Custom symbol for QwtPlotMarker

[ChrisW67]

... and what is wrong with calling a virtual function? Nothing, and it has nothing to do with the error message you are getting either I guess.

How about you actually try to participate in solving your problem in future. Just saying "It doesn't work", or asking over and over and over for someone to give you a canned solution you can copy without thought, is often unproductive and unlikely to win you friends. Tells us what errors you are seeing, what you have tried to fix it etc. Ask a smart question.

Just to see the end of this, a complete example with a custom pixmap as the symbol for both a marker and the data points:

#include <QApplication>                                                                                              
#include <QPainter>                                                                                                  
 
#include <qwt_plot_curve.h>                                                                                          
#include <qwt_plot.h>                                                                                                
#include <qwt_plot_marker.h>                                                                                         
#include <qwt_symbol.h>                                                                                              
 
class Symbol:public QwtSymbol                                                                                        
{                                                                                                                    
public:                                                                                                              
    Symbol(const QPixmap &pixmap);                                                                                   
    QSize boundingSize() const;                                                                                      
    void drawSymbols( QPainter *, const QPointF *, int numPoints ) const;                                            
private:                                                                                                             
    QPixmap m_pixmap;                                                                                                
};                                                                                                                   
 
Symbol::Symbol(const QPixmap &pixmap):                                                                               
    QwtSymbol(QwtSymbol::UserStyle),
    m_pixmap(pixmap)
{
}
 
QSize Symbol::boundingSize() const
{
    return m_pixmap.size();
}
 
 
void Symbol::drawSymbols(QPainter *painter, const QPointF *points, int numPoints) const
{
    painter->save();
    for(int i = 0; i < numPoints; ++i) 
        painter->drawPixmap(points[i], m_pixmap);
    painter->restore();
}
 
int main (int argc, char **argv)
{
    QApplication a(argc, argv);
 
    const int Size = 30;
    double xval[Size];
    double yval[Size];
    for(int i = 0; i < Size; ++i) {   
        xval[i] = double(i) * 10.0 / double(Size - 1);
        yval[i] = qSin(xval[i]) * qCos(2.0 * xval[i]);
    }
 
    QwtPlot myPlot;
    QwtPlotCurve curve("Curve");
    curve.setRawSamples(xval, yval, Size);
    QPixmap p1("p1.png"); 
    curve.setSymbol(new Symbol(p1));
    curve.attach(&myPlot);
 
    QwtPlotMarker mrk;
    mrk.setLinePen(QPen(Qt::black, 0, Qt::DashDotLine));
    mrk.setValue(0.5, 0.5);
    mrk.setLineStyle(QwtPlotMarker::HLine);
    QPixmap p2("p2.png"); 
    mrk.setSymbol(new Symbol(p2));    
    mrk.attach(&myPlot);
 
    myPlot.resize(640,480);
    myPlot.show();
 
    return a.exec();
}

#include <QApplication>                                                                                              
#include <QPainter>                                                                                                  
                                                                                                                     
#include <qwt_plot_curve.h>                                                                                          
#include <qwt_plot.h>                                                                                                
#include <qwt_plot_marker.h>                                                                                         
#include <qwt_symbol.h>                                                                                              
                                                                                                                     
class Symbol:public QwtSymbol                                                                                        
{                                                                                                                    
public:                                                                                                              
    Symbol(const QPixmap &pixmap);                                                                                   
    QSize boundingSize() const;                                                                                      
    void drawSymbols( QPainter *, const QPointF *, int numPoints ) const;                                            
private:                                                                                                             
    QPixmap m_pixmap;                                                                                                
};                                                                                                                   
                                                                                                                     
Symbol::Symbol(const QPixmap &pixmap):                                                                               
    QwtSymbol(QwtSymbol::UserStyle),
    m_pixmap(pixmap)
{
}

QSize Symbol::boundingSize() const
{
    return m_pixmap.size();
}


void Symbol::drawSymbols(QPainter *painter, const QPointF *points, int numPoints) const
{
    painter->save();
    for(int i = 0; i < numPoints; ++i) 
        painter->drawPixmap(points[i], m_pixmap);
    painter->restore();
}

int main (int argc, char **argv)
{
    QApplication a(argc, argv);

    const int Size = 30;
    double xval[Size];
    double yval[Size];
    for(int i = 0; i < Size; ++i) {   
        xval[i] = double(i) * 10.0 / double(Size - 1);
        yval[i] = qSin(xval[i]) * qCos(2.0 * xval[i]);
    }

    QwtPlot myPlot;
    QwtPlotCurve curve("Curve");
    curve.setRawSamples(xval, yval, Size);
    QPixmap p1("p1.png"); 
    curve.setSymbol(new Symbol(p1));
    curve.attach(&myPlot);

    QwtPlotMarker mrk;
    mrk.setLinePen(QPen(Qt::black, 0, Qt::DashDotLine));
    mrk.setValue(0.5, 0.5);
    mrk.setLineStyle(QwtPlotMarker::HLine);
    QPixmap p2("p2.png"); 
    mrk.setSymbol(new Symbol(p2));    
    mrk.attach(&myPlot);

    myPlot.resize(640,480);
    myPlot.show();

    return a.exec();
}

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Built and tested Qwt 6.0.1 on Linux. Make your own p1.png and p2.png markers.

[sonulohani]

Thank you ChrisW67, you're awesome.

---

Added after 1 34 minutes:

Sir,
I want to ask one last thing i.e.; whenever i am trying to write class code i.e.; symbol, in header file then it is giving error as first defined here pointing to constructor. Why is this happening????

[sonulohani]

I understood what is the problem. A very very thanks to you. Its working now. And sorry for querying again and again. I sometimes become insane. But atlast by your help, i figured out what was my mistake. May God bless you.