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+****************************************************************************/
+
+/*!
+    \example mainwindows/application
+    \title Application Example
+
+    The Application example shows how to implement a standard GUI
+    application with menus, toolbars, and a status bar. The example
+    itself is a simple text editor program built around QPlainTextEdit.
+
+    \image application.png Screenshot of the Application example
+
+    Nearly all of the code for the Application example is in the \c
+    MainWindow class, which inherits QMainWindow. QMainWindow
+    provides the framework for windows that have menus, toolbars,
+    dock windows, and a status bar. The application provides
+    \menu{File}, \menu{Edit}, and \menu{Help} entries in the menu
+    bar, with the following popup menus:
+
+    \image application-menus.png The Application example's menu system
+
+    The status bar at the bottom of the main window shows a
+    description of the menu item or toolbar button under the cursor.
+
+    To keep the example simple, recently opened files aren't shown in
+    the \menu{File} menu, even though this feature is desired in 90%
+    of applications. The \l{mainwindows/recentfiles}{Recent Files}
+    example shows how to implement this. Furthermore, this example
+    can only load one file at a time. The \l{mainwindows/sdi}{SDI}
+    and \l{mainwindows/mdi}{MDI} examples shows how to lift these
+    restrictions.
+
+    \section1 MainWindow Class Definition
+
+    Here's the class definition:
+
+    \snippet examples/mainwindows/application/mainwindow.h 0
+
+    The public API is restricted to the constructor. In the \c
+    protected section, we reimplement QWidget::closeEvent() to detect
+    when the user attempts to close the window, and warn the user
+    about unsaved changes. In the \c{private slots} section, we
+    declare slots that correspond to menu entries, as well as a
+    mysterious \c documentWasModified() slot. Finally, in the \c
+    private section of the class, we have various members that will
+    be explained in due time.
+
+    \section1 MainWindow Class Implementation
+
+    \snippet examples/mainwindows/application/mainwindow.cpp 0
+
+    We start by including \c <QtGui>, a header file that contains the
+    definition of all classes in the \l QtCore and \l QtGui
+    libraries. This saves us from the trouble of having to include
+    every class individually. We also include \c mainwindow.h.
+
+    You might wonder why we don't include \c <QtGui> in \c
+    mainwindow.h and be done with it. The reason is that including
+    such a large header from another header file can rapidly degrade
+    performances. Here, it wouldn't do any harm, but it's still
+    generally a good idea to include only the header files that are
+    strictly necessary from another header file.
+
+    \snippet examples/mainwindows/application/mainwindow.cpp 1
+    \snippet examples/mainwindows/application/mainwindow.cpp 2
+
+    In the constructor, we start by creating a QPlainTextEdit widget as a
+    child of the main window (the \c this object). Then we call
+    QMainWindow::setCentralWidget() to tell that this is going to be
+    the widget that occupies the central area of the main window,
+    between the toolbars and the status bar.
+
+    Then we call \c createActions(), \c createMenus(), \c
+    createToolBars(), and \c createStatusBar(), four private
+    functions that set up the user interface. After that, we call \c
+    readSettings() to restore the user's preferences.
+
+    We establish a signal-slot connection between the QPlainTextEdit's
+    document object and our \c documentWasModified() slot. Whenever
+    the user modifies the text in the QPlainTextEdit, we want to update
+    the title bar to show that the file was modified.
+
+    At the end, we set the window title using the private
+    \c setCurrentFile() function. We'll come back to this later.
+
+    \target close event handler
+    \snippet examples/mainwindows/application/mainwindow.cpp 3
+    \snippet examples/mainwindows/application/mainwindow.cpp 4
+
+    When the user attempts to close the window, we call the private
+    function \c maybeSave() to give the user the possibility to save
+    pending changes. The function returns true if the user wants the
+    application to close; otherwise, it returns false. In the first
+    case, we save the user's preferences to disk and accept the close
+    event; in the second case, we ignore the close event, meaning
+    that the application will stay up and running as if nothing
+    happened.
+
+    \snippet examples/mainwindows/application/mainwindow.cpp 5
+    \snippet examples/mainwindows/application/mainwindow.cpp 6
+
+    The \c newFile() slot is invoked when the user selects
+    \menu{File|New} from the menu. We call \c maybeSave() to save any
+    pending changes and if the user accepts to go on, we clear the
+    QPlainTextEdit and call the private function \c setCurrentFile() to
+    update the window title and clear the
+    \l{QWidget::windowModified}{windowModified} flag.
+
+    \snippet examples/mainwindows/application/mainwindow.cpp 7
+    \snippet examples/mainwindows/application/mainwindow.cpp 8
+
+    The \c open() slot is invoked when the user clicks
+    \menu{File|Open}. We pop up a QFileDialog asking the user to
+    choose a file. If the user chooses a file (i.e., \c fileName is
+    not an empty string), we call the private function \c loadFile()
+    to actually load the file.
