---
name: "QwtPlotBarChart"
section: "3"
platform: "linux"
package: "libqwt-doc"
version: "6.1.4-2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/QwtPlotBarChart"
---

# QwtPlotBarChart(3)

QwtPlotBarChart displays a series of a values as bars.

## NAME

QwtPlotBarChart - **QwtPlotBarChart** displays a series of a values as bars.

## SYNOPSIS

`#include <qwt_plot_barchart.h>`

Inherits **QwtPlotAbstractBarChart**, and **QwtSeriesStore\< QPointF \>**.

### Public Types

enum **LegendMode** { **LegendChartTitle**, **LegendBarTitles** }\
 Legend modes.

### Public Member Functions

**QwtPlotBarChart** (const QString &**title**=QString())\
 **QwtPlotBarChart** (const **QwtText** &**title**)\
 virtual **~QwtPlotBarChart** ()\
 Destructor.  virtual int **rtti** () const\
 void **setSamples** (const QVector\< QPointF \> &)\
 void **setSamples** (const QVector\< double \> &)\
 void **setSamples** (**QwtSeriesData**\< QPointF \> \*)\
 void **setSymbol** (**QwtColumnSymbol** \*)\
 Assign a symbol.  const **QwtColumnSymbol** \* **symbol** () const\
 void **setLegendMode** (**LegendMode**)\
 **LegendMode** **legendMode** () const\
 virtual void **drawSeries** (QPainter \*painter, const **QwtScaleMap** &xMap, const **QwtScaleMap** &yMap, const QRectF &canvasRect, int from, int to) const\
 virtual QRectF **boundingRect** () const\
 virtual **QwtColumnSymbol** \* **specialSymbol** (int sampleIndex, const QPointF &) const\
 virtual **QwtText** **barTitle** (int sampleIndex) const\
 Return the title of a bar.

### Protected Member Functions

virtual void **drawSample** (QPainter \*painter, const **QwtScaleMap** &xMap, const **QwtScaleMap** &yMap, const QRectF &canvasRect, const **QwtInterval** &boundingInterval, int index, const QPointF &**sample**) const\
 virtual void **drawBar** (QPainter \*, int sampleIndex, const QPointF &**sample**, const **QwtColumnRect** &) const\
 QList\< **QwtLegendData** \> **legendData** () const\
 Return all information, that is needed to represent the item on the legend.  **QwtGraphic** **legendIcon** (int index, const QSizeF &) const\

## Detailed Description

**QwtPlotBarChart** displays a series of a values as bars.

Each bar might be customized individually by implementing a **specialSymbol()**. Otherwise it is rendered using a default symbol.

Depending on its **orientation()** the bars are displayed horizontally or vertically. The bars cover the interval between the **baseline()** and the value.

By activating the LegendBarTitles mode each sample will have its own entry on the legend.

The most common use case of a bar chart is to display a list of y coordinates, where the x coordinate is simply the index in the list. But for other situations ( f.e. when values are related to dates ) it is also possible to set x coordinates explicitly.

**See also:**

**QwtPlotMultiBarChart**, **QwtPlotHistogram**, **QwtPlotCurve::Sticks**, **QwtPlotSeriesItem::orientation()**, **QwtPlotAbstractBarChart::baseline()**

## Member Enumeration Documentation

### enum QwtPlotBarChart::LegendMode

Legend modes. The default setting is **QwtPlotBarChart::LegendChartTitle**.

**See also:**

**setLegendMode()**, **legendMode()**

**Enumerator**

- *LegendChartTitle*

  *One entry on the legend showing the default symbol and the* **title()** *of the chart*

**See also:**

**QwtPlotItem::title()**

- *LegendBarTitles*

  *One entry for each value showing the individual symbol of the corresponding bar and the bar title.*

**See also:**

**specialSymbol()***,* **barTitle()**

## Constructor & Destructor Documentation

### QwtPlotBarChart::QwtPlotBarChart (const QString & title = `QString()`)` [explicit]`

*Constructor*

**Parameters:**

*title Title of the curve*

### QwtPlotBarChart::QwtPlotBarChart (const QwtText & title)` [explicit]`

*Constructor*

**Parameters:**

*title Title of the curve*

## Member Function Documentation

### QwtText QwtPlotBarChart::barTitle (int sampleIndex) const` [virtual]`

*Return the title of a bar. In LegendBarTitles mode the title is displayed on the legend entry corresponding to a bar.*

*The default implementation is a dummy, that is intended to be overloaded.*

**Parameters:**

*sampleIndex Index of the bar*

**Returns:**

*An empty text*

**See also:**

**LegendBarTitles**

### QRectF QwtPlotBarChart::boundingRect () const` [virtual]`

**Returns:**

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

*Reimplemented from* **QwtPlotSeriesItem***.*

### void QwtPlotBarChart::drawBar (QPainter \* painter, int sampleIndex, const QPointF & sample, const QwtColumnRect & rect) const` [protected]`, ` [virtual]`

