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QwtPicker(3) Qwt User's Guide QwtPicker(3)

NAME

QwtPicker - QwtPicker provides selections on a widget.

SYNOPSIS

#include <qwt_picker.h>

Inherits QObject, and QwtEventPattern.

Inherited by QwtPlotPicker.

Public Types


enum RubberBand { NoRubberBand = 0, HLineRubberBand, VLineRubberBand, CrossRubberBand, RectRubberBand, EllipseRubberBand, PolygonRubberBand, UserRubberBand = 100 }
enum DisplayMode { AlwaysOff, AlwaysOn, ActiveOnly }
Display mode. enum ResizeMode { Stretch, KeepSize }

Public Slots


void setEnabled (bool)
En/disable the picker.

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. DisplayMode trackerMode () const
void setResizeMode (ResizeMode)
Set the resize mode. 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. 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. QPoint trackerPosition () const
virtual QRect trackerRect (const QFont &) const
QPolygon selection () const

Protected Member Functions


virtual QPolygon adjustedPoints (const QPolygon &) const
Map the pickedPoints() into a selection() 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. virtual bool accept (QPolygon &) const
Validate and fix up the selection. 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

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

Display never.
Display always.
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

All points are scaled according to the new size,.
All points remain unchanged.

enum QwtPicker::RubberBand

Rubber band style

The default value is QwtPicker::NoRubberBand.

See also:

setRubberBand(), rubberBand()

Enumerator

No rubberband.
A horizontal line ( only for QwtPickerMachine::PointSelection )
A vertical line ( only for QwtPickerMachine::PointSelection )
A crosshair ( only for QwtPickerMachine::PointSelection )
A rectangle ( only for QwtPickerMachine::RectSelection )
An ellipse ( only for QwtPickerMachine::RectSelection )
A polygon ( only for QwtPickerMachine::PolygonSelection )
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()

Author

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Wed Jan 2 2019 Version 6.1.4