QwtPlotHistogram - QwtPlotHistogram represents a series of samples, where an interval is associated with a value ( $y = f([x1, x2])$ ).

NAME

QwtPlotHistogram − QwtPlotHistogram represents a series of samples, where an interval is associated with a value ( $y = f([x1,x2])$ ).

SYNOPSIS

#include <qwt_plot_histogram.h>

Inherits QwtPlotSeriesItem, and QwtSeriesStore< QwtIntervalSample >.

Public Types

enum HistogramStyle { Outline, Columns, Lines, UserStyle = 100 }

Public Types inherited from QwtPlotItem

enum RttiValues { Rtti_PlotItem = 0, Rtti_PlotGrid, Rtti_PlotScale, Rtti_PlotLegend, Rtti_PlotMarker, Rtti_PlotCurve, Rtti_PlotSpectroCurve, Rtti_PlotIntervalCurve, Rtti_PlotHistogram, Rtti_PlotSpectrogram, Rtti_PlotGraphic, Rtti_PlotTradingCurve, Rtti_PlotBarChart, Rtti_PlotMultiBarChart, Rtti_PlotShape, Rtti_PlotTextLabel, Rtti_PlotZone, Rtti_PlotVectorField, Rtti_PlotUserItem = 1000 }
Runtime type information.
enum ItemAttribute { Legend = 0x01, AutoScale = 0x02, Margins = 0x04 }
Plot Item Attributes.
enum ItemInterest { ScaleInterest = 0x01, LegendInterest = 0x02 }
Plot Item Interests.
enum RenderHint { RenderAntialiased = 0x1 }
Render hints.
typedef QFlags< ItemAttribute > ItemAttributes
typedef QFlags< ItemInterest > ItemInterests
typedef QFlags< RenderHint > RenderHints

Public Member Functions

QwtPlotHistogram (const QString &title=QString())
QwtPlotHistogram (const QwtText &title)
virtual ˜QwtPlotHistogram ()
Destructor.
virtual int rtti () const override
void setPen (const QColor &, qreal width=0.0, Qt::PenStyle=Qt::SolidLine)
void setPen (const QPen &)
const QPen & pen () const
void setBrush (const QBrush &)
const QBrush & brush () const
void setSamples (const QVector< QwtIntervalSample > &)
void setSamples (QwtSeriesData< QwtIntervalSample > *)
void setBaseline (double)
Set the value of the baseline.
double baseline () const
void setStyle (HistogramStyle style)
HistogramStyle style () const
void setSymbol (const QwtColumnSymbol *)
Assign a symbol.
const QwtColumnSymbol * symbol () const
virtual void drawSeries (QPainter *, const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRectF &canvasRect, int from, int to) const override
virtual QRectF boundingRect () const override
virtual QwtGraphic legendIcon (int index, const QSizeF &) const override

Public Member Functions inherited from QwtPlotSeriesItem

QwtPlotSeriesItem (const QString &title=QString())
QwtPlotSeriesItem (const QwtText &title)
virtual ˜QwtPlotSeriesItem ()
Destructor.
void setOrientation (Qt::Orientation)
Qt::Orientation orientation () const
virtual void draw (QPainter *, const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRectF &canvasRect) const override
Draw the complete series.
virtual void updateScaleDiv (const QwtScaleDiv &, const QwtScaleDiv &) override
Update the item to changes of the axes scale division.

