QwtPlotZoomer question

**falconium** · 11th May 2011, 20:26

I know it is time consuming to go through the code, but this is what I had done earlier, but didn't work. You can check the code above, but better to check code below, as it has a modified zoomer that causes to go only one stack back on right mouse click, doesn't go back to 0 immediately.

Please, point it out for me where should I put it in the code....

Qt Code:

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#include <qapplication.h>
#include <qlayout.h>
#include <qlabel.h>
#include <qtime>
#include <qpainter.h>
#include "chartplot.h"
 
class PlotPicker : public QwtPlotPicker
{
public:
    PlotPicker(QwtPlot::Axis xAxis,
               QwtPlot::Axis yAxis,
               QwtPicker::RubberBand rb,
               QwtPicker::DisplayMode dm,
               QwtPlotCanvas* canvas) : QwtPlotPicker( xAxis, yAxis, rb , dm , canvas)
    {
        setStateMachine(new QwtPickerTrackerMachine());
        setRubberBandPen(QPen(Qt::DotLine));
        setRubberBand(QwtPicker::CrossRubberBand);
    }
 
private:
    QwtText trackerTextF(const QPointF &pos) const
    {
        QwtText text("X = " + QDateTime::fromTime_t(pos.x()).toString("yyyy.MM.dd. hh:mm:ss") + "\nY = " + QString::number(pos.y()));
        QColor bgColor(Qt::lightGray);
        bgColor.setAlpha(100);
        text.setBackgroundBrush(QBrush(bgColor));
        return text;
    }
 
};
 
QwtScaleDiv ChartPlot::scaleDiv()
{
    QList<double> ticks[QwtScaleDiv::NTickTypes];
 
    QList<double> &majorTicks = ticks[QwtScaleDiv::MajorTick];
    QList<double> &mediumTicks = ticks[QwtScaleDiv::MediumTick];
    QList<double> &minorTicks = ticks[QwtScaleDiv::MinorTick];
 
    if (xData.count()<11)
    {
        foreach (double value, xData)
            majorTicks += value;
 
        if (xData.count()>1)
        {
            for (int i = 0; i < xData.count() - 1; i++)
                for (int j = 1; j < 6; j++)
                    mediumTicks += xData[i] + j * (xData[i+1] - xData[i]) / 5;
 
            for (int i = 0; i < xData.count() - 1; i++)
                for (int j = 1; j < 11; j++)
                    minorTicks += xData[i] + j * (xData[i+1] - xData[i]) / 10;
        }
    }
    else
    {
 
//       Quantity-based division
 
//        QVector<double> tempXData;
//        for (int i=0; i<11; i++)
//        {
//            int value = (i*(xData.count()-1)/10);
//            tempXData.append(xData[value]);
//            majorTicks += tempXData[i];
//        }
 
//      Value-based division
        QVector<double> tempXData;
        for (int i=0; i<11; i++)
        {
            tempXData.append(xData[0] + i*(xData[xData.count()-1] - xData[0])/10);
            majorTicks += tempXData.last();
        }
        for (int i = 0; i < tempXData.count() - 1; i++)
            for (int j = 1; j < 6; j++)
                mediumTicks += tempXData[i] + j * (tempXData[i+1] - tempXData[i]) / 5;
        for (int i = 0; i < tempXData.count() - 1; i++)
            for (int j = 1; j < 11; j++)
                minorTicks += tempXData[i] + j * (tempXData[i+1] - tempXData[i]) / 10;
    }
 
    return QwtScaleDiv(xData.first(), xData.last(), ticks);
}
 
class Zoomer: public QwtPlotZoomer
{
public:
    Zoomer(int xAxis, int yAxis, QwtPlotCanvas *canvas) : QwtPlotZoomer(xAxis, yAxis, canvas)
    {
        setMousePattern(QwtEventPattern::MouseSelect2, Qt::RightButton, Qt::ControlModifier);
        setMousePattern(QwtEventPattern::MouseSelect3, Qt::RightButton);
        setZoomBase();
    }
};
 
