QwtWheel - Man Page


QwtWheel ā€”

The Wheel Widget. Ā 


#include <qwt_wheel.h>

Inherits QwtAbstractSlider.

Public Types

enum ScrollMode { ScrNone, ScrMouse, ScrTimer, ScrDirect, ScrPage }

Public Slots

virtual void fitValue (double val)
virtual void incValue (int steps)
virtual void setReadOnly (bool)
virtual void setValue (double val)


void sliderMoved (double value)
void sliderPressed ()
void sliderReleased ()
void valueChanged (double value)

Public Member Functions

virtual void incPages (int)
int internalBorder () const
bool isReadOnly () const
bool isValid () const
double mass () const
double maxValue () const
virtual QSize minimumSizeHint () const
double minValue () const
Qt::Orientation orientation () const
int pageSize () const
bool periodic () const
QwtWheel (QWidget *parent=NULL)
void setInternalBorder (int width)
void setMass (double val)
virtual void setOrientation (Qt::Orientation)
void setPeriodic (bool tf)
void setRange (double vmin, double vmax, double vstep=0.0, int pagesize=1)
void setStep (double)
void setTickCnt (int cnt)
void setTotalAngle (double angle)
void setTracking (bool enable)
void setUpdateTime (int t)
void setValid (bool valid)
void setViewAngle (double angle)
void setWheelWidth (int w)
virtual QSize sizeHint () const
double step () const
void stopMoving ()
int tickCnt () const
double totalAngle () const
double value () const
double viewAngle () const
virtual ~QwtWheel ()

Protected Member Functions

void draw (QPainter *, const QRect &)
void drawWheel (QPainter *, const QRect &)
void drawWheelBackground (QPainter *, const QRect &)
double exactPrevValue () const
double exactValue () const
virtual void getScrollMode (const QPoint &, int &scrollMode, int &direction)
virtual double getValue (const QPoint &)
virtual void keyPressEvent (QKeyEvent *e)
void layoutWheel (bool update=true)
virtual void mouseMoveEvent (QMouseEvent *e)
double mouseOffset () const
virtual void mousePressEvent (QMouseEvent *e)
virtual void mouseReleaseEvent (QMouseEvent *e)
virtual void paintEvent (QPaintEvent *e)
virtual void paletteChange (const QPalette &)
double prevValue () const
virtual void rangeChange ()
virtual void resizeEvent (QResizeEvent *e)
int scrollMode () const
void setColorArray ()
void setMouseOffset (double)
virtual void setPosition (const QPoint &)
virtual void stepChange ()
virtual void timerEvent (QTimerEvent *e)
virtual void valueChange ()
virtual void wheelEvent (QWheelEvent *e)

Detailed Description

The Wheel Widget.

The wheel widget can be used to change values over a very large range in very small steps. Using the setMass member, it can be configured as a flywheel.

See also:

The radio example.

Member Enumeration Documentation

enum QwtAbstractSlider::ScrollMode [inherited] Scroll mode

See also:


Constructor & Destructor Documentation

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


QwtWheel::~QwtWheel () [virtual]


Member Function Documentation

void QwtWheel::draw (QPainter *painter, const QRect &) [protected] Redraw panel and wheel


painter Painter

void QwtWheel::drawWheel (QPainter *painter, const QRect &r) [protected]

Redraw the wheel. Parameters:

painter painter
r contents rectangle

void QwtWheel::drawWheelBackground (QPainter *painter, const QRect &r) [protected] Draw the Wheel's background gradient


painter Painter
r Bounding rectangle

double QwtDoubleRange::exactPrevValue () const [protected, inherited]

Returns the exact previous value.

double QwtDoubleRange::exactValue () const [protected, inherited]

Returns the exact value. The exact value is the value which QwtDoubleRange::value would return if the value were not adjusted to the step raster. It differs from the current value only if QwtDoubleRange::fitValue or QwtDoubleRange::incValue have been used before. This function is intended for internal use in derived classes.

void QwtAbstractSlider::fitValue (doublevalue) [virtual, slot, inherited]

Set the slider's value to the nearest integer multiple of the step size. Parameters:

value Value

See also:

setValue(), incValue()

Reimplemented from QwtDoubleRange.

void QwtWheel::getScrollMode (const QPoint &p, int &scrollMode, int &direction) [protected, virtual]

Determine the scrolling mode and direction corresponding to a specified point. Parameters:

p point
scrollMode scrolling mode
direction direction

Implements QwtAbstractSlider.

double QwtWheel::getValue (const QPoint &p) [protected, virtual]

Determine the value corresponding to a specified point.

