QAbstractSlider Class

The QAbstractSlider class provides an integer value within a range. More...

Header:	#include <QAbstractSlider>
qmake:	QT += widgets
Inherits:	QWidget
Inherited By:	QDial, QScrollBar, and QSlider

• List of all members, including inherited members

Public Types

enum	SliderAction { SliderNoAction, SliderSingleStepAdd, SliderSingleStepSub, SliderPageStepAdd, SliderPageStepSub, …, SliderMove }

Properties

invertedAppearance : bool invertedControls : bool maximum : int minimum : int orientation : Qt::Orientation pageStep : int

singleStep : int sliderDown : bool sliderPosition : int tracking : bool value : int

Public Functions

	QAbstractSlider(QWidget *parent = nullptr)
virtual	~QAbstractSlider()
bool	hasTracking() const
bool	invertedAppearance() const
bool	invertedControls() const
bool	isSliderDown() const
int	maximum() const
int	minimum() const
Qt::Orientation	orientation() const
int	pageStep() const
void	setInvertedAppearance(bool)
void	setInvertedControls(bool)
void	setMaximum(int)
void	setMinimum(int)
void	setPageStep(int)
void	setSingleStep(int)
void	setSliderDown(bool)
void	setSliderPosition(int)
void	setTracking(bool enable)
int	singleStep() const
int	sliderPosition() const
void	triggerAction(QAbstractSlider::SliderAction action)
int	value() const

Public Slots

void	setOrientation(Qt::Orientation)
void	setRange(int min, int max)
void	setValue(int)

Signals

void	actionTriggered(int action)
void	rangeChanged(int min, int max)
void	sliderMoved(int value)
void	sliderPressed()
void	sliderReleased()
void	valueChanged(int value)

Protected Types

enum	SliderChange { SliderRangeChange, SliderOrientationChange, SliderStepsChange, SliderValueChange }

Protected Functions

QAbstractSlider::SliderAction	repeatAction() const
void	setRepeatAction(QAbstractSlider::SliderAction action, int thresholdTime = 500, int repeatTime = 50)
virtual void	sliderChange(QAbstractSlider::SliderChange change)

Reimplemented Protected Functions

virtual void	changeEvent(QEvent *ev) override
virtual bool	event(QEvent *e) override
virtual void	keyPressEvent(QKeyEvent *ev) override
virtual void	timerEvent(QTimerEvent *e) override
virtual void	wheelEvent(QWheelEvent *e) override

Detailed Description

The class is designed as a common super class for widgets like QScrollBar, QSlider and QDial.

Here are the main properties of the class:

1. value: The bounded integer that QAbstractSlider maintains.
2. minimum: The lowest possible value.
3. maximum: The highest possible value.
4. singleStep: The smaller of two natural steps that an abstract sliders provides and typically corresponds to the user pressing an arrow key.
5. pageStep: The larger of two natural steps that an abstract slider provides and typically corresponds to the user pressing PageUp or PageDown.
6. tracking: Whether slider tracking is enabled.
7. sliderPosition: The current position of the slider. If tracking is enabled (the default), this is identical to value.

Unity (1) may be viewed as a third step size. setValue() lets you set the current value to any integer in the allowed range, not just minimum() + n * singleStep() for integer values of n. Some widgets may allow the user to set any value at all; others may just provide multiples of singleStep() or pageStep().

QAbstractSlider emits a comprehensive set of signals:

Signal	Emitted when
valueChanged()	the value has changed. The tracking determines whether this signal is emitted during user interaction.
sliderPressed()	the user starts to drag the slider.
sliderMoved()	the user drags the slider.
sliderReleased()	the user releases the slider.
actionTriggered()	a slider action was triggerd.
rangeChanged()	a the range has changed.

QAbstractSlider provides a virtual sliderChange() function that is well suited for updating the on-screen representation of sliders. By calling triggerAction(), subclasses trigger slider actions. Two helper functions QStyle::sliderPositionFromValue() and QStyle::sliderValueFromPosition() help subclasses and styles to map screen coordinates to logical range values.

See also QAbstractSpinBox, QSlider, QDial, QScrollBar, and Sliders Example.

