QDial Class

The QDial class provides a rounded range control (like a speedometer or potentiometer). More...

Header:	#include <QDial>
CMake:	find_package(Qt6 COMPONENTS Widgets REQUIRED) target_link_libraries(mytarget PRIVATE Qt6::Widgets)
qmake:	QT += widgets
Inherits:	QAbstractSlider

• List of all members, including inherited members

Properties

• notchSize : const int
• notchTarget : qreal
• notchesVisible : bool
• wrapping : bool

Public Functions

	QDial(QWidget *parent = nullptr)
virtual	~QDial()
int	notchSize() const
qreal	notchTarget() const
bool	notchesVisible() const
void	setNotchTarget(double target)
bool	wrapping() const

Reimplemented Public Functions

virtual QSize	minimumSizeHint() const override
virtual QSize	sizeHint() const override

Public Slots

void	setNotchesVisible(bool visible)
void	setWrapping(bool on)

Protected Functions

virtual void

initStyleOption(QStyleOptionSlider *option) const

Reimplemented Protected Functions

virtual bool	event(QEvent *e) override
virtual void	mouseMoveEvent(QMouseEvent *e) override
virtual void	mousePressEvent(QMouseEvent *e) override
virtual void	mouseReleaseEvent(QMouseEvent *e) override
virtual void	paintEvent(QPaintEvent *pe) override
virtual void	resizeEvent(QResizeEvent *e) override
virtual void	sliderChange(QAbstractSlider::SliderChange change) override

Detailed Description

QDial is used when the user needs to control a value within a program-definable range, and the range either wraps around (for example, with angles measured from 0 to 359 degrees) or the dialog layout needs a square widget.

Since QDial inherits from QAbstractSlider, the dial behaves in a similar way to a slider. When wrapping() is false (the default setting) there is no real difference between a slider and a dial. They both share the same signals, slots and member functions. Which one you use depends on the expectations of your users and on the type of application.

The dial initially emits valueChanged() signals continuously while the slider is being moved; you can make it emit the signal less often by disabling the tracking property. The sliderMoved() signal is emitted continuously even when tracking is disabled.

The dial also emits sliderPressed() and sliderReleased() signals when the mouse button is pressed and released. Note that the dial's value can change without these signals being emitted since the keyboard and wheel can also be used to change the value.

Unlike the slider, QDial attempts to draw a "nice" number of notches rather than one per line step. If possible, the number of notches drawn is one per line step, but if there aren't enough pixels to draw every one, QDial will skip notches to try and draw a uniform set (e.g. by drawing every second or third notch).

Like the slider, the dial makes the QAbstractSlider function setValue() available as a slot.

The dial's keyboard interface is fairly simple: The left/up and right/down arrow keys adjust the dial's value by the defined singleStep, Page Up and Page Down by the defined pageStep, and the Home and End keys set the value to the defined minimum and maximum values.

If you are using the mouse wheel to adjust the dial, the increment value is determined by the lesser value of wheelScrollLines multiplied by singleStep, and pageStep.

See also QScrollBar, QSpinBox, QSlider, GUI Design Handbook: Slider, and Sliders Example.

Member Function Documentation

QDial::QDial(QWidget *parent = nullptr)

Constructs a dial.

The parent argument is sent to the QAbstractSlider constructor.

[virtual] QDial::~QDial()

Destroys the dial.

[override virtual protected] bool QDial::event(QEvent *e)

Reimplements: QAbstractSlider::event(QEvent *e).

[virtual protected] void QDial::initStyleOption(QStyleOptionSlider *option) const

Initialize option with the values from this QDial. This method is useful for subclasses when they need a QStyleOptionSlider, but don't want to fill in all the information themselves.

See also QStyleOption::initFrom().

[override virtual] QSize QDial::minimumSizeHint() const

Reimplements an access function for property: QWidget::minimumSizeHint.

[override virtual protected] void QDial::mouseMoveEvent(QMouseEvent *e)

Reimplements: QWidget::mouseMoveEvent(QMouseEvent *event).

[override virtual protected] void QDial::mousePressEvent(QMouseEvent *e)

Reimplements: QWidget::mousePressEvent(QMouseEvent *event).

[override virtual protected] void QDial::mouseReleaseEvent(QMouseEvent *e)

Reimplements: QWidget::mouseReleaseEvent(QMouseEvent *event).

[override virtual protected] void QDial::paintEvent(QPaintEvent *pe)

Reimplements: QWidget::paintEvent(QPaintEvent *event).

[override virtual protected] void QDial::resizeEvent(QResizeEvent *e)

Reimplements: QWidget::resizeEvent(QResizeEvent *event).

[override virtual] QSize QDial::sizeHint() const

Reimplements an access function for property: QWidget::sizeHint.

[override virtual protected] void QDial::sliderChange(QAbstractSlider::SliderChange change)

Reimplements: QAbstractSlider::sliderChange(QAbstractSlider::SliderChange change).