QwtSyntheticPointData(3)

📦

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🎀 `QwtSyntheticPointData(3)` — Library Functions Manual 🎀

okay bestie, welcome to the Library Functions Manual page for QwtSyntheticPointData(3) 💅 this is synthetic point data and it’s lowkey iconic.

💖 NAME 💖

QwtSyntheticPointData — synthetic point data, periodt ✨

🌈 SYNOPSIS 🌈

#include <qwt_point_data.h>

Inherits QwtSeriesData< QPointF >.

🫶 Public Member Functions

QwtSyntheticPointData (size_t size, const QwtInterval &=QwtInterval()) — constructor vibes.
void setSize (size_t size) — change the number of points.
virtual size_t size () const override — get the number of points.
void setInterval (const QwtInterval &) — set the bounding interval.
QwtInterval interval () const — get the bounding interval.
virtual QRectF boundingRect () const override — calculate the bounding rectangle.
virtual QPointF sample (size_t index) const override — calculate the point from an index.
virtual double y (double x) const =0 — calculate a y value for an x value.
virtual double x (uint index) const — calculate an x-value from an index.
virtual void setRectOfInterest (const QRectF &) override — set the “rectangle of interest”.
QRectF rectOfInterest () const — get the “rectangle of interest”.

🦋 Public Member Functions inherited from `QwtSeriesData< QPointF >`

QwtSeriesData () — Constructor.
virtual ~QwtSeriesData () — Destructor.
QPointF firstSample () const — first sample, bestie.
QPointF lastSample () const — last sample, bestie.

🌸 Additional Inherited Members

Protected Attributes inherited from `QwtSeriesData< QPointF >`

QRectF cachedBoundingRect — can be used to cache a calculated bounding rectangle. slay for performance 💅

✨ Detailed Description ✨

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 — literally the main character energy of plot data 🫶

🧚 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, const QwtInterval & interval = QwtInterval())`

Constructor. okay so here’s what you pass in:

size — Number of points.
interval — Bounding interval for the points.

💜 Member Function Documentation 💜

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

Calculate the bounding rectangle. This implementation literally 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) — no cap, that’s the move.

Returns: Bounding rectangle.

Reimplemented from QwtSeriesData< QPointF >.

Definition at line 105 of file qwt_point_data.cpp.

`QwtInterval QwtSyntheticPointData::interval () const`

Returns: Bounding interval.

`QRectF QwtSyntheticPointData::rectOfInterest () const`

Returns: “rectangle of interest”.

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

Calculate the point from an index.

index — Index.

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

⚠️ Warning: For invalid indices (index < 0 || index >= size()) (0, 0) is returned. so bestie, vibe-check your index first 😭

Implements QwtSeriesData< QPointF >.

Definition at line 125 of file qwt_point_data.cpp.

`void QwtSyntheticPointData::setInterval (const QwtInterval & interval)`

Set the bounding interval.

interval — Interval.

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

Set the “rectangle of interest” — yes, the original doc says “Set a the”, and we keep the iconique typo energy 😭💅

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().

`void QwtSyntheticPointData::setSize (size_t size)`

Change the number of points.

size — Number of points.

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

Returns: Number of points.

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

Calculate an 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”.

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 an x value.

x — x value.

Returns: Corresponding y value.

👑 AUTHOR 👑

Generated automatically by Doxygen for Qwt User's Guide from the source code.

mwah 💖 source/version sign-off: this page is from the Qwt User's Guide, page QwtSyntheticPointData(3), and the original footer has no date listed, so I’m not inventing one 🎀 bye bestie, go make those synthetic points look iconic ✨

📦 where this page comes from

alpine 3.24: qwt-doc 6.3.0-r0 · custom
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash-1017 on 2026-11-04: a language model's rewrite of the original, under its terms

QwtSyntheticPointData(3)

🎀 QwtSyntheticPointData(3) — Library Functions Manual 🎀

💖 NAME 💖

🌈 SYNOPSIS 🌈

🫶 Public Member Functions

🦋 Public Member Functions inherited from QwtSeriesData< QPointF >

🌸 Additional Inherited Members

Protected Attributes inherited from QwtSeriesData< QPointF >

✨ Detailed Description ✨

🧚 Example

🛠️ Constructor & Destructor Documentation 🛠️

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

💜 Member Function Documentation 💜

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

QwtInterval QwtSyntheticPointData::interval () const

QRectF QwtSyntheticPointData::rectOfInterest () const

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

void QwtSyntheticPointData::setInterval (const QwtInterval & interval)

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

void QwtSyntheticPointData::setSize (size_t size)

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

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

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