Implements QwtAbstractSlider.

void QwtDoubleRange::incPages (intnPages) [virtual, inherited]

Increment the value by a specified number of pages. Parameters:

nPages Number of pages to increment. A negative number decrements the value.


The Page size is specified in the constructor.

void QwtAbstractSlider::incValue (intsteps) [virtual, slot, inherited]

Increment the value by a specified number of steps. Parameters:

steps number of steps

See also:


Reimplemented from QwtDoubleRange.

int QwtWheel::internalBorder () const Returns

Internal border width of the wheel.

See also:


bool QwtAbstractSlider::isReadOnly () const [inherited] In read only mode the slider can't be controlled by mouse or keyboard.


true if read only

See also:


bool QwtAbstractSlider::isValid () const [inline, inherited] See also


Reimplemented from QwtDoubleRange.

void QwtAbstractSlider::keyPressEvent (QKeyEvent *e) [protected, virtual, inherited] Handles key events

  • Key_Down, KeyLeft
    Decrement by 1
  • Key_Up, Key_Right
    Increment by 1

e Key event

See also:


Reimplemented in QwtCompass, and QwtDial.

void QwtWheel::layoutWheel (boolupdate = true) [protected]

Recalculate the slider's geometry and layout based on.

double QwtWheel::mass () const [virtual] Returns


Reimplemented from QwtAbstractSlider.

double QwtDoubleRange::maxValue () const [inherited]

Returns the value of the second border of the range. maxValue returns the value which has been specified as the second parameter in QwtDoubleRange::setRange.

See also:


QSize QwtWheel::minimumSizeHint () const [virtual]

Return a minimum size hint. Warning:

The return value is based on the wheel width.

double QwtDoubleRange::minValue () const [inherited]

Returns the value at the first border of the range. minValue returns the value which has been specified as the first parameter in setRange().

See also:


void QwtAbstractSlider::mouseMoveEvent (QMouseEvent *e) [protected, virtual, inherited] Mouse Move Event handler


e Mouse event

void QwtAbstractSlider::mousePressEvent (QMouseEvent *e) [protected, virtual, inherited] Mouse press event handler


e Mouse event

void QwtAbstractSlider::mouseReleaseEvent (QMouseEvent *e) [protected, virtual, inherited] Mouse Release Event handler


e Mouse event

Qt::Orientation QwtAbstractSlider::orientation () const [inherited] Returns


See also:


int QwtDoubleRange::pageSize () const [inherited]

Returns the page size in steps.

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

Qt Paint Event.

void QwtWheel::paletteChange (const QPalette &) [protected, virtual]

Call update() when the palette changes.

bool QwtDoubleRange::periodic () const [inherited]

Returns true if the range is periodic. See also:


double QwtDoubleRange::prevValue () const [protected, inherited]

Returns the previous value.

void QwtDoubleRange::rangeChange () [protected, virtual, inherited]

Notify a change of the range. This virtual function is called whenever the range changes. The default implementation does nothing.

Reimplemented in QwtCounter, QwtDial, and QwtSlider.

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

Qt Resize Event.

void QwtWheel::setColorArray () [protected]

Set up the color array for the background pixmap.

void QwtWheel::setInternalBorder (intw)

Set the internal border width of the wheel. The internal border must not be smaller than 1 and is limited in dependence on the wheel's size. Values outside the allowed range will be clipped.

The internal border defaults to 2.


w border width

See also:


void QwtWheel::setMass (doubleval) [virtual]

Set the mass of the wheel. Assigning a mass turns the wheel into a flywheel.


val the wheel's mass

Reimplemented from QwtAbstractSlider.

void QwtWheel::setOrientation (Qt::Orientationo) [virtual]

Set the wheel's orientation. Parameters:

o Orientation. Allowed values are Qt::Horizontal and Qt::Vertical. Defaults to Qt::Horizontal.

See also:


Reimplemented from QwtAbstractSlider.

void QwtDoubleRange::setPeriodic (booltf) [inherited]

Make the range periodic. When the range is periodic, the value will be set to a point inside the interval such that

point = value + n * width .fi

if the user tries to set a new value which is outside the range. If the range is nonperiodic (the default), values outside the range will be clipped.

  tf true for a periodic range

void QwtAbstractSlider::setPosition (const QPoint &p) [protected, virtual, inherited] Move the slider to a specified point, adjust the value and emit signals if necessary.

void QwtDoubleRange::setRange (doublevmin, doublevmax, doublevstep = 0.0, intpageSize = 1) [inherited]

Specify range and step size. Parameters:

vmin lower boundary of the interval
vmax higher boundary of the interval
vstep step width
pageSize page size in steps

  • A change of the range changes the value if it lies outside the new range. The current value will *not* be adjusted to the new step raster.
  • vmax < vmin is allowed.
  • If the step size is left out or set to zero, it will be set to 1/100 of the interval length.
  • If the step size has an absurd value, it will be corrected to a better one.

void QwtAbstractSlider::setReadOnly (boolreadOnly) [virtual, slot, inherited] En/Disable read only mode

In read only mode the slider can't be controlled by mouse or keyboard.


readOnly Enables in case of true

See also:


void QwtDoubleRange::setStep (doublevstep) [inherited]

Change the step raster. Parameters:

vstep new step width


The value will not be adjusted to the new step raster.

