aligning plots and color bar

[embeddedmz]

You're right Uwe !

Now it looks better but there's still some adjustments that have to be made and I hope that you can help me :

aligning_waterfall_plot_axis_progress.jpg

First of all, there's these 2 lines in the constructor that triggers everything, the issue is that if I don't rescale X axis of one of the two plots, the alignement logic will not be executed and I don't know how to handle this (plotmatrix playground). For example, to obtain the result shown in the screenshot above, I used the zoomer to zoom a region of the waterfall.

connect(m_plotCurve->axisWidget(QwtPlot::xBottom), &QwtScaleWidget::scaleDivChanged,
            this,                          &Waterfallplot::scaleDivChanged/*, Qt::QueuedConnection*/);
    connect(m_plotSpectrogram->axisWidget(QwtPlot::xBottom), &QwtScaleWidget::scaleDivChanged,
            this,                                &Waterfallplot::scaleDivChanged/*,Qt::QueuedConnection*/);
 
void Waterfallplot::scaleDivChanged()
{
    // apparently, m_inScaleSync is a hack that can be replaced by
    // blocking signals on a widget but that could be cumbersome
    // or not possible as the Qwt API doesn't provide any mean to do that
    if (m_inScaleSync)
    {
        return;
    }
    m_inScaleSync = true;
 
    QwtPlot* updatedPlot;
    if (m_plotCurve->axisWidget(QwtPlot::xBottom) == sender())
    {
        updatedPlot = m_plotCurve;
    }
    else if (m_plotSpectrogram->axisWidget(QwtPlot::xBottom) == sender())
    {
        updatedPlot = m_plotSpectrogram;
    }
    else
    {
        updatedPlot = nullptr;
    }
 
    if (updatedPlot)
    {
        QwtPlot* plotToUpdate = (updatedPlot == m_plotCurve) ? m_plotSpectrogram : m_plotCurve;
        plotToUpdate->setAxisScaleDiv(QwtPlot::xBottom,
                                      updatedPlot->axisScaleDiv(QwtPlot::xBottom));
        updateLayout();
    }
 
    m_inScaleSync = false;
}
 
void Waterfallplot::alignAxis(int axisId)
{
    // 1. Align Vertical Axis (only left or right)
    double maxExtent = 0;
 
    {
        QwtScaleWidget* scaleWidget = m_plotCurve->axisWidget(axisId);
 
        QwtScaleDraw* sd = scaleWidget->scaleDraw();
        sd->setMinimumExtent(0.0);
 
        const double extent = sd->extent(scaleWidget->font());
        if (extent > maxExtent)
        {
            maxExtent = extent;
        }
    }
 
    {
        QwtScaleWidget* scaleWidget = m_plotSpectrogram->axisWidget(axisId);
 
        QwtScaleDraw* sd = scaleWidget->scaleDraw();
        sd->setMinimumExtent( 0.0 );
 
        const double extent = sd->extent(scaleWidget->font());
        if (extent > maxExtent)
        {
            maxExtent = extent;
        }
    }
 
    {
        QwtScaleWidget* scaleWidget = m_plotCurve->axisWidget(axisId);
        scaleWidget->scaleDraw()->setMinimumExtent(maxExtent);
    }
 
    {
        QwtScaleWidget* scaleWidget = m_plotSpectrogram->axisWidget(axisId);
        scaleWidget->scaleDraw()->setMinimumExtent(maxExtent);
    }
}
 
void Waterfallplot::alignAxisForColorBar()
{
    auto s1 = m_plotSpectrogram->axisWidget(QwtPlot::yRight);
    auto s2 = m_plotCurve->axisWidget(QwtPlot::yRight);
 
    s2->scaleDraw()->setMinimumExtent( 0.0 );
 
    qreal extent = s1->scaleDraw()->extent(s1->font());
    extent -= s2->scaleDraw()->extent(s2->font());
    extent += s1->colorBarWidth() + s1->spacing();
 
    s2->scaleDraw()->setMinimumExtent(extent);
}
 
void Waterfallplot::updateLayout()
{
    // 1. Align Vertical Axis (only left or right)
    alignAxis(QwtPlot::yLeft);
    alignAxisForColorBar();
 
