Qwt User's Guide 6.1.1

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QwtPicker Class Reference

QwtPicker provides selections on a widget. More...

`#include <qwt_picker.h>`

Inheritance diagram for QwtPicker:
[legend]

## Public Types
enum | RubberBand { NoRubberBand = 0, HLineRubberBand, VLineRubberBand, CrossRubberBand, RectRubberBand, EllipseRubberBand, PolygonRubberBand, UserRubberBand = 100 }
enum | DisplayMode { AlwaysOff, AlwaysOn, ActiveOnly }
| Display mode. More...
enum | ResizeMode { Stretch, KeepSize }
Public Types inherited from QwtEventPattern
enum | MousePatternCode { MouseSelect1, MouseSelect2, MouseSelect3, MouseSelect4, MouseSelect5, MouseSelect6, MousePatternCount }
| Symbolic mouse input codes. More...
enum | KeyPatternCode { KeySelect1, KeySelect2, KeyAbort, KeyLeft, KeyRight, KeyUp, KeyDown, KeyRedo, KeyUndo, KeyHome, KeyPatternCount }
| Symbolic keyboard input codes. More...

## Public Slots
void | setEnabled (bool)
| En/disable the picker. More...

## Signals
void | activated (bool on)
void | selected (const QPolygon &polygon)
void | appended (const QPoint &pos)
void | moved (const QPoint &pos)
void | removed (const QPoint &pos)
void | changed (const QPolygon &selection)

## Public Member Functions
| QwtPicker (QWidget *parent)
| QwtPicker (RubberBand rubberBand, DisplayMode trackerMode, QWidget *)
virtual | ~QwtPicker ()
| Destructor.
void | setStateMachine (QwtPickerMachine *)
const QwtPickerMachine * | stateMachine () const
QwtPickerMachine * | stateMachine ()
void | setRubberBand (RubberBand)
RubberBand | rubberBand () const
void | setTrackerMode (DisplayMode)
| Set the display mode of the tracker. More...
DisplayMode | trackerMode () const
void | setResizeMode (ResizeMode)
| Set the resize mode. More...
ResizeMode | resizeMode () const
void | setRubberBandPen (const QPen &)
QPen | rubberBandPen () const
void | setTrackerPen (const QPen &)
QPen | trackerPen () const
void | setTrackerFont (const QFont &)
QFont | trackerFont () const
bool | isEnabled () const
bool | isActive () const
virtual bool | eventFilter (QObject *, QEvent *)
| Event filter. More...
QWidget * | parentWidget ()
| Return the parent widget, where the selection happens.
const QWidget * | parentWidget () const
| Return the parent widget, where the selection happens.
virtual QPainterPath | pickArea () const
virtual void | drawRubberBand (QPainter *) const
virtual void | drawTracker (QPainter *) const
virtual QRegion | rubberBandMask () const
virtual QwtText | trackerText (const QPoint &pos) const
| Return the label for a position. More...
QPoint | trackerPosition () const
virtual QRect | trackerRect (const QFont &) const
QPolygon | selection () const
Public Member Functions inherited from QwtEventPattern
| QwtEventPattern ()
virtual | ~QwtEventPattern ()
| Destructor.
void | initMousePattern (int numButtons)
void | initKeyPattern ()
void | setMousePattern (MousePatternCode, Qt::MouseButton button, Qt::KeyboardModifiers=Qt::NoModifier)
void | setKeyPattern (KeyPatternCode, int keyCode, Qt::KeyboardModifiers modifierCodes=Qt::NoModifier)
void | setMousePattern (const QVector< MousePattern > &)
| Change the mouse event patterns.
void | setKeyPattern (const QVector< KeyPattern > &)
| Change the key event patterns.
const QVector< MousePattern > & | mousePattern () const
const QVector< KeyPattern > & | keyPattern () const
QVector< MousePattern > & | mousePattern ()
QVector< KeyPattern > & | keyPattern ()
bool | mouseMatch (MousePatternCode, const QMouseEvent *) const
| Compare a mouse event with an event pattern. More...
bool | keyMatch (KeyPatternCode, const QKeyEvent *) const
| Compare a key event with an event pattern. More...

