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+/****************************************************************************
+**
+** Copyright (C) 2011 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.
+**
+** $QT_BEGIN_LICENSE:FDL$
+** 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 Free Documentation License
+** 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.
+**
+** If you have questions regarding the use of this file, please contact
+** Nokia at qt-info@nokia.com.
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+/*!
+    \example widgets/sliders
+    \title Sliders Example
+
+    Qt provides three types of slider-like widgets: QSlider,
+    QScrollBar and QDial. They all inherit most of their
+    functionality from QAbstractSlider, and can in theory replace
+    each other in an application since the differences only concern
+    their look and feel. This example shows what they look like, how
+    they work and how their behavior and appearance can be
+    manipulated through their properties.
+
+    The example also demonstrates how signals and slots can be used to
+    synchronize the behavior of two or more widgets.
+
+    \image sliders-example.png Screenshot of the Sliders example
+
+    The Sliders example consists of two classes:
+
+    \list
+
+    \o \c SlidersGroup is a custom widget. It combines a QSlider, a
+    QScrollBar and a QDial.
+
+    \o \c Window is the main widget combining a QGroupBox and a
+    QStackedWidget. In this example, the QStackedWidget provides a
+    stack of two \c SlidersGroup widgets. The QGroupBox contain
+    several widgets that control the behavior of the slider-like
+    widgets.
+
+    \endlist
+
+    First we will review the \c Window class, then we
+    will take a look at the \c SlidersGroup class.
+
+    \section1 Window Class Definition
+
+    \snippet examples/widgets/sliders/window.h 0
+
+    The \c Window class inherits from QWidget. It displays the slider
+    widgets and allows the user to set their minimum, maximum and
+    current values and to customize their appearance, key bindings
+    and orientation. We use a private \c createControls() function to
+    create the widgets that provide these controlling mechanisms and
+    to connect them to the slider widgets.
+
+    \section1 Window Class Implementation
+
+    \snippet examples/widgets/sliders/window.cpp 0
+
+    In the constructor we first create the two \c SlidersGroup
+    widgets that display the slider widgets horizontally and
+    vertically, and add them to the QStackedWidget. QStackedWidget
+    provides a stack of widgets where only the top widget is visible.
+    With \c createControls() we create a connection from a
+    controlling widget to the QStackedWidget, making the user able to
+    choose between horizontal and vertical orientation of the slider
+    widgets. The rest of the controlling mechanisms is implemented by
+    the same function call.
+
+    \snippet examples/widgets/sliders/window.cpp 1
+    \snippet examples/widgets/sliders/window.cpp 2
+
+    Then we connect the \c horizontalSliders, \c verticalSliders and
+    \c valueSpinBox to each other, so that the slider widgets and the
+    control widget will behave synchronized when the current value of
+    one of them changes. The \c valueChanged() signal is emitted with
+    the new value as argument. The \c setValue() slot sets the
+    current value of the widget to the new value, and emits \c
+    valueChanged() if the new value is different from the old one.
+
+    We put the group of control widgets and the stacked widget in a
+    horizontal layout before we initialize the minimum, maximum and
+    current values. The initialization of the current value will
+    propagate to the slider widgets through the connection we made
+    between \c valueSpinBox and the \c SlidersGroup widgets. The
+    minimum and maximum values propagate through the connections we
+    created with \c createControls().
+
+    \snippet examples/widgets/sliders/window.cpp 3
+    \snippet examples/widgets/sliders/window.cpp 4
+
+    In the private \c createControls() function, we let a QGroupBox
+    (\c controlsGroup) display the control widgets. A group box can
+    provide a frame, a title and a keyboard shortcut, and displays
+    various other widgets inside itself. The group of control widgets
+    is composed by two checkboxes, three spin boxes (with labels) and
+    one combobox.
+
+    After creating the labels, we create the two checkboxes.
+    Checkboxes are typically used to represent features in an
+    application that can be enabled or disabled. When \c
+    invertedAppearance is enabled, the slider values are inverted.
+    The table below shows the appearance for the different
+    slider-like widgets:
+
+    \table
+    \header \o                \o{2,1} QSlider                   \o{2,1} QScrollBar                \o{2,1} QDial
+    \header \o                \o Normal        \o Inverted      \o Normal        \o Inverted      \o Normal         \o Inverted
+    \row    \o Qt::Horizontal \o Left to right \o Right to left \o Left to right \o Right to left \o Clockwise \o Counterclockwise
+    \row    \o Qt::Vertical   \o Bottom to top \o Top to bottom \o Top to bottom \o Bottom to top \o Clockwise \o Counterclockwise
+    \endtable
+
+    It is common to invert the appearance of a vertical QSlider. A
+    vertical slider that controls volume, for example, will typically
+    go from bottom to top (the non-inverted appearance), whereas a
+    vertical slider that controls the position of an object on screen
+    might go from top to bottom, because screen coordinates go from
+    top to bottom.
+
+    When the \c invertedKeyBindings option is enabled (corresponding
+    to the QAbstractSlider::invertedControls property), the slider's
+    wheel and key events are inverted. The normal key bindings mean
+    that scrolling the mouse wheel "up" or using keys like page up
+    will increase the slider's current value towards its maximum.
