b.setText(b.text() + sizeText);

    return b;

}

void Zoomer::drawRubberBand(QPainter* painter) const

{

    const double FILL_ALPHA = 0.2;

    QColor color = painter->pen().color();

    color.setAlphaF(FILL_ALPHA);

    painter->setBrush(color);

    ScrollZoomer::drawRubberBand(painter);

}

QRegion Zoomer::rubberBandMask() const

{

    const QPolygon pa = selection();

    if (pa.count() < 2)

    {

        return QRegion();

    }

    const QRect r = QRect(pa.first(), pa.last()).normalized().adjusted(0, 0, 1, 1);

    return QRegion(r);

}

void Zoomer::drawTracker(QPainter* painter) const

{

    if (isActive())

    {

        QwtPlotZoomer::drawTracker(painter);

    }

    else if (dispChannels.length())

    {

        drawValues(painter);

    }

}

void Zoomer::drawValues(QPainter* painter) const

{

    painter->save();

    double x = invTransform(trackerPosition()).x();

    auto values = findValues(x);

    // draw vertical line

    painter->setPen(linePen);

    const QRect pRect = pickArea().boundingRect().toRect();

    int px = trackerPosition().x();

    painter->drawLine(px, pRect.top(), px, pRect.bottom());

    // draw sample values

    for (int ci = 0; ci < values.size(); ci++)

    {

        if (!dispChannels[ci]->visible()) continue;

        double val = values[ci];

        if (!std::isnan(val))

        {

            auto p = transform(QPointF(x, val));

            painter->setBrush(dispChannels[ci]->color());

            painter->setPen(Qt::NoPen);

            painter->drawEllipse(p, VALUE_POINT_DIAM, VALUE_POINT_DIAM);

            // We give a very small (1x1) rectangle but disable clipping

            painter->drawText(QRectF(p.x() + VALUE_TEXT_MARGIN, p.y(), 1, 1),

                              Qt::AlignVCenter | Qt::TextDontClip,

                              QString("%1").arg(val));

        }

    }

    painter->restore();

}

QVector<double> Zoomer::findValues(double x) const

{

    unsigned nc = dispChannels.length();

    QVector<double> result(nc);

    for (unsigned ci = 0; ci < nc; ci++)

    {

        if (dispChannels[ci]->visible())

        {

            result[ci] = dispChannels[ci]->findValue(x);

        }

    }

    return result;

}

QRect Zoomer::trackerRect(const QFont& font) const

{

    if (isActive())

    {

        return QwtPlotZoomer::trackerRect(font);

    }

    else

    {

        return valueTrackerRect(font);

    }

}

QRect Zoomer::valueTrackerRect(const QFont& font) const

{

    // TODO: consider using actual tracker values for width calculation

    const int textWidth = qCeil(QwtText("-8.8888888").textSize(font).width());

    const int width = textWidth + VALUE_POINT_DIAM + VALUE_TEXT_MARGIN;

    const int x = trackerPosition().x() - VALUE_POINT_DIAM;

    const auto pickRect = pickArea().boundingRect();

    return QRect(x, pickRect.y(), width, pickRect.height());

}