simple.cpp

QWT5.01用于Qt开发的二维图形库程序

#include <qapplication.h>
#include <qwt_plot.h>
#include <qwt_plot_marker.h>
#include <qwt_plot_curve.h>
#include <qwt_legend.h>
#include <qwt_data.h>
#include <qwt_text.h>
#include <math.h>

//-----------------------------------------------------------------
//              simple.cpp
//
//      A simple example which shows how to use QwtPlot and QwtData
//-----------------------------------------------------------------

class SimpleData: public QwtData
{
    // The x values depend on its index and the y values
    // can be calculated from the corresponding x value. 
    // So we don磘 need to store the values.
    // Such an implementation is slower because every point 
    // has to be recalculated for every replot, but it demonstrates how
    // QwtData can be used.

public:
    SimpleData(double(*y)(double), size_t size):
        d_size(size),
        d_y(y)
    {
    }

    virtual QwtData *copy() const
    {
        return new SimpleData(d_y, d_size);
    }

    virtual size_t size() const
    {
        return d_size;
    }

    virtual double x(size_t i) const
    {
        return 0.1 * i;
    }

    virtual double y(size_t i) const
    {
        return d_y(x(i));
    }
private:
    size_t d_size;
    double(*d_y)(double);
};

class Plot : public QwtPlot
{
public:
    Plot();
};


Plot::Plot()
{
    setTitle("A Simple QwtPlot Demonstration");
    insertLegend(new QwtLegend(), QwtPlot::RightLegend);

    // Set axis titles
    setAxisTitle(xBottom, "x -->");
    setAxisTitle(yLeft, "y -->");
    
    // Insert new curves
    QwtPlotCurve *cSin = new QwtPlotCurve("y = sin(x)");
#if QT_VERSION >= 0x040000
    cSin->setRenderHint(QwtPlotItem::RenderAntialiased);
#endif
    cSin->setPen(QPen(Qt::red));
    cSin->attach(this);

    QwtPlotCurve *cCos = new QwtPlotCurve("y = cos(x)");
#if QT_VERSION >= 0x040000
    cCos->setRenderHint(QwtPlotItem::RenderAntialiased);
#endif
    cCos->setPen(QPen(Qt::blue));
    cCos->attach(this);

    // Create sin and cos data
    const int nPoints = 100;
    cSin->setData(SimpleData(::sin, nPoints));
    cCos->setData(SimpleData(::cos, nPoints));

    // Insert markers
    
    //  ...a horizontal line at y = 0...
    QwtPlotMarker *mY = new QwtPlotMarker();
    mY->setLabel(QString::fromLatin1("y = 0"));
    mY->setLabelAlignment(Qt::AlignRight|Qt::AlignTop);
    mY->setLineStyle(QwtPlotMarker::HLine);
    mY->setYValue(0.0);
    mY->attach(this);

    //  ...a vertical line at x = 2 * pi
    QwtPlotMarker *mX = new QwtPlotMarker();
    mX->setLabel(QString::fromLatin1("x = 2 pi"));
    mX->setLabelAlignment(Qt::AlignRight|Qt::AlignTop);
    mX->setLineStyle(QwtPlotMarker::VLine);
    mX->setXValue(6.284);
    mX->attach(this);
}

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

    Plot plot;
#if QT_VERSION < 0x040000
    a.setMainWidget(&plot);
#endif
    plot.resize(600,400);
    plot.show();
    return a.exec(); 
}