Qwt User's Guide  6.1.0
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QwtSyntheticPointData Class Referenceabstract

Synthetic point data. More...

#include <qwt_point_data.h>

Inheritance diagram for QwtSyntheticPointData:
Inheritance graph
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Public Member Functions

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

Additional Inherited Members

- Protected Attributes inherited from QwtSeriesData< QPointF >
QRectF d_boundingRect
 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():
{
}
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( new 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 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

Implements QwtSeriesData< QPointF >.

QwtInterval QwtSyntheticPointData::interval ( ) const
Returns
Bounding interval
See Also
setInterval(), size()
QRectF QwtSyntheticPointData::rectOfInterest ( ) const
Returns
"rectangle 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 "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 >.

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

Parameters
indexIndex of the requested point
Returns
Calculated x coordinate
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