4;
            double x5, y5, x6, y6;
            double x7, y7, x8, y8;

            for (int i = 0; i < numLines; i++) {
                double angle = 2 * M_PI * i / numLines;  // Use M_PI for Pi
                double startX = centerX + lineLength * qCos(angle);
                double startY = centerY + lineLength * qSin(angle);
                double endX = centerX - lineLength * qCos(angle);
                double endY = centerY - lineLength * qSin(angle);

                // Assign values to variables based on line index
                if (i == 0) {
                    x1 = startX;
                    y1 = startY;
                    x2 = endX;
                    y2 = endY;
                } else if (i == 1) {
                    x3 = startX;
                    y3 = startY;
                    x4 = endX;
                    y4 = endY;
                } else if (i == 2) {
                    x5 = startX;
                    y5 = startY;
                    x6 = endX;
                    y6 = endY;
                } else if (i == 3) {
                    x7 = startX;
                    y7 = startY;
                    x8 = endX;
                    y8 = endY;
                }

                //            QGraphicsLineItem *line = 
                // new QGraphicsLineItem(startX, startY, endX, endY);
                //            line->setPen(linePen);
                //            scene->addItem(line);
            }

            diamondGroup->addToGroup(DrawCrawnLine(x1,y1,x3,y3));
            diamondGroup->addToGroup(DrawCrawnLine(x3,y3,x5,y5));
            diamondGroup->addToGroup(DrawCrawnLine(x5,y5,x7,y7));
            diamondGroup->addToGroup(DrawCrawnLine(x7,y7,x2,y2));
            diamondGroup->addToGroup(DrawCrawnLine(x2,y2,x4,y4));
            diamondGroup->addToGroup(DrawCrawnLine(x4,y4,x6,y6));
            diamondGroup->addToGroup(DrawCrawnLine(x6,y6,x8,y8));
            diamondGroup->addToGroup(DrawCrawnLine(x8,y8,x1,y1));

            diamondGroup->addToGroup(DrawCrawnAngle
                       (centerX,centerY, circleRadius, x1, y1));
            diamondGroup->addToGroup(DrawCrawnAngle
                       (centerX,centerY, circleRadius, x2, y2));
            diamondGroup->addToGroup(DrawCrawnAngle
                       (centerX,centerY, circleRadius, x3, y3));
            diamondGroup->addToGroup(DrawCrawnAngle
                       (centerX,centerY, circleRadius, x4, y4));
            diamondGroup->addToGroup(DrawCrawnAngle
                       (centerX,centerY, circleRadius, x5, y5));
            diamondGroup->addToGroup(DrawCrawnAngle
                       (centerX,centerY, circleRadius, x6, y6));
            diamondGroup->addToGroup(DrawCrawnAngle
                       (centerX,centerY, circleRadius, x7, y7));
            diamondGroup->addToGroup( DrawCrawnAngle
                       (centerX,centerY, circleRadius, x8, y8));
            scene->addItem(diamondGroup);
        }
        else {
            // Remove the circle from the scene
            QList<QGraphicsItem *> items = scene->items();
            for (QGraphicsItem *item : items) {
                if (item->type() == QGraphicsEllipseItem::Type || 
                    item->type() == QGraphicsLineItem::Type) {
                    scene->removeItem(item);
                    delete item;
                }
            }
            // Set the button color back to red
            //ui->circlebtn->setStyleSheet("background-color: red;");
            ui->drawDiamondbtn->setStyleSheet
                           ("background-color: red;");
        }
        isDimond_Drawn = !isDimond_Drawn;
    }
	
QGraphicsLineItem* MainWindow::DrawCrawnLine
    (double startX, double startY, double endX, double endY)
{
    QGraphicsLineItem *line = new QGraphicsLineItem
                              (startX, startY, endX, endY);
    line->setPen(QPen(Qt::green));
    return line;
}

QGraphicsLineItem* MainWindow::DrawCrawnAngle(int centerX, int centerY, 
int circleRadius, double startX, double startY)
{
    // Draw a CrawnAngle line degrees above the circle's circumference
    QPen CrawnAngleLinePen(Qt::green);  // Set the CrawnAngle line color
    CrawnAngleLinePen.setWidth(1);

    // Calculate the angle 5 degrees above the circle's circumference
    double angleToCircumference = qAtan2(startY - centerY, startX - centerX);
    double angleForPinkLine = angleToCircumference - 
    qDegreesToRadians(static_cast<double>(0.01)); // Convert degrees 
                                                        // to radians

    // Calculate the line's end point on the circle's circumference
    double endXOnCircumference = centerX + 
                      circleRadius * qCos(angleForPinkLine);
    double endYOnCircumference = centerY + circleRadius * 
                      qSin(angleForPinkLine);

    QGraphicsLineItem *CrawnAngleLine = new QGraphicsLineItem
        (startX, startY, endXOnCircumference, endYOnCircumference);
    CrawnAngleLine->setPen(CrawnAngleLinePen);
    //scene->addItem(CrawnAngleLine);
    return CrawnAngleLine;
}	

void MainWindow::on_XrotationLineEdit_textChanged(const QString &text)
{
    bool conversionOk;
    int rotationAngle = text.toInt(&conversionOk);

    if (conversionOk) {
        // Find the diamond group in the scene
        QGraphicsItemGroup *diamondGroup = nullptr;
        QList<QGraphicsItem *> items = scene->items();
        for (QGraphicsItem *item : items) {
            if (item->type() == QGraphicsItemGroup::Type) {
                diamondGroup = dynamic_cast<QGraphicsItemGroup *>(item);
                break;
            }
        }

        if (diamondGroup) {
            // Apply rotation to the diamond group
            diamondGroup->setTransformOriginPoint
                     (diamondGroup->boundingRect().center());
            diamondGroup->setRotation(rotationAngle);
        }
    }
}