Физические координаты в логические, хит-тест и QPainter

void MainWindow::paintEvent(QPaintEvent* event)
{
    QPainter painter(this);
    painter.setRenderHint(QPainter::Antialiasing, true);
    int side = qMin(width(), height());
    painter.setViewport((width() - side) / 2, (height() - side) / 2, side, side);
    painter.setWindow(-50, -50, 100, 100);
 
    // painting //
    DrawPoints(&painter, 50);
    //...
}

void MainWindow::paintEvent(QPaintEvent* event)
{
    QPainter painter(this);
    painter.setRenderHint(QPainter::Antialiasing, true);
    int side = qMin(width(), height());
    painter.setViewport((width() - side) / 2, (height() - side) / 2, side, side);
    painter.setWindow(-1 * side / 2, -1 * side / 2, side, side);
 
    radius = side / 2 - 50;
    DrawGraph(&painter);
 
}

void MainWindow::mousePressEvent(QMouseEvent *event)
{
    QPoint point;
 
    if(event->button() == Qt::LeftButton)
    {
        // phisical coords to logical coords
        point.setX(event->x() - width() / 2);
        point.setY(event->y() - height() / 2);
 
        logicalPoint = point;
        NodeHitTest();
    }
}