{

                    posPx = sp;

                    break;

                }

            }

        }

        double pos = this->position(posPx);

        currentPosPx = posPx;

        if (event->type() == QEvent::MouseButtonPress &&

            mouseEvent->button() == Qt::LeftButton)

        {

            pressed = true; // not yet started

            firstPos = pos;

            firstPosPx = posPx;

        }

        else if (event->type() == QEvent::MouseMove)

        {

            // make sure pick size is big enough, so that just

            // clicking won't trigger pick

            if (!started && pressed && (fabs(posPx-firstPosPx) > MIN_PICK_SIZE))

            {

                started = true;

            }

            pickerOverlay->updateOverlay();

            scaleOverlay->updateOverlay();

        }

        else // event->type() == QEvent::MouseButtonRelease

        {

            pressed = false;

            if (started)

            {

                // finalize

                started = false;

                emit picked(firstPos, pos);

            }

        }

        return true;

    }

    else if (event->type() == QEvent::Leave)

    {

        scaleOverlay->updateOverlay();

        pickerOverlay->updateOverlay();

        return true;

    }

    else

    {

#define SCALEPICKER_H

#include <QObject>

#include <QMouseEvent>

#include <QPen>

#include <QWidget>

#include <QList>

#include <QMap>

#include <qwt_scale_widget.h>

#include <qwt_widget_overlay.h>

class ScalePicker : public QObject

{

    Q_OBJECT

public:

    ScalePicker(QwtScaleWidget* scaleWidget, QWidget* canvas);

    virtual bool eventFilter(QObject*, QEvent*);

    void drawPlotOverlay(QPainter*); // called from ScalePickerOverlay

    void drawScaleOverlay(QPainter*); // called from ScaleOverlay

    void setPen(QPen pen);

signals:

    void picked(double firstPos, double lastPos);

private:

    QwtScaleWidget* _scaleWidget;

    QWidget* _canvas;

    QwtWidgetOverlay* pickerOverlay; // will be PlotOverlay

    QwtWidgetOverlay* scaleOverlay;  // will be ScaleOverlay

    QPen _pen;

    bool pressed;

    bool started;

    double firstPos; // converted to plot coordinates

    double firstPosPx; // pixel coordinates

    double currentPosPx; // current position in pixel coordinates

    QList<int> snapPoints;

    /// used to restore precision of snappoints that is lost due to rounding

    QMap<int, double> snapPointMap;

    double position(double) const; // returns the axis mouse position relative to plot coordinates

    int positionPx(QMouseEvent*); // returns the axis mouse position in pixels

    double posCanvasPx(double pos) const; // returns the given position in canvas coordinates

    void drawTriangle(QPainter* painter, int position);

    QwtText trackerText() const;

     /// Returns tracker text position