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QwtKnob(3) Qwt User's Guide QwtKnob(3)

NAME

QwtKnob -
The Knob Widget.
 

SYNOPSIS

#include <qwt_knob.h>
Inherits QwtAbstractSlider, and QwtAbstractScale.

Public Types


enum ScrollMode { ScrNone, ScrMouse, ScrTimer, ScrDirect, ScrPage }
 
enum Symbol { Line, Dot }
 

Public Slots


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

Signals


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

Public Member Functions


bool autoScale () const
 
int borderWidth () const
 
virtual void incPages (int)
 
bool isReadOnly () const
 
bool isValid () const
 
int knobWidth () const
 
virtual double mass () const
 
double maxValue () const
 
virtual QSize minimumSizeHint () const
 
double minValue () const
 
Qt::Orientation orientation () const
 
int pageSize () const
 
bool periodic () const
 
QwtKnob (QWidget *parent=NULL)
 
const QwtRoundScaleDraw * scaleDraw () const
 
QwtRoundScaleDraw * scaleDraw ()
 
QwtScaleEngine * scaleEngine ()
 
const QwtScaleEngine * scaleEngine () const
 
const QwtScaleMap & scaleMap () const
 
int scaleMaxMajor () const
 
int scaleMaxMinor () const
 
void setAutoScale ()
 
void setBorderWidth (int bw)
 
void setKnobWidth (int w)
 
virtual void setMass (double val)
 
virtual void setOrientation (Qt::Orientation o)
 
void setPeriodic (bool tf)
 
void setRange (double vmin, double vmax, double vstep=0.0, int pagesize=1)
 
void setScale (const QwtScaleDiv &s)
 
void setScale (double vmin, double vmax, double step=0.0)
 
void setScale (const QwtDoubleInterval &, double step=0.0)
 
void setScaleDraw (QwtRoundScaleDraw *)
 
void setScaleEngine (QwtScaleEngine *)
 
void setScaleMaxMajor (int ticks)
 
void setScaleMaxMinor (int ticks)
 
void setStep (double)
 
void setSymbol (Symbol)
 
void setTotalAngle (double angle)
 
void setTracking (bool enable)
 
void setUpdateTime (int t)
 
void setValid (bool valid)
 
virtual QSize sizeHint () const
 
double step () const
 
void stopMoving ()
 
Symbol symbol () const
 
double totalAngle () const
 
double value () const
 
virtual ~QwtKnob ()
 

Protected Member Functions


const QwtAbstractScaleDraw * abstractScaleDraw () const
 
QwtAbstractScaleDraw * abstractScaleDraw ()
 
void draw (QPainter *p, const QRect &ur)
 
void drawKnob (QPainter *p, const QRect &r)
 
void drawMarker (QPainter *p, double arc, const QColor &c)
 
double exactPrevValue () const
 
double exactValue () const
 
virtual void keyPressEvent (QKeyEvent *e)
 
virtual void mouseMoveEvent (QMouseEvent *e)
 
double mouseOffset () const
 
virtual void mousePressEvent (QMouseEvent *e)
 
virtual void mouseReleaseEvent (QMouseEvent *e)
 
virtual void paintEvent (QPaintEvent *e)
 
double prevValue () const
 
void rescale (double vmin, double vmax, double step=0.0)
 
virtual void resizeEvent (QResizeEvent *e)
 
int scrollMode () const
 
void setAbstractScaleDraw (QwtAbstractScaleDraw *)
 
void setMouseOffset (double)
 
virtual void setPosition (const QPoint &)
 
virtual void stepChange ()
 
virtual void timerEvent (QTimerEvent *e)
 
virtual void wheelEvent (QWheelEvent *e)
 

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 QwtAbstractSlider::ScrollMode [inherited] Scroll mode

See also:
getScrollMode()
 

enum QwtKnob::Symbol Symbol

See also:
QwtKnob::QwtKnob()
 

Constructor & Destructor Documentation

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

Parameters:
parent Parent widget
 

QwtKnob::~QwtKnob () [virtual]

Destructor.

Member Function Documentation

const QwtAbstractScaleDraw * QwtAbstractScale::abstractScaleDraw () const [protected, inherited] Returns:

Scale draw
See also:
setAbstractScaleDraw()
 

QwtAbstractScaleDraw * QwtAbstractScale::abstractScaleDraw () [protected, inherited] Returns:

Scale draw
See also:
setAbstractScaleDraw()
 

bool QwtAbstractScale::autoScale () const [inherited] Returns:

true if autoscaling is enabled
 

int QwtKnob::borderWidth () const

Return the border width.

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

Parameters:
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
 

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 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.
Warning:
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:
setValue()
 
Reimplemented from QwtDoubleRange.

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

Returns:
true if read only
See also:
setReadOnly()
 

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

QwtDblRange::isValid()
 
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
Parameters:
e Key event
See also:
isReadOnly()
 
Reimplemented in QwtCompass, and QwtDial.

int QwtKnob::knobWidth () const

Return the width of the knob.

double QwtAbstractSlider::mass () const [virtual, inherited] Returns:

mass
See also:
setMass()
 
Reimplemented in QwtWheel.

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:
setRange()
 

QSize QwtKnob::minimumSizeHint () const [virtual]

Return a minimum size hint. Warning:
The return value of QwtKnob::minimumSizeHint() depends on the font and the scale.
 

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:
setRange()
 

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

Parameters:
e Mouse event
 

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

Parameters:
e Mouse event
 

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

Parameters:
e Mouse event
 

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

Orientation
See also:
setOrientation()
 

int QwtDoubleRange::pageSize () const [inherited]

Returns the page size in steps.

