diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/examples/imagegestures.qdoc | 116 |
1 files changed, 116 insertions, 0 deletions
diff --git a/doc/src/examples/imagegestures.qdoc b/doc/src/examples/imagegestures.qdoc new file mode 100644 index 0000000..33c1ace --- /dev/null +++ b/doc/src/examples/imagegestures.qdoc @@ -0,0 +1,116 @@ +/**************************************************************************** +** +** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies). +** All rights reserved. +** Contact: Nokia Corporation (qt-info@nokia.com) +** +** This file is part of the documentation 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 Technology Preview License Agreement accompanying +** this package. +** +** 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 1.1, included in the file LGPL_EXCEPTION.txt in this package. +** +** If you have questions regarding the use of this file, please contact +** Nokia at qt-info@nokia.com. +** +** +** +** +** +** +** +** +** $QT_END_LICENSE$ +** +****************************************************************************/ + +/*! + \example gestures/imagegestures + \title Image Gestures Example + + This example shows how to enable gestures for a widget and use gesture input + to perform actions. + + \image imagegestures-example.png Screenshot of the Image Gestures example. + + 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. +*/ |