Member Type Documentation

enum QAbstractSlider::SliderAction

Constant	Value
QAbstractSlider::SliderNoAction	0
QAbstractSlider::SliderSingleStepAdd	1
QAbstractSlider::SliderSingleStepSub	2
QAbstractSlider::SliderPageStepAdd	3
QAbstractSlider::SliderPageStepSub	4
QAbstractSlider::SliderToMinimum	5
QAbstractSlider::SliderToMaximum	6
QAbstractSlider::SliderMove	7

enum QAbstractSlider::SliderChange

Constant	Value
QAbstractSlider::SliderRangeChange	0
QAbstractSlider::SliderOrientationChange	1
QAbstractSlider::SliderStepsChange	2
QAbstractSlider::SliderValueChange	3

Member Function Documentation

QAbstractSlider::QAbstractSlider(QWidget *parent = nullptr)

Constructs an abstract slider.

The parent argument is sent to the QWidget constructor.

The minimum defaults to 0, the maximum to 99, with a singleStep size of 1 and a pageStep size of 10, and an initial value of 0.

[signal] void QAbstractSlider::actionTriggered(int action)

This signal is emitted when the slider action action is triggered. Actions are SliderSingleStepAdd, SliderSingleStepSub, SliderPageStepAdd, SliderPageStepSub, SliderToMinimum, SliderToMaximum, and SliderMove.

When the signal is emitted, the sliderPosition has been adjusted according to the action, but the value has not yet been propagated (meaning the valueChanged() signal was not yet emitted), and the visual display has not been updated. In slots connected to this signal you can thus safely adjust any action by calling setSliderPosition() yourself, based on both the action and the slider's value.

See also triggerAction().

[signal] void QAbstractSlider::rangeChanged(int min, int max)

This signal is emitted when the slider range has changed, with min being the new minimum, and max being the new maximum.

See also minimum and maximum.

[slot] void QAbstractSlider::setRange(int min, int max)

Sets the slider's minimum to min and its maximum to max.

If max is smaller than min, min becomes the only legal value.

See also minimum and maximum.

[signal] void QAbstractSlider::sliderMoved(int value)

This signal is emitted when sliderDown is true and the slider moves. This usually happens when the user is dragging the slider. The value is the new slider position.

This signal is emitted even when tracking is turned off.

Note: Notifier signal for property sliderPosition.

See also setTracking(), valueChanged(), isSliderDown(), sliderPressed(), and sliderReleased().

[signal] void QAbstractSlider::sliderPressed()

This signal is emitted when the user presses the slider with the mouse, or programmatically when setSliderDown(true) is called.

See also sliderReleased(), sliderMoved(), and isSliderDown().

[signal] void QAbstractSlider::sliderReleased()

This signal is emitted when the user releases the slider with the mouse, or programmatically when setSliderDown(false) is called.

See also sliderPressed(), sliderMoved(), and sliderDown.

[signal] void QAbstractSlider::valueChanged(int value)

This signal is emitted when the slider value has changed, with the new slider value as argument.

Note: Notifier signal for property value.

[virtual] QAbstractSlider::~QAbstractSlider()

Destroys the slider.

[override virtual protected] void QAbstractSlider::changeEvent(QEvent *ev)

Reimplements: QWidget::changeEvent(QEvent *event).

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

Reimplements: QWidget::event(QEvent *event).

[override virtual protected] void QAbstractSlider::keyPressEvent(QKeyEvent *ev)

Reimplements: QWidget::keyPressEvent(QKeyEvent *event).

[protected] QAbstractSlider::SliderAction QAbstractSlider::repeatAction() const

Returns the current repeat action.

See also setRepeatAction().

[protected] void QAbstractSlider::setRepeatAction(QAbstractSlider::SliderAction action, int thresholdTime = 500, int repeatTime = 50)

Sets action action to be triggered repetitively in intervals of repeatTime, after an initial delay of thresholdTime.

See also triggerAction() and repeatAction().

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

Reimplement this virtual function to track slider changes such as SliderRangeChange, SliderOrientationChange, SliderStepsChange, or SliderValueChange. The default implementation only updates the display and ignores the change parameter.

[override virtual protected] void QAbstractSlider::timerEvent(QTimerEvent *e)

Reimplements: QObject::timerEvent(QTimerEvent *event).

void QAbstractSlider::triggerAction(QAbstractSlider::SliderAction action)

Triggers a slider action. Possible actions are SliderSingleStepAdd, SliderSingleStepSub, SliderPageStepAdd, SliderPageStepSub, SliderToMinimum, SliderToMaximum, and SliderMove.

See also actionTriggered().

[override virtual protected] void QAbstractSlider::wheelEvent(QWheelEvent *e)

Reimplements: QWidget::wheelEvent(QWheelEvent *event).