QwtWidgetOverlay(widget)

{

    _picker = picker;

}

void ScaleOverlay::drawOverlay(QPainter* painter) const

{

    _picker->drawScaleOverlay(painter);

}

ScalePicker::ScalePicker(QwtScaleWidget* scaleWidget, QWidget* canvas) :

    QObject(scaleWidget)

{

    _scaleWidget = scaleWidget;

    _canvas = canvas;

    scaleWidget->installEventFilter(this);

    scaleWidget->setMouseTracking(true);

    pickerOverlay = new PlotOverlay(canvas, this);

    scaleOverlay = new ScaleOverlay(scaleWidget, this);

    started = false;

    pressed = false;

}

bool ScalePicker::eventFilter(QObject* object, QEvent* event)

{

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

        event->type() == QEvent::MouseButtonRelease ||

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

    {

        QMouseEvent* mouseEvent = (QMouseEvent*) event;

        double pos = this->position(mouseEvent);

        double posPx = this->positionPx(mouseEvent);

        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;

                emit pickStarted(pos);

            }

            else if (started)

            {

                pickerOverlay->updateOverlay();

                emit picking(firstPos, pos);

            }

            scaleOverlay->updateOverlay();

        }

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

        {

            if (started)

            {

                // finalize

                started = false;

                pressed = false;

                emit picked(firstPos, pos);

            }

        }

        return true;

    }

    else

    {

        return QObject::eventFilter(object, event);

    }

}

void ScalePicker::drawPlotOverlay(QPainter* painter)

{

    if (started)

    {

        painter->save();

        painter->setPen(_pen);

        QRect rect;

        if (_scaleWidget->alignment() == QwtScaleDraw::BottomScale ||

            _scaleWidget->alignment() == QwtScaleDraw::TopScale)

        {

            int height = painter->device()->height();

            rect = QRect(posCanvasPx(firstPosPx), 0, currentPosPx-firstPosPx, height);

        }

        else // vertical

        {

            int width = painter->device()->width();

            rect = QRect(0, posCanvasPx(firstPosPx), width, currentPosPx-firstPosPx);

        }

        painter->drawRect(rect);

        painter->restore();