QwtKnob(3)

Qwt User's Guide

QwtKnob(3)

NAME

QwtKnob - The Knob Widget.

SYNOPSIS

#include <qwt_knob.h>

Inherits QwtAbstractSlider.

Public Types

enum KnobStyle { Flat, Raised, Sunken, Styled }
Style of the knob surface. enum MarkerStyle { NoMarker = -1, Tick, Triangle, Dot, Nub, Notch }
Marker type.

Public Member Functions

QwtKnob (QWidget *parent=NULL)
Constructor. virtual ~QwtKnob ()
Destructor. void setAlignment (Qt::Alignment)
Set the alignment of the knob. Qt::Alignment alignment () const
void setKnobWidth (int)
Change the knob's width. int knobWidth () const
Return the width of the knob. void setNumTurns (int)
Set the number of turns. int numTurns () const
void setTotalAngle (double angle)
Set the total angle by which the knob can be turned. double totalAngle () const
void setKnobStyle (KnobStyle)
Set the knob type. KnobStyle knobStyle () const
void setBorderWidth (int)
Set the knob's border width. int borderWidth () const
Return the border width. void setMarkerStyle (MarkerStyle)
Set the marker type of the knob. MarkerStyle markerStyle () const
void setMarkerSize (int)
Set the size of the marker. int markerSize () const
virtual QSize sizeHint () const override
virtual QSize minimumSizeHint () const override
void setScaleDraw (QwtRoundScaleDraw *)
const QwtRoundScaleDraw * scaleDraw () const
QwtRoundScaleDraw * scaleDraw ()
QRect knobRect () const

Protected Member Functions

virtual void paintEvent (QPaintEvent *) override
virtual void changeEvent (QEvent *) override
virtual void drawKnob (QPainter *, const QRectF &) const
Draw the knob. virtual void drawFocusIndicator (QPainter *) const
virtual void drawMarker (QPainter *, const QRectF &, double angle) const
Draw the marker at the knob's front. virtual double scrolledTo (const QPoint &) const override
Determine the value for a new position of the mouse. virtual bool isScrollPosition (const QPoint &) const override
Determine what to do when the user presses a mouse button.

Additional Inherited Members

Detailed Description

The Knob Widget.

The QwtKnob widget imitates look and behavior of a volume knob on a radio. It looks similar to QDial - not to QwtDial.

The value range of a knob might be divided into several turns.

The layout of the knob depends on the knobWidth().

width > 0 The diameter of the knob is fixed and the knob is aligned according to the alignment() flags inside of the contentsRect().
width <= 0 The knob is extended to the minimum of width/height of the contentsRect() and aligned in the other direction according to alignment().

Setting a fixed knobWidth() is helpful to align several knobs with different scale labels.

Definition at line 42 of file qwt_knob.h.

Member Enumeration Documentation

enum QwtKnob::KnobStyle

Style of the knob surface. Depending on the KnobStyle the surface of the knob is filled from the brushes of the widget palette().

See also

setKnobStyle(), knobStyle()

Enumerator

Flat: Fill the knob with a brush from QPalette::Button.
Raised: Build a gradient from QPalette::Midlight and QPalette::Button.
Sunken: Build a gradient from QPalette::Midlight, QPalette::Button and QPalette::Midlight
Styled: Build a radial gradient from QPalette::Button like it is used for QDial in various Qt styles.

Definition at line 66 of file qwt_knob.h.

enum QwtKnob::MarkerStyle

Marker type. The marker indicates the current value on the knob The default setting is a Notch marker.

See also

setMarkerStyle(), setMarkerSize()

Enumerator

NoMarker: Don't paint any marker.
Tick: Paint a single tick in QPalette::ButtonText color.
Triangle: Paint a triangle in QPalette::ButtonText color.
Dot: Paint a circle in QPalette::ButtonText color.
Nub: Draw a raised ellipse with a gradient build from QPalette::Light and QPalette::Mid
Notch: Draw a sunken ellipse with a gradient build from QPalette::Light and QPalette::Mid

Definition at line 95 of file qwt_knob.h.

Constructor & Destructor Documentation

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

Constructor. Construct a knob with an angle of 270°. The style is QwtKnob::Raised and the marker style is QwtKnob::Notch. The width of the knob is set to 50 pixels.

Parameters

parent Parent widget

See also

setTotalAngle()

Definition at line 103 of file qwt_knob.cpp.

Member Function Documentation

Qt::Alignment QwtKnob::alignment () const

Returns

Alignment of the knob inside of contentsRect()

See also

setAlignment(), knobWidth(), knobRect()

Definition at line 743 of file qwt_knob.cpp.

void QwtKnob::changeEvent (QEvent * event) [override], [protected], [virtual]

Handle QEvent::StyleChange and QEvent::FontChange;

Calculate the bounding rectangle of the knob without the scale

isScrollPosition()

Implements QwtAbstractSlider.

Definition at line 373 of file qwt_knob.cpp.

void QwtKnob::setAlignment (Qt::Alignment alignment)

Set the alignment of the knob. Similar to a QLabel::alignment() the flags decide how to align the knob inside of contentsRect().

The default setting is Qt::AlignCenter

Parameters

alignment Or'd alignment flags

See also

alignment(), setKnobWidth(), knobRect()

Definition at line 730 of file qwt_knob.cpp.

void QwtKnob::setBorderWidth (int borderWidth)

Set the knob's border width.

Parameters

borderWidth new border width

Definition at line 790 of file qwt_knob.cpp.

void QwtKnob::setKnobStyle (KnobStyle knobStyle)

Set the knob type.

Parameters

knobStyle Knob type

See also

knobStyle(), setBorderWidth()

Definition at line 131 of file qwt_knob.cpp.

void QwtKnob::setKnobWidth (int width)

Change the knob's width. Setting a fixed value for the diameter of the knob is helpful for aligning several knobs in a row.

Parameters

width New width

See also

knobWidth(), setAlignment()

Note

Modifies the sizePolicy()

Definition at line 759 of file qwt_knob.cpp.

void QwtKnob::setMarkerSize (int size)

Set the size of the marker. When setting a size <= 0 the marker will automatically scaled to 40% of the radius of the knob.

See also

markerSize(), markerStyle()

Definition at line 812 of file qwt_knob.cpp.

void QwtKnob::setMarkerStyle (MarkerStyle markerStyle)

Set the marker type of the knob.

Parameters

markerStyle Marker type

See also

markerStyle(), setMarkerSize()

Definition at line 155 of file qwt_knob.cpp.

void QwtKnob::setNumTurns (int numTurns)

Set the number of turns. When numTurns > 1 the knob can be turned several times around its axis

•: otherwise the total angle is floored to 360°.

See also

numTurns(), totalAngle(), setTotalAngle()

Definition at line 219 of file qwt_knob.cpp.

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()

Definition at line 259 of file qwt_knob.cpp.

void QwtKnob::setTotalAngle (double angle)

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

Parameters

angle Angle in degrees.

The angle has to be between [10, 360] degrees. Angles above 360 ( so that the knob can be turned several times around its axis ) have to be set using setNumTurns().

The default angle is 270 degrees.

See also

totalAngle(), setNumTurns()

Definition at line 185 of file qwt_knob.cpp.

QSize QwtKnob::sizeHint () const [override], [virtual]

Returns

sizeHint()

Definition at line 833 of file qwt_knob.cpp.

double QwtKnob::totalAngle () const

Returns

the total angle

See also

setTotalAngle(), setNumTurns(), numTurns()

Definition at line 205 of file qwt_knob.cpp.

Author

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Sun Jul 18 2021

Version 6.2.0