Public Member Functions inherited from QwtPlotItem

QwtPlotItem ()
QwtPlotItem (const QString &title)
QwtPlotItem (const QwtText &title)
virtual ˜QwtPlotItem ()
Destroy the QwtPlotItem.
void attach (QwtPlot *plot)
Attach the item to a plot.
void detach ()
This method detaches a QwtPlotItem from any QwtPlot it has been associated with.
QwtPlot * plot () const
Return attached plot.
void setTitle (const QString &title)
void setTitle (const QwtText &title)
const QwtText & title () const
void setItemAttribute (ItemAttribute, bool on=true)
bool testItemAttribute (ItemAttribute) const
void setItemInterest (ItemInterest, bool on=true)
bool testItemInterest (ItemInterest) const
void setRenderHint (RenderHint, bool on=true)
bool testRenderHint (RenderHint) const
void setRenderThreadCount (uint numThreads)
uint renderThreadCount () const
void setLegendIconSize (const QSize &)
QSize legendIconSize () const
double z () const
void setZ (double z)
Set the z value.
void show ()
Show the item.
void hide ()
Hide the item.
virtual void setVisible (bool)
bool isVisible () const
void setAxes (QwtAxisId xAxis, QwtAxisId yAxis)
void setXAxis (QwtAxisId)
QwtAxisId xAxis () const
Return xAxis.
void setYAxis (QwtAxisId)
QwtAxisId yAxis () const
Return yAxis.
virtual void itemChanged ()
virtual void legendChanged ()
virtual void getCanvasMarginHint (const QwtScaleMap &xMap, const QwtScaleMap &yMap, const QRectF &canvasRect, double &left, double &top, double &right, double &bottom) const
Calculate a hint for the canvas margin.
virtual void updateLegend (const QwtPlotItem *, const QList< QwtLegendData > &)
Update the item to changes of the legend info.
QRectF scaleRect (const QwtScaleMap &, const QwtScaleMap &) const
Calculate the bounding scale rectangle of 2 maps.
QRectF paintRect (const QwtScaleMap &, const QwtScaleMap &) const
Calculate the bounding paint rectangle of 2 maps.
virtual QList< QwtLegendData > legendData () const
Return all information, that is needed to represent the item on the legend.

Public Member Functions inherited from QwtAbstractSeriesStore

virtual ˜QwtAbstractSeriesStore ()
Destructor.

Public Member Functions inherited from QwtSeriesStore< QwtIntervalSample >

QwtSeriesStore ()
Constructor The store contains no series.
˜QwtSeriesStore ()
Destructor.
void setData (QwtSeriesData< QwtIntervalSample > *series)
QwtSeriesData< QwtIntervalSample > * data ()
const QwtSeriesData< QwtIntervalSample > * data () const
QwtIntervalSample sample (int index) const
virtual size_t dataSize () const override
virtual QRectF dataRect () const override
virtual void setRectOfInterest (const QRectF &rect) override
QwtSeriesData< QwtIntervalSample > * swapData (QwtSeriesData< QwtIntervalSample > *series)

Protected Member Functions

virtual QwtColumnRect columnRect (const QwtIntervalSample &, const QwtScaleMap &, const QwtScaleMap &) const
virtual void drawColumn (QPainter *, const QwtColumnRect &, const QwtIntervalSample &) const
void drawColumns (QPainter *, const QwtScaleMap &xMap, const QwtScaleMap &yMap, int from, int to) const
void drawOutline (QPainter *, const QwtScaleMap &xMap, const QwtScaleMap &yMap, int from, int to) const
void drawLines (QPainter *, const QwtScaleMap &xMap, const QwtScaleMap &yMap, int from, int to) const

Protected Member Functions inherited from QwtPlotSeriesItem

virtual void dataChanged () override
dataChanged() indicates, that the series has been changed.

Protected Member Functions inherited from QwtPlotItem

QwtGraphic defaultIcon (const QBrush &, const QSizeF &) const
Return a default icon from a brush.

Detailed Description

QwtPlotHistogram represents a series of samples, where an interval is associated with a value ( $y = f([x1,x2])$ ).

The representation depends on the style() and an optional symbol() that is displayed for each interval.

Note

The term "histogram" is used in a different way in the areas of digital image processing and statistics. Wikipedia introduces the terms "image histogram" and "color histogram" to avoid confusions. While "image histograms" can be displayed by a QwtPlotCurve there is no applicable plot item for a "color histogram" yet.

See also

QwtPlotBarChart, QwtPlotMultiBarChart

Definition at line 41 of file qwt_plot_histogram.h.

Member Enumeration Documentation

enum QwtPlotHistogram::HistogramStyle

Histogram styles. The default style is QwtPlotHistogram::Columns.

See also

setStyle(), style(), setSymbol(), symbol(), setBaseline()

Enumerator
Outline

Draw an outline around the area, that is build by all intervals using the pen() and fill it with the brush(). The outline style requires, that the intervals are in increasing order and not overlapping.

Columns

Draw a column for each interval. When a symbol() has been set the symbol is used otherwise the column is displayed as plain rectangle using pen() and brush().

Lines

Draw a simple line using the pen() for each interval.

