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+++ b/src/gui/kernel/qgesturerecognizer.cpp Mon Jan 11 14:00:40 2010 +0000
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+/****************************************************************************
+**
+** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
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+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qgesturerecognizer.h"
+
+#include "private/qgesture_p.h"
+
+QT_BEGIN_NAMESPACE
+
+/*!
+ \class QGestureRecognizer
+ \since 4.6
+ \brief The QGestureRecognizer class provides the infrastructure for gesture recognition.
+ \ingroup gestures
+
+ Gesture recognizers are responsible for creating and managing QGesture objects and
+ monitoring input events sent to QWidget and QGraphicsObject subclasses.
+ QGestureRecognizer is the base class for implementing custom gestures.
+
+ Developers that only need to provide gesture recognition for standard gestures do not
+ need to use this class directly. Instances will be created behind the scenes by the
+ framework.
+
+ \section1 Recognizing Gestures
+
+ The process of recognizing gestures involves filtering input events sent to specific
+ objects, and modifying the associated QGesture objects to include relevant information
+ about the user's input.
+
+ Gestures are created when the framework calls createGesture() to handle user input
+ for a particular instance of a QWidget or QGraphicsObject subclass. A QGesture object
+ is created for each widget or item that is configured to use gestures.
+
+ Once a QGesture has been created for a target object, the gesture recognizer will
+ receive events for it in its filterEvent() handler function.
+
+ When a gesture is canceled, the reset() function is called, giving the recognizer the
+ chance to update the appropriate properties in the corresponding QGesture object.
+
+ \section1 Supporting New Gestures
+
+ To add support for new gestures, you need to derive from QGestureRecognizer to create
+ a custom recognizer class, construct an instance of this class, and register it with
+ the application by calling QApplication::registerGestureRecognizer(). You can also
+ subclass QGesture to create a custom gesture class, or rely on dynamic properties
+ to express specific details of the gesture you want to handle.
+
+ Your custom QGestureRecognizer subclass needs to reimplement the filterEvent() function
+ to handle and filter the incoming input events for QWidget and QGraphicsObject subclasses.
+ Although the logic for gesture recognition is implemented in this function, you can
+ store persistent information about the state of the recognition process in the QGesture
+ object supplied. The filterEvent() function must return a value of Qt::GestureState that
+ indicates the state of recognition for a given gesture and target object. This determines
+ whether or not a gesture event will be delivered to a target object.
+
+ If you choose to represent a gesture by a custom QGesture subclass, you will need to
+ reimplement the createGesture() function to construct instances of your gesture class.
+ Similarly, you may need to reimplement the reset() function if your custom gesture
+ objects need to be specially handled when a gesture is canceled.
+
+ \sa QGesture
+*/
+
+/*!
+ \enum QGestureRecognizer::ResultFlags
+
+ This enum describes the result of the current event filtering step in
+ a gesture recognizer state machine.
+
+ The result consists of a state value (one of Ignore, NotGesture,
+ MaybeGesture, GestureTriggered, GestureFinished) and an optional hint
+ (ConsumeEventHint).
+
+ \value Ignore The event does not change the state of the recognizer.
+
+ \value NotGesture The event made it clear that it is not a gesture. If the
+ gesture recognizer was in GestureTriggered state before, then the gesture
+ is canceled and the appropriate QGesture object will be delivered to the
+ target as a part of a QGestureEvent.
+
+ \value MaybeGesture The event changed the internal state of the recognizer,
+ but it isn't clear yet if it is a gesture or not. The recognizer needs to
+ filter more events to decide. Gesture recognizers in the MaybeGesture state
+ may be reset automatically if they take too long to recognize gestures.
+
+ \value GestureTriggered The gesture has been triggered and the appropriate
+ QGesture object will be delivered to the target as a part of a
+ QGestureEvent.
+
+ \value GestureFinished The gesture has been finished successfully and the
+ appropriate QGesture object will be delivered to the target as a part of a
+ QGestureEvent.
+
+ \value ConsumeEventHint This hint specifies that the gesture framework should
+ consume the filtered event and not deliver it to the receiver.
+
+ \omitvalue ResultState_Mask
+ \omitvalue ResultHint_Mask
+
+ \sa QGestureRecognizer::filterEvent()
+*/
+
+/*!
+ Constructs a new gesture recognizer object.
+*/
+QGestureRecognizer::QGestureRecognizer()
+{
+}
+
+/*!
+ Destroys the gesture recognizer.
+*/
+QGestureRecognizer::~QGestureRecognizer()
+{
+}
+
+/*!
+ This function is called by Qt to create a new QGesture object for the
+ given \a target (QWidget or QGraphicsObject).
+
+ Reimplement this function to create a custom QGesture-derived gesture
+ object if necessary.
+*/
+QGesture *QGestureRecognizer::createGesture(QObject *target)
+{
+ Q_UNUSED(target);
+ return new QGesture;
+}
+
+/*!
+ This function is called by the framework to reset a given \a 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.
+*/
+void QGestureRecognizer::reset(QGesture *gesture)
+{
+ if (gesture) {
+ QGesturePrivate *d = gesture->d_func();
+ d->state = Qt::NoGesture;
+ d->hotSpot = QPointF();
+ d->targetObject = 0;
+ }
+}
+
+/*!
+ \fn QGestureRecognizer::filterEvent(QGesture *gesture, QObject *watched, QEvent *event)
+
+ Handles the given \a event for the \a watched object, updating the state of the \a 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
+ \a gesture object is set depending on the result.
+
+ \sa Qt::GestureState
+*/
+
+QT_END_NAMESPACE