    // 2. Replot
    m_plotCurve->replot();
    m_plotSpectrogram->replot();
}

connect(m_plotCurve->axisWidget(QwtPlot::xBottom), &QwtScaleWidget::scaleDivChanged,
            this,                          &Waterfallplot::scaleDivChanged/*, Qt::QueuedConnection*/);
    connect(m_plotSpectrogram->axisWidget(QwtPlot::xBottom), &QwtScaleWidget::scaleDivChanged,
            this,                                &Waterfallplot::scaleDivChanged/*,Qt::QueuedConnection*/);

void Waterfallplot::scaleDivChanged()
{
    // apparently, m_inScaleSync is a hack that can be replaced by
    // blocking signals on a widget but that could be cumbersome
    // or not possible as the Qwt API doesn't provide any mean to do that
    if (m_inScaleSync)
    {
        return;
    }
    m_inScaleSync = true;
    
    QwtPlot* updatedPlot;
    if (m_plotCurve->axisWidget(QwtPlot::xBottom) == sender())
    {
        updatedPlot = m_plotCurve;
    }
    else if (m_plotSpectrogram->axisWidget(QwtPlot::xBottom) == sender())
    {
        updatedPlot = m_plotSpectrogram;
    }
    else
    {
        updatedPlot = nullptr;
    }
    
    if (updatedPlot)
    {
        QwtPlot* plotToUpdate = (updatedPlot == m_plotCurve) ? m_plotSpectrogram : m_plotCurve;
        plotToUpdate->setAxisScaleDiv(QwtPlot::xBottom,
                                      updatedPlot->axisScaleDiv(QwtPlot::xBottom));
        updateLayout();
    }
    
    m_inScaleSync = false;
}

void Waterfallplot::alignAxis(int axisId)
{
    // 1. Align Vertical Axis (only left or right)
    double maxExtent = 0;

    {
        QwtScaleWidget* scaleWidget = m_plotCurve->axisWidget(axisId);

        QwtScaleDraw* sd = scaleWidget->scaleDraw();
        sd->setMinimumExtent(0.0);

        const double extent = sd->extent(scaleWidget->font());
        if (extent > maxExtent)
        {
            maxExtent = extent;
        }
    }

    {
        QwtScaleWidget* scaleWidget = m_plotSpectrogram->axisWidget(axisId);

        QwtScaleDraw* sd = scaleWidget->scaleDraw();
        sd->setMinimumExtent( 0.0 );

        const double extent = sd->extent(scaleWidget->font());
        if (extent > maxExtent)
        {
            maxExtent = extent;
        }
    }

    {
        QwtScaleWidget* scaleWidget = m_plotCurve->axisWidget(axisId);
        scaleWidget->scaleDraw()->setMinimumExtent(maxExtent);
    }

    {
        QwtScaleWidget* scaleWidget = m_plotSpectrogram->axisWidget(axisId);
        scaleWidget->scaleDraw()->setMinimumExtent(maxExtent);
    }
}

void Waterfallplot::alignAxisForColorBar()
{
    auto s1 = m_plotSpectrogram->axisWidget(QwtPlot::yRight);
    auto s2 = m_plotCurve->axisWidget(QwtPlot::yRight);

    s2->scaleDraw()->setMinimumExtent( 0.0 );

    qreal extent = s1->scaleDraw()->extent(s1->font());
    extent -= s2->scaleDraw()->extent(s2->font());
    extent += s1->colorBarWidth() + s1->spacing();

    s2->scaleDraw()->setMinimumExtent(extent);
}

void Waterfallplot::updateLayout()
{
    // 1. Align Vertical Axis (only left or right)
    alignAxis(QwtPlot::yLeft);
    alignAxisForColorBar();
    
    // 2. Replot
    m_plotCurve->replot();
    m_plotSpectrogram->replot();
}

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Please can you take a look at what I did : https://github.com/embeddedmz/QwtWaterfallplot and help me to enhance it.

I think it's a good idea to create a new Qwt example, for the data one can use the spectrogram example data and display it slowly ! Otherwise, I'm going to add a curve plot at the left of the spectrogram, and that will allow a user to select a point on the spectrogram and use the curve plot above the waterfall to plot the layer in function of the spectrogram X axis and the the curve plot at the left of the spectrogram will be used to plot the vertical waterfall slice in function of time (the curves reflects the cross described by the point). I think this is a better example.

Thanks.