QwtSyntheticPointData - Synthetic point data.

NAME

QwtSyntheticPointData − Synthetic point data.

SYNOPSIS

#include <qwt_point_data.h>

Inherits QwtSeriesData< QPointF >.

Public Member Functions

QwtSyntheticPointData (size_t size, const QwtInterval &=QwtInterval())
void setSize (size_t size)
virtual size_t size () const override
void setInterval (const QwtInterval &)
QwtInterval interval () const
virtual QRectF boundingRect () const override
Calculate the bounding rectangle.
virtual QPointF sample (size_t index) const override
virtual double y (double x) const =0
virtual double x (uint index) const
virtual void setRectOfInterest (const QRectF &) override
QRectF rectOfInterest () const

Public Member Functions inherited from QwtSeriesData< QPointF >

QwtSeriesData ()
Constructor.
virtual ˜QwtSeriesData ()
Destructor.
QPointF firstSample () const
QPointF lastSample () const

Additional Inherited Members

Protected Attributes inherited from QwtSeriesData< QPointF >

QRectF cachedBoundingRect
Can be used to cache a calculated bounding rectangle.

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 "rectangle 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( QwtAxis::XBottom, 0.0, 10.0 );
plot.setAxisScale( QwtAxis::YLeft, −1.0, 1.0 );

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

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

Definition at line 157 of file qwt_point_data.h.

Constructor & Destructor Documentation

QwtSyntheticPointData::QwtSyntheticPointData (size_t size, constQwtInterval & interval = QwtInterval())

Constructor

Parameters

size Number of points
interval Bounding interval for the points

See also

setInterval(), setSize()

Definition at line 20 of file qwt_point_data.cpp.

Member Function Documentation

QRectF QwtSyntheticPointData::boundingRect () const [override], [virtual]

Calculate the bounding rectangle. 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

Reimplemented from QwtSeriesData< QPointF >.

Definition at line 105 of file qwt_point_data.cpp.

QwtInterval QwtSyntheticPointData::interval () const

Returns

Bounding interval

See also

setInterval(), size()

Definition at line 62 of file qwt_point_data.cpp.

QRectF QwtSyntheticPointData::rectOfInterest () const

Returns

"rectangle of interest"

See also

setRectOfInterest()

Definition at line 89 of file qwt_point_data.cpp.

QPointF QwtSyntheticPointData::sample (size_t index) const [override],[virtual]

Calculate the point from an index

Parameters

index Index

Returns

QPointF(x(index), y(x(index)));

Warning

For invalid indices ( index < 0 || index >= size() ) (0, 0) is returned.

Implements QwtSeriesData< QPointF >.

Definition at line 125 of file qwt_point_data.cpp.

void QwtSyntheticPointData::setInterval (const QwtInterval & interval)

Set the bounding interval

Parameters

interval Interval

See also

interval(), setSize()

Definition at line 53 of file qwt_point_data.cpp.

void QwtSyntheticPointData::setRectOfInterest (const QRectF & rect)[override], [virtual]

Set a the "rectangle 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 >.

Definition at line 78 of file qwt_point_data.cpp.

void QwtSyntheticPointData::setSize (size_t size)

Change the number of points

Parameters

size Number of points

See also

size(), setInterval()

Definition at line 33 of file qwt_point_data.cpp.

size_t QwtSyntheticPointData::size () const [override], [virtual]

Returns

Number of points

See also

setSize(), interval()

Implements QwtSeriesData< QPointF >.

Definition at line 42 of file qwt_point_data.cpp.

double QwtSyntheticPointData::x (uint index) const [virtual]

Calculate a x-value from an index

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

Parameters

index Index of the requested point

Returns

Calculated x coordinate

See also

interval(), rectOfInterest(), y()

Definition at line 148 of file qwt_point_data.cpp.

virtual double QwtSyntheticPointData::y (double x) const [pure virtual]

Calculate a y value for a x value

Parameters

x x value

Returns

Corresponding y value

Author

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Updated 2026-06-01 - jenkler.se | uex.se