QwtAbstractSlider - Man Page

An abstract base class for slider widgets with a scale.

Synopsis

#include <qwt_abstract_slider.h>

Inherits QwtAbstractScale.

Inherited by QwtDial, QwtKnob, and QwtSlider.

Public Slots

void setValue (double value)

Signals

void valueChanged (double value)
Notify a change of value.
void sliderPressed ()
void sliderReleased ()
void sliderMoved (double value)

Public Member Functions

QwtAbstractSlider (QWidget *parent=NULL)
Constructor.
virtual ~QwtAbstractSlider ()
Destructor.
void setValid (bool)
bool isValid () const
double value () const
Returns the current value.
void setWrapping (bool)
bool wrapping () const
void setTotalSteps (uint)
Set the number of steps.
uint totalSteps () const
void setSingleSteps (uint)
Set the number of steps for a single increment.
uint singleSteps () const
void setPageSteps (uint)
Set the number of steps for a page increment.
uint pageSteps () const
void setStepAlignment (bool)
Enable step alignment.
bool stepAlignment () const
void setTracking (bool)
Enables or disables tracking.
bool isTracking () const
void setReadOnly (bool)
bool isReadOnly () const
void setInvertedControls (bool)
bool invertedControls () const

Protected Member Functions

virtual void mousePressEvent (QMouseEvent *)
virtual void mouseReleaseEvent (QMouseEvent *)
virtual void mouseMoveEvent (QMouseEvent *)
virtual void keyPressEvent (QKeyEvent *)
virtual void wheelEvent (QWheelEvent *)
virtual bool isScrollPosition (const QPoint &pos) const =0
Determine what to do when the user presses a mouse button.
virtual double scrolledTo (const QPoint &pos) const =0
Determine the value for a new position of the movable part of the slider.
void incrementValue (int stepCount)
virtual void scaleChange ()
virtual void sliderChange ()
Calling update()
double incrementedValue (double value, int stepCount) const

Detailed Description

An abstract base class for slider widgets with a scale.

A slider widget displays a value according to a scale. The class is designed as a common super class for widgets like QwtKnob, QwtDial and QwtSlider.

When the slider is nor readOnly() its value can be modified by keyboard, mouse and wheel inputs.

The range of the slider is divided into a number of steps from which the value increments according to user inputs depend. Only for linear scales the number of steps correspond with a fixed step size.

Constructor & Destructor Documentation

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

Constructor. The scale is initialized to [0.0, 100.0], the number of steps is set to 100 with 1 and 10 and single an page step sizes. Step alignment is enabled.

The initial value is invalid.

Parameters

parent Parent widget

Member Function Documentation

double QwtAbstractSlider::incrementedValue (double value, int stepCount) const [protected]

Increment a value

Parameters

value Value
stepCount Number of steps

Returns

Incremented value

void QwtAbstractSlider::incrementValue (int stepCount) [protected]

Increment the slider

The step size depends on the number of totalSteps()

Parameters

stepCount Number of steps

See also

setTotalSteps(), incrementedValue()

bool QwtAbstractSlider::invertedControls () const

Returns

True, when the controls are inverted

See also

setInvertedControls()

bool QwtAbstractSlider::isReadOnly () const

In read only mode the slider can't be controlled by mouse or keyboard.

Returns

true if read only

See also

setReadOnly()

virtual bool QwtAbstractSlider::isScrollPosition (const QPoint & pos) const [protected], [pure virtual]

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

Parameters

pos Mouse position

Return values

True,when pos is a valid scroll position

See also

scrolledTo()

Implemented in QwtKnob, QwtDial, and QwtSlider.

bool QwtAbstractSlider::isTracking () const

Returns

True, when tracking has been enabled

See also

setTracking()

bool QwtAbstractSlider::isValid () const

Returns

True, when the value is invalid

void QwtAbstractSlider::keyPressEvent (QKeyEvent * event) [protected], [virtual]

Handles key events

QwtAbstractSlider handles the following keys:

  • Qt::Key_Left
    Add/Subtract singleSteps() in direction to lowerBound();
  • Qt::Key_Right
    Add/Subtract singleSteps() in direction to upperBound();
  • Qt::Key_Down
    Subtract singleSteps(), when invertedControls() is false
  • Qt::Key_Up
    Add singleSteps(), when invertedControls() is false
  • Qt::Key_PageDown
    Subtract pageSteps(), when invertedControls() is false
  • Qt::Key_PageUp
    Add pageSteps(), when invertedControls() is false
  • Qt::Key_Home
    Set the value to the minimum()
  • Qt::Key_End
    Set the value to the maximum()
Parameters

event Key event

See also

isReadOnly()

Reimplemented in QwtCompass.

void QwtAbstractSlider::mouseMoveEvent (QMouseEvent * event) [protected], [virtual]

Mouse Move Event handler

Parameters

event Mouse event

void QwtAbstractSlider::mousePressEvent (QMouseEvent * event) [protected], [virtual]

Mouse press event handler

Parameters

event Mouse event

Reimplemented in QwtSlider.

void QwtAbstractSlider::mouseReleaseEvent (QMouseEvent * event) [protected], [virtual]

Mouse Release Event handler

Parameters

event Mouse event

Reimplemented in QwtSlider.

uint QwtAbstractSlider::pageSteps () const

Returns

Number of steps

See also

setPageSteps(), totalSteps(), singleSteps()

void QwtAbstractSlider::scaleChange () [protected], [virtual]

Update the slider according to modifications of the scale

Reimplemented from QwtAbstractScale.

