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+** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
+** Contact:
+** This file is part of the documentation of the Qt Toolkit.
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and Digia. For licensing terms and
+** conditions see For further information
+** use the contact form at
+** GNU Free Documentation License Usage
+** Alternatively, this file may be used under the terms of the GNU Free
+** Documentation License version 1.3 as published by the Free Software
+** Foundation and appearing in the file included in the packaging of
+** this file. Please review the following information to ensure
+** the GNU Free Documentation License version 1.3 requirements
+** will be met:
+ \example gestures/imagegestures
+ \title Image Gestures Example
+ This example shows how to enable gestures for a widget and use gesture input
+ to perform actions.
+ We use two classes to create the user interface for the application: \c MainWidget
+ and \c ImageWidget. The \c MainWidget class is simply used as a container for the
+ \c ImageWidget class, which we will configure to accept gesture input. Since we
+ are interested in the way gestures are used, we will concentrate on the
+ implementation of the \c ImageWidget class.
+ \section1 ImageWidget Class Definition
+ The \c ImageWidget class is a simple QWidget subclass that reimplements the general
+ QWidget::event() handler function in addition to several more specific event handlers:
+ \snippet examples/gestures/imagegestures/imagewidget.h class definition begin
+ \dots
+ \snippet examples/gestures/imagegestures/imagewidget.h class definition end
+ We also implement a private helper function, \c gestureEvent(), to help manage
+ gesture events delivered to the widget, and three functions to perform actions
+ based on gestures: \c panTriggered(), \c pinchTriggered() and \c swipeTriggered().
+ \section1 ImageWidget Class Implementation
+ In the widget's constructor, we begin by setting up various parameters that will
+ be used to control the way images are displayed.
+ \snippet examples/gestures/imagegestures/imagewidget.cpp constructor
+ We enable three of the standard gestures for the widget by calling QWidget::grabGesture()
+ with the types of gesture we need. These will be recognized by the application's
+ default gesture recognizer, and events will be delivered to our widget.
+ Since QWidget does not define a specific event handler for gestures, the widget
+ needs to reimplement the general QWidget::event() to receive gesture events.
+ \snippet examples/gestures/imagegestures/imagewidget.cpp event handler
+ We implement the event handler to delegate gesture events to a private function
+ specifically written for the task, and pass all other events to QWidget's
+ implementation.
+ The \c gestureHandler() function examines the gestures supplied by the
+ newly-delivered QGestureEvent. Since only one gesture of a given type can be
+ used on a widget at any particular time, we can check for each gesture type
+ using the QGestureEvent::gesture() function:
+ \snippet examples/gestures/imagegestures/imagewidget.cpp gesture event handler
+ If a QGesture object is supplied for a certain type of gesture, we call a special
+ purpose function to deal with it, casting the gesture object to the appropriate
+ QGesture subclass.
+ To illustrate how a standard gesture can be interpreted by an application, we
+ show the implementation of the \c swipeTriggered() function, which handles the
+ gesture associated with a brushing or swiping motion on the user's display or
+ input device:
+ \snippet examples/gestures/imagegestures/imagewidget.cpp swipe function
+ The QSwipeGesture class provides specialized functions and defines a enum
+ to make it more convenient for developers to discover which direction, if
+ any, the user swiped the display. Here, we simply navigate to the previous
+ image in the collection if the user swiped upwards or to the left; otherwise
+ we navigate to the next image in the collection.
+ The other gestures are also handled by special purpose functions, but use
+ the values of properties held by the QGesture object passed to them.