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/*!

    \page qt4-mainwindow.html

    \title The Qt 4 Main Window Classes

    \contentspage {What's New in Qt 4}{Home}

    \previouspage The Scribe Classes

    \nextpage The New Qt Designer

    Qt 4 introduces a new set of main window classes that supersede the

    Qt 3 main window classes, providing a more efficient implementation

    while remaining easy to use.

    \tableofcontents

    \section1 Overview of the Main Window Classes

    The main window-related classes have been redesigned to satisfy a

    number of requirements, addressing issues raised by our customers and

    internal developers. The aim of this redesign is to provide a more

    consistent and efficient framework for main window management.

    \section1 The Main Window Classes

    Qt 4 provides the following classes for managing main windows and

    associated user interface components:

    \list

    \o QMainWindow remains the central class around which applications

       can be built. The interface to this class has been simplified, and

       much of the functionality previously included in this class is now

       present in the companion QDockWidget and QToolBar classes.

    \o QDockWidget provides a widget that can be used to create

       detachable tool palettes or helper windows. Dock widgets keep track

       of their own properties, and they can be moved, closed, and floated

       as external windows.

    \o QToolBar provides a generic toolbar widget that can hold a

       number of different action-related widgets, such as buttons,

       drop-down menus, comboboxes, and spin boxes. The emphasis on a

       unified action model in Qt 4 means that toolbars cooperate well

       with menus and keyboard shortcuts.

    \endlist

    \section1 Example Code

    Using QMainWindow is straightforward. Generally, we subclass

    QMainWindow and set up menus, toolbars, and dock widgets inside

    the QMainWindow constructor.

    To add a menu bar to the main window, we simply create the menus, and

    add them to the main window's menu bar. Note that the

    QMainWindow::menuBar() function will automatically create the menu bar

    the first time it is called. You can also call

    QMainWindow::setMenuBar() to use a custom menu bar in the main window.

    \snippet doc/src/snippets/code/doc_src_qt4-mainwindow.qdoc 0

    \dots

    \snippet examples/mainwindows/menus/mainwindow.cpp 5

    \dots

    Once actions have been created, we can add them to the main window

    components. To begin with, we add them to the pop-up menus:

    \snippet examples/mainwindows/menus/mainwindow.cpp 10

    \dots

    \snippet examples/mainwindows/menus/mainwindow.cpp 11

    \dots

    The QToolBar and QMenu classes use Qt's action system to provide a

    consistent API. In the above code, some existing actions were added to

    the file menu with the QMenu::addAction() function. QToolBar also

    provides this function, making it easy to reuse actions in different

    parts of the main window. This avoids unnecessary duplication of work.

    We create a toolbar as a child of the main window, and add the desired

    actions to it:

    \snippet examples/mainwindows/sdi/mainwindow.cpp 0

    \dots

    \snippet doc/src/snippets/code/doc_src_qt4-mainwindow.qdoc 1

    In this example, the toolbar is restricted to the top and bottom

    toolbar areas of the main window, and is initially placed in the

    top tool bar area. We can see that the actions specified by \c

    newAct and \c openAct will be displayed both on the toolbar and in

    the file menu.

    QDockWidget is used in a similar way to QToolBar. We create a

    dock widget as a child of the main window, and add widgets as children

    of the dock widget:

    \snippet doc/src/snippets/dockwidgets/mainwindow.cpp 0

    In this example, the dock widget can only be placed in the left and

    right dock areas, and it is initially placed in the left dock area. 

    The QMainWindow API allows the programmer to customize which dock

    widget areas occupy the four corners of the dock widget area. If

    required, the default can be changed with the

    QMainWindow::setCorner() function:

    \snippet doc/src/snippets/code/doc_src_qt4-mainwindow.qdoc 2

    The following diagram shows the configuration produced by the above code.

    Note that the left and right dock widgets will occupy the top and bottom

    corners of the main window in this layout.

