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

# QwtPlotTextLabel(3)

A plot item, which displays a text label.

## NAME

QwtPlotTextLabel - A plot item, which displays a text label.

## SYNOPSIS

`#include <qwt_plot_textlabel.h>`

Inherits **QwtPlotItem**.

### Public Member Functions

**QwtPlotTextLabel** ()\
 Constructor.  virtual **~QwtPlotTextLabel** ()\
 Destructor.  virtual int **rtti** () const\
 void **setText** (const **QwtText** &)\
 **QwtText** **text** () const\
 void **setMargin** (int **margin**)\
 int **margin** () const\
 virtual QRectF **textRect** (const QRectF &, const QSizeF &) const\
 Align the text label.

### Protected Member Functions

virtual void **draw** (QPainter \*, const **QwtScaleMap** &, const **QwtScaleMap** &, const QRectF &) const\
 void **invalidateCache** ()\
 Invalidate all internal cache.

### Additional Inherited Members

## Detailed Description

A plot item, which displays a text label.

**QwtPlotTextLabel** displays a text label aligned to the plot canvas.

In opposite to **QwtPlotMarker** the position of the label is unrelated to plot coordinates.

As drawing a text is an expensive operation the label is cached in a pixmap to speed up replots.

**Example**

The following code shows how to add a title.

```
QwtText title( "Plot Title" );
title.setRenderFlags( Qt::AlignHCenter | Qt::AlignTop );
QFont font;
font.setBold( true );
title.setFont( font );
QwtPlotTextLabel *titleItem = new QwtPlotTextLabel();
titleItem->setText( title );
titleItem->attach( plot );
```

**See also:**

**QwtPlotMarker**

## Constructor & Destructor Documentation

### QwtPlotTextLabel::QwtPlotTextLabel ()

Constructor. Initializes an text label with an empty text

Sets the following item attributes:

- •

  **QwtPlotItem::AutoScale**: true

- •

  **QwtPlotItem::Legend**: false

The z value is initialized by 150

**See also:**

**QwtPlotItem::setItemAttribute()**, **QwtPlotItem::setZ()**

## Member Function Documentation

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

Draw the text label

**Parameters:**

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

**See also:**

**textRect()**

Implements **QwtPlotItem**.

### int QwtPlotTextLabel::margin () const

**Returns:**

Margin added to the contentsMargins() of the canvas

**See also:**

**setMargin()**

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

**Returns:**

**QwtPlotItem::Rtti\_PlotTextLabel**

Reimplemented from **QwtPlotItem**.

### void QwtPlotTextLabel::setMargin (int margin)

Set the margin

The margin is the distance between the contentsRect() of the plot canvas and the rectangle where the label can be displayed.

**Parameters:**

*margin* Margin

**See also:**

**margin()**, **textRect()**

### void QwtPlotTextLabel::setText (const QwtText & text)

Set the text

The label will be aligned to the plot canvas according to the alignment flags of text.

**Parameters:**

*text* Text to be displayed

**See also:**

**text()**, **QwtText::renderFlags()**

### QwtText QwtPlotTextLabel::text () const

**Returns:**

Text to be displayed

**See also:**

**setText()**

### QRectF QwtPlotTextLabel::textRect (const QRectF & rect, const QSizeF & textSize) const` [virtual]`

Align the text label.

**Parameters:**

*rect* Canvas rectangle with margins subtracted \
 *textSize* Size required to draw the text

**Returns:**

A rectangle aligned according the the alignment flags of the text.

**See also:**

**setMargin()**, **QwtText::renderFlags()**, **QwtText::textSize()**

## Author

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