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    scene.clear();
    QPen dashPen;
    dashPen.setStyle(Qt::DashLine);
    for (int i = 0; i < Points.size() - 1; i++)
    {
        QPointF p1, p2;
        QLineF polyLine;
        p1 = Points[i];
        p2 = Points[i+1];
        polyLine = QLineF(p1, p2);

        polyLine->setPen(dashPen);
        scene.addLine(polyLine);
        polyLine = QLineF();
        p1 = QPointF();
        p2 = QPointF();
    }

i < Points.size() - 1

for (int i = 0; i < Points.size() - 1; i++)
        scene.addLine(QPointF(Points[i], Points[i+1]), QPen(Qt::DashLine));

void
MainWindow::autoscale()
{
    if (!Points.size())
        return;
    double xmin = Points[0].x(), ymin = Points[0].y();
    double xmax = xmin, ymax = ymin;

    for (unsigned i = 1; i < Points.size(); ++i)
    {
        if (Points[i].x() < xmin) xmin = Points[i].x();
        if (Points[i].x() > xmax) xmax = Points[i].x();
        if (Points[i].y() < ymin) ymin = Points[i].y();
        if (Points[i].y() > ymax) ymax = Points[i].y();
    }
    QRectF rect(QPointF(xmin, ymin), QPointF(xmax, ymax));

    double mx = rect.width() * 0.05;
    double my = rect.height() * 0.05;
    rect.adjust(-mx, -my, mx, my);

    scene.setSceneRect(rect);
    ui.graphicsView->fitInView(rect, Qt::KeepAspectRatio);

    ui.graphicsView->centerOn(rect.center());
}