class Grid: public QwtPlotGrid
{
public:
    Grid()
    {
        enableXMin(true);
        setMajPen(QPen(Qt::white, 0, Qt::DotLine));
        setMinPen(QPen(Qt::lightGray, 0 , Qt::DotLine));
    }
 
    virtual void updateScaleDiv(const QwtScaleDiv &xMap, const QwtScaleDiv &yMap)
    {
        QList<double> ticks[QwtScaleDiv::NTickTypes];
 
        ticks[QwtScaleDiv::MajorTick] = xMap.ticks(QwtScaleDiv::MajorTick);
        ticks[QwtScaleDiv::MinorTick] = xMap.ticks(QwtScaleDiv::MinorTick);
 
        QwtPlotGrid::updateScaleDiv(QwtScaleDiv(xMap.lowerBound(), xMap.upperBound(), ticks), yMap);
    }
};
 
class TimeScaleDraw: public QwtScaleDraw
{
public:
    TimeScaleDraw()
    {
        setTickLength(QwtScaleDiv::MajorTick, 8);
        setTickLength(QwtScaleDiv::MinorTick, 2);
        setTickLength(QwtScaleDiv::MediumTick, 4);
        setLabelRotation(0);
        setLabelAlignment(Qt::AlignHCenter | Qt::AlignVCenter);
        setSpacing(15);
    }
 
    virtual QwtText label(double value) const
    {
        QDateTime time;
        time = time.fromTime_t(value);
        return time.toString("yyyy.MM.dd.\nhh:mm:ss");
    }
};
 
class Background: public QwtPlotItem
{
public:
    Background()
    {
        setZ(0.0);
    }
 
    virtual int rtti() const
    {
        return QwtPlotItem::Rtti_PlotUserItem;
    }
 
    virtual void draw(QPainter *painter,
                      const QwtScaleMap &,
                      const QwtScaleMap &,
                      const QRectF &rect) const
    {
        QColor color(Qt::gray);
        color = color.darker(150);
        painter->fillRect(rect, color);
    }
};
 
class ChartCurve: public QwtPlotCurve
{
public:
    ChartCurve(const QString &title) : QwtPlotCurve(title)
    {
        setRenderHint(QwtPlotItem::RenderAntialiased);
    }
 
    void setColor(const QColor &color)
    {
        QColor c = color;
        c.setAlpha(150);
 
        setPen(c);
        setBrush(c);
    }
};
 
ChartPlot::ChartPlot(QStandardItemModel *model, bool isSplineUsed, QWidget *parent) : QwtPlot(parent)
{
    this->model = model;
    splineUsed = isSplineUsed;
 
    setAutoReplot(false);
 
    plotLayout()->setAlignCanvasToScales(true);
 
    signs = new QwtLegend;
    signs->setItemMode(QwtLegend::CheckableItem);
    insertLegend(signs, QwtPlot::RightLegend);
 
    setAxisTitle(QwtPlot::xBottom, "Report time");
    setAxisScaleDraw(QwtPlot::xBottom, new TimeScaleDraw());
 
    scaleWidget = axisWidget(QwtPlot::xBottom);
    const int fmh = QFontMetrics(scaleWidget->font()).height();
    scaleWidget->setMinBorderDist(0, fmh / 2);
 
    setAxisTitle(QwtPlot::yLeft, "Quantity");
 
    grid = new Grid;
    grid->attach(this);
 
    bg = new Background();
    bg->attach(this);
 
    countPlot();
 
    scaleEngineX = new QwtLinearScaleEngine;
    scaleEngineX->setAttribute(QwtScaleEngine::Floating, true);
    setAxisScaleEngine(QwtPlot::xBottom, scaleEngineX);
    setAxisScaleDiv(QwtPlot::xBottom, scaleDiv());
 
