Odd plotting behaviour

[ajb]

I'm experiencing really odd behaviour with a Qwt plot. I'm plotting several datasets as QwtPlotCurves onto a QwtPlot, one dataset at a time, when a user clicks a button on the main app window.

First call to plotting object (creates QwtPlot) - first plot appears fine.
Second call to plotting object - no change; second plot doesn't appear.
Third call - both second and third plots now appear.
Fourth call - no change.
Fifth call - fourth and fifth plots appear.
etc

Below is the code from the plotting class.

DataPlotter::DataPlotter(QWidget *parent, QString strTitle, double minLambda, double maxLambda):  QwtPlot(parent)
{
    canvas()->setFrameStyle(QFrame::Box | QFrame::Plain );
    canvas()->setLineWidth(1);
    insertLegend(new QwtLegend(), QwtPlot::BottomLegend);
    setTitle(strTitle);
    setAxisTitle(QwtPlot::xBottom, "Wavelength (nm)");
    setAxisScale(QwtPlot::xBottom, minLambda, maxLambda);
    setAxisTitle(QwtPlot::yLeft, "Normalized Power");
    setAxisScale(QwtPlot::yLeft, 0, 1.2);
}
 
void DataPlotter::addPlot(double** data, int numPoints, QString strCurveLabel)
{
    double x[numPoints];
    double y[numPoints];
    for (int i = 0; i < numPoints; i++){
        x[i] = data[i][0];
        y[i] = data[i][1];        
    }
    QwtPlotCurve *c = new QwtPlotCurve(strCurveLabel);
    c->setPen(QPen(Qt::red));
    c->attach(this);
    c->setData(x, y, numPoints);    
}

DataPlotter::DataPlotter(QWidget *parent, QString strTitle, double minLambda, double maxLambda):  QwtPlot(parent)
{
    canvas()->setFrameStyle(QFrame::Box | QFrame::Plain );
    canvas()->setLineWidth(1);
    insertLegend(new QwtLegend(), QwtPlot::BottomLegend);
    setTitle(strTitle);
    setAxisTitle(QwtPlot::xBottom, "Wavelength (nm)");
    setAxisScale(QwtPlot::xBottom, minLambda, maxLambda);
    setAxisTitle(QwtPlot::yLeft, "Normalized Power");
    setAxisScale(QwtPlot::yLeft, 0, 1.2);
}

void DataPlotter::addPlot(double** data, int numPoints, QString strCurveLabel)
{
    double x[numPoints];
    double y[numPoints];
    for (int i = 0; i < numPoints; i++){
        x[i] = data[i][0];
        y[i] = data[i][1];        
    }
    QwtPlotCurve *c = new QwtPlotCurve(strCurveLabel);
    c->setPen(QPen(Qt::red));
    c->attach(this);
    c->setData(x, y, numPoints);    
}

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And here's the code calling the DataPlotter object from the main window, to update the plot:

void MainWindow::drawCurvesOnPlotViewer(double** source, int numLambda, QString strTitle)
{
    double minLambda = ui->selectMinLambda->text().toDouble();
    double maxLambda = ui->selectMaxLambda->text().toDouble();
    QString strPlotTitle = "Transmittance Plots";
    QLayout *layout;
 
    // check if plotViewer QWidget already exists
    if (plotViewer == 0) {
        plotViewer = new QWidget();
        plotViewer->setFixedSize(500,500);
        plotViewer->setAttribute(Qt::WA_DeleteOnClose);
        connect(plotViewer, SIGNAL(destroyed()), this, SLOT(closePlot()));
    }
 
    // check if DataPlotter object already exists
    if (blnPlot == 0) {
        plot = new DataPlotter(plotViewer,strPlotTitle,minLambda,maxLambda);
        plot->addPlot(source,numLambda,strTitle);
        layout = new QHBoxLayout;
        layout->addWidget(plot);
        plotViewer->setLayout(layout);
        blnPlot = 1;
    } else {
        plot->addPlot(source,numLambda,strTitle);        
    }
 
    plotViewer->show();
 
}

void MainWindow::drawCurvesOnPlotViewer(double** source, int numLambda, QString strTitle)
{
    double minLambda = ui->selectMinLambda->text().toDouble();
    double maxLambda = ui->selectMaxLambda->text().toDouble();
    QString strPlotTitle = "Transmittance Plots";
    QLayout *layout;

    // check if plotViewer QWidget already exists
    if (plotViewer == 0) {
        plotViewer = new QWidget();
        plotViewer->setFixedSize(500,500);
        plotViewer->setAttribute(Qt::WA_DeleteOnClose);
        connect(plotViewer, SIGNAL(destroyed()), this, SLOT(closePlot()));
    }

    // check if DataPlotter object already exists
    if (blnPlot == 0) {
        plot = new DataPlotter(plotViewer,strPlotTitle,minLambda,maxLambda);
        plot->addPlot(source,numLambda,strTitle);
        layout = new QHBoxLayout;
        layout->addWidget(plot);
        plotViewer->setLayout(layout);
        blnPlot = 1;
    } else {
        plot->addPlot(source,numLambda,strTitle);        
    }

    plotViewer->show();

}

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Any ideas as to what could be causing this? Any suggestions would be greatly appreciated, as I've been banging my head over this all day.

Cheers!

[Uwe]

QwtPlot::replot is missing.

Uwe

[ajb]

Yep that did it, thanks very much!