How do I rotate a QPolygon

[rawfool]

I'm having a problem rotating polygon. Below is the code how I tried. Please guide me. Thank you.

void Dialog::draw_needle()
{
    QPolygon needle;
    needle.setPoints(4, 0,7, 14,0, 160,7, 14,14);
    needle.translate((this->width()/2), (this->height()/2)+30 );
 
    QPainter painter(this);
    painter.setPen(QPen(QColor(79, 106, 25), 1, Qt::SolidLine, Qt::RoundCap, Qt::RoundJoin));
    painter.setBrush(QColor(122, 163, 39));
    painter.drawConvexPolygon(needle);
    painter.rotate(45);
}
 
void Dialog::paintEvent(QPaintEvent *event)
{
    draw_dial();
    draw_needle();
}

void Dialog::draw_needle()
{
    QPolygon needle;
    needle.setPoints(4, 0,7, 14,0, 160,7, 14,14);
    needle.translate((this->width()/2), (this->height()/2)+30 );

    QPainter painter(this);
    painter.setPen(QPen(QColor(79, 106, 25), 1, Qt::SolidLine, Qt::RoundCap, Qt::RoundJoin));
    painter.setBrush(QColor(122, 163, 39));
    painter.drawConvexPolygon(needle);
    painter.rotate(45);
}

void Dialog::paintEvent(QPaintEvent *event)
{
    draw_dial();
    draw_needle();
}

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