## Protected Member Functions
virtual QPolygon | adjustedPoints (const QPolygon &) const
| Map the pickedPoints() into a selection() More...
virtual void | transition (const QEvent *)
virtual void | begin ()
virtual void | append (const QPoint &)
virtual void | move (const QPoint &)
virtual void | remove ()
virtual bool | end (bool ok=true)
| Close a selection setting the state to inactive. More...
virtual bool | accept (QPolygon &) const
| Validate and fix up the selection. More...
virtual void | reset ()
virtual void | widgetMousePressEvent (QMouseEvent *)
virtual void | widgetMouseReleaseEvent (QMouseEvent *)
virtual void | widgetMouseDoubleClickEvent (QMouseEvent *)
virtual void | widgetMouseMoveEvent (QMouseEvent *)
virtual void | widgetWheelEvent (QWheelEvent *)
virtual void | widgetKeyPressEvent (QKeyEvent *)
virtual void | widgetKeyReleaseEvent (QKeyEvent *)
virtual void | widgetEnterEvent (QEvent *)
virtual void | widgetLeaveEvent (QEvent *)
virtual void | stretchSelection (const QSize &oldSize, const QSize &newSize)
virtual void | updateDisplay ()
| Update the state of rubber band and tracker label.
const QwtWidgetOverlay * | rubberBandOverlay () const
const QwtWidgetOverlay * | trackerOverlay () const
const QPolygon & | pickedPoints () const
Protected Member Functions inherited from QwtEventPattern
virtual bool | mouseMatch (const MousePattern &, const QMouseEvent *) const
| Compare a mouse event with an event pattern. More...
virtual bool | keyMatch (const KeyPattern &, const QKeyEvent *) const
| Compare a key event with an event pattern. More...

## Detailed Description

QwtPicker provides selections on a widget.

QwtPicker filters all enter, leave, mouse and keyboard events of a widget and translates them into an array of selected points.

The way how the points are collected depends on type of state machine that is connected to the picker. Qwt offers a couple of predefined state machines for selecting:

- Nothing
  QwtPickerTrackerMachine
- Single points
  QwtPickerClickPointMachine, QwtPickerDragPointMachine
- Rectangles
  QwtPickerClickRectMachine, QwtPickerDragRectMachine
- Polygons
  QwtPickerPolygonMachine

While these state machines cover the most common ways to collect points it is also possible to implement individual machines as well.

QwtPicker translates the picked points into a selection using the adjustedPoints() method. adjustedPoints() is intended to be reimplemented to fix up the selection according to application specific requirements. (F.e. when an application accepts rectangles of a fixed aspect ratio only.)

Optionally QwtPicker support the process of collecting points by a rubber band and tracker displaying a text for the current mouse position.

Example

      #include <qwt_picker.h>
      #include <qwt_picker_machine.h>

      QwtPicker *picker = new QwtPicker(widget);
      picker->setStateMachine(new QwtPickerDragRectMachine);
      picker->setTrackerMode(QwtPicker::ActiveOnly);
      picker->setRubberBand(QwtPicker::RectRubberBand);

  The state machine triggers the following commands:

- begin()
  Activate/Initialize the selection.
- append()
  Add a new point
- move()
  Change the position of the last point.
- remove()
  Remove the last point.
- end()
  Terminate the selection and call accept to validate the picked points.

The picker is active (isActive()), between begin() and end(). In active state the rubber band is displayed, and the tracker is visible in case of trackerMode is ActiveOnly or AlwaysOn.

The cursor can be moved using the arrow keys. All selections can be aborted using the abort key. (QwtEventPattern::KeyPatternCode)

Warning
  In case of QWidget::NoFocus the focus policy of the observed widget is set to QWidget::WheelFocus and mouse tracking will be manipulated while the picker is active, or if trackerMode() is AlwayOn.

## Member Enumeration Documentation

enum QwtPicker::DisplayMode

Display mode.

See Also
  setTrackerMode(), trackerMode(), isActive()

Enumerator
AlwaysOff | Display never.
AlwaysOn | Display always.
ActiveOnly | Display only when the selection is active.

enum QwtPicker::ResizeMode

Controls what to do with the selected points of an active selection when the observed widget is resized.

The default value is QwtPicker::Stretch.

See Also
  setResizeMode()

Enumerator
Stretch | All points are scaled according to the new size,.
KeepSize | All points remain unchanged.

enum QwtPicker::RubberBand

Rubber band style

The default value is QwtPicker::NoRubberBand.

