Problems with QwtZoomer

[Quereinsteiger]

Hi,
I'm new to Qt/Qwt and I have a problem with the zoomer.
Within my program I use geographical coordinates to visualize some 'z' values and therefore I use QwtPlot, especially depending on scales sometimes zooming is necessary.

Here I use an adapted Zoomer class from the bode example:

class MyZoomer: public QwtPlotZoomer
{
public:
    MyZoomer(QwtPlotCanvas *canvas):
        QwtPlotZoomer(canvas)
    {
        setTrackerMode(AlwaysOn);
 
    }
 
    virtual QwtText trackerText(const QwtDoublePoint &pos) const
    {
        QColor bg(Qt::white);
#if QT_VERSION >= 0x040300
        bg.setAlpha(200);
#endif
 
        QwtText text = QwtPlotZoomer::trackerText(pos);
        text.setBackgroundBrush( QBrush( bg ));
        return text;
    }
};

class MyZoomer: public QwtPlotZoomer
{
public:
    MyZoomer(QwtPlotCanvas *canvas):
        QwtPlotZoomer(canvas)
    {
        setTrackerMode(AlwaysOn);

    }

    virtual QwtText trackerText(const QwtDoublePoint &pos) const
    {
        QColor bg(Qt::white);
#if QT_VERSION >= 0x040300
        bg.setAlpha(200);
#endif

        QwtText text = QwtPlotZoomer::trackerText(pos);
        text.setBackgroundBrush( QBrush( bg ));
        return text;
    }
};

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Zoom in and out works perfectly on the first loaded file.
My problem appears if I load a second file. The initial plot shows the correct "new" coordinate space, but if I try to zoom in it collapse and ends up in a region far off and the Picker show (0.000,0.000). I tried to find some postings with a similar problem and I found:
first
second

I think I've the same problem like kota, but the solutions to set a new zoomBase and/or to re-enable autoscaling doesn't work or I use it wrong.

This is my complete code fragment:

ui->PlotInitial->detachItems();
 
    //** [Setup grid scheme]!
    ui->PlotInitial->setCanvasBackground(QColor(Qt::white));
    QwtPlotGrid *grid = new QwtPlotGrid;
    grid->enableXMin(true);
    grid->enableYMin(true);
    grid->setMajPen(QPen(Qt::black, 0, Qt::DotLine));
    grid->setMinPen(QPen(Qt::gray, 0 , Qt::DotLine));
    grid->attach(ui->PlotInitial);
    //** [Setup grid scheme]!
 
 
    QString appPath = QApplication::applicationDirPath();
    QString ColorMapFile = appPath + "/crp/topo.crp";
    vector< vector<double> > ColorMatrix = make_2DimVector <double>(256, 4);
    LoadFileIntoMatrix(ColorMapFile, ColorMatrix, 4, 256);
 
    QwtArray< double > xVal, yVal;
 
    double xmax = 0, ymax = 0, zmax = 0;
    double xmin = 10000000000,  ymin = 10000000000, zmin = 10000000000;
 
    for (int i = 0; i < Rows;i ++) {
       if (BigMatrix[i][0] < xmin)  xmin  = BigMatrix[i][0];
       if (BigMatrix[i][0] > xmax) xmax = BigMatrix[i][0];
       if (BigMatrix[i][1] < ymin)  ymin  = BigMatrix[i][1];
       if (BigMatrix[i][1] > ymax) ymax = BigMatrix[i][1];
 
       if (BigMatrix[i][2] > zmax) zmax = BigMatrix[i][2];
       if (BigMatrix[i][2] < zmin)  zmin  = BigMatrix[i][2];
    }
 
     double zKorrektur = 0;
     if (zmin < 0) {
         zmax = zmax + abs(zmin);
         zKorrektur = abs(zmin);
     }
 
     for (int i = 0; i < Rows;i ++) {
       xVal.push_back(BigMatrix[i][0]);
       yVal.push_back(BigMatrix[i][1]);
 
       double zVal = BigMatrix[i][2] + zKorrektur;
 
       int ColorIndex = (zVal * 255) / zmax;
       // Insert new curves
       QwtSymbol symb;
       symb.setStyle(QwtSymbol::Ellipse);
 
       QColor Color2Set = QColor::fromRgb(ColorMatrix[ColorIndex][1],ColorMatrix[ColorIndex][2],ColorMatrix[ColorIndex][3]);
       symb.setBrush(Color2Set);
       symb.setPen(Color2Set);
       symb.setSize(5);
 
      QwtPlotCurve *cScatter = new QwtPlotCurve();
      cScatter->setStyle(QwtPlotCurve::NoCurve);
      cScatter->setSymbol(symb);
      cScatter->setData(xVal,yVal);
      cScatter->attach(ui->PlotInitial);
      xVal.clear();
      yVal.clear();
    }
 
