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

QwtKnob - The Knob Widget.

#include <qwt_knob.h>

Inherits QwtAbstractSlider.


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


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
virtual QSize minimumSizeHint () const
void setScaleDraw (QwtRoundScaleDraw *)
const QwtRoundScaleDraw * scaleDraw () const
QwtRoundScaleDraw * scaleDraw ()
QRect knobRect () const


virtual void paintEvent (QPaintEvent *)
virtual void changeEvent (QEvent *)
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
Determine the value for a new position of the mouse. virtual bool isScrollPosition (const QPoint &) const
Determine what to do when the user presses a mouse button.

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().

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

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

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

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

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

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()

Returns:

Alignment of the knob inside of contentsRect()

See also:

setAlignment(), knobWidth(), knobRect()

Handle QEvent::StyleChange and QEvent::FontChange;

Parameters:

event Change event

Draw the focus indicator

Parameters:

painter Painter

Draw the knob.

Parameters:

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

Draw the marker at the knob's front.

Parameters:

painter Painter
rect Bounding rectangle of the knob without scale
angle Angle of the marker in degrees ( clockwise, 0 at the 12 o'clock position )

Determine what to do when the user presses a mouse button.

Parameters:

pos Mouse position

Return values:

True,when pos is inside the circle of the knob.

See also:

scrolledTo()

Implements QwtAbstractSlider.

Calculate the bounding rectangle of the knob without the scale

Returns:

Bounding rectangle of the knob

See also:

knobWidth(), alignment(), QWidget::contentsRect()

QwtKnob::KnobStyle QwtKnob::knobStyle () const

Returns:

Marker type of the knob

See also:

setKnobStyle(), setBorderWidth()

Returns:

Marker size

See also:

setMarkerSize()

QwtKnob::MarkerStyle QwtKnob::markerStyle () const

Returns:

Marker type of the knob

See also:

setMarkerStyle(), setMarkerSize()

Returns:

Minimum size hint

See also:

sizeHint()

Returns:

Number of turns.

When the total angle is below 360° numTurns() is ceiled to 1.

See also:

setNumTurns(), setTotalAngle(), totalAngle()

Repaint the knob

Parameters:

event Paint event

Returns:

the scale draw of the knob

See also:

setScaleDraw()

QwtRoundScaleDraw * QwtKnob::scaleDraw ()

Returns:

the scale draw of the knob

See also:

setScaleDraw()

Determine the value for a new position of the mouse.

Parameters:

pos Mouse position

Returns:

Value for the mouse position

See also:

isScrollPosition()

Implements QwtAbstractSlider.

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()

Set the knob's border width.

Parameters:

borderWidth new border width

Set the knob type.

Parameters:

knobStyle Knob type

See also:

knobStyle(), setBorderWidth()

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()

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()

Set the marker type of the knob.

Parameters:

markerStyle Marker type

See also:

markerStyle(), setMarkerSize()

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()

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()

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()

Returns:

sizeHint()

Returns:

the total angle

See also:

setTotalAngle(), setNumTurns(), numTurns()

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Wed Jan 2 2019 Version 6.1.4