See Also
  setRubberBand(), rubberBand()

Enumerator
NoRubberBand | No rubberband.
HLineRubberBand | A horizontal line ( only for QwtPickerMachine::PointSelection )
VLineRubberBand | A vertical line ( only for QwtPickerMachine::PointSelection )
CrossRubberBand | A crosshair ( only for QwtPickerMachine::PointSelection )
RectRubberBand | A rectangle ( only for QwtPickerMachine::RectSelection )
EllipseRubberBand | An ellipse ( only for QwtPickerMachine::RectSelection )
PolygonRubberBand | A polygon ( only for QwtPickerMachine::PolygonSelection )
UserRubberBand | Values >= UserRubberBand can be used to define additional rubber bands.

## Constructor & Destructor Documentation

QwtPicker::QwtPicker | ( | QWidget * | parent | ) |
| explicit

Constructor

Creates an picker that is enabled, but without a state machine. rubber band and tracker are disabled.

Parameters

  parent | Parent widget, that will be observed

QwtPicker::QwtPicker | ( | RubberBand | rubberBand,
|  | DisplayMode | trackerMode,
|  | QWidget * | parent
| ) |  |
| explicit

Constructor

Parameters

  rubberBand | Rubber band style
  trackerMode | Tracker mode
  parent | Parent widget, that will be observed

## Member Function Documentation

bool QwtPicker::accept | ( | QPolygon & | selection | ) | const
| protected virtual

Validate and fix up the selection.

Accepts all selections unmodified

Parameters

  selection | Selection to validate and fix up

Returns
  true, when accepted, false otherwise

Reimplemented in QwtPlotZoomer.

void QwtPicker::activated | ( | bool | on | ) |
| signal

A signal indicating, when the picker has been activated. Together with setEnabled() it can be used to implement selections with more than one picker.

Parameters

  on | True, when the picker has been activated

QPolygon QwtPicker::adjustedPoints | ( | const QPolygon & | points | ) | const
| protected virtual

Map the pickedPoints() into a selection()

adjustedPoints() maps the points, that have been collected on the parentWidget() into a selection(). The default implementation simply returns the points unmodified.

The reason, why a selection() differs from the picked points depends on the application requirements. F.e. :

- A rectangular selection might need to have a specific aspect ratio only.
- A selection could accept non intersecting polygons only.
- ...
  The example below is for a rectangular selection, where the first point is the center of the selected rectangle.
  Example

        QPolygon MyPicker::adjustedPoints(const QPolygon &points) const
        {
            QPolygon adjusted;
            if ( points.size() == 2 )
            {
                const int width = qAbs(points[1].x() - points[0].x());
                const int height = qAbs(points[1].y() - points[0].y());

                QRect rect(0, 0, 2 * width, 2 * height);
                rect.moveCenter(points[0]);

                adjusted += rect.topLeft();
                adjusted += rect.bottomRight();
            }
            return adjusted;
        }

  Parameters

    points | Selected points

  Returns
    Selected points unmodified

void QwtPicker::append | ( | const QPoint & | pos | ) |
| protected virtual

Append a point to the selection and update rubber band and tracker. The appended() signal is emitted.

Parameters

  pos | Additional point

See Also
  isActive(), begin(), end(), move(), appended()

Reimplemented in QwtPlotPicker.

void QwtPicker::appended | ( | const QPoint & | pos | ) |
| signal

A signal emitted when a point has been appended to the selection

Parameters

  pos | Position of the appended point.

See Also
  append(). moved()

void QwtPicker::begin | ( |  | ) |
| protected virtual

Open a selection setting the state to active

See Also
  isActive(), end(), append(), move()

Reimplemented in QwtPlotZoomer.

void QwtPicker::changed | ( | const QPolygon & | selection | ) |
| signal

A signal emitted when the active selection has been changed. This might happen when the observed widget is resized.

Parameters

  selection | Changed selection

See Also
  stretchSelection()

void QwtPicker::drawRubberBand | ( | QPainter * | painter | ) | const
| virtual

Draw a rubber band, depending on rubberBand()

Parameters

  painter | Painter, initialized with a clip region

See Also
  rubberBand(), RubberBand

void QwtPicker::drawTracker | ( | QPainter * | painter | ) | const
| virtual

Draw the tracker

Parameters

  painter | Painter

See Also
  trackerRect(), trackerText()

bool QwtPicker::end | ( | bool | ok = `true` | ) |
| protected virtual

Close a selection setting the state to inactive.