    scaleEngineY = new QwtLinearScaleEngine;
    scaleEngineY->setAttribute(QwtScaleEngine::IncludeReference, true);
    scaleEngineY->setReference(0);
    setAxisScaleEngine(QwtPlot::yLeft, scaleEngineY);
 
    picker = new PlotPicker(QwtPlot::xBottom,
                                        QwtPlot::yLeft,
                                        QwtPlotPicker::CrossRubberBand,
                                        QwtPicker::ActiveOnly,
                                        this->canvas());
    replot();
    zoomer = new Zoomer(QwtPlot::xBottom, QwtPlot::yLeft, this->canvas());
    zoomer->setZoomBase(false);
    connect(this, SIGNAL(legendChecked(QwtPlotItem *, bool)),  SLOT(showCurve(QwtPlotItem *, bool)));
}
 
void ChartPlot::showCurve(QwtPlotItem *item, const bool &on, const bool &replt)
{
    item->setVisible(on);
    QWidget *w = legend()->find(item);
    if (w && w->inherits("QwtLegendItem")) ((QwtLegendItem *)w)->setChecked(on);
    if (replt) replot();
}
 
void ChartPlot::useSpline(bool on, bool refresh)
{
    if (on)
    {
        for (int i=0; i<curve.count(); i++)
        {
            curveFitter = new QwtSplineCurveFitter;
            curve.at(i)->setCurveFitter(curveFitter);
        }
    }
    else
    {
        for (int i=0; i<curve.count(); i++)
        {
            curveFitter = new QwtWeedingCurveFitter;
            curve.at(i)->setCurveFitter(curveFitter);
        }
    }
    if (refresh) replot();
}
 
void ChartPlot::countPlot()
{
    // Store current visibility of curves if they exist, otherwise initialize visibility to true
    QList<bool> visible;
    if (curve.isEmpty())
    {
        for (int column = 1; column < model->columnCount(); column++)
            visible.append(true);
    }
    else
    {
        for (int column = 1; column < model->columnCount(); column++)
        {
            visible.append(curve[column - 1]->isVisible());
            curve[column - 1]->detach();
        }
        curve.clear();
    }
    // Read X-axis data from table
    for (int row=0; row<model->rowCount(); row++)
    {
        QDateTime xDateTime = model->item(row, 0)->data(Qt::EditRole).toDateTime();
        xData << xDateTime.toTime_t();
    }
    // Read Y-axis data from table
    for (int column = 1; column < model->columnCount(); column++)
    {
        QVector<double> yData;
 
        curve.append(new ChartCurve(model->horizontalHeaderItem(column)->text()));
        curve.last()->setStyle(QwtPlotCurve::Lines);
        QVariant decoration = model->item(0, column)->data(Qt::DecorationRole);
        if (decoration.type() == QVariant::Color)
        {
            curve.last()->setColor(decoration.value<QColor>());
        }
        curve.last()->setCurveAttribute(QwtPlotCurve::Fitted, true);
        curve.last()->setZ(curve.last()->z() - 1);
        curve.last()->attach(this);
 
        for (int row=0; row<model->rowCount(); row++)
        {
            yData << model->item(row, column)->data(Qt::EditRole).toDouble();
        }
        curve.last()->setSamples(xData, yData);
        showCurve(curve.last(), visible[column - 1], false);
    }
    useSpline(splineUsed, false);
}

#include <qapplication.h>
#include <qlayout.h>
#include <qlabel.h>
#include <qtime>
#include <qpainter.h>
#include "chartplot.h"

class PlotPicker : public QwtPlotPicker
{
public:
    PlotPicker(QwtPlot::Axis xAxis,
               QwtPlot::Axis yAxis,
               QwtPicker::RubberBand rb,
               QwtPicker::DisplayMode dm,
               QwtPlotCanvas* canvas) : QwtPlotPicker( xAxis, yAxis, rb , dm , canvas)
    {
        setStateMachine(new QwtPickerTrackerMachine());
        setRubberBandPen(QPen(Qt::DotLine));
        setRubberBand(QwtPicker::CrossRubberBand);
    }

private:
    QwtText trackerTextF(const QPointF &pos) const
    {
        QwtText text("X = " + QDateTime::fromTime_t(pos.x()).toString("yyyy.MM.dd. hh:mm:ss") + "\nY = " + QString::number(pos.y()));
        QColor bgColor(Qt::lightGray);
        bgColor.setAlpha(100);
        text.setBackgroundBrush(QBrush(bgColor));
        return text;
    }

