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Diffstat (limited to 'doc/src/snippets/gestures/qgesture.cpp')
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diff --git a/doc/src/snippets/gestures/qgesture.cpp b/doc/src/snippets/gestures/qgesture.cpp new file mode 100644 index 0000000..79dcae1 --- /dev/null +++ b/doc/src/snippets/gestures/qgesture.cpp @@ -0,0 +1,283 @@ +/**************************************************************************** +** +** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies). +** Contact: Nokia Corporation (qt-info@nokia.com) +** +** This file is part of the QtGui module of the Qt Toolkit. +** +** $QT_BEGIN_LICENSE:LGPL$ +** No Commercial Usage +** This file contains pre-release code and may not be distributed. +** You may use this file in accordance with the terms and conditions +** contained in the either Technology Preview License Agreement or the +** Beta Release License Agreement. +** +** GNU Lesser General Public License Usage +** Alternatively, this file may be used under the terms of the GNU Lesser +** General Public License version 2.1 as published by the Free Software +** Foundation and appearing in the file LICENSE.LGPL included in the +** packaging of this file. Please review the following information to +** ensure the GNU Lesser General Public License version 2.1 requirements +** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html. +** +** In addition, as a special exception, Nokia gives you certain +** additional rights. These rights are described in the Nokia Qt LGPL +** Exception version 1.0, included in the file LGPL_EXCEPTION.txt in this +** package. +** +** GNU General Public License Usage +** Alternatively, this file may be used under the terms of the GNU +** General Public License version 3.0 as published by the Free Software +** Foundation and appearing in the file LICENSE.GPL included in the +** packaging of this file. Please review the following information to +** ensure the GNU General Public License version 3.0 requirements will be +** met: http://www.gnu.org/copyleft/gpl.html. +** +** If you are unsure which license is appropriate for your use, please +** contact the sales department at http://qt.nokia.com/contact. +** $QT_END_LICENSE$ +** +****************************************************************************/ + +#include "qgesture.h" +#include <private/qgesture_p.h> +#include "qgraphicsitem.h" + +QT_BEGIN_NAMESPACE + + +class QEventFilterProxyGraphicsItem : public QGraphicsItem +{ +public: + QEventFilterProxyGraphicsItem(QGesture *g) + : gesture(g) + { + } + bool sceneEventFilter(QGraphicsItem *, QEvent *event) + { + return gesture ? gesture->filterEvent(event) : false; + } + QRectF boundingRect() const { return QRectF(); } + void paint(QPainter*, const QStyleOptionGraphicsItem*, QWidget*) { } + +private: + QGesture *gesture; +}; + +/*! + \class QGesture + \since 4.6 + + \brief The QGesture class is the base class for implementing custom + gestures. + + This class represents both an object that recognizes a gesture out of a set + of input events (a gesture recognizer), and a gesture object itself that + can be used to get extended information about the triggered gesture. + + The class has a list of properties that can be queried by the user to get + some gesture-specific parameters (for example, an offset of a Pan gesture). + + Usually gesture recognizer implements a state machine, storing its state + internally in the recognizer object. The recognizer receives input events + through the \l{QGesture::}{filterEvent()} virtual function and decides + whether the event should change the state of the recognizer by emitting an + appropriate signal. + + Input events should be either fed to the recognizer one by one with a + filterEvent() function, or the gesture recognizer should be attached to an + object it filters events for by specifying it as a parent object. The + QGesture object installs itself as an event filter to the parent object + automatically, the unsetObject() function should be used to remove an event + filter from the parent object. To make a + gesture that operates on a QGraphicsItem, both the appropriate QGraphicsView + should be passed as a parent object and setGraphicsItem() functions should + be used to attach a gesture to a graphics item. + + This is a base class, to create a custom gesture type, you should subclass + it and implement its pure virtual functions. + + \sa QPanGesture +*/ + +/*! \fn bool QGesture::filterEvent(QEvent *event) + + Parses input \a event and emits a signal when detects a gesture. + + In your reimplementation of this