The selection is validated and maybe fixed by accept().

Parameters

  ok | If true, complete the selection and emit a selected signal otherwise discard the selection.

Returns
  true if the selection is accepted, false otherwise

See Also
  isActive(), begin(), append(), move(), selected(), accept()

Reimplemented in QwtPlotZoomer, and QwtPlotPicker.

bool QwtPicker::eventFilter | ( | QObject * | object,
|  | QEvent * | event
| ) |  |
| virtual

Event filter.

When isEnabled() is true all events of the observed widget are filtered. Mouse and keyboard events are translated into widgetMouse- and widgetKey- and widgetWheel-events. Paint and Resize events are handled to keep rubber band and tracker up to date.

Parameters

  object | Object to be filtered
  event | Event

Returns
  Always false.

See Also
  widgetEnterEvent(), widgetLeaveEvent(), widgetMousePressEvent(), widgetMouseReleaseEvent(), widgetMouseDoubleClickEvent(), widgetMouseMoveEvent(), widgetWheelEvent(), widgetKeyPressEvent(), widgetKeyReleaseEvent(), QObject::installEventFilter(), QObject::event()

bool QwtPicker::isActive | ( |  | ) | const

A picker is active between begin() and end().

Returns
  true if the selection is active.

bool QwtPicker::isEnabled | ( |  | ) | const

Returns
  true when enabled, false otherwise

See Also
  setEnabled(), eventFilter()

void QwtPicker::move | ( | const QPoint & | pos | ) |
| protected virtual

Move the last point of the selection The moved() signal is emitted.

Parameters

  pos | New position

See Also
  isActive(), begin(), end(), append()

Reimplemented in QwtPlotPicker.

void QwtPicker::moved | ( | const QPoint & | pos | ) |
| signal

A signal emitted whenever the last appended point of the selection has been moved.

Parameters

  pos | Position of the moved last point of the selection.

See Also
  move(), appended()

QPainterPath QwtPicker::pickArea | ( |  | ) | const
| virtual

Find the area of the observed widget, where selection might happen.

Returns
  parentWidget()->contentsRect()

const QPolygon & QwtPicker::pickedPoints | ( |  | ) | const
| protected

Return the points, that have been collected so far. The selection() is calculated from the pickedPoints() in adjustedPoints().

Returns
  Picked points

void QwtPicker::remove | ( |  | ) |
| protected virtual

Remove the last point of the selection The removed() signal is emitted.

See Also
  isActive(), begin(), end(), append(), move()

void QwtPicker::removed | ( | const QPoint & | pos | ) |
| signal

A signal emitted whenever the last appended point of the selection has been removed.

Parameters

  pos | Position of the point, that has been removed

See Also
  remove(), appended()

void QwtPicker::reset | ( |  | ) |
| protected virtual

Reset the state machine and terminate ( end(false) ) the selection

QwtPicker::ResizeMode QwtPicker::resizeMode | ( |  | ) | const

Returns
  Resize mode

See Also
  setResizeMode(), ResizeMode

QwtPicker::RubberBand QwtPicker::rubberBand | ( |  | ) | const

Returns
  Rubber band style

See Also
  setRubberBand(), RubberBand, rubberBandPen()

QRegion QwtPicker::rubberBandMask | ( |  | ) | const
| virtual

Calculate the mask for the rubber band overlay

Returns
  Region for the mask

See Also
  QWidget::setMask()

const QwtWidgetOverlay * QwtPicker::rubberBandOverlay | ( |  | ) | const
| protected

Returns
  Overlay displaying the rubber band

QPen QwtPicker::rubberBandPen | ( |  | ) | const

Returns
  Rubber band pen

See Also
  setRubberBandPen(), rubberBand()

void QwtPicker::selected | ( | const QPolygon & | polygon | ) |
| signal

A signal emitting the selected points, at the end of a selection.

Parameters

  polygon | Selected points

QPolygon QwtPicker::selection | ( |  | ) | const

Returns
  Selected points

See Also
  pickedPoints(), adjustedPoints()

void QwtPicker::setEnabled | ( | bool | enabled | ) |
| slot

En/disable the picker.

When enabled is true an event filter is installed for the observed widget, otherwise the event filter is removed.

Parameters

  enabled | true or false

See Also
  isEnabled(), eventFilter()

void QwtPicker::setResizeMode | ( | ResizeMode | mode | ) |

Set the resize mode.