Reimplemented in QwtDial, and QwtSlider.

virtual double QwtAbstractSlider::scrolledTo (const QPoint & pos) const [protected], [pure virtual]

Determine the value for a new position of the movable part of the slider.

Parameters

pos Mouse position

Returns

Value for the mouse position

See also

isScrollPosition()

Implemented in QwtKnob, QwtDial, and QwtSlider.

void QwtAbstractSlider::setInvertedControls (bool on)

Invert wheel and key events

Usually scrolling the mouse wheel 'up' and using keys like page up will increase the slider's value towards its maximum. When invertedControls() is enabled the value is scrolled towards its minimum.

Inverting the controls might be f.e. useful for a vertical slider with an inverted scale ( decreasing from top to bottom ).

Parameters

on Invert controls, when true

See also

invertedControls(), keyEvent(), wheelEvent()

void QwtAbstractSlider::setPageSteps (uint stepCount)

Set the number of steps for a page increment. The range of the slider is divided into a number of steps from which the value increments according to user inputs depend.

Parameters

stepCount Number of steps

See also

pageSteps(), setTotalSteps(), setSingleSteps()

void QwtAbstractSlider::setReadOnly (bool on)

En/Disable read only mode

In read only mode the slider can't be controlled by mouse or keyboard.

Parameters

on Enables in case of true

See also

isReadOnly()

Warning

The focus policy is set to Qt::StrongFocus or Qt::NoFocus

void QwtAbstractSlider::setSingleSteps (uint stepCount)

Set the number of steps for a single increment. The range of the slider is divided into a number of steps from which the value increments according to user inputs depend.

Parameters

stepCount Number of steps

See also

singleSteps(), setTotalSteps(), setPageSteps()

void QwtAbstractSlider::setStepAlignment (bool on)

Enable step alignment. When step alignment is enabled values resulting from slider movements are aligned to the step size.

Parameters

on Enable step alignment when true

See also

stepAlignment()

void QwtAbstractSlider::setTotalSteps (uint stepCount)

Set the number of steps. The range of the slider is divided into a number of steps from which the value increments according to user inputs depend.

The default setting is 100.

Parameters

stepCount Number of steps

See also

totalSteps(), setSingleSteps(), setPageSteps()

void QwtAbstractSlider::setTracking (bool on)

Enables or disables tracking. If tracking is enabled, the slider emits the valueChanged() signal while the movable part of the slider is being dragged. If tracking is disabled, the slider emits the valueChanged() signal only when the user releases the slider.

Tracking is enabled by default.

Parameters

on true (enable) or false (disable) tracking.

See also

isTracking(), sliderMoved()

void QwtAbstractSlider::setValid (bool on)

Set the value to be valid/invalid

Parameters

on When true, the value is invalidated

See also

setValue()

void QwtAbstractSlider::setValue (double value) [slot]

Set the slider to the specified value

Parameters

value New value

See also

setValid(), sliderChange(), valueChanged()

void QwtAbstractSlider::setWrapping (bool on)

If wrapping is true stepping up from upperBound() value will take you to the minimum() value and vice versa.

Parameters

on En/Disable wrapping

See also

wrapping()

uint QwtAbstractSlider::singleSteps () const

Returns

Number of steps

See also

setSingleSteps(), totalSteps(), pageSteps()

void QwtAbstractSlider::sliderMoved (double value) [signal]

This signal is emitted when the user moves the slider with the mouse.

Parameters

value New value

See also

valueChanged()

void QwtAbstractSlider::sliderPressed () [signal]

This signal is emitted when the user presses the movable part of the slider.

void QwtAbstractSlider::sliderReleased () [signal]

This signal is emitted when the user releases the movable part of the slider.

bool QwtAbstractSlider::stepAlignment () const

Returns

True, when step alignment is enabled

See also

setStepAlignment()

uint QwtAbstractSlider::totalSteps () const

Returns

Number of steps

See also

setTotalSteps(), singleSteps(), pageSteps()

void QwtAbstractSlider::valueChanged (double value) [signal]

Notify a change of value. When tracking is enabled (default setting), this signal will be emitted every time the value changes.

Parameters

value New value

See also

setTracking(), sliderMoved()

void QwtAbstractSlider::wheelEvent (QWheelEvent * event) [protected], [virtual]

Wheel Event handler

In/decreases the value by s number of steps. The direction depends on the invertedControls() property.

When the control or shift modifier is pressed the wheel delta ( divided by 120 ) is mapped to an increment according to pageSteps(). Otherwise it is mapped to singleSteps().

Parameters

event Wheel event

Reimplemented in QwtDial.

bool QwtAbstractSlider::wrapping () const

Returns

True, when wrapping is set

See also

setWrapping()

Author

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Info

Mon Jun 1 2020 Version 6.1.5 Qwt User's Guide