Problem with qwt6 and saving plot as image

[discovery]

Hello,

I wanted to save a plot as an image and I have a problem with that. I found QwtPlotRender class and renderDocument() method but isn't work as I expected. Small example explain what I mean.

QwtPlot *plot = new QwtPlot(this);
    plot->setTitle(trUtf8("Tytuł nowy"));
 
    QwtPlotCurve *curve_samples = new QwtPlotCurve();
    curve_samples->attach(plot);
    curve_samples->setRawSamples(x, y, 100);
    curve_samples->setTitle("Title of cuvere_sample");
    curve_samples->setPen(QPen(QColor(Qt::red)));
    curve_samples->setCurveAttribute(QwtPlotCurve::Fitted, true);
 
    plot->setAxisTitle(QwtPlot::xBottom, "test");
 
    ui->verticalLayout->addWidget(plot);
 
    QwtPlotRenderer *renderer = new QwtPlotRenderer();
    renderer->renderDocument(plot, "/home/discovery/test.png", QSizeF(150, 100));

QwtPlot *plot = new QwtPlot(this);
    plot->setTitle(trUtf8("Tytuł nowy"));

    QwtPlotCurve *curve_samples = new QwtPlotCurve();
    curve_samples->attach(plot);
    curve_samples->setRawSamples(x, y, 100);
    curve_samples->setTitle("Title of cuvere_sample");
    curve_samples->setPen(QPen(QColor(Qt::red)));
    curve_samples->setCurveAttribute(QwtPlotCurve::Fitted, true);

    plot->setAxisTitle(QwtPlot::xBottom, "test");

    ui->verticalLayout->addWidget(plot);

    QwtPlotRenderer *renderer = new QwtPlotRenderer();
    renderer->renderDocument(plot, "/home/discovery/test.png", QSizeF(150, 100));

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The problem is with QwtPlotCurve, samples are not saved on image.

app_window.jpg
Plot in my application.
test.png
Plot saved in png file.

Did I do something wrong? I am quite beginner with qwt library

[Uwe]

Did I do something wrong?

You have to do a replot before you call the renderer.

Uwe

[discovery]

Of course! Thank you so much for help, I have spend several hours today on googling to find solution.