+    Inverted, the same wheel and key events will move the value
+    toward the slider's minimum. This can be useful if the \e
+    appearance of a slider is inverted: Some users might expect the
+    keys to still work the same way on the value, whereas others
+    might expect \key PageUp to mean "up" on the screen.
+
+    Note that for horizontal and vertical scroll bars, the key
+    bindings are inverted by default: \key PageDown increases the
+    current value, and \key PageUp decreases it.
+
+    \snippet examples/widgets/sliders/window.cpp 5
+    \snippet examples/widgets/sliders/window.cpp 6
+
+    Then we create the spin boxes. QSpinBox allows the user to choose
+    a value by clicking the up and down buttons or pressing the \key
+    Up and \key Down keys on the keyboard to modify the value
+    currently displayed. The user can also type in the value
+    manually. The spin boxes control the minimum, maximum and current
+    values for the QSlider, QScrollBar, and QDial widgets.
+
+    We create a QComboBox that allows the user to choose the
+    orientation of the slider widgets. The QComboBox widget is a
+    combined button and popup list. It provides a means of presenting
+    a list of options to the user in a way that takes up the minimum
+    amount of screen space.
+
+    \snippet examples/widgets/sliders/window.cpp 7
+    \snippet examples/widgets/sliders/window.cpp 8
+
+    We synchronize the behavior of the control widgets and the slider
+    widgets through their signals and slots. We connect each control
+    widget to both the horizontal and vertical group of slider
+    widgets. We also connect \c orientationCombo to the
+    QStackedWidget, so that the correct "page" is shown. Finally, we
+    lay out the control widgets in a QGridLayout within the \c
+    controlsGroup group box.
+
+    \section1 SlidersGroup Class Definition
+
+    \snippet examples/widgets/sliders/slidersgroup.h 0
+
+    The \c SlidersGroup class inherits from QGroupBox. It provides a
+    frame and a title, and contains a QSlider, a QScrollBar and a
+    QDial.
+
+    We provide a \c valueChanged() signal and a public \c setValue()
+    slot with equivalent functionality to the ones in QAbstractSlider
+    and QSpinBox. In addition, we implement several other public
+    slots to set the minimum and maximum value, and invert the slider
+    widgets' appearance as well as key bindings.
+
+    \section1 SlidersGroup Class Implementation
+
+    \snippet examples/widgets/sliders/slidersgroup.cpp 0
+
+    First we create the slider-like widgets with the appropiate
+    properties. In particular we set the focus policy for each
+    widget. Qt::FocusPolicy is an enum type that defines the various
+    policies a widget can have with respect to acquiring keyboard
+    focus. The Qt::StrongFocus policy means that the widget accepts
+    focus by both tabbing and clicking.
+
+    Then we connect the widgets with each other, so that they will
+    stay synchronized when the current value of one of them changes.
+
+    \snippet examples/widgets/sliders/slidersgroup.cpp 1
+    \snippet examples/widgets/sliders/slidersgroup.cpp 2
+
+    We connect \c {dial}'s \c valueChanged() signal to the
+    \c{SlidersGroup}'s \c valueChanged() signal, to notify the other
+    widgets in the application (i.e., the control widgets) of the
+    changed value.
+
+    \snippet examples/widgets/sliders/slidersgroup.cpp 3
+    \codeline
+    \snippet examples/widgets/sliders/slidersgroup.cpp 4
+
+    Finally, depending on the \l {Qt::Orientation}{orientation} given
+    at the time of construction, we choose and create the layout for
+    the slider widgets within the group box.
+
+    \snippet examples/widgets/sliders/slidersgroup.cpp 5
+    \snippet examples/widgets/sliders/slidersgroup.cpp 6
+
+    The \c setValue() slot sets the value of the QSlider. We don't
+    need to explicitly call
+    \l{QAbstractSlider::setValue()}{setValue()} on the QScrollBar and
+    QDial widgets, since QSlider will emit the
+    \l{QAbstractSlider::valueChanged()}{valueChanged()} signal when
+    its value changes, triggering a domino effect.
+
+    \snippet examples/widgets/sliders/slidersgroup.cpp 7
+    \snippet examples/widgets/sliders/slidersgroup.cpp 8
+    \codeline
+    \snippet examples/widgets/sliders/slidersgroup.cpp 9
+    \snippet examples/widgets/sliders/slidersgroup.cpp 10
+
+    The \c setMinimum() and \c setMaximum() slots are used by the \c
+    Window class to set the range of the QSlider, QScrollBar, and
+    QDial widgets.
+
+    \snippet examples/widgets/sliders/slidersgroup.cpp 11
+    \snippet examples/widgets/sliders/slidersgroup.cpp 12
+    \codeline
+    \snippet examples/widgets/sliders/slidersgroup.cpp 13
+    \snippet examples/widgets/sliders/slidersgroup.cpp 14
+
+    The \c invertAppearance() and \c invertKeyBindings() slots
+    control the child widgets'
+    \l{QAbstractSlider::invertedAppearance}{invertedAppearance} and
+    \l{QAbstractSlider::invertedControls}{invertedControls}
+    properties.
+*/