QSwipeGestureRecognizer Class Reference

#include <qstandardgestures_p.h>

Inheritance diagram for QSwipeGestureRecognizer:

Public Functions
QGesture *	create (QObject *target)
	This function is called by Qt to create a new QGesture object for the given target (QWidget or QGraphicsObject). More...
	QSwipeGestureRecognizer ()
QGestureRecognizer::Result	recognize (QGesture *state, QObject *watched, QEvent *event)
	Handles the given event for the watched object, updating the state of the gesture object as required, and returns a suitable result for the current recognition step. More...
void	reset (QGesture *state)
	This function is called by the framework to reset a given gesture. More...
Public Functions inherited from QGestureRecognizer
	QGestureRecognizer ()
	Constructs a new gesture recognizer object. More...
virtual	~QGestureRecognizer ()
	Destroys the gesture recognizer. More...

Additional Inherited Members
Public Types inherited from QGestureRecognizer
enum	ResultFlag {   Ignore = 0x0001, MayBeGesture = 0x0002, TriggerGesture = 0x0004, FinishGesture = 0x0008,   CancelGesture = 0x0010, ResultState_Mask = 0x00ff, ConsumeEventHint = 0x0100, ResultHint_Mask = 0xff00 }
	This enum describes the result of the current event filtering step in a gesture recognizer state machine. More...
Static Public Functions inherited from QGestureRecognizer
static Qt::GestureType	registerRecognizer (QGestureRecognizer *recognizer)
	Registers the given recognizer in the gesture framework and returns a gesture ID for it. More...
static void	unregisterRecognizer (Qt::GestureType type)
	Unregisters all gesture recognizers of the specified type. More...

Detailed Description

Definition at line 83 of file qstandardgestures_p.h.

Constructors and Destructors

QSwipeGestureRecognizer()

QSwipeGestureRecognizer::QSwipeGestureRecognizer

(

)

Definition at line 281 of file qstandardgestures.cpp.

{
}

Functions

create()

QGesture * QSwipeGestureRecognizer::create ( QObject *  target )

virtual

This function is called by Qt to create a new QGesture object for the given target (QWidget or QGraphicsObject).

Reimplement this function to create a custom QGesture-derived gesture object if necessary.

The application takes ownership of the created gesture object.

Reimplemented from QGestureRecognizer.

Definition at line 285 of file qstandardgestures.cpp.

{
    if (target && target->isWidgetType()) {
        static_cast<QWidget *>(target)->setAttribute(Qt::WA_AcceptTouchEvents);
    }
    return new QSwipeGesture;
}

recognize()

QGestureRecognizer::Result QSwipeGestureRecognizer::recognize ( QGesture *  gesture, QObject *  watched, QEvent *  event  )

virtual

Handles the given event for the watched object, updating the state of the gesture object as required, and returns a suitable result for the current recognition step.

This function is called by the framework to allow the recognizer to filter input events dispatched to QWidget or QGraphicsObject instances that it is monitoring.

The result reflects how much of the gesture has been recognized. The state of the gesture object is set depending on the result.

See also

QGestureRecognizer::Result

Implements QGestureRecognizer.

Definition at line 293 of file qstandardgestures.cpp.

{
    QSwipeGesture *q = static_cast<QSwipeGesture *>(state);
    QSwipeGesturePrivate *d = q->d_func();

    const QTouchEvent *ev = static_cast<const QTouchEvent *>(event);

    QGestureRecognizer::Result result;

    switch (event->type()) {
    case QEvent::TouchBegin: {
        d->velocityValue = 1;
        d->time.start();
        d->started = true;
        result = QGestureRecognizer::MayBeGesture;
        break;
    }
    case QEvent::TouchEnd: {
        if (q->state() != Qt::NoGesture) {
            result = QGestureRecognizer::FinishGesture;
        } else {
            result = QGestureRecognizer::CancelGesture;
        }
        break;
    }
    case QEvent::TouchUpdate: {
        if (!d->started)
            result = QGestureRecognizer::CancelGesture;
        else if (ev->touchPoints().size() == 3) {
            QTouchEvent::TouchPoint p1 = ev->touchPoints().at(0);
            QTouchEvent::TouchPoint p2 = ev->touchPoints().at(1);
            QTouchEvent::TouchPoint p3 = ev->touchPoints().at(2);