The resize mode controls what to do with the selected points of an active selection when the observed widget is resized.

Stretch means the points are scaled according to the new size, KeepSize means the points remain unchanged.

The default mode is Stretch.

Parameters

  mode | Resize mode

See Also
  resizeMode(), ResizeMode

void QwtPicker::setRubberBand | ( | RubberBand | rubberBand | ) |

Set the rubber band style

Parameters

  rubberBand | Rubber band style The default value is NoRubberBand.

See Also
  rubberBand(), RubberBand, setRubberBandPen()

void QwtPicker::setRubberBandPen | ( | const QPen & | pen | ) |

Set the pen for the rubberband

Parameters

  pen | Rubber band pen

See Also
  rubberBandPen(), setRubberBand()

void QwtPicker::setStateMachine | ( | QwtPickerMachine * | stateMachine | ) |

Set a state machine and delete the previous one

Parameters

  stateMachine | State machine

See Also
  stateMachine()

void QwtPicker::setTrackerFont | ( | const QFont & | font | ) |

Set the font for the tracker

Parameters

  font | Tracker font

See Also
  trackerFont(), setTrackerMode(), setTrackerPen()

void QwtPicker::setTrackerMode | ( | DisplayMode | mode | ) |

Set the display mode of the tracker.

A tracker displays information about current position of the cursor as a string. The display mode controls if the tracker has to be displayed whenever the observed widget has focus and cursor (AlwaysOn), never (AlwaysOff), or only when the selection is active (ActiveOnly).

Parameters

  mode | Tracker display mode

Warning
  In case of AlwaysOn, mouseTracking will be enabled for the observed widget.

See Also
  trackerMode(), DisplayMode

void QwtPicker::setTrackerPen | ( | const QPen & | pen | ) |

Set the pen for the tracker

Parameters

  pen | Tracker pen

See Also
  trackerPen(), setTrackerMode(), setTrackerFont()

const QwtPickerMachine * QwtPicker::stateMachine | ( |  | ) | const

Returns
  Assigned state machine

See Also
  setStateMachine()

QwtPickerMachine * QwtPicker::stateMachine | ( |  | ) |

Returns
  Assigned state machine

See Also
  setStateMachine()

void QwtPicker::stretchSelection | ( | const QSize & | oldSize,
|  | const QSize & | newSize
| ) |  |
| protected virtual

Scale the selection by the ratios of oldSize and newSize The changed() signal is emitted.

Parameters

  oldSize | Previous size
  newSize | Current size

See Also
  ResizeMode, setResizeMode(), resizeMode()

QFont QwtPicker::trackerFont | ( |  | ) | const

Returns
  Tracker font

See Also
  setTrackerFont(), trackerMode(), trackerPen()

QwtPicker::DisplayMode QwtPicker::trackerMode | ( |  | ) | const

Returns
  Tracker display mode

See Also
  setTrackerMode(), DisplayMode

const QwtWidgetOverlay * QwtPicker::trackerOverlay | ( |  | ) | const
| protected

Returns
  Overlay displaying the tracker text

QPen QwtPicker::trackerPen | ( |  | ) | const

Returns
  Tracker pen

See Also
  setTrackerPen(), trackerMode(), trackerFont()

QPoint QwtPicker::trackerPosition | ( |  | ) | const

Returns
  Current position of the tracker

QRect QwtPicker::trackerRect | ( | const QFont & | font | ) | const
| virtual

Calculate the bounding rectangle for the tracker text from the current position of the tracker

Parameters

  font | Font of the tracker text

Returns
  Bounding rectangle of the tracker text

See Also
  trackerPosition()

QwtText QwtPicker::trackerText | ( | const QPoint & | pos | ) | const
| virtual

Return the label for a position.

In case of HLineRubberBand the label is the value of the y position, in case of VLineRubberBand the value of the x position. Otherwise the label contains x and y position separated by a ',' .

The format for the string conversion is "%d".

Parameters

  pos | Position

Returns
  Converted position as string

Reimplemented in QwtPlotPicker.

void QwtPicker::transition | ( | const QEvent * | event | ) |
| protected virtual

Passes an event to the state machine and executes the resulting commands. Append and Move commands use the current position of the cursor ( QCursor::pos() ).