*Draw a bar*

**Parameters:**

*painter Painter* \
 *sampleIndex Index of the sample represented by the bar* \
 *sample Value of the sample* \
 *rect Bounding rectangle of the bar*

### void QwtPlotBarChart::drawSample (QPainter \* painter, const QwtScaleMap & xMap, const QwtScaleMap & yMap, const QRectF & canvasRect, const QwtInterval & boundingInterval, int index, const QPointF & sample) const` [protected]`, ` [virtual]`

*Draw a sample*

**Parameters:**

*painter Painter* \
 *xMap x map* \
 *yMap y map* \
 *canvasRect Contents rect of the canvas* \
 *boundingInterval Bounding interval of sample values* \
 *index Index of the sample* \
 *sample Value of the sample*

**See also:**

**drawSeries()**

### void QwtPlotBarChart::drawSeries (QPainter \* painter, const QwtScaleMap & xMap, const QwtScaleMap & yMap, const QRectF & canvasRect, int from, int to) const` [virtual]`

*Draw an interval of the bar chart*

**Parameters:**

*painter Painter* \
 *xMap Maps x-values into pixel coordinates.* \
 *yMap Maps y-values into pixel coordinates.* \
 *canvasRect Contents rect of the canvas* \
 *from Index of the first point to be painted* \
 *to Index of the last point to be painted. If to \< 0 the curve will be painted to its last point.*

**See also:**

*drawSymbols()*

*Implements* **QwtPlotSeriesItem***.*

### QList\< QwtLegendData \> QwtPlotBarChart::legendData () const` [protected]`, ` [virtual]`

*Return all information, that is needed to represent the item on the legend. In case of LegendBarTitles an entry for each bar is returned, otherwise the chart is represented like any other plot item from its* **title()** *and the* **legendIcon()***.*

**Returns:**

*Information, that is needed to represent the item on the legend*

**See also:**

**title()***,* **setLegendMode()***,* **barTitle()***,* **QwtLegend***,* **QwtPlotLegendItem**

*Reimplemented from* **QwtPlotItem***.*

### QwtGraphic QwtPlotBarChart::legendIcon (int index, const QSizeF & size) const` [protected]`, ` [virtual]`

**Returns:**

*Icon representing a bar or the chart on the legend*

*When the* **legendMode()** *is LegendBarTitles the icon shows the bar corresponding to index - otherwise the bar displays the default symbol.*

**Parameters:**

*index Index of the legend entry* \
 *size Icon size*

**See also:**

**setLegendMode()***,* **drawBar()***,* **QwtPlotItem::setLegendIconSize()***,* **QwtPlotItem::legendData()**

*Reimplemented from* **QwtPlotItem***.*

### QwtPlotBarChart::LegendMode QwtPlotBarChart::legendMode () const

**Returns:**

*Legend mode*

**See also:**

**setLegendMode()**

### int QwtPlotBarChart::rtti () const` [virtual]`

**Returns:**

**QwtPlotItem::Rtti\_PlotBarChart**

*Reimplemented from* **QwtPlotItem***.*

### void QwtPlotBarChart::setLegendMode (LegendMode mode)

*Set the mode that decides what to display on the legend*

*In case of LegendBarTitles* **barTitle()** *needs to be overloaded to return individual titles for each bar.*

**Parameters:**

*mode New mode*

**See also:**

**legendMode()***,* **legendData()***,* **barTitle()***,* **QwtPlotItem::ItemAttribute**

### void QwtPlotBarChart::setSamples (const QVector\< QPointF \> & samples)

*Initialize data with an array of points*

**Parameters:**

*samples Vector of points*

**Note:**

*QVector is implicitly shared*

*QPolygonF is derived from QVector\<QPointF\>*

### void QwtPlotBarChart::setSamples (const QVector\< double \> & samples)

*Initialize data with an array of doubles*

*The indices in the array are taken as x coordinate, while the doubles are interpreted as y values.*

**Parameters:**

*samples Vector of y coordinates*

**Note:**

*QVector is implicitly shared*

### void QwtPlotBarChart::setSamples (QwtSeriesData\< QPointF \> \* 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.*

### void QwtPlotBarChart::setSymbol (QwtColumnSymbol \* symbol)

*Assign a symbol. The bar chart will take the ownership of the symbol, hence the previously set symbol will be delete by setting a new one. If* `symbol` *is* `NULL` *no symbol will be drawn.*

**Parameters:**

*symbol Symbol*

**See also:**

**symbol()**

### QwtColumnSymbol \* QwtPlotBarChart::specialSymbol (int sampleIndex, const QPointF & sample) const` [virtual]`

*Needs to be overloaded to return a non default symbol for a specific sample*

**Parameters:**

*sampleIndex Index of the sample represented by the bar* \
 *sample Value of the sample*

**Returns:**

*NULL, indicating to use the default symbol*

### const QwtColumnSymbol \* QwtPlotBarChart::symbol () const

**Returns:**

*Current symbol or NULL, when no symbol has been assigned*

**See also:**

**setSymbol()**

## Author

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