QwtPlotPicker stay visible after DoubleMouseClick

Hello,

i use in my QwtPlot a curve tracker like in the playground example "CurveTracker".

Code:

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#include "curvetracker.h"
#include <qwt_picker_machine.h>
#include <qwt_series_data.h>
#include <qwt_plot.h>
#include <qwt_plot_curve.h>
 
struct compareX
{
    inline bool operator()( const double x, const QPointF &pos ) const
    {
        return ( x < pos.x() );
    }
};
 
CurveTracker::CurveTracker( QWidget *canvas ):
    QwtPlotPicker( canvas )
{
    setTrackerMode( QwtPlotPicker::ActiveOnly );
    setRubberBand( VLineRubberBand );
 
    setStateMachine( new QwtPickerDragPointMachine() );
}
 
QRect CurveTracker::trackerRect( const QFont &font ) const
{
    QRect r = QwtPlotPicker::trackerRect( font );
 
    // align r to the first curve
 
    const QwtPlotItemList curves = plot()->itemList( QwtPlotItem::Rtti_PlotCurve );
    if ( curves.size() > 0 )
    {
        QPointF pos = invTransform( trackerPosition() );
 
        const QLineF line = curveLineAt(    
            static_cast<const QwtPlotCurve *>( curves[0] ), pos.x() );
        if ( !line.isNull() )
        {
            const double curveY = line.pointAt(
                ( pos.x() - line.p1().x() ) / line.dx() ).y();
 
            pos.setY( curveY );
            pos = transform( pos );
 
            r.moveBottom( pos.y() );
        }
    }
 
    return r;
}
 
QwtText CurveTracker::trackerTextF( const QPointF &pos ) const
{
    QwtText trackerText;
 
    trackerText.setColor( Qt::black );
 
    QColor c( "#333333" );
    trackerText.setBorderPen( QPen( c, 2 ) );
    c.setAlpha( 200 );
    trackerText.setBackgroundBrush( c );
 
    QString info;
 
    const QwtPlotItemList curves = 
        plot()->itemList( QwtPlotItem::Rtti_PlotCurve );
 
    for ( int i = 0; i < curves.size(); i++ )
    {
        const QString curveInfo = curveInfoAt( 
            static_cast<const QwtPlotCurve *>( curves[i] ), pos );
 
        if ( !curveInfo.isEmpty() )
        {
            if ( !info.isEmpty() )
                info += "<br>";
 
            info += curveInfo;
        }
    }
 
    trackerText.setText( info );
    return trackerText;
}
 
QString CurveTracker::curveInfoAt( 
    const QwtPlotCurve *curve, const QPointF &pos ) const
{
    const QLineF line = curveLineAt( curve, pos.x() );
    if ( line.isNull() )
        return QString::null;
 
    const double y = line.pointAt( 
        ( pos.x() - line.p1().x() ) / line.dx() ).y();
 
    QString info( "<font color=""%1"">%2</font>" );
    return info.arg( curve->pen().color().name() ).arg( y );
}
 
QLineF CurveTracker::curveLineAt( 
    const QwtPlotCurve *curve, double x ) const
{
    QLineF line;
 
    if ( curve->dataSize() >= 2 )
    {
        const QRectF br = curve->boundingRect();
        if ( ( br.width() > 0 ) && ( x >= br.left() ) && ( x <= br.right() ) )
        {
            int index = qwtUpperSampleIndex<QPointF>( 
                *curve->data(), x, compareX() );
 
            if ( index == -1 && 
                x == curve->sample( curve->dataSize() - 1 ).x() )
            {
                // the last sample is excluded from qwtUpperSampleIndex
                index = curve->dataSize() - 1;
            }
 
            if ( index > 0 )
            {
                line.setP1( curve->sample( index - 1 ) );
                line.setP2( curve->sample( index ) );
            }
        }
    }
 
    return line;
}

---

This works and i get always the values from the actual Mouse Position.

Now i want to double Click at a selected position and want the tracker to stay visible also when i move the mouse outside the plot area.

How can i manage this?

Thanks for help

DSP

This first step is to terminate the picker on double clicks, what can be done by overloading the transition() method of your QwtPickerMachine. Have a look at the code in qwt_picker_machine.cpp and you will know what to do.
Then I would connect a slot to the QwtPlotPicker::selected signal, where you simply insert a QwtPlotMarker at the selected position, that looks like the cursor of the picker.

Uwe

Hi Uwe,

sorry i didn't get it.

My CurveTracker class is derived from QwtPlotPicker.
Where should i overload the transition function from QwtPickerMachine class?

Do i have to write a own MyPickerMachine class and handle all the stuff there?
Then i could overload the transistion function and could try to catch the double click event.
Who does emit the selected signal?

Thanks for further explanations

Quote:

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Originally Posted by DSP

My CurveTracker class is derived from QwtPlotPicker.
Where should i overload the transition function from QwtPickerMachine class?

---

Inherit from whatever machine your picker is using ( in the curvetracker example it is a QwtPickerDragPointMachine ), extend/configure it by overloading its virtual methods ad then add it with:

Code:

---

yourPicker->setStateMachine( yourStateMachine )

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Of course you can also write your own state machine from scratch if you prefer that.

Quote:

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Who does emit the selected signal?

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Well a picker is for selecting points/rects/polygons ( in your case a point ) and the selected signal emits the result of the selection, what should contain the position, where to insert the marker.

Uwe