};

QwtScaleDiv ChartPlot::scaleDiv()
{
    QList<double> ticks[QwtScaleDiv::NTickTypes];

    QList<double> &majorTicks = ticks[QwtScaleDiv::MajorTick];
    QList<double> &mediumTicks = ticks[QwtScaleDiv::MediumTick];
    QList<double> &minorTicks = ticks[QwtScaleDiv::MinorTick];

    if (xData.count()<11)
    {
        foreach (double value, xData)
            majorTicks += value;

        if (xData.count()>1)
        {
            for (int i = 0; i < xData.count() - 1; i++)
                for (int j = 1; j < 6; j++)
                    mediumTicks += xData[i] + j * (xData[i+1] - xData[i]) / 5;

            for (int i = 0; i < xData.count() - 1; i++)
                for (int j = 1; j < 11; j++)
                    minorTicks += xData[i] + j * (xData[i+1] - xData[i]) / 10;
        }
    }
    else
    {

//       Quantity-based division

//        QVector<double> tempXData;
//        for (int i=0; i<11; i++)
//        {
//            int value = (i*(xData.count()-1)/10);
//            tempXData.append(xData[value]);
//            majorTicks += tempXData[i];
//        }

//      Value-based division
        QVector<double> tempXData;
        for (int i=0; i<11; i++)
        {
            tempXData.append(xData[0] + i*(xData[xData.count()-1] - xData[0])/10);
            majorTicks += tempXData.last();
        }
        for (int i = 0; i < tempXData.count() - 1; i++)
            for (int j = 1; j < 6; j++)
                mediumTicks += tempXData[i] + j * (tempXData[i+1] - tempXData[i]) / 5;
        for (int i = 0; i < tempXData.count() - 1; i++)
            for (int j = 1; j < 11; j++)
                minorTicks += tempXData[i] + j * (tempXData[i+1] - tempXData[i]) / 10;
    }

    return QwtScaleDiv(xData.first(), xData.last(), ticks);
}

class Zoomer: public QwtPlotZoomer
{
public:
    Zoomer(int xAxis, int yAxis, QwtPlotCanvas *canvas) : QwtPlotZoomer(xAxis, yAxis, canvas)
    {
        setMousePattern(QwtEventPattern::MouseSelect2, Qt::RightButton, Qt::ControlModifier);
        setMousePattern(QwtEventPattern::MouseSelect3, Qt::RightButton);
        setZoomBase();
    }
};

class Grid: public QwtPlotGrid
{
public:
    Grid()
    {
        enableXMin(true);
        setMajPen(QPen(Qt::white, 0, Qt::DotLine));
        setMinPen(QPen(Qt::lightGray, 0 , Qt::DotLine));
    }

    virtual void updateScaleDiv(const QwtScaleDiv &xMap, const QwtScaleDiv &yMap)
    {
        QList<double> ticks[QwtScaleDiv::NTickTypes];

        ticks[QwtScaleDiv::MajorTick] = xMap.ticks(QwtScaleDiv::MajorTick);
        ticks[QwtScaleDiv::MinorTick] = xMap.ticks(QwtScaleDiv::MinorTick);

