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

# QwtDialNeedle(3)

Base class for needles that can be used in a QwtDial.

## NAME

QwtDialNeedle - Base class for needles that can be used in a **QwtDial**.

## SYNOPSIS

`#include <qwt_dial_needle.h>`

Inherited by **QwtCompassMagnetNeedle**, **QwtCompassWindArrow**, and **QwtDialSimpleNeedle**.

### Public Member Functions

**QwtDialNeedle** ()\
 Constructor.  virtual **~QwtDialNeedle** ()\
 Destructor.  virtual void **setPalette** (const QPalette &)\
 const QPalette & **palette** () const\
 virtual void **draw** (QPainter \*painter, const QPointF &center, double length, double direction, QPalette::ColorGroup=QPalette::Active) const\

### Protected Member Functions

virtual void **drawNeedle** (QPainter \*painter, double length, QPalette::ColorGroup colorGroup) const =0\
 Draw the needle.  virtual void **drawKnob** (QPainter \*, double width, const QBrush &, bool sunken) const\
 Draw the knob.

## Detailed Description

Base class for needles that can be used in a **QwtDial**.

**QwtDialNeedle** is a pointer that indicates a value by pointing to a specific direction.

**See also:**

**QwtDial**, **QwtCompass**

## Member Function Documentation

### void QwtDialNeedle::draw (QPainter \* painter, const QPointF & center, double length, double direction, QPalette::ColorGroup colorGroup = `QPalette::Active`) const` [virtual]`

Draw the needle

**Parameters:**

*painter* Painter \
 *center* Center of the dial, start position for the needle \
 *length* Length of the needle \
 *direction* Direction of the needle, in degrees counter clockwise \
 *colorGroup* Color group, used for painting

### virtual void QwtDialNeedle::drawNeedle (QPainter \* painter, double length, QPalette::ColorGroup colorGroup) const` [protected]`, ` [pure virtual]`

Draw the needle. The origin of the needle is at position (0.0, 0.0 ) pointing in direction 0.0 ( = east ).

The painter is already initialized with translation and rotation.

**Parameters:**

*painter* Painter \
 *length* Length of the needle \
 *colorGroup* Color group, used for painting

**See also:**

**setPalette()**, **palette()**

Implemented in **QwtCompassWindArrow**, **QwtCompassMagnetNeedle**, and **QwtDialSimpleNeedle**.

### const QPalette & QwtDialNeedle::palette () const

**Returns:**

the palette of the needle.

### void QwtDialNeedle::setPalette (const QPalette & palette)` [virtual]`

Sets the palette for the needle.

**Parameters:**

*palette* New Palette

## Author

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