    //ui->PlotInitial->setAxisScale(QwtPlot::yLeft, ymin, ymax);
    //ui->PlotInitial->setAxisScale(QwtPlot::xBottom, xmin, xmax);
    //ui->PlotInitial->replot();
 
    ui->PlotInitial->setAxisAutoScale(QwtPlot::yLeft);
    ui->PlotInitial->setAxisAutoScale(QwtPlot::xBottom);
 
 
    //** [Zoomfunctions!]
    zoomerI = new MyZoomer(ui->PlotInitial->canvas());
    zoomerI->setZoomBase();
 
    #if QT_VERSION < 0x040000
    zoomerI->setMousePattern(QwtEventPattern::MouseSelect2,
        Qt::RightButton, Qt::ControlButton);
    #else
    zoomerI->setMousePattern(QwtEventPattern::MouseSelect2,
        Qt::RightButton, Qt::ControlModifier);
    #endif
    zoomerI->setMousePattern(QwtEventPattern::MouseSelect3,
        Qt::RightButton);
    //** [Zoomfunctions!]

ui->PlotInitial->detachItems();

    //** [Setup grid scheme]!
    ui->PlotInitial->setCanvasBackground(QColor(Qt::white));
    QwtPlotGrid *grid = new QwtPlotGrid;
    grid->enableXMin(true);
    grid->enableYMin(true);
    grid->setMajPen(QPen(Qt::black, 0, Qt::DotLine));
    grid->setMinPen(QPen(Qt::gray, 0 , Qt::DotLine));
    grid->attach(ui->PlotInitial);
    //** [Setup grid scheme]!


    QString appPath = QApplication::applicationDirPath();
    QString ColorMapFile = appPath + "/crp/topo.crp";
    vector< vector<double> > ColorMatrix = make_2DimVector <double>(256, 4);
    LoadFileIntoMatrix(ColorMapFile, ColorMatrix, 4, 256);

    QwtArray< double > xVal, yVal;

    double xmax = 0, ymax = 0, zmax = 0;
    double xmin = 10000000000,  ymin = 10000000000, zmin = 10000000000;

    for (int i = 0; i < Rows;i ++) {
       if (BigMatrix[i][0] < xmin)  xmin  = BigMatrix[i][0];
       if (BigMatrix[i][0] > xmax) xmax = BigMatrix[i][0];
       if (BigMatrix[i][1] < ymin)  ymin  = BigMatrix[i][1];
       if (BigMatrix[i][1] > ymax) ymax = BigMatrix[i][1];

       if (BigMatrix[i][2] > zmax) zmax = BigMatrix[i][2];
       if (BigMatrix[i][2] < zmin)  zmin  = BigMatrix[i][2];
    }
    
     double zKorrektur = 0;
     if (zmin < 0) {
         zmax = zmax + abs(zmin);
         zKorrektur = abs(zmin);
     }

     for (int i = 0; i < Rows;i ++) {
       xVal.push_back(BigMatrix[i][0]);
       yVal.push_back(BigMatrix[i][1]);

       double zVal = BigMatrix[i][2] + zKorrektur;

       int ColorIndex = (zVal * 255) / zmax;
       // Insert new curves
       QwtSymbol symb;
       symb.setStyle(QwtSymbol::Ellipse);

       QColor Color2Set = QColor::fromRgb(ColorMatrix[ColorIndex][1],ColorMatrix[ColorIndex][2],ColorMatrix[ColorIndex][3]);
       symb.setBrush(Color2Set);
       symb.setPen(Color2Set);
       symb.setSize(5);

      QwtPlotCurve *cScatter = new QwtPlotCurve();
      cScatter->setStyle(QwtPlotCurve::NoCurve);
      cScatter->setSymbol(symb);
      cScatter->setData(xVal,yVal);
      cScatter->attach(ui->PlotInitial);
      xVal.clear();
      yVal.clear();
    }

    //ui->PlotInitial->setAxisScale(QwtPlot::yLeft, ymin, ymax);
    //ui->PlotInitial->setAxisScale(QwtPlot::xBottom, xmin, xmax);
    //ui->PlotInitial->replot();

    ui->PlotInitial->setAxisAutoScale(QwtPlot::yLeft);
    ui->PlotInitial->setAxisAutoScale(QwtPlot::xBottom);


    //** [Zoomfunctions!]
    zoomerI = new MyZoomer(ui->PlotInitial->canvas());
    zoomerI->setZoomBase();

    #if QT_VERSION < 0x040000
    zoomerI->setMousePattern(QwtEventPattern::MouseSelect2,
        Qt::RightButton, Qt::ControlButton);
    #else
    zoomerI->setMousePattern(QwtEventPattern::MouseSelect2,
        Qt::RightButton, Qt::ControlModifier);
    #endif
    zoomerI->setMousePattern(QwtEventPattern::MouseSelect3,
        Qt::RightButton);
    //** [Zoomfunctions!]

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I hope its not to confusing, but any help will be appreciated.

Thank you and kind regards!

[Uwe]

What happened to your previous zoomer object ?

If you already have one you don't have to create a second one - reset the zoom base of the existing one instead.

Uwe

[Quereinsteiger]

Thats it, sometimes thinks are that easy.