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

# QwtPlotMarker(3)

A class for drawing markers.

## NAME

QwtPlotMarker - A class for drawing markers.

## SYNOPSIS

`#include <qwt_plot_marker.h>`

Inherits **QwtPlotItem**.

### Public Types

enum **LineStyle** { **NoLine**, **HLine**, **VLine**, **Cross** }\

### Public Member Functions

**QwtPlotMarker** (const QString &**title**=QString())\
 Sets alignment to Qt::AlignCenter, and style to **QwtPlotMarker::NoLine**.  **QwtPlotMarker** (const **QwtText** &**title**)\
 Sets alignment to Qt::AlignCenter, and style to **QwtPlotMarker::NoLine**.  virtual **~QwtPlotMarker** ()\
 Destructor.  virtual int **rtti** () const\
 double **xValue** () const\
 Return x Value.  double **yValue** () const\
 Return y Value.  QPointF **value** () const\
 Return Value.  void **setXValue** (double)\
 Set X Value.  void **setYValue** (double)\
 Set Y Value.  void **setValue** (double, double)\
 Set Value.  void **setValue** (const QPointF &)\
 Set Value.  void **setLineStyle** (**LineStyle**)\
 Set the line style.  **LineStyle** **lineStyle** () const\
 void **setLinePen** (const QColor &, qreal width=0.0, Qt::PenStyle=Qt::SolidLine)\
 void **setLinePen** (const QPen &)\
 const QPen & **linePen** () const\
 void **setSymbol** (const **QwtSymbol** \*)\
 Assign a symbol.  const **QwtSymbol** \* **symbol** () const\
 void **setLabel** (const **QwtText** &)\
 Set the label.  **QwtText** **label** () const\
 void **setLabelAlignment** (Qt::Alignment)\
 Set the alignment of the label.  Qt::Alignment **labelAlignment** () const\
 void **setLabelOrientation** (Qt::Orientation)\
 Set the orientation of the label.  Qt::Orientation **labelOrientation** () const\
 void **setSpacing** (int)\
 Set the spacing.  int **spacing** () const\
 virtual void **draw** (QPainter \*, const **QwtScaleMap** &xMap, const **QwtScaleMap** &yMap, const QRectF &) const\
 virtual QRectF **boundingRect** () const\
 virtual **QwtGraphic** **legendIcon** (int index, const QSizeF &) const\

### Protected Member Functions

virtual void **drawLines** (QPainter \*, const QRectF &, const QPointF &) const\
 virtual void **drawLabel** (QPainter \*, const QRectF &, const QPointF &) const\

## Detailed Description

A class for drawing markers.

A marker can be a horizontal line, a vertical line, a symbol, a label or any combination of them, which can be drawn around a center point inside a bounding rectangle.

The **setSymbol()** member assigns a symbol to the marker. The symbol is drawn at the specified point.

With **setLabel()**, a label can be assigned to the marker. The **setLabelAlignment()** member specifies where the label is drawn. All the Align\*-constants in Qt::AlignmentFlags (see Qt documentation) are valid. The interpretation of the alignment depends on the marker's line style. The alignment refers to the center point of the marker, which means, for example, that the label would be printed left above the center point if the alignment was set to Qt::AlignLeft \| Qt::AlignTop.

**Note:**

**QwtPlotTextLabel** is intended to align a text label according to the geometry of canvas ( unrelated to plot coordinates )

## Member Enumeration Documentation

### enum QwtPlotMarker::LineStyle

Line styles.

**See also:**

**setLineStyle()**, **lineStyle()**

**Enumerator**

- *NoLine*

  *No line.*

- *HLine*

  *A horizontal line.*

- *VLine*

  *A vertical line.*

- *Cross*

  *A crosshair.*

## Member Function Documentation

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

**Returns:**

*An invalid bounding rect: QRectF(1.0, 1.0, -2.0, -2.0)*

**Note:**

*A width or height \< 0.0 is ignored by the autoscaler*

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

### void QwtPlotMarker::draw (QPainter \* painter, const QwtScaleMap & xMap, const QwtScaleMap & yMap, const QRectF & canvasRect) const` [virtual]`

*Draw the marker*

**Parameters:**

*painter Painter* \
 *xMap x Scale Map* \
 *yMap y Scale Map* \
 *canvasRect Contents rectangle of the canvas in painter coordinates*

