Abstract interface for iterating over samples. More...
#include <qwt_series_data.h>
Public Member Functions | |
| QwtSeriesData () | |
| Constructor. | |
| virtual | ~QwtSeriesData () |
| Destructor. | |
| virtual size_t | size () const =0 |
| virtual T | sample (size_t i) const =0 |
| Return a sample. | |
| virtual QRectF | boundingRect () const =0 |
| Calculate the bounding rect of all samples. | |
| virtual void | setRectOfInterest (const QRectF &rect) |
| Set a the "rect of interest". | |
Protected Attributes | |
| QRectF | cachedBoundingRect |
| Can be used to cache a calculated bounding rectangle. | |
Detailed Description
class QwtSeriesData< T >
Abstract interface for iterating over samples.
Qwt offers several implementations of the QwtSeriesData API, but in situations, where data of an application specific format needs to be displayed, without having to copy it, it is recommended to implement an individual data access.
A subclass of QwtSeriesData<QPointF> must implement:
- size()
Should return number of data points. - sample()
Should return values x and y values of the sample at specific position as QPointF object. - boundingRect()
Should return the bounding rectangle of the data series. It is used for autoscaling and might help certain algorithms for displaying the data. You can use qwtBoundingRect() for an implementation but often it is possible to implement a more efficient algorithm depending on the characteristics of the series. The member cachedBoundingRect is intended for caching the calculated rectangle.
Member Function Documentation
◆ boundingRect()
|
pure virtual |
Calculate the bounding rect of all samples.
The bounding rect is necessary for autoscaling and can be used for a couple of painting optimizations.
qwtBoundingRect(...) offers slow implementations iterating over the samples. For large sets it is recommended to implement something faster f.e. by caching the bounding rectangle.
- Returns
- Bounding rectangle
Implemented in QwtSyntheticPointData, QwtPointSeriesData, QwtPoint3DSeriesData, QwtIntervalSeriesData, QwtSetSeriesData, QwtVectorFieldData, and QwtTradingChartData.
◆ sample()
|
pure virtual |
Return a sample.
- Parameters
-
i Index
- Returns
- Sample at position i
Implemented in QwtPointArrayData< T >, QwtCPointerData< T >, QwtValuePointData< T >, QwtCPointerValueData< T >, QwtSyntheticPointData, QwtArraySeriesData< T >, QwtArraySeriesData< QPointF >, QwtArraySeriesData< QwtIntervalSample >, QwtArraySeriesData< QwtOHLCSample >, QwtArraySeriesData< QwtPoint3D >, QwtArraySeriesData< QwtSetSample >, and QwtArraySeriesData< QwtVectorFieldSample >.
◆ setRectOfInterest()
|
virtual |
Set a the "rect of interest".
QwtPlotSeriesItem defines the current area of the plot canvas as "rectangle of interest" ( QwtPlotSeriesItem::updateScaleDiv() ). It can be used to implement different levels of details.
The default implementation does nothing.
- Parameters
-
rect Rectangle of interest
Reimplemented in QwtSyntheticPointData.
◆ size()
|
pure virtual |
- Returns
- Number of samples
Implemented in QwtPointArrayData< T >, QwtCPointerData< T >, QwtValuePointData< T >, QwtCPointerValueData< T >, QwtSyntheticPointData, QwtArraySeriesData< T >, QwtArraySeriesData< QPointF >, QwtArraySeriesData< QwtIntervalSample >, QwtArraySeriesData< QwtOHLCSample >, QwtArraySeriesData< QwtPoint3D >, QwtArraySeriesData< QwtSetSample >, and QwtArraySeriesData< QwtVectorFieldSample >.
The documentation for this class was generated from the following files:
- /home/runner/work/QWT/QWT/src/qwt_plot_barchart.h
- /home/runner/work/QWT/QWT/src/qwt_series_data.h