        QwtPlotGrid::updateScaleDiv(QwtScaleDiv(xMap.lowerBound(), xMap.upperBound(), ticks), yMap);
    }
};

class TimeScaleDraw: public QwtScaleDraw
{
public:
    TimeScaleDraw()
    {
        setTickLength(QwtScaleDiv::MajorTick, 8);
        setTickLength(QwtScaleDiv::MinorTick, 2);
        setTickLength(QwtScaleDiv::MediumTick, 4);
        setLabelRotation(0);
        setLabelAlignment(Qt::AlignHCenter | Qt::AlignVCenter);
        setSpacing(15);
    }

    virtual QwtText label(double value) const
    {
        QDateTime time;
        time = time.fromTime_t(value);
        return time.toString("yyyy.MM.dd.\nhh:mm:ss");
    }
};

class Background: public QwtPlotItem
{
public:
    Background()
    {
        setZ(0.0);
    }

    virtual int rtti() const
    {
        return QwtPlotItem::Rtti_PlotUserItem;
    }

    virtual void draw(QPainter *painter,
                      const QwtScaleMap &,
                      const QwtScaleMap &,
                      const QRectF &rect) const
    {
        QColor color(Qt::gray);
        color = color.darker(150);
        painter->fillRect(rect, color);
    }
};

class ChartCurve: public QwtPlotCurve
{
public:
    ChartCurve(const QString &title) : QwtPlotCurve(title)
    {
        setRenderHint(QwtPlotItem::RenderAntialiased);
    }

    void setColor(const QColor &color)
    {
        QColor c = color;
        c.setAlpha(150);

        setPen(c);
        setBrush(c);
    }
};

ChartPlot::ChartPlot(QStandardItemModel *model, bool isSplineUsed, QWidget *parent) : QwtPlot(parent)
{
    this->model = model;
    splineUsed = isSplineUsed;

    setAutoReplot(false);

    plotLayout()->setAlignCanvasToScales(true);

    signs = new QwtLegend;
    signs->setItemMode(QwtLegend::CheckableItem);
    insertLegend(signs, QwtPlot::RightLegend);

    setAxisTitle(QwtPlot::xBottom, "Report time");
    setAxisScaleDraw(QwtPlot::xBottom, new TimeScaleDraw());

    scaleWidget = axisWidget(QwtPlot::xBottom);
    const int fmh = QFontMetrics(scaleWidget->font()).height();
    scaleWidget->setMinBorderDist(0, fmh / 2);

    setAxisTitle(QwtPlot::yLeft, "Quantity");

    grid = new Grid;
    grid->attach(this);

    bg = new Background();
    bg->attach(this);

    countPlot();

    scaleEngineX = new QwtLinearScaleEngine;
    scaleEngineX->setAttribute(QwtScaleEngine::Floating, true);
    setAxisScaleEngine(QwtPlot::xBottom, scaleEngineX);
    setAxisScaleDiv(QwtPlot::xBottom, scaleDiv());

    scaleEngineY = new QwtLinearScaleEngine;
    scaleEngineY->setAttribute(QwtScaleEngine::IncludeReference, true);
    scaleEngineY->setReference(0);
    setAxisScaleEngine(QwtPlot::yLeft, scaleEngineY);

    picker = new PlotPicker(QwtPlot::xBottom,
                                        QwtPlot::yLeft,
                                        QwtPlotPicker::CrossRubberBand,
                                        QwtPicker::ActiveOnly,
                                        this->canvas());
    replot();
    zoomer = new Zoomer(QwtPlot::xBottom, QwtPlot::yLeft, this->canvas());
    zoomer->setZoomBase(false);
    connect(this, SIGNAL(legendChecked(QwtPlotItem *, bool)),  SLOT(showCurve(QwtPlotItem *, bool)));
}

void ChartPlot::showCurve(QwtPlotItem *item, const bool &on, const bool &replt)
{
    item->setVisible(on);
    QWidget *w = legend()->find(item);
    if (w && w->inherits("QwtLegendItem")) ((QwtLegendItem *)w)->setChecked(on);
    if (replt) replot();
}

