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/*!

    \example widgets/groupbox

    \title Group Box Example

    The Group Box example shows how to use the different kinds of group

    boxes in Qt.

    Group boxes are container widgets that organize buttons into groups,

    both logically and on screen. They manage the interactions between

    the user and the application so that you do not have to enforce

    simple constraints.

    Group boxes are usually used to organize check boxes and radio

    buttons into exclusive groups.

    \image groupbox-example.png

    The Group Boxes example consists of a single \c Window class that

    is used to show four group boxes: an exclusive radio button group,

    a non-exclusive checkbox group, an exclusive radio button group

    with an enabling checkbox, and a group box with normal push buttons.

    \section1 Window Class Definition

    The \c Window class is a subclass of \c QWidget that is used to

    display a number of group boxes. The class definition contains

    functions to construct each group box and populate it with different

    selections of button widgets:

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

    In the example, the widget will be used as a top-level window, so

    the constructor is defined so that we do not have to specify a parent

    widget.

    \section1 Window Class Implementation

    The constructor creates a grid layout and fills it with each of the

    group boxes that are to be displayed:

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

    The functions used to create each group box each return a

    QGroupBox to be inserted into the grid layout.

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

    The first group box contains and manages three radio buttons. Since

    the group box contains only radio buttons, it is exclusive by

    default, so only one radio button can be checked at any given time.

    We check the first radio button to ensure that the button group

    contains one checked button.

    \snippet examples/widgets/groupbox/window.cpp 3

    We use a vertical layout within the group box to present the

    buttons in the form of a vertical list, and return the group

    box to the constructor.

    The second group box is itself checkable, providing a convenient

    way to disable all the buttons inside it. Initially, it is

    unchecked, so the group box itself must be checked before any of

    the radio buttons inside can be checked.

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

    The group box contains three exclusive radio buttons, and an

    independent checkbox. For consistency, one radio button must be

    checked at all times, so we ensure that the first one is initially

    checked.

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

    The buttons are arranged in the same way as those in the first

    group box.

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

    The third group box is constructed with a "flat" style that is

    better suited to certain types of dialog.

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

    This group box contains only checkboxes, so it is non-exclusive by

    default. This means that each checkbox can be checked independently

    of the others.

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

    Again, we use a vertical layout within the group box to present

    the buttons in the form of a vertical list.

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

    The final group box contains only push buttons and, like the

    second group box, it is checkable.

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

    We create a normal button, a toggle button, and a flat push button:

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

    Push buttons can be used to display popup menus. We create one, and

    attach a simple menu to it:

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

    Finally, we lay out the widgets vertically, and return the group box

    that we created:

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

*/