Qwt User's Guide  6.0.2
Public Member Functions
QwtSyntheticPointData Class Reference

#include <qwt_series_data.h>

Inheritance diagram for QwtSyntheticPointData:
Inheritance graph
[legend]

List of all members.

Public Member Functions

 QwtSyntheticPointData (size_t size, const QwtInterval &=QwtInterval())
virtual QRectF boundingRect () const
QwtInterval interval () const
QRectF rectOfInterest () const
virtual QPointF sample (size_t i) const
void setInterval (const QwtInterval &)
virtual void setRectOfInterest (const QRectF &)
void setSize (size_t size)
size_t size () const
virtual double x (uint index) const
virtual double y (double x) const =0
- Public Member Functions inherited from QwtSeriesData< QPointF >
 QwtSeriesData ()
virtual ~QwtSeriesData ()

Additional Inherited Members

- Protected Attributes inherited from QwtSeriesData< QPointF >
QRectF d_boundingRect

Detailed Description

Synthetic point data.

QwtSyntheticPointData provides a fixed number of points for an interval. The points are calculated in equidistant steps in x-direction.

If the interval is invalid, the points are calculated for the "rect of interest", what normally is the displayed area on the plot canvas. In this mode you get different levels of detail, when zooming in/out.

Example

The following example shows how to implement a sinus curve.

#include <cmath>
#include <qwt_series_data.h>
#include <qwt_plot_curve.h>
#include <qwt_plot.h>
#include <qapplication.h>

class SinusData: public QwtSyntheticPointData
{
public:
    SinusData():
        QwtSyntheticPointData(100)
    {
    }
    virtual double y(double x) const
    {
        return qSin(x);
    }
};

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

    QwtPlot plot;
    plot.setAxisScale(QwtPlot::xBottom, 0.0, 10.0);
    plot.setAxisScale(QwtPlot::yLeft, -1.0, 1.0);

    QwtPlotCurve *curve = new QwtPlotCurve("y = sin(x)");
    curve->setData(SinusData());
    curve->attach(&plot);

    plot.show();
    return a.exec();
}

Constructor & Destructor Documentation

QwtSyntheticPointData::QwtSyntheticPointData ( size_t  size,
const QwtInterval interval = QwtInterval() 
)

Constructor

Parameters:
sizeNumber of points
intervalBounding interval for the points
See also:
setInterval(), setSize()

Member Function Documentation

QRectF QwtSyntheticPointData::boundingRect ( ) const
virtual

Calculate the bounding rect.

This implementation iterates over all points, what could often be implemented much faster using the characteristics of the series. When there are many points it is recommended to overload and reimplement this method using the characteristics of the series ( if possible ).

Returns:
Bounding rectangle

Implements QwtSeriesData< QPointF >.

QwtInterval QwtSyntheticPointData::interval ( ) const
Returns:
Bounding interval
See also:
setInterval(), size()
QRectF QwtSyntheticPointData::rectOfInterest ( ) const
Returns:
"rect of interest"
See also:
setRectOfInterest()
QPointF QwtSyntheticPointData::sample ( size_t  index) const
virtual

Calculate the point from an index

Parameters:
indexIndex
Returns:
QPointF(x(index), y(x(index)));
Warning:
For invalid indices ( index < 0 || index >= size() ) (0, 0) is returned.

Implements QwtSeriesData< QPointF >.

void QwtSyntheticPointData::setInterval ( const QwtInterval interval)

Set the bounding interval

Parameters:
intervalInterval
See also:
interval(), setSize()
void QwtSyntheticPointData::setRectOfInterest ( const QRectF &  rect)
virtual

Set a the "rect of interest"

QwtPlotSeriesItem defines the current area of the plot canvas as "rect of interest" ( QwtPlotSeriesItem::updateScaleDiv() ).

If interval().isValid() == false the x values are calculated in the interval rect.left() -> rect.right().

See also:
rectOfInterest()

Reimplemented from QwtSeriesData< QPointF >.

void QwtSyntheticPointData::setSize ( size_t  size)

Change the number of points

Parameters:
sizeNumber of points
See also:
size(), setInterval()
size_t QwtSyntheticPointData::size ( ) const
virtual
Returns:
Number of points
See also:
setSize(), interval()

Implements QwtSeriesData< QPointF >.

double QwtSyntheticPointData::x ( uint  index) const
virtual

Calculate a x-value from an index

x values are calculated by deviding an interval into equidistant steps. If !interval().isValid() the interval is calculated from the "rect of interest".

See also:
interval(), rectOfInterest(), y()
virtual double QwtSyntheticPointData::y ( double  x) const
pure virtual

Calculate a y value for a x value

Parameters:
xx value
Returns:
Corresponding y value