void ChartPlot::useSpline(bool on, bool refresh)
{
    if (on)
    {
        for (int i=0; i<curve.count(); i++)
        {
            curveFitter = new QwtSplineCurveFitter;
            curve.at(i)->setCurveFitter(curveFitter);
        }
    }
    else
    {
        for (int i=0; i<curve.count(); i++)
        {
            curveFitter = new QwtWeedingCurveFitter;
            curve.at(i)->setCurveFitter(curveFitter);
        }
    }
    if (refresh) replot();
}

void ChartPlot::countPlot()
{
    // Store current visibility of curves if they exist, otherwise initialize visibility to true
    QList<bool> visible;
    if (curve.isEmpty())
    {
        for (int column = 1; column < model->columnCount(); column++)
            visible.append(true);
    }
    else
    {
        for (int column = 1; column < model->columnCount(); column++)
        {
            visible.append(curve[column - 1]->isVisible());
            curve[column - 1]->detach();
        }
        curve.clear();
    }
    // Read X-axis data from table
    for (int row=0; row<model->rowCount(); row++)
    {
        QDateTime xDateTime = model->item(row, 0)->data(Qt::EditRole).toDateTime();
        xData << xDateTime.toTime_t();
    }
    // Read Y-axis data from table
    for (int column = 1; column < model->columnCount(); column++)
    {
        QVector<double> yData;

        curve.append(new ChartCurve(model->horizontalHeaderItem(column)->text()));
        curve.last()->setStyle(QwtPlotCurve::Lines);
        QVariant decoration = model->item(0, column)->data(Qt::DecorationRole);
        if (decoration.type() == QVariant::Color)
        {
            curve.last()->setColor(decoration.value<QColor>());
        }
        curve.last()->setCurveAttribute(QwtPlotCurve::Fitted, true);
        curve.last()->setZ(curve.last()->z() - 1);
        curve.last()->attach(this);

        for (int row=0; row<model->rowCount(); row++)
        {
            yData << model->item(row, column)->data(Qt::EditRole).toDouble();
        }
        curve.last()->setSamples(xData, yData);
        showCurve(curve.last(), visible[column - 1], false);
    }
    useSpline(splineUsed, false);
}

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I have tried many combinations of calling setZoomBase() and adding Zoomer to plot, no success.

Maybe it would be easier to understand if you could just show me the line where I should put it. I even checked your code, and examples (randomplot uses the same code as me), no success.

Could the solution be inside rescale() of Zoomer class? Please, help, my application is finished, running smoothly, except this one.

**pkj** · 17th May 2011, 17:52

Here is my understanding of zoomer.
Default scales are 1000 for both the axes. So first you need to setZoomBase() after you do setSamples(). However, when you do zoom in, the autoscales are set to off. This is done implicitly. So we also need to setAutoScale(). The place to do that is in the slot for the signal zoomed(QRectF) of zoomer. Some code to explain it..

Qt Code:

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connect(d_zoomer, SIGNAL(zoomed(QRectF), this, SLOT(autoRescale(QRectF)); //d_zoomer is zoomer's pointer

connect(d_zoomer, SIGNAL(zoomed(QRectF), this, SLOT(autoRescale(QRectF)); //d_zoomer is zoomer's pointer

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function implementation...

Qt Code:

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void myPlot::autoRescale(QRectF)
{
    if(d_zoomer->zoomRectIndex()==0) // autorescale only if u are at base... otherwise u defined scales by zoomer right..
      {
          setAxisAutoScale(yLeft);
          setAxisAutoScale(xBottom);
          d_zoomer->setZoomBase(); 
      }
}

void myPlot::autoRescale(QRectF)
{
    if(d_zoomer->zoomRectIndex()==0) // autorescale only if u are at base... otherwise u defined scales by zoomer right..
      {
          setAxisAutoScale(yLeft);
          setAxisAutoScale(xBottom);
          d_zoomer->setZoomBase(); 
      }
}

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HTH

**falconium** · 17th May 2011, 21:56

Thanks, it could be the reason! I also thought that it could rather be about that zoomer drops the original scaling after zooming. I'm going to give it a try, and let you know about the result.