protected:

    virtual void drawOverlay(QPainter*) const;

private:

    ScalePicker* _picker;

};

PlotOverlay::PlotOverlay(QWidget* widget, ScalePicker* picker) :

    QwtWidgetOverlay(widget)

{

    _picker = picker;

}

void PlotOverlay::drawOverlay(QPainter* painter) const

{

    _picker->drawPlotOverlay(painter);

}

class ScaleOverlay : public QwtWidgetOverlay

{

public:

    ScaleOverlay(QWidget* widget, ScalePicker* picker);

protected:

    virtual void drawOverlay(QPainter*) const;

private:

    ScalePicker* _picker;

};

ScaleOverlay::ScaleOverlay(QWidget* widget, ScalePicker* picker) :

    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)

    {

        updateSnapPoints();

        QMouseEvent* mouseEvent = (QMouseEvent*) event;

        int posPx = this->positionPx(mouseEvent);

        // do snapping unless Shift is pressed

        if (! (mouseEvent->modifiers() & Qt::ShiftModifier))

        {

            for (auto sp : snapPoints)

            {

                if (std::abs(posPx-sp) <= SNAP_DISTANCE)

                {

                    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

    {

        return QObject::eventFilter(object, event);

    }

}

const int TEXT_MARGIN = 4;

void ScalePicker::drawPlotOverlay(QPainter* painter)

{

    const double FILL_ALPHA = 0.2;

    painter->save();

    painter->setPen(_pen);

    if (started)

    {

        QColor color = _pen.color();

        color.setAlphaF(FILL_ALPHA);

        painter->setBrush(color);

        QRect rect;

        QwtText text = trackerText();

        auto tSize = text.textSize(painter->font());

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

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

        {

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

            int pickWidth = currentPosPx-firstPosPx;

            rect = QRect(posCanvasPx(firstPosPx), 0, pickWidth, canvasHeight);

        }

        else // vertical

        {

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

            int pickHeight = currentPosPx-firstPosPx;

            rect = QRect(0, posCanvasPx(firstPosPx), canvasWidth, pickHeight);

        }

        painter->drawRect(rect);

        text.draw(painter, pickTrackerTextRect(painter, rect, tSize));

    }

    else if (_scaleWidget->underMouse())

    {

        // draw tracker text centered on cursor

        QwtText text = trackerText();

        auto tsize = text.textSize(painter->font());

        text.draw(painter, trackerTextRect(painter, currentPosPx, tsize));

    }

    painter->restore();

}

QwtText ScalePicker::trackerText() const

{

    double pos;

    // use stored value if snapped to restore precision

    if (snapPointMap.contains(currentPosPx))

    {

        pos = snapPointMap[currentPosPx];

    }

    else

    {

        pos = position(currentPosPx);

    }

    return QwtText(QString("%1").arg(pos));

}

QRectF ScalePicker::trackerTextRect(QPainter* painter, int posPx, QSizeF textSize) const

{

    int canvasPosPx = posCanvasPx(posPx);

    QPointF topLeft;

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

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

/*

  Copyright © 2017 Hasan Yavuz Özderya

  This file is part of serialplot.

  serialplot is free software: you can redistribute it and/or modify

  it under the terms of the GNU General Public License as published by

  the Free Software Foundation, either version 3 of the License, or

  (at your option) any later version.

  serialplot is distributed in the hope that it will be useful,

  but WITHOUT ANY WARRANTY; without even the implied warranty of

  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License

  along with serialplot.  If not, see <http://www.gnu.org/licenses/>.

*/

#ifndef SCALEPICKER_H

#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

    QRectF trackerTextRect(QPainter* painter, int posPx, QSizeF textSize) const;

    /// Returns the text position for tracker text shown during picking

    QRectF pickTrackerTextRect(QPainter* painter, QRect pickRect, QSizeF textSize) const;

private slots:

    void updateSnapPoints();

};

#endif // SCALEPICKER_H