Qwt User's Guide 6.0.1

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# QwtAbstractSlider Class Reference

An abstract base class for slider widgets. More...

`#include <qwt_abstract_slider.h>`

Inheritance diagram for QwtAbstractSlider:
[legend]

List of all members.

## Public Types
enum | ScrollMode { ScrNone, ScrMouse, ScrTimer, ScrDirect, ScrPage }
## Public Slots
virtual void | fitValue (double val)
virtual void | incValue (int steps)
virtual void | setReadOnly (bool)
virtual void | setValue (double val)
## Signals
void | sliderMoved (double value)
void | sliderPressed ()
void | sliderReleased ()
void | valueChanged (double value)
## Public Member Functions
virtual void | incPages (int)
bool | isReadOnly () const
bool | isValid () const
virtual double | mass () const
double | maxValue () const
double | minValue () const
Qt::Orientation | orientation () const
int | pageSize () const
bool | periodic () const
| QwtAbstractSlider (Qt::Orientation, QWidget *parent=NULL)
virtual void | setMass (double val)
virtual void | setOrientation (Qt::Orientation o)
void | setPeriodic (bool tf)
void | setRange (double vmin, double vmax, double vstep=0.0, int pagesize=1)
void | setStep (double)
void | setTracking (bool enable)
void | setUpdateTime (int t)
void | setValid (bool valid)
double | step () const
void | stopMoving ()
double | value () const
virtual | ~QwtAbstractSlider ()
## Protected Member Functions
double | exactPrevValue () const
double | exactValue () const
virtual void | getScrollMode (const QPoint &pos, ScrollMode &scrollMode, int &direction) const =0
virtual double | getValue (const QPoint &p)=0
virtual void | keyPressEvent (QKeyEvent *e)
virtual void | mouseMoveEvent (QMouseEvent *e)
double | mouseOffset () const
virtual void | mousePressEvent (QMouseEvent *e)
virtual void | mouseReleaseEvent (QMouseEvent *e)
double | prevValue () const
virtual void | rangeChange ()
int | scrollMode () const
void | setMouseOffset (double)
virtual void | setPosition (const QPoint &)
virtual void | stepChange ()
virtual void | timerEvent (QTimerEvent *e)
virtual void | valueChange ()
virtual void | wheelEvent (QWheelEvent *e)

## Detailed Description

An abstract base class for slider widgets.

QwtAbstractSlider is a base class for slider widgets. It handles mouse events and updates the slider's value accordingly. Derived classes only have to implement the getValue() and getScrollMode() members, and should react to a valueChange(), which normally requires repainting.

## Member Enumeration Documentation

enum QwtAbstractSlider::ScrollMode

Scroll mode

See also:
  getScrollMode()

Enumerator:

  ScrNone | Scrolling switched off. Don't change the value.
  ScrMouse | Change the value while the user keeps the button pressed and moves the mouse.
  ScrTimer | Automatic scrolling. Increment the value in the specified direction as long as the user keeps the button pressed.
  ScrPage | Automatic scrolling. Same as ScrTimer, but increment by page size.

## Constructor & Destructor Documentation

QwtAbstractSlider::QwtAbstractSlider | ( | Qt::Orientation | orientation,
|  | QWidget * | parent = `NULL`
| ) |  | `[explicit]`

Constructor.

Parameters:

  orientation | Orientation
  parent | Parent widget

QwtAbstractSlider::~QwtAbstractSlider | ( |  | ) | `[virtual]`

Destructor.

## Member Function Documentation

double QwtDoubleRange::exactPrevValue | ( |  | ) | const`[protected, inherited]`

Returns the exact previous value.

double QwtDoubleRange::exactValue | ( |  | ) | const`[protected, inherited]`

Returns the exact value.

The exact value is the value which QwtDoubleRange::value would return if the value were not adjusted to the step raster. It differs from the current value only if fitValue() or incValue() have been used before. This function is intended for internal use in derived classes.

void QwtAbstractSlider::fitValue | ( | double | value | ) | `[virtual, slot]`

Set the slider's value to the nearest integer multiple of the step size.

Parameters:

  value | Value

See also:
  setValue(), incValue()

Reimplemented from QwtDoubleRange.

virtual void QwtAbstractSlider::getScrollMode | ( | const QPoint & | pos,
|  | ScrollMode & | scrollMode,
|  | int & | direction
| ) |  | const`[protected, pure virtual]`

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

This function is abstract and has to be implemented by derived classes. It is called on a mousePress event. The derived class can determine what should happen next in dependence of the position where the mouse was pressed by returning scrolling mode and direction.

Parameters:

  pos | point where the mouse was pressed

Return values:

  scrollMode | The scrolling mode
  direction | direction: 1, 0, or -1.