            if (d->lastPositions[0].isNull()) {
                d->lastPositions[0] = p1.startScreenPos().toPoint();
                d->lastPositions[1] = p2.startScreenPos().toPoint();
                d->lastPositions[2] = p3.startScreenPos().toPoint();
            }
            d->hotSpot = p1.screenPos();
            d->isHotSpotSet = true;

            int xDistance = (p1.screenPos().x() - d->lastPositions[0].x() +
                             p2.screenPos().x() - d->lastPositions[1].x() +
                             p3.screenPos().x() - d->lastPositions[2].x()) / 3;
            int yDistance = (p1.screenPos().y() - d->lastPositions[0].y() +
                             p2.screenPos().y() - d->lastPositions[1].y() +
                             p3.screenPos().y() - d->lastPositions[2].y()) / 3;

            const int distance = xDistance >= yDistance ? xDistance : yDistance;
            int elapsedTime = d->time.restart();
            if (!elapsedTime)
                elapsedTime = 1;
            d->velocityValue = 0.9 * d->velocityValue + distance / elapsedTime;
            d->swipeAngle = QLineF(p1.startScreenPos(), p1.screenPos()).angle();

            static const int MoveThreshold = 50;
            if (xDistance > MoveThreshold || yDistance > MoveThreshold) {
                // measure the distance to check if the direction changed
                d->lastPositions[0] = p1.screenPos().toPoint();
                d->lastPositions[1] = p2.screenPos().toPoint();
                d->lastPositions[2] = p3.screenPos().toPoint();
                QSwipeGesture::SwipeDirection horizontal =
                        xDistance > 0 ? QSwipeGesture::Right : QSwipeGesture::Left;
                QSwipeGesture::SwipeDirection vertical =
                        yDistance > 0 ? QSwipeGesture::Down : QSwipeGesture::Up;
                if (d->verticalDirection == QSwipeGesture::NoDirection)
                    d->verticalDirection = vertical;
                if (d->horizontalDirection == QSwipeGesture::NoDirection)
                    d->horizontalDirection = horizontal;
                if (d->verticalDirection != vertical || d->horizontalDirection != horizontal) {
                    // the user has changed the direction!
                    result = QGestureRecognizer::CancelGesture;
                }
                result = QGestureRecognizer::TriggerGesture;
            } else {
                if (q->state() != Qt::NoGesture)
                    result = QGestureRecognizer::TriggerGesture;
                else
                    result = QGestureRecognizer::MayBeGesture;
            }
        } else if (ev->touchPoints().size() > 3) {
            result = QGestureRecognizer::CancelGesture;
        } else { // less than 3 touch points
            if (d->started && (ev->touchPointStates() & Qt::TouchPointPressed))
                result = QGestureRecognizer::CancelGesture;
            else if (d->started)
                result = QGestureRecognizer::Ignore;
            else
                result = QGestureRecognizer::MayBeGesture;
        }
        break;
    }
    case QEvent::MouseButtonPress:
    case QEvent::MouseMove:
    case QEvent::MouseButtonRelease:
        result = QGestureRecognizer::Ignore;
        break;
    default:
        result = QGestureRecognizer::Ignore;
        break;
    }
    return result;
}

reset()

void QSwipeGestureRecognizer::reset ( QGesture *  gesture )

virtual

This function is called by the framework to reset a given gesture.

Reimplement this function to implement additional requirements for custom QGesture objects. This may be necessary if you implement a custom QGesture whose properties need special handling when the gesture is reset.

Reimplemented from QGestureRecognizer.

Definition at line 399 of file qstandardgestures.cpp.

{
    QSwipeGesture *q = static_cast<QSwipeGesture *>(state);
    QSwipeGesturePrivate *d = q->d_func();

    d->verticalDirection = d->horizontalDirection = QSwipeGesture::NoDirection;
    d->swipeAngle = 0;

    d->lastPositions[0] = d->lastPositions[1] = d->lastPositions[2] = QPoint();
    d->started = false;
    d->velocityValue = 0;
    d->time.invalidate();

    QGestureRecognizer::reset(state);
}

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The documentation for this class was generated from the following files:

• /src/gui/kernel/qstandardgestures_p.h
• /src/gui/kernel/qstandardgestures.cpp