UserStyle

Styles >= UserStyle are reserved for derived classes that overload drawSeries() with additional application specific ways to display a histogram.

Definition at line 52 of file qwt_plot_histogram.h.

Constructor & Destructor Documentation

QwtPlotHistogram::QwtPlotHistogram (const QString & title = QString())[explicit]

Constructor

Parameters

title Title of the histogram.

Definition at line 74 of file qwt_plot_histogram.cpp.

QwtPlotHistogram::QwtPlotHistogram (const QwtText & title) [explicit]

Constructor

Parameters

title Title of the histogram.

Definition at line 64 of file qwt_plot_histogram.cpp.

QwtPlotHistogram::˜QwtPlotHistogram () [virtual]

Destructor.

Definition at line 81 of file qwt_plot_histogram.cpp.

Member Function Documentation

double QwtPlotHistogram::baseline () const

Returns

Value of the baseline

See also

setBaseline()

Definition at line 253 of file qwt_plot_histogram.cpp.

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

Returns

Bounding rectangle of all samples. For an empty series the rectangle is invalid.

Reimplemented from QwtPlotSeriesItem.

Definition at line 262 of file qwt_plot_histogram.cpp.

const QBrush & QwtPlotHistogram::brush () const

Returns

Brush used in a style() depending way.

See also

setPen(), brush()

Definition at line 189 of file qwt_plot_histogram.cpp.

QwtColumnRect QwtPlotHistogram::columnRect (const QwtIntervalSample &sample, const QwtScaleMap & xMap, const QwtScaleMap & yMap) const[protected], [virtual]

Calculate the area that is covered by a sample

Parameters

sample Sample
xMap Maps x-values into pixel coordinates.
yMap Maps y-values into pixel coordinates.

Returns

Rectangle, that is covered by a sample

Definition at line 602 of file qwt_plot_histogram.cpp.

void QwtPlotHistogram::drawColumn (QPainter * painter, const QwtColumnRect& rect, const QwtIntervalSample & sample) const [protected], [virtual]

Draw a column for a sample in Columns style().

When a symbol() has been set the symbol is used otherwise the column is displayed as plain rectangle using pen() and brush().

Parameters

painter Painter
rect Rectangle where to paint the column in paint device coordinates
sample Sample to be displayed

Note

In applications, where different intervals need to be displayed in a different way ( f.e different colors or even using different symbols) it is recommended to overload drawColumn().

Definition at line 653 of file qwt_plot_histogram.cpp.

void QwtPlotHistogram::drawColumns (QPainter * painter, const QwtScaleMap &xMap, const QwtScaleMap & yMap, int from, int to) const [protected]

Draw a histogram in Columns style()

Parameters

painter Painter
xMap Maps x-values into pixel coordinates.
yMap Maps y-values into pixel coordinates.
from Index of the first sample to be painted
to Index of the last sample to be painted. If to < 0 the histogram will be painted to its last point.

See also

setStyle(), style(), setSymbol(), drawColumn()

Definition at line 461 of file qwt_plot_histogram.cpp.

void QwtPlotHistogram::drawLines (QPainter * painter, const QwtScaleMap &xMap, const QwtScaleMap & yMap, int from, int to) const [protected]

Draw a histogram in Lines style()

Parameters

See also

setStyle(), style(), setPen()

Definition at line 493 of file qwt_plot_histogram.cpp.

void QwtPlotHistogram::drawOutline (QPainter * painter, const QwtScaleMap &xMap, const QwtScaleMap & yMap, int from, int to) const [protected]

Draw a histogram in Outline style()

Parameters

See also

setStyle(), style()

Warning

The outline style requires, that the intervals are in increasing order and not overlapping.

Definition at line 376 of file qwt_plot_histogram.cpp.

void QwtPlotHistogram::drawSeries (QPainter * painter, const QwtScaleMap &xMap, const QwtScaleMap & yMap, const QRectF & canvasRect, int from,int to) const [override], [virtual]

Draw a subset of the histogram samples

Parameters

painter Painter
xMap Maps x-values into pixel coordinates.
yMap Maps y-values into pixel coordinates.
canvasRect Contents rectangle of the canvas
from Index of the first sample to be painted
to Index of the last sample to be painted. If to < 0 the series will be painted to its last sample.

