QwtKnob.qt5 - Man Page


#include <qwt_knob.h>

Inherits QwtAbstractSlider, and QwtAbstractScale.

Public Types

enum Symbol { Line, Dot }

Public Member Functions

QwtKnob (QWidget *parent=NULL)
virtual ~QwtKnob ()
int borderWidth () const
int knobWidth () const
virtual QSize minimumSizeHint () const
const QwtRoundScaleDraw * scaleDraw () const
QwtRoundScaleDraw * scaleDraw ()
void setBorderWidth (int bw)
void setKnobWidth (int w)
void setScaleDraw (QwtRoundScaleDraw *)
void setSymbol (Symbol)
void setTotalAngle (double angle)
virtual QSize sizeHint () const
Symbol symbol () const
double totalAngle () const

Protected Member Functions

void draw (QPainter *p, const QRect &ur)
void drawKnob (QPainter *p, const QRect &r)
void drawMarker (QPainter *p, double arc, const QColor &c)
virtual void paintEvent (QPaintEvent *e)
virtual void resizeEvent (QResizeEvent *e)

Additional Inherited Members

Detailed Description

The Knob Widget.

The QwtKnob widget imitates look and behaviour of a volume knob on a radio. It contains a scale around the knob which is set up automatically or can be configured manually (see QwtAbstractScale). Automatic scrolling is enabled when the user presses a mouse button on the scale. For a description of signals, slots and other members, see QwtAbstractSlider.

See also:

QwtAbstractSlider and QwtAbstractScale for the descriptions of the inherited members.

Member Enumeration Documentation

enum QwtKnob::Symbol


See also:


Constructor & Destructor Documentation

QwtKnob::QwtKnob (QWidget *parent = NULL) [explicit]



parent Parent widget

Member Function Documentation

void QwtKnob::draw (QPainter *painter, const QRect &rect) [protected]

Repaint the knob


painter Painter
rect Update rectangle

void QwtKnob::drawKnob (QPainter *painter, const QRect &r) [protected]

Draw the knob. Parameters:

painter painter
r Bounding rectangle of the knob (without scale)

void QwtKnob::drawMarker (QPainter *p, doublearc, const QColor &c) [protected]

Draw the marker at the knob's front. Parameters:

p Painter
arc Angle of the marker
c Marker color

QSize QwtKnob::minimumSizeHint () const [virtual]

Return a minimum size hint. Warning:

The return value of QwtKnob::minimumSizeHint() depends on the font and the scale.

void QwtKnob::paintEvent (QPaintEvent *e) [protected], [virtual]

Repaint the knob


e Paint event

void QwtKnob::resizeEvent (QResizeEvent *e) [protected], [virtual]

Qt Resize Event

const QwtRoundScaleDraw * QwtKnob::scaleDraw () const


the scale draw of the knob

See also:


QwtRoundScaleDraw * QwtKnob::scaleDraw ()


the scale draw of the knob

See also:


void QwtKnob::setBorderWidth (intbw)

Set the knob's border width. Parameters:

bw new border width

void QwtKnob::setKnobWidth (intw)

Change the knob's width. The specified width must be >= 5, or it will be clipped.


w New width

void QwtKnob::setScaleDraw (QwtRoundScaleDraw *scaleDraw)

Change the scale draw of the knob

For changing the labels of the scales, it is necessary to derive from QwtRoundScaleDraw and overload QwtRoundScaleDraw::label().

See also:


void QwtKnob::setSymbol (QwtKnob::Symbols)

Set the symbol of the knob. See also:


void QwtKnob::setTotalAngle (doubleangle)

Set the total angle by which the knob can be turned. Parameters:

angle Angle in degrees.

The default angle is 270 degrees. It is possible to specify an angle of more than 360 degrees so that the knob can be turned several times around its axis.

QSize QwtKnob::sizeHint () const [virtual]



QwtKnob::Symbol QwtKnob::symbol () const


symbol of the knob

See also:



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Tue Nov 20 2012 Version 5.2.3 Qwt User's Guide