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/*! 

    \example widgets/spinboxes

    \title Spin Boxes Example

    The Spin Boxes example shows how to use the many different types of spin boxes

    available in Qt, from a simple QSpinBox widget to more complex editors like

    the QDateTimeEdit widget.

    \image spinboxes-example.png

    The example consists of a single \c Window class that is used to display the

    different spin box-based widgets available with Qt.

    \section1 Window Class Definition

    The \c Window class inherits QWidget and contains two slots that are used

    to provide interactive features:

    \snippet examples/widgets/spinboxes/window.h 0

    The private functions are used to set up each type of spin box in the window.

    We use member variables to keep track of various widgets so that they can

    be reconfigured when required.

    \section1 Window Class Implementation

    The constructor simply calls private functions to set up the different types

    of spin box used in the example, and places each group in a layout:

    \snippet examples/widgets/spinboxes/window.cpp 0

    We use the layout to manage the arrangement of the window's child widgets,

    and change the window title.

    The \c createSpinBoxes() function constructs a QGroupBox and places three

    QSpinBox widgets inside it with descriptive labels to indicate the types of

    input they expect.

    \snippet examples/widgets/spinboxes/window.cpp 1

    The first spin box shows the simplest way to use QSpinBox. It accepts values

    from -20 to 20, the current value can be increased or decreased by 1 with

    either the arrow buttons or \key{Up} and \key{Down} keys, and the default

    value is 0.

    The second spin box uses a larger step size and displays a suffix to

    provide more information about the type of data the number represents:

    \snippet examples/widgets/spinboxes/window.cpp 2

    This spin box also displays a

    \l{QAbstractSpinBox::specialValueText}{special value} instead of the minimum

    value defined for it. This means that it will never show \gui{0%}, but will

    display \gui{Automatic} when the minimum value is selected.

    The third spin box shows how a prefix can be used:

    \snippet examples/widgets/spinboxes/window.cpp 4

    For simplicity, we show a spin box with a prefix and no suffix. It is also

    possible to use both at the same time.

    \snippet examples/widgets/spinboxes/window.cpp 5

    The rest of the function sets up a layout for the group box and places each

    of the widgets inside it.

    The \c createDateTimeEdits() function constructs another group box with a

    selection of spin boxes used for editing dates and times.

    \snippet examples/widgets/spinboxes/window.cpp 6

    The first spin box is a QDateEdit widget that is able to accept dates

    within a given range specified using QDate values. The arrow buttons and

    \key{Up} and \key{Down} keys can be used to increase and decrease the

    values for year, month, and day when the cursor is in the relevant section.

    The second spin box is a QTimeEdit widget:

    \snippet examples/widgets/spinboxes/window.cpp 7

    Acceptable values for the time are defined using QTime values.

    The third spin box is a QDateTimeEdit widget that can display both date and

    time values, and we place a label above it to indicate the range of allowed

    times for a meeting. These widgets will be updated when the user changes a

    format string.

    \snippet examples/widgets/spinboxes/window.cpp 8

    The format string used for the date time editor, which is also shown in the

    string displayed by the label, is chosen from a set of strings in a combobox:

    \snippet examples/widgets/spinboxes/window.cpp 9

    \codeline

    \snippet examples/widgets/spinboxes/window.cpp 10

    A signal from this combobox is connected to a slot in the \c Window class

    (shown later).

    \snippet examples/widgets/spinboxes/window.cpp 11

    Each child widget of the group box in placed in a layout.

    The \c setFormatString() slot is called whenever the user selects a new

    format string in the combobox. The display format for the QDateTimeEdit

    widget is set using the raw string passed by the signal:

    \snippet examples/widgets/spinboxes/window.cpp 12

    Depending on the visible sections in the widget, we set a new date or time

    range, and update the associated label to provide relevant information for

    the user:

    \snippet examples/widgets/spinboxes/window.cpp 13

    When the format string is changed, there will be an appropriate label and

    entry widget for dates, times, or both types of input.

    The \c createDoubleSpinBoxes() function constructs three spin boxes that are

    used to input double-precision floating point numbers:

    \snippet examples/widgets/spinboxes/window.cpp 14

    Before the QDoubleSpinBox widgets are constructed, we create a spin box to

    control how many decimal places they show. By default, only two decimal places

    are shown in the following spin boxes, each of which is the equivalent of a

    spin box in the group created by the \c createSpinBoxes() function.

    The first double spin box shows a basic double-precision spin box with the

    same range, step size, and default value as the first spin box in the

    \c createSpinBoxes() function:

    \snippet examples/widgets/spinboxes/window.cpp 15

    However, this spin box also allows non-integer values to be entered.

    The second spin box displays a suffix and shows a special value instead

    of the minimum value:

    \snippet examples/widgets/spinboxes/window.cpp 16

    The third spin box displays a prefix instead of a suffix:

    \snippet examples/widgets/spinboxes/window.cpp 17

    We connect the QSpinBox widget that specifies the precision to a slot in

    the \c Window class.

    \snippet examples/widgets/spinboxes/window.cpp 18

    The rest of the function places each of the widgets into a layout for the

    group box.

    The \c changePrecision() slot is called when the user changes the value in

    the precision spin box:

    \snippet examples/widgets/spinboxes/window.cpp 19

    This function simply uses the integer supplied by the signal to specify the

    number of decimal places in each of the QDoubleSpinBox widgets. Each one

    of these will be updated automatically when their

    \l{QDoubleSpinBox::decimals}{decimals} property is changed.

*/