*Implements* **QwtPlotItem***.*

### void QwtPlotMarker::drawLabel (QPainter \* painter, const QRectF & canvasRect, const QPointF & pos) const` [protected]`, ` [virtual]`

*Align and draw the text label of the marker*

**Parameters:**

*painter Painter* \
 *canvasRect Contents rectangle of the canvas in painter coordinates* \
 *pos Position of the marker, translated into widget coordinates*

**See also:**

**drawLabel()***,* **QwtSymbol::drawSymbol()**

### void QwtPlotMarker::drawLines (QPainter \* painter, const QRectF & canvasRect, const QPointF & pos) const` [protected]`, ` [virtual]`

*Draw the lines marker*

**Parameters:**

*painter Painter* \
 *canvasRect Contents rectangle of the canvas in painter coordinates* \
 *pos Position of the marker, translated into widget coordinates*

**See also:**

**drawLabel()***,* **QwtSymbol::drawSymbol()**

### QwtText QwtPlotMarker::label () const

**Returns:**

*the label*

**See also:**

**setLabel()**

### Qt::Alignment QwtPlotMarker::labelAlignment () const

**Returns:**

*the label alignment*

**See also:**

**setLabelAlignment()***,* **setLabelOrientation()**

### Qt::Orientation QwtPlotMarker::labelOrientation () const

**Returns:**

*the label orientation*

**See also:**

**setLabelOrientation()***,* **labelAlignment()**

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

**Returns:**

*Icon representing the marker on the legend*

**Parameters:**

*index Index of the legend entry ( usually there is only one )* \
 *size Icon size*

**See also:**

**setLegendIconSize()***,* **legendData()**

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

### const QPen & QwtPlotMarker::linePen () const

**Returns:**

*the line pen*

**See also:**

**setLinePen()**

### QwtPlotMarker::LineStyle QwtPlotMarker::lineStyle () const

**Returns:**

*the line style*

**See also:**

**setLineStyle()**

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

**Returns:**

**QwtPlotItem::Rtti\_PlotMarker**

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

### void QwtPlotMarker::setLabel (const QwtText & label)

*Set the label.*

**Parameters:**

*label Label text*

**See also:**

**label()**

### void QwtPlotMarker::setLabelAlignment (Qt::Alignment align)

*Set the alignment of the label. In case of* **QwtPlotMarker::HLine** *the alignment is relative to the y position of the marker, but the horizontal flags correspond to the canvas rectangle. In case of* **QwtPlotMarker::VLine** *the alignment is relative to the x position of the marker, but the vertical flags correspond to the canvas rectangle.*

*In all other styles the alignment is relative to the marker's position.*

**Parameters:**

*align Alignment.*

**See also:**

**labelAlignment()***,* **labelOrientation()**

### void QwtPlotMarker::setLabelOrientation (Qt::Orientation orientation)

*Set the orientation of the label. When orientation is Qt::Vertical the label is rotated by 90.0 degrees ( from bottom to top ).*

**Parameters:**

*orientation Orientation of the label*

**See also:**

**labelOrientation()***,* **setLabelAlignment()**

### void QwtPlotMarker::setLinePen (const QColor & color, qreal width = `0.0`, Qt::PenStyle style = `Qt::SolidLine`)

*Build and assign a line 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()*

### void QwtPlotMarker::setLinePen (const QPen & pen)

*Specify a pen for the line.*

**Parameters:**

*pen New pen*

**See also:**

**linePen()**

### void QwtPlotMarker::setLineStyle (LineStyle style)

*Set the line style.*

**Parameters:**

*style Line style.*

**See also:**

**lineStyle()**

### void QwtPlotMarker::setSpacing (int spacing)

*Set the spacing. When the label is not centered on the marker position, the spacing is the distance between the position and the label.*

**Parameters:**

*spacing Spacing*

**See also:**

**spacing()***,* **setLabelAlignment()**

### void QwtPlotMarker::setSymbol (const QwtSymbol \* symbol)

*Assign a symbol.*

**Parameters:**

*symbol New symbol*

**See also:**

**symbol()**

### int QwtPlotMarker::spacing () const

**Returns:**

*the spacing*

**See also:**

**setSpacing()**

### const QwtSymbol \* QwtPlotMarker::symbol () const

**Returns:**

*the symbol*

**See also:**

**setSymbol()***,* **QwtSymbol**

## Author

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