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    QwtPlotZoomer* zoomer = new MyZoomer(canvas());

    zoomer->setMousePattern(QwtEventPattern::MouseSelect2,Qt::RightButton, Qt::ControlModifier);

    zoomer->setMousePattern(QwtEventPattern::MouseSelect3,Qt::RightButton);

    QwtPlotPanner *panner = new QwtPlotPanner(canvas());
    panner->setAxisEnabled(QwtPlot::yRight, false);
    panner->setMouseButton(Qt::MidButton);

    // Avoid jumping when labels with more/less digits
    // appear/disappear when scrolling vertically

    const QFontMetrics fm(axisWidget(QwtPlot::yLeft)->font());
    QwtScaleDraw *sd = axisScaleDraw(QwtPlot::yLeft);
    sd->setMinimumExtent( fm.width("10.0") );

    const QColor c(Qt::darkBlue);
    zoomer->setRubberBandPen(c);
    zoomer->setTrackerPen(c);

class MyZoomer: public QwtPlotZoomer
{
public:
    MyZoomer(QwtPlotCanvas *canvas):QwtPlotZoomer(canvas)
    {
        setTrackerMode(AlwaysOn);
    }
    virtual QwtText trackerText(const QwtDoublePoint &pos) const
    {
        QColor bg(Qt::white);
        bg.setAlpha(200);
        QwtText text = QwtPlotZoomer::trackerText(pos);
        text.setBackgroundBrush( QBrush( bg ));
        return text;
    }
};

/*!
  \brief Event filter

  When isEnabled() == true all events of the observed widget are filtered.
  Mouse and keyboard events are translated into widgetMouse- and widgetKey-
  and widgetWheel-events. Paint and Resize events are handled to keep 
  rubberband and tracker up to date.

  \sa event(), widgetMousePressEvent(), widgetMouseReleaseEvent(),
      widgetMouseDoubleClickEvent(), widgetMouseMoveEvent(),
      widgetWheelEvent(), widgetKeyPressEvent(), widgetKeyReleaseEvent()
*/
bool QwtPicker::eventFilter(QObject *o, QEvent *e)
{
    if ( o && o == parentWidget() )
    {
        switch(e->type())
        {
            case QEvent::Resize:
            {
                const QResizeEvent *re = (QResizeEvent *)e;
                if ( d_data->resizeMode == Stretch )
                    stretchSelection(re->oldSize(), re->size());

                if ( d_data->rubberBandWidget )
                    d_data->rubberBandWidget->resize(re->size());
             
                if ( d_data->trackerWidget )
                    d_data->trackerWidget->resize(re->size());
                break;
            }
            case QEvent::Leave:
                widgetLeaveEvent(e);
                break;
            case QEvent::MouseButtonPress:
                widgetMousePressEvent((QMouseEvent *)e);
                break;
            case QEvent::MouseButtonRelease:
                widgetMouseReleaseEvent((QMouseEvent *)e);
                break;
            case QEvent::MouseButtonDblClick:
                widgetMouseDoubleClickEvent((QMouseEvent *)e);
                break;
            case QEvent::MouseMove:
                widgetMouseMoveEvent((QMouseEvent *)e);
                break;
            case QEvent::KeyPress:
                widgetKeyPressEvent((QKeyEvent *)e);
                break;
            case QEvent::KeyRelease:
                widgetKeyReleaseEvent((QKeyEvent *)e);
                break;
            case QEvent::Wheel:
                widgetWheelEvent((QWheelEvent *)e);
                break;
            default:
                break;
        }
    }
    return false;
}

main@krchome:/tmp/masterPlot$ valgrind --malloc-fill=80 --free-fill=ff ./myPlot