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+/****************************************************************************
+**
+** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** Contact: Qt Software Information (qt-info@nokia.com)
+**
+** This file is part of the documentation of the Qt Toolkit.
+**
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+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
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+** Beta Release License Agreement.
+**
+** GNU Lesser General Public License Usage
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+** 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
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+**
+** 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
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+**
+** GNU General Public License Usage
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+** General Public License version 3.0 as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL included in the
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+**
+** If you are unsure which license is appropriate for your use, please
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+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+/*!
+    \example widgets/wiggly
+    \title Wiggly Example
+
+    The Wiggly example shows how to animate a widget using
+    QBasicTimer and \l{QObject::timerEvent()}{timerEvent()}. In
+    addition, the example demonstrates how to use QFontMetrics to
+    determine the size of text on screen.
+
+    \image wiggly-example.png Screenshot of the Wiggly example
+
+    QBasicTimer is a low-level class for timers. Unlike QTimer,
+    QBasicTimer doesn't inherit from QObject; instead of emitting a
+    \l{QTimer::timeout()}{timeout()} signal when a certain amount of
+    time has passed, it sends a QTimerEvent to a QObject of our
+    choice. This makes QBasicTimer a more lightweight alternative to
+    QTimer. Qt's built-in widgets use it internally, and it is
+    provided in Qt's API for highly-optimized applications (e.g.,
+    \l{Qt for Embedded Linux} applications).
+
+    The example consists of two classes:
+
+    \list
+    \o \c WigglyWidget is the custom widget displaying the text
+        in a wiggly line.
+
+    \o \c Dialog is the dialog widget allowing the user to enter a
+        text. It combines a \c WigglyWidget and a \c QLineEdit.
+    \endlist
+
+    We will first take a quick look at the \c Dialog class, then we
+    will review the \c WigglyWidget class.
+
+    \section1 Dialog Class Definition
+
+    \snippet examples/widgets/wiggly/dialog.h 0
+
+    The \c Dialog class provides a dialog widget that allows the user
+    to enter a text. The text is then rendered by \c WigglyWidget.
+
+    \section1 Dialog Class Implementation
+
+    \snippet examples/widgets/wiggly/dialog.cpp 0
+
+    In the constructor we create a wiggly widget along with a
+    \l{QLineEdit}{line edit}, and we put the two widgets in a
+    vertical layout. We connect the line edit's \l
+    {QLineEdit::textChanged()}{textChanged()} signal to the wiggly
+    widget's \c setText() slot to obtain the real time interaction
+    with the wiggly widget. The widget's default text is "Hello
+    world!".
+
+    \section1 WigglyWidget Class Definition
+
+    \snippet examples/widgets/wiggly/wigglywidget.h 0
+
+    The \c WigglyWidget class provides the wiggly line displaying the
+    text. We subclass QWidget and reimplement the standard \l
+    {QWidget::paintEvent()}{paintEvent()} and \l
+    {QObject::timerEvent()}{timerEvent()} functions to draw and update
+    the widget. In addition we implement a public \c setText() slot
+    that sets the widget's text.
+
+    The \c timer variable, of type QBasicTimer, is used to update the
+    widget at regular intervals, making the widget move. The \c text
+    variable is used to store the currently displayed text, and \c
+    step to calculate position and color for each character on the
+    wiggly line.
+
+    \section1 WigglyWidget Class Implementation
+
+    \snippet examples/widgets/wiggly/wigglywidget.cpp 0
+
+    In the constructor, we make the widget's background slightly
+    lighter than the usual background using the QPalette::Midlight
+    color role. The background role defines the brush from the
+    widget's palette that Qt uses to paint the background. Then we
+    enlarge the widget's font with 20 points.
+
+    Finally we start the timer; the call to QBasicTimer::start()
+    makes sure that \e this particular wiggly widget will receive the
+    timer events generated when the timer times out (every 60
+    milliseconds).
+
+    \snippet examples/widgets/wiggly/wigglywidget.cpp 1
+    \snippet examples/widgets/wiggly/wigglywidget.cpp 2
+
+    The \c paintEvent() function is called whenever a QPaintEvent is
+    sent to the widget. Paint events are sent to widgets that need to
+    update themselves, for instance when part of a widget is exposed
+    because a covering widget was moved. For the wiggly widget, a
+    paint event will also be generated every 60 milliseconds from
+    the \c timerEvent() slot.
+
+    The \c sineTable represents y-values of the sine curve,
+    multiplied by 100. It is used to make the wiggly widget move
+    along the sine curve.
+
+    The QFontMetrics object provides information about the widget's
+    font. The \c x variable is the horizontal position where we start
+    drawing the text. The \c y variable is the vertical position of
+    the text's base line. Both variables are computed so that the
+    text is horizontally and vertically centered. To compute the base
+    line, we take into account the font's ascent (the height of the
+    font above the base line) and font's descent (the height of the
+    font below the base line). If the descent equals the ascent, they
+    cancel out each other and the base line is at \c height() / 2.
+
+    \snippet examples/widgets/wiggly/wigglywidget.cpp 3
+    \snippet examples/widgets/wiggly/wigglywidget.cpp 4
+
+    Each time the \c paintEvent() function is called, we create a
+    QPainter object \c painter to draw the contents of the widget.
+    For each character in \c text, we determine the color and the
+    position on the wiggly line based on \c step. In addition, \c x
+    is incremented by the character's width.
+
+    For simplicity, we assume that QFontMetrics::width(\c text)
+    returns the sum of the individual character widths
+    (QFontMetrics::width(\c text[i])). In practice, this is not
+    always the case because QFontMetrics::width(\c text) also takes
+    into account the kerning between certain letters (e.g., 'A' and
+    'V'). The result is that the text isn't perfectly centered. You
+    can verify this by typing "AVAVAVAVAVAV" in the line edit.
+
+    \snippet examples/widgets/wiggly/wigglywidget.cpp 5
+    \snippet examples/widgets/wiggly/wigglywidget.cpp 6
+
+    The \c timerEvent() function receives all the timer events that
+    are generated for this widget. If a timer event is sent from the
+    widget's QBasicTimer, we increment \c step to make the text move,
+    and call QWidget::update() to refresh the display. Any other
+    timer event is passed on to the base class's implementation of
+    the \l{QWidget::timerEvent()}{timerEvent()} function.
+
+    The QWidget::update() slot does not cause an immediate repaint;
+    instead the slot schedules a paint event for processing when Qt
+    returns to the main event loop. The paint events are then handled
+    by \c{WigglyWidget}'s \c paintEvent() function.
+*/