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

Parameters:
e Paint event
 

bool QwtDoubleRange::periodic () const [inherited]

Returns true if the range is periodic. See also:
setPeriodic()
 

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

Returns the previous value.

void QwtAbstractScale::rescale (doublevmin, doublevmax, doublestepSize = 0.0) [protected, inherited] Recalculate the scale division and update the scale draw.

Parameters:
vmin Lower limit of the scale interval
 
vmax Upper limit of the scale interval
 
stepSize Major step size
See also:
scaleChange()
 

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

const QwtRoundScaleDraw * QwtKnob::scaleDraw () const Returns:

the scale draw of the knob
See also:
setScaleDraw()
 

QwtRoundScaleDraw * QwtKnob::scaleDraw () Returns:

the scale draw of the knob
See also:
setScaleDraw()
 

const QwtScaleEngine * QwtAbstractScale::scaleEngine () const [inherited] Returns:

Scale engine
See also:
setScaleEngine()
 

QwtScaleEngine * QwtAbstractScale::scaleEngine () [inherited] Returns:

Scale engine
See also:
setScaleEngine()
 

const QwtScaleMap & QwtAbstractScale::scaleMap () const [inherited] Returns:

abstractScaleDraw()->scaleMap()
 

int QwtAbstractScale::scaleMaxMajor () const [inherited] Returns:

Max. number of major tick intervals The default value is 5.
 

int QwtAbstractScale::scaleMaxMinor () const [inherited] Returns:

Max. number of minor tick intervals The default value is 3.
 

void QwtAbstractScale::setAbstractScaleDraw (QwtAbstractScaleDraw *scaleDraw) [protected, inherited]

Set a scale draw. scaleDraw has to be created with new and will be deleted in ~QwtAbstractScale or the next call of setAbstractScaleDraw.

void QwtAbstractScale::setAutoScale () [inherited]

Advise the widget to control the scale range internally. Autoscaling is on by default.
See also:
setScale(), autoScale()
 

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.
Parameters:
w New width
 

void QwtAbstractSlider::setMass (doubleval) [virtual, inherited]

Set the slider's mass for flywheel effect. If the slider's mass is greater then 0, it will continue to move after the mouse button has been released. Its speed decreases with time at a rate depending on the slider's mass. A large mass means that it will continue to move for a long time.
Derived widgets may overload this function to make it public.
Parameters:
val New mass in kg
See also:
mass()
 
Reimplemented in QwtWheel.

void QwtAbstractSlider::setOrientation (Qt::Orientationo) [virtual, inherited]

Set the orientation. Parameters:
o Orientation. Allowed values are Qt::Horizontal and Qt::Vertical.
 
Reimplemented in QwtSlider, and QwtWheel.

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.

Parameters:

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
Warning:
•
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.
Parameters:
readOnly Enables in case of true
See also:
isReadOnly()
 

void QwtAbstractScale::setScale (const QwtScaleDiv &scaleDiv) [inherited]

Specify a scale. Disable autoscaling and define a scale by a scale division
Parameters:
scaleDiv Scale division
See also:
setAutoScale()
 

void QwtAbstractScale::setScale (doublevmin, doublevmax, doublestepSize = 0.0) [inherited]

Specify a scale. Disable autoscaling and define a scale by an interval and a step size
Parameters:
vmin lower limit of the scale interval
 
vmax upper limit of the scale interval
 
stepSize major step size
See also:
setAutoScale()
 

void QwtAbstractScale::setScale (const QwtDoubleInterval &interval, doublestepSize = 0.0) [inherited]

Specify a scale. Disable autoscaling and define a scale by an interval and a step size
Parameters:
interval Interval
 
stepSize major step size
See also:
setAutoScale()
 

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:
scaleDraw()
 

void QwtAbstractScale::setScaleEngine (QwtScaleEngine *scaleEngine) [inherited]

Set a scale engine. The scale engine is responsible for calculating the scale division, and in case of auto scaling how to align the scale.
scaleEngine has to be created with new and will be deleted in ~QwtAbstractScale or the next call of setScaleEngine.

void QwtAbstractScale::setScaleMaxMajor (intticks) [inherited]

Set the maximum number of major tick intervals. The scale's major ticks are calculated automatically such that the number of major intervals does not exceed ticks. The default value is 5.
Parameters:
ticks maximal number of major ticks.
See also:
QwtAbstractScaleDraw
 

void QwtAbstractScale::setScaleMaxMinor (intticks) [inherited]

Set the maximum number of minor tick intervals. The scale's minor ticks are calculated automatically such that the number of minor intervals does not exceed ticks. The default value is 3.
Parameters:
ticks
See also:
QwtAbstractScaleDraw
 

void QwtDoubleRange::setStep (doublevstep) [inherited]

Change the step raster. Parameters:
vstep new step width
Warning:
The value will not be adjusted to the new step raster.
 
Reimplemented in QwtCounter.

void QwtKnob::setSymbol (QwtKnob::Symbols)

Set the symbol of the knob. See also:
symbol()
 

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.

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.
Parameters:
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:
getScrollMode()
 

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

valid true/false
See also:
QwtDblRange::isValid()
 
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.
Parameters:
val new value
See also:
fitValue()
 
Reimplemented from QwtDoubleRange.

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

minimumSizeHint()
 

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

Parameters:
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.

QwtKnob::Symbol QwtKnob::symbol () const Returns:

symbol of the knob
See also:
setSymbol()
 

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

Parameters:
e Timer event
 

double QwtKnob::totalAngle () const

Return the total angle.

double QwtDoubleRange::value () const [inherited]

Returns the current value.
Reimplemented in QwtCounter.

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() ).
Parameters:
value new value
 

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

Parameters:
e Whell event
 
 

Author

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