See also

drawOutline(), drawLines(), drawColumns

Implements QwtPlotSeriesItem.

Definition at line 334 of file qwt_plot_histogram.cpp.

QwtGraphic QwtPlotHistogram::legendIcon (int index, const QSizeF & size)const [override], [virtual]

A plain rectangle without pen using the brush()

Parameters

index Index of the legend entry ( ignored as there is only one )
size Icon size

Returns

A graphic displaying the icon

See also

QwtPlotItem::setLegendIconSize(), QwtPlotItem::legendData()

Reimplemented from QwtPlotItem.

Definition at line 688 of file qwt_plot_histogram.cpp.

const QPen & QwtPlotHistogram::pen () const

Returns

Pen used in a style() depending way.

See also

setPen(), brush()

Definition at line 163 of file qwt_plot_histogram.cpp.

int QwtPlotHistogram::rtti () const [override], [virtual]

Returns

QwtPlotItem::Rtti_PlotHistogram

Reimplemented from QwtPlotItem.

Definition at line 290 of file qwt_plot_histogram.cpp.

void QwtPlotHistogram::setBaseline (double value)

Set the value of the baseline. Each column representing an QwtIntervalSample is defined by its interval and the interval between baseline and the value of the sample.

The default value of the baseline is 0.0.

Parameters

value Value of the baseline

See also

baseline()

Definition at line 240 of file qwt_plot_histogram.cpp.

void QwtPlotHistogram::setBrush (const QBrush & brush)

Assign a brush, that is used in a style() depending way.

Parameters

brush New brush

See also

pen(), brush()

Definition at line 174 of file qwt_plot_histogram.cpp.

void QwtPlotHistogram::setPen (const QColor & color, qreal width = 0.0,Qt::PenStyle style = Qt::SolidLine)

Build and assign a pen

In Qt5 the default pen width is 1.0 ( 0.0 in Qt4 ) what makes it non cosmetic ( see QPen::isCosmetic() ). This method has been introduced to hide this incompatibility.

Parameters

color Pen color
width Pen width
style Pen style

See also

pen(), brush()

Definition at line 137 of file qwt_plot_histogram.cpp.

void QwtPlotHistogram::setPen (const QPen & pen)

Assign a pen, that is used in a style() depending way.

Parameters

pen New pen

See also

pen(), brush()

Definition at line 148 of file qwt_plot_histogram.cpp.

void QwtPlotHistogram::setSamples (const QVector< QwtIntervalSample > &samples)

Initialize data with an array of samples.

Parameters

samples Vector of points

Definition at line 299 of file qwt_plot_histogram.cpp.

void QwtPlotHistogram::setSamples (QwtSeriesData< QwtIntervalSample > *data)

Assign a series of samples

setSamples() is just a wrapper for setData() without any additional value - beside that it is easier to find for the developer.

Parameters

data Data

Warning

The item takes ownership of the data object, deleting it when its not used anymore.

Definition at line 315 of file qwt_plot_histogram.cpp.

void QwtPlotHistogram::setStyle (HistogramStyle style)

Set the histogram’s drawing style

Parameters

style Histogram style

See also

HistogramStyle, style()

Definition at line 104 of file qwt_plot_histogram.cpp.

void QwtPlotHistogram::setSymbol (const QwtColumnSymbol * symbol)

Assign a symbol. In Column style an optional symbol can be assigned, that is responsible for displaying the rectangle that is defined by the interval and the distance between baseline() and value. When no symbol has been defined the area is displayed as plain rectangle using pen() and brush().

See also

style(), symbol(), drawColumn(), pen(), brush()

Note

In applications, where different intervals need to be displayed in a different way ( f.e different colors or even using different symbols) it is recommended to overload drawColumn().

Definition at line 208 of file qwt_plot_histogram.cpp.

QwtPlotHistogram::HistogramStyle QwtPlotHistogram::style () const

Returns

Style of the histogram

See also

HistogramStyle, setStyle()

Definition at line 119 of file qwt_plot_histogram.cpp.

const QwtColumnSymbol * QwtPlotHistogram::symbol () const

Returns

Current symbol or NULL, when no symbol has been assigned

See also

setSymbol()

Definition at line 224 of file qwt_plot_histogram.cpp.

Author

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