Implemented in QwtDial, QwtKnob, QwtSlider, and QwtWheel.

virtual double QwtAbstractSlider::getValue | ( | const QPoint & | p | ) | `[protected, pure virtual]`

Determine the value corresponding to a specified poind.

This is an abstract virtual function which is called when the user presses or releases a mouse button or moves the mouse. It has to be implemented by the derived class.

Parameters:

  p | point

Implemented in QwtDial, QwtKnob, QwtSlider, and QwtWheel.

void QwtDoubleRange::incPages | ( | int | nPages | ) | `[virtual, inherited]`

Increment the value by a specified number of pages.

Parameters:

  nPages | Number of pages to increment. A negative number decrements the value.

Warning:
  The Page size is specified in the constructor.

void QwtAbstractSlider::incValue | ( | int | steps | ) | `[virtual, slot]`

Increment the value by a specified number of steps.

Parameters:

  steps | number of steps

See also:
  setValue()

Reimplemented from QwtDoubleRange.

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()

bool QwtAbstractSlider::isValid | ( |  | ) | const`[inline]`

See also:
  QwtDblRange::isValid()

Reimplemented from QwtDoubleRange.

void QwtAbstractSlider::keyPressEvent | ( | QKeyEvent * | e | ) | `[protected, virtual]`

Handles key events

- Key_Down, KeyLeft
  Decrement by 1
- Key_Up, Key_Right
  Increment by 1

Parameters:

  e | Key event

See also:
  isReadOnly()

Reimplemented in QwtCompass, and QwtDial.

double QwtAbstractSlider::mass | ( |  | ) | const`[virtual]`

Returns:
  mass

See also:
  setMass()

Reimplemented in QwtWheel.

double QwtDoubleRange::maxValue | ( |  | ) | const`[inherited]`

Returns the value of the second border of the range.

maxValue returns the value which has been specified as the second parameter in QwtDoubleRange::setRange.

See also:
  setRange()

Reimplemented in QwtCounter.

double QwtDoubleRange::minValue | ( |  | ) | const`[inherited]`

Returns the value at the first border of the range.

minValue returns the value which has been specified as the first parameter in setRange().

See also:
  setRange()

Reimplemented in QwtCounter.

void QwtAbstractSlider::mouseMoveEvent | ( | QMouseEvent * | e | ) | `[protected, virtual]`

Mouse Move Event handler

Parameters:

  e | Mouse event

double QwtAbstractSlider::mouseOffset | ( |  | ) | const`[protected]`

See also:
  setMouseOffset()

void QwtAbstractSlider::mousePressEvent | ( | QMouseEvent * | e | ) | `[protected, virtual]`

Mouse press event handler

Parameters:

  e | Mouse event

void QwtAbstractSlider::mouseReleaseEvent | ( | QMouseEvent * | e | ) | `[protected, virtual]`

Mouse Release Event handler

Parameters:

  e | Mouse event

Qt::Orientation QwtAbstractSlider::orientation | ( |  | ) | const

Returns:
  Orientation

See also:
  setOrientation()

int QwtDoubleRange::pageSize | ( |  | ) | const`[inherited]`

Returns the page size in steps.

bool QwtDoubleRange::periodic | ( |  | ) | const`[inherited]`

Returns true if the range is periodic.

See also:
  setPeriodic()

double QwtDoubleRange::prevValue | ( |  | ) | const`[protected, inherited]`

Returns the previous value.

void QwtDoubleRange::rangeChange | ( |  | ) | `[protected, virtual, inherited]`

Notify a change of the range.

This virtual function is called whenever the range changes. The default implementation does nothing.

Reimplemented in QwtCounter, QwtDial, and QwtSlider.

int QwtAbstractSlider::scrollMode | ( |  | ) | const`[protected]`

sa ScrollMode

void QwtAbstractSlider::setMass | ( | double | val | ) | `[virtual]`

Set the slider's mass for flywheel effect.

If the slider's mass is greater then 0, it will continue to move after the mouse button has been released. Its speed decreases with time at a rate depending on the slider's mass. A large mass means that it will continue to move for a long time.

Derived widgets may overload this function to make it public.

Parameters:

  val | New mass in kg

See also:
  mass()

Reimplemented in QwtWheel.

void QwtAbstractSlider::setMouseOffset | ( | double | offset | ) | `[protected]`

See also:
  mouseOffset()

void QwtAbstractSlider::setOrientation | ( | Qt::Orientation | o | ) | `[virtual]`

Set the orientation.

Parameters:

  o | Orientation. Allowed values are Qt::Horizontal and Qt::Vertical.

