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+
+/*!
+ \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.
+*/