Syncing many QwtPlots with QwtPlotPickers

I have many QwtPlot objects sharing the same points data in XY coordinates. There can be like 10 curves in one plot. I want display some curves in first plot window and some other curves in second, etc.

Each plot would have drawn their y-axis but there would be only one common x-axis. Plots are stacked vertically and I want one common vertical tracker .

I have some ideas but would this work ?

- each QwtPlot has QwtPlotPicker installed and can draw vertical tracker.
- each plot has slot for 'selected' signal from the picker
- when plot receives 'selected' from picker it sends same signal to other plots with same arguments (that contain position)

I think this could work if the plot sizes are exactly the same. Would it be better to have plot translate mouse point to curve's point in x-axis and send that info to others?

I am going to try to create a top level container, vertical layout that can draw vertical line. I then map mouse events to children QwtPlot widgets... from there I should be able to draw tracker with curve values.

Attachment 11968Ok, seems almost to be working:

Attachment 11968

Looks like my mapping is a little bit off. Mouse is a little left from the 0 point but it reads more than zero:


Here's the code I'm using

Code:

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//global vertical line on top level widget that holds individual pots, picker for global point
    picker = new QwtPicker(QwtPlotPicker::VLineRubberBand, QwtPicker::AlwaysOn,
                                      this);
    picker->setStateMachine(new QwtPickerTrackerMachine);
    picker->setTrackerMode(QwtPicker::AlwaysOff);
    picker->setRubberBand(QwtPicker::VLineRubberBand);
    picker->setRubberBandPen(QColor(Qt::blue));
 
    connect(picker, SIGNAL(moved(const QPoint&)),this,SLOT(onMoved(const QPoint&)));

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Code:

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void MultiPlot::onMoved(const QPoint &p)
{
    QPoint global= this->mapToGlobal(p);
    qDebug() << "onMoved" << p <<", global:" << global << "plot1 fromglobal: " << plot1->mapFromGlobal(global);
 
    QPoint pos=plot1->mapFromGlobal(global);
 
    //invTransform
    QwtScaleMap xMap = plot1->canvasMap( QwtPlot::xBottom );
    QwtScaleMap yMap = plot1->canvasMap( QwtPlot::yLeft );
 
    QPointF posF = QPointF(
        xMap.invTransform( pos.x() ),
        yMap.invTransform( pos.y() )
    );
 
    plot1Picker->onSelected(posF);
    qDebug() << "posF=" << posF;
 
    global= this->mapToGlobal(p);
    qDebug() << "onMoved" << p <<", global:" << global << "plot2 fromglobal: " << plot2->mapFromGlobal(global);
 
    QPoint pos2=plot2->mapFromGlobal(global);
 
    //invTransform
    xMap = plot2->canvasMap( QwtPlot::xBottom );
    yMap = plot2->canvasMap( QwtPlot::yLeft );
 
    QPointF pos2F = QPointF(
        xMap.invTransform( pos2.x() ),
        yMap.invTransform( pos2.y() )
    );
 
    plot2Picker->onSelected(pos2F);
 
    qDebug() << "pos2F=" << pos2F;
 
}

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