function, if you want to filter the \a + event out, i.e. stop it being handled further, return true; otherwise + return false; + + This is a pure virtual function that needs to be implemented in subclasses. +*/ + +/*! \fn void QGesture::started() + + The signal is emitted when the gesture is started. Extended information + about the gesture is contained in the signal sender object. + + In addition to started(), a triggered() signal should also be emitted. +*/ + +/*! \fn void QGesture::triggered() + + The signal is emitted when the gesture is detected. Extended information + about the gesture is contained in the signal sender object. +*/ + +/*! \fn void QGesture::finished() + + The signal is emitted when the gesture is finished. Extended information + about the gesture is contained in the signal sender object. +*/ + +/*! \fn void QGesture::cancelled() + + The signal is emitted when the gesture is cancelled, for example the reset() + function is called while the gesture was in the process of emitting a + triggered() signal. Extended information about the gesture is contained in + the sender object. +*/ + + +/*! + Creates a new gesture handler object and marks it as a child of \a parent. + + The \a parent object is also the default event source for the gesture, + meaning that the gesture installs itself as an event filter for the \a + parent. + + \sa setGraphicsItem() +*/ +QGesture::QGesture(QObject *parent) + : QObject(*new QGesturePrivate, parent) +{ + if (parent) + parent->installEventFilter(this); +} + +/*! \internal + */ +QGesture::QGesture(QGesturePrivate &dd, QObject *parent) + : QObject(dd, parent) +{ + if (parent) + parent->installEventFilter(this); +} + +/*! + Destroys the gesture object. +*/ +QGesture::~QGesture() +{ +} + +/*! \internal + */ +bool QGesture::eventFilter(QObject *receiver, QEvent *event) +{ + Q_D(QGesture); + if (d->graphicsItem && receiver == parent()) + return false; + return filterEvent(event); +} + +/*! + \property QGesture::state + + \brief The current state of the gesture. +*/ + +/*! + Returns the gesture recognition state. + */ +Qt::GestureState QGesture::state() const +{ + return d_func()->state; +} + +/*! + Sets this gesture's recognition state to \a state and emits appropriate + signals. + + This functions emits the signals according to the old state and the new + \a state, and it should be called after all the internal properties have been + initialized. + + \sa started(), triggered(), finished(), cancelled() + */ +void QGesture::updateState(Qt::GestureState state) +{ + Q_D(QGesture); + if (d->state == state) { + if (state == Qt::GestureUpdated) + emit triggered(); + return; + } + const Qt::GestureState oldState = d->state; + d->state = state; + if (state != Qt::NoGesture && oldState > state) { + // comparing the state as ints: state should only be changed from + // started to (optionally) updated and to finished. + qWarning("QGesture::updateState: incorrect new state"); + return; + } + if (oldState == Qt::NoGesture) + emit started(); + if (state == Qt::GestureUpdated) + emit triggered(); + else if (state == Qt::GestureFinished) + emit finished(); + else if (state == Qt::NoGesture) + emit cancelled(); + + if (state == Qt::GestureFinished) { + // gesture is finished, so we reset the internal state. + d->state = Qt::NoGesture; + } +} + +/*! + Sets the \a graphicsItem the gesture is filtering events for. + + The gesture will install an event filter to the \a graphicsItem and + redirect them to the filterEvent() function. + + \sa graphicsItem() +*/ +void QGesture::setGraphicsItem(QGraphicsItem *graphicsItem) +{ + Q_D(QGesture); + if (d->graphicsItem && d->eventFilterProxyGraphicsItem) + d->graphicsItem->removeSceneEventFilter(d->eventFilterProxyGraphicsItem); + d->graphicsItem = graphicsItem; + if (!d->eventFilterProxyGraphicsItem) + d->eventFilterProxyGraphicsItem = new QEventFilterProxyGraphicsItem(this); + if (graphicsItem) + graphicsItem->installSceneEventFilter(d->eventFilterProxyGraphicsItem); +} + +/*! + Returns the graphics item the gesture is filtering events for. + + \sa setGraphicsItem() +*/ +QGraphicsItem* QGesture::graphicsItem() const +{ + return d_func()->graphicsItem; +} + +/*! \fn void QGesture::reset() + + Resets the internal state of the gesture. This function might be called by + the filterEvent() implementation in a derived class, or by the user to + cancel a gesture. The base class implementation calls + updateState(Qt::NoGesture) which emits the cancelled() + signal if the state() of the gesture indicated it was active. +*/ +void QGesture::reset() +{ + updateState(Qt::NoGesture); +} + +QT_END_NAMESPACE |