Parameters

  event | Event

void QwtPicker::widgetEnterEvent | ( | QEvent * | event | ) |
| protected virtual

Handle a enter event for the observed widget.

Parameters

  event | Qt event

See Also
  eventFilter(), widgetMousePressEvent(), widgetMouseReleaseEvent(), widgetMouseDoubleClickEvent(), widgetWheelEvent(), widgetKeyPressEvent(), widgetKeyReleaseEvent()

void QwtPicker::widgetKeyPressEvent | ( | QKeyEvent * | keyEvent | ) |
| protected virtual

Handle a key press event for the observed widget.

Selections can be completely done by the keyboard. The arrow keys move the cursor, the abort key aborts a selection. All other keys are handled by the current state machine.

Parameters

  keyEvent | Key event

See Also
  eventFilter(), widgetMousePressEvent(), widgetMouseReleaseEvent(), widgetMouseDoubleClickEvent(), widgetMouseMoveEvent(), widgetWheelEvent(), widgetKeyReleaseEvent(), stateMachine(), QwtEventPattern::KeyPatternCode

Reimplemented in QwtPlotZoomer.

void QwtPicker::widgetKeyReleaseEvent | ( | QKeyEvent * | keyEvent | ) |
| protected virtual

Handle a key release event for the observed widget.

Passes the event to the state machine.

Parameters

  keyEvent | Key event

See Also
  eventFilter(), widgetMousePressEvent(), widgetMouseReleaseEvent(), widgetMouseDoubleClickEvent(), widgetMouseMoveEvent(), widgetWheelEvent(), widgetKeyPressEvent(), stateMachine()

void QwtPicker::widgetLeaveEvent | ( | QEvent * | event | ) |
| protected virtual

Handle a leave event for the observed widget.

Parameters

  event | Qt event

See Also
  eventFilter(), widgetMousePressEvent(), widgetMouseReleaseEvent(), widgetMouseDoubleClickEvent(), widgetWheelEvent(), widgetKeyPressEvent(), widgetKeyReleaseEvent()

void QwtPicker::widgetMouseDoubleClickEvent | ( | QMouseEvent * | mouseEvent | ) |
| protected virtual

Handle mouse double click event for the observed widget.

Parameters

  mouseEvent | Mouse event

See Also
  eventFilter(), widgetMousePressEvent(), widgetMouseReleaseEvent(), widgetMouseMoveEvent(), widgetWheelEvent(), widgetKeyPressEvent(), widgetKeyReleaseEvent()

void QwtPicker::widgetMouseMoveEvent | ( | QMouseEvent * | mouseEvent | ) |
| protected virtual

Handle a mouse move event for the observed widget.

Parameters

  mouseEvent | Mouse event

See Also
  eventFilter(), widgetMousePressEvent(), widgetMouseReleaseEvent(), widgetMouseDoubleClickEvent(), widgetWheelEvent(), widgetKeyPressEvent(), widgetKeyReleaseEvent()

void QwtPicker::widgetMousePressEvent | ( | QMouseEvent * | mouseEvent | ) |
| protected virtual

Handle a mouse press event for the observed widget.

Parameters

  mouseEvent | Mouse event

See Also
  eventFilter(), widgetMouseReleaseEvent(), widgetMouseDoubleClickEvent(), widgetMouseMoveEvent(), widgetWheelEvent(), widgetKeyPressEvent(), widgetKeyReleaseEvent()

void QwtPicker::widgetMouseReleaseEvent | ( | QMouseEvent * | mouseEvent | ) |
| protected virtual

Handle a mouse release event for the observed widget.

Parameters

  mouseEvent | Mouse event

See Also
  eventFilter(), widgetMousePressEvent(), widgetMouseDoubleClickEvent(), widgetMouseMoveEvent(), widgetWheelEvent(), widgetKeyPressEvent(), widgetKeyReleaseEvent()

Reimplemented in QwtPlotZoomer.

void QwtPicker::widgetWheelEvent | ( | QWheelEvent * | wheelEvent | ) |
| protected virtual

Handle a wheel event for the observed widget.

Move the last point of the selection in case of isActive() == true

Parameters

  wheelEvent | Wheel event

See Also
  eventFilter(), widgetMousePressEvent(), widgetMouseReleaseEvent(), widgetMouseDoubleClickEvent(), widgetMouseMoveEvent(), widgetKeyPressEvent(), widgetKeyReleaseEvent()