Reimplemented in QwtSlider, and QwtWheel.

void QwtDoubleRange::setPeriodic | ( | bool | tf | ) | `[inherited]`

Make the range periodic.

When the range is periodic, the value will be set to a point inside the interval such that

    point = value + n * width

if the user tries to set a new value which is outside the range. If the range is nonperiodic (the default), values outside the range will be clipped.

Parameters:

  tf | true for a periodic range

void QwtAbstractSlider::setPosition | ( | const QPoint & | p | ) | `[protected, virtual]`

Move the slider to a specified point, adjust the value and emit signals if necessary.

void QwtDoubleRange::setRange | ( | double | vmin,
|  | double | vmax,
|  | double | vstep = `0.0`,
|  | int | pageSize = `1`
| ) |  | `[inherited]`

Specify range and step size.

Parameters:

  vmin | lower boundary of the interval
  vmax | higher boundary of the interval
  vstep | step width
  pageSize | page size in steps

Warning:
  - A change of the range changes the value if it lies outside the new range. The current value will *not* be adjusted to the new step raster.
  - vmax < vmin is allowed.
  - If the step size is left out or set to zero, it will be set to 1/100 of the interval length.
  - If the step size has an absurd value, it will be corrected to a better one.

void QwtAbstractSlider::setReadOnly | ( | bool | readOnly | ) | `[virtual, slot]`

En/Disable read only mode

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

Parameters:

  readOnly | Enables in case of true

See also:
  isReadOnly()

void QwtDoubleRange::setStep | ( | double | vstep | ) | `[inherited]`

Change the step raster.

Parameters:

  vstep | new step width

Warning:
  The value will not be adjusted to the new step raster.

Reimplemented in QwtCounter.

void QwtAbstractSlider::setTracking | ( | bool | enable | ) |

Enables or disables tracking.

If tracking is enabled, the slider emits a valueChanged() signal whenever its value changes (the default behaviour). If tracking is disabled, the value changed() signal will only be emitted if:

- the user releases the mouse button and the value has changed or
- at the end of automatic scrolling.

Tracking is enabled by default.

Parameters:

  enable | `true` (enable) or `false` (disable) tracking.

void QwtAbstractSlider::setUpdateTime | ( | int | t | ) |

Specify the update interval for automatic scrolling.

Parameters:

  t | update interval in milliseconds

See also:
  getScrollMode()

void QwtAbstractSlider::setValid | ( | bool | valid | ) | `[inline]`

Parameters:

  valid | true/false

See also:
  QwtDblRange::isValid()

Reimplemented from QwtDoubleRange.

void QwtAbstractSlider::setValue | ( | double | val | ) | `[virtual, slot]`

Move the slider to a specified value.

This function can be used to move the slider to a value which is not an integer multiple of the step size.

Parameters:

  val | new value

See also:
  fitValue()

Reimplemented from QwtDoubleRange.

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

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

Parameters:

  value | new value

void QwtAbstractSlider::sliderPressed | ( |  | ) | `[signal]`

This signal is emitted when the user presses the movable part of the slider (start ScrMouse Mode).

void QwtAbstractSlider::sliderReleased | ( |  | ) | `[signal]`

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

double QwtDoubleRange::step | ( |  | ) | const`[inherited]`

Returns:
  the step size

See also:
  setStep(), setRange()

Reimplemented in QwtCounter.

void QwtDoubleRange::stepChange | ( |  | ) | `[protected, virtual, inherited]`

Notify a change of the step size.

This virtual function is called whenever the step size changes. The default implementation does nothing.

void QwtAbstractSlider::stopMoving | ( |  | ) |

Stop updating if automatic scrolling is active.

void QwtAbstractSlider::timerEvent | ( | QTimerEvent * | e | ) | `[protected, virtual]`

Qt timer event

Parameters:

  e | Timer event

double QwtDoubleRange::value | ( |  | ) | const`[inherited]`

Returns the current value.

Reimplemented in QwtCounter.

void QwtAbstractSlider::valueChange | ( |  | ) | `[protected, virtual]`

Notify change of value

This function can be reimplemented by derived classes in order to keep track of changes, i.e. repaint the widget. The default implementation emits a valueChanged() signal if tracking is enabled.

Reimplemented from QwtDoubleRange.

Reimplemented in QwtDial, QwtSlider, and QwtWheel.

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

Notify a change of value.

In the default setting (tracking enabled), this signal will be emitted every time the value changes ( see setTracking() ).

Parameters:

  value | new value

void QwtAbstractSlider::wheelEvent | ( | QWheelEvent * | e | ) | `[protected, virtual]`

Wheel Event handler

Parameters:

  e | Whell event