Reimplemented in QwtCounter.

void QwtWheel::setTickCnt (intcnt)

Adjust the number of grooves in the wheel's surface. The number of grooves is limited to 6 <= cnt <= 50. Values outside this range will be clipped. The default value is 10.


cnt Number of grooves per 360 degrees

See also:


void QwtWheel::setTotalAngle (doubleangle)

Set the total angle which the wheel can be turned. One full turn of the wheel corresponds to an angle of 360 degrees. A total angle of n*360 degrees means that the wheel has to be turned n times around its axis to get from the minimum value to the maximum value.

The default setting of the total angle is 360 degrees.


angle total angle in degrees

See also:


void QwtAbstractSlider::setTracking (boolenable) [inherited]

Enables or disables tracking. If tracking is enabled, the slider emits a valueChanged() signal whenever its value changes (the default behaviour). If tracking is disabled, the value changed() signal will only be emitted if:

  • the user releases the mouse button and the value has changed or
  • at the end of automatic scrolling.

Tracking is enabled by default.


enable true (enable) or false (disable) tracking.

void QwtAbstractSlider::setUpdateTime (intt) [inherited]

Specify the update interval for automatic scrolling. Parameters:

t update interval in milliseconds

See also:


void QwtAbstractSlider::setValid (boolvalid) [inline, inherited] Parameters

valid true/false

See also:


Reimplemented from QwtDoubleRange.

void QwtAbstractSlider::setValue (doubleval) [virtual, slot, inherited]

Move the slider to a specified value. This function can be used to move the slider to a value which is not an integer multiple of the step size.


val new value

See also:


Reimplemented from QwtDoubleRange.

void QwtWheel::setViewAngle (doubleangle)

Specify the visible portion of the wheel. You may use this function for fine-tuning the appearance of the wheel. The default value is 175 degrees. The value is limited from 10 to 175 degrees.


angle Visible angle in degrees

See also:

viewAngle(), setTotalAngle()

void QwtWheel::setWheelWidth (intw)

Set the width of the wheel. Corresponds to the wheel height for horizontal orientation, and the wheel width for vertical orientation.


w the wheel's width

QSize QwtWheel::sizeHint () const [virtual] Returns

a size hint

void QwtAbstractSlider::sliderMoved (doublevalue) [signal, inherited] This signal is emitted when the user moves the slider with the mouse.


value new value

void QwtAbstractSlider::sliderPressed () [signal, inherited] This signal is emitted when the user presses the movable part of the slider (start ScrMouse Mode).

void QwtAbstractSlider::sliderReleased () [signal, inherited] This signal is emitted when the user releases the movable part of the slider.

double QwtDoubleRange::step () const [inherited] Returns

the step size

See also:

setStep(), setRange()

Reimplemented in QwtCounter.

void QwtDoubleRange::stepChange () [protected, virtual, inherited]

Notify a change of the step size. This virtual function is called whenever the step size changes. The default implementation does nothing.

void QwtAbstractSlider::stopMoving () [inherited]

Stop updating if automatic scrolling is active.

int QwtWheel::tickCnt () const Returns

Number of grooves in the wheel's surface.

See also:


void QwtAbstractSlider::timerEvent (QTimerEvent *e) [protected, virtual, inherited] Qt timer event


e Timer event

double QwtWheel::totalAngle () const Returns

Total angle which the wheel can be turned.

See also:


double QwtDoubleRange::value () const [inherited]

Returns the current value.

Reimplemented in QwtCounter.

void QwtWheel::valueChange () [protected, virtual]

Notify value change.

Reimplemented from QwtAbstractSlider.

void QwtAbstractSlider::valueChanged (doublevalue) [signal, inherited]

Notify a change of value. In the default setting (tracking enabled), this signal will be emitted every time the value changes ( see setTracking() ).


value new value

double QwtWheel::viewAngle () const Returns

Visible portion of the wheel

See also:

setViewAngle(), totalAngle()

void QwtAbstractSlider::wheelEvent (QWheelEvent *e) [protected, virtual, inherited] Wheel Event handler


e Whell event


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Mon Aug 1 2011 Version 5.2.2 Qwt User's Guide