    \image mainwindow-docks-example.png

    Once all of the main window components have been set up, the central widget

    is created and installed by using code similar to the following:

    \snippet doc/src/snippets/code/doc_src_qt4-mainwindow.qdoc 3

    The central widget can be any subclass of QWidget.

    \section1 What's Changed since Qt 3?

    The main window classes in Qt 4 adds new functionality, mainly to

    the dock widgets and toolbars. We have also made changes to the

    design of the framework.

    Although the QMainWindow class in Qt 3 provided support for

    toolbars, dock widgets, and other standard user interface

    components, its design meant that these items were managed

    through a large number of QMainWindow member functions. In Qt 4,

    the QMainWindow class delegates many of the management tasks to

    QDockWidget and QToolBar (allowing more consistent behavior to be

    defined and implemented).

    The dock widget and toolbar classes are now separated into

    independent classes. (write some more here)

    (It is intended that these changes allow more consistent behavior 

    to be defined and implemented (which? example). In

    response to feedback from customers, we hope to improve these classes 

    even further.)

    \section2 New Functionality

    Dock widgets are animated when docking or

    detaching from a dock area. The dock areas will also adjust their

    size to show where the dock widget will dock when it hovers over

    it. This animation can be turned off with \c setAnimated(). 

    By default, dock widgets are added to the dock areas in a single

    row. By setting nesting enabled with \c setDockNestingEnabled(),

    the widgets can be added both vertically and horizontally.

    Two dock widgets can occupy the same space in a dock area. The user

    can then choose which widget that is visible with a tab bar that

    is located below the widgets. The QMainWindow::tabifyDockWidget() 

    joins two tab widgets in such a tabbed dock area. (revise the

    entire paragraph)

    \section2 Independent QDockWidget And QToolBar Classes

    Toolbar and dock window functionality is provided by two independent

    classes: QToolBar and QDockWidget. Toolbars and dock widgets

    reside in separate areas, with toolbars outside the dock widget

    area. This behavior differs from the Qt 3 behavior, where

    QToolBar inherited functionality from QDockWidget, and both types of

    component shared the same areas. The result is a more consistent

    and predictable experience for users. Toolbars and dock widgets

    provide feedback while being dragged into their new positions.

    \image mainwindow-docks.png

    The diagram above shows the layout of a main window that contains both

    toolbars and dock widgets. Each corner area can be used by either

    of the adjacent dock widget areas, allowing dock widget behavior and

    main window layout to be specified precisely.

    Toolbars and dock widgets are child widgets of the main window. They

    are no longer reparented into a dock area widget by the main window.

    Instead, layouts are used to manage the placement of toolbars and dock

    widgets. One consequence is that the old QDockArea class is no

    longer required in Qt 4.

    \section2 Code Change Examples

    QMainWindow retains the menuBar() function, but menus are always

    constructed using QAction objects. All kinds of menus are

    constructed using the general QMenu class.

    Qt 3:

    \snippet doc/src/snippets/code/doc_src_qt4-mainwindow.qdoc 4

    Qt 4:

    \snippet doc/src/snippets/code/doc_src_qt4-mainwindow.qdoc 5

    Toolbars follow the same pattern as menus, with the new, more

    consistent behavior:

    Qt 3:

    \snippet doc/src/snippets/code/doc_src_qt4-mainwindow.qdoc 6

    Qt 4:

    \snippet doc/src/snippets/code/doc_src_qt4-mainwindow.qdoc 7

    The behavior of dock widgets is now configured through the member

    functions of QDockWidget. For example, compare the old and new ways

    of creating a dock widget in the dock area on the left hand side of the

    main window.

    In Qt 3:

    \snippet doc/src/snippets/code/doc_src_qt4-mainwindow.qdoc 8

    In Qt 4:

    \snippet doc/src/snippets/code/doc_src_qt4-mainwindow.qdoc 9

*/