+
+    \snippet examples/mainwindows/application/mainwindow.cpp 9
+    \snippet examples/mainwindows/application/mainwindow.cpp 10
+
+    The \c save() slot is invoked when the user clicks
+    \menu{File|Save}. If the user hasn't provided a name for the file
+    yet, we call \c saveAs(); otherwise, we call the private function
+    \c saveFile() to actually save the file.
+
+    \snippet examples/mainwindows/application/mainwindow.cpp 11
+    \snippet examples/mainwindows/application/mainwindow.cpp 12
+
+    In \c saveAs(), we start by popping up a QFileDialog asking the
+    user to provide a name. If the user clicks \gui{Cancel}, the
+    returned file name is empty, and we do nothing.
+
+    \snippet examples/mainwindows/application/mainwindow.cpp 13
+    \snippet examples/mainwindows/application/mainwindow.cpp 14
+
+    The application's About box is done using one statement, using
+    the QMessageBox::about() static function and relying on its
+    support for an HTML subset.
+
+    The \l{QObject::tr()}{tr()} call around the literal string marks
+    the string for translation. It is a good habit to call
+    \l{QObject::tr()}{tr()} on all user-visible strings, in case you
+    later decide to translate your application to other languages.
+    The \l{Internationalization with Qt} overview convers
+    \l{QObject::tr()}{tr()} in more detail.
+
+    \snippet examples/mainwindows/application/mainwindow.cpp 15
+    \snippet examples/mainwindows/application/mainwindow.cpp 16
+
+    The \c documentWasModified() slot is invoked each time the text
+    in the QPlainTextEdit changes because of user edits. We call
+    QWidget::setWindowModified() to make the title bar show that the
+    file was modified. How this is done varies on each platform.
+
+    \snippet examples/mainwindows/application/mainwindow.cpp 17
+    \snippet examples/mainwindows/application/mainwindow.cpp 18
+    \dots
+    \snippet examples/mainwindows/application/mainwindow.cpp 22
+
+    The \c createActions() private function, which is called from the
+    \c MainWindow constructor, creates \l{QAction}s. The code is very
+    repetitive, so we show only the actions corresponding to
+    \menu{File|New}, \menu{File|Open}, and \menu{Help|About Qt}.
+
+    A QAction is an object that represents one user action, such as
+    saving a file or invoking a dialog. An action can be put in a
+    QMenu or a QToolBar, or both, or in any other widget that
+    reimplements QWidget::actionEvent().
+
+    An action has a text that is shown in the menu, an icon, a
+    shortcut key, a tooltip, a status tip (shown in the status bar),
+    a "What's This?" text, and more. It emits a
+    \l{QAction::triggered()}{triggered()} signal whenever the user
+    invokes the action (e.g., by clicking the associated menu item or
+    toolbar button). We connect this signal to a slot that performs
+    the actual action.
+
+    The code above contains one more idiom that must be explained.
+    For some of the actions, we specify an icon as a QIcon to the
+    QAction constructor. The QIcon constructor takes the file name
+    of an image that it tries to load. Here, the file name starts
+    with \c{:}. Such file names aren't ordinary file names, but
+    rather path in the executable's stored resources. We'll come back
+    to this when we review the \c application.qrc file that's part of
+    the project.
+
+    \snippet examples/mainwindows/application/mainwindow.cpp 23
+    \snippet examples/mainwindows/application/mainwindow.cpp 24
+
+    The \gui{Edit|Cut} and \gui{Edit|Copy} actions must be available
+    only when the QPlainTextEdit contains selected text. We disable them
+    by default and connect the QPlainTextEdit::copyAvailable() signal to
+    the QAction::setEnabled() slot, ensuring that the actions are
+    disabled when the text editor has no selection.
+
+    \snippet examples/mainwindows/application/mainwindow.cpp 25
+    \snippet examples/mainwindows/application/mainwindow.cpp 27
+
+    Creating actions isn't sufficient to make them available to the
+    user; we must also add them to the menu system. This is what \c
+    createMenus() does. We create a \menu{File}, an \menu{Edit}, and
+    a \menu{Help} menu. QMainWindow::menuBar() lets us access the
+    window's menu bar widget. We don't have to worry about creating
+    the menu bar ourselves; the first time we call this function, the
+    QMenuBar is created.
+
+    Just before we create the \menu{Help} menu, we call
+    QMenuBar::addSeparator(). This has no effect for most widget
+    styles (e.g., Windows and Mac OS X styles), but for Motif-based
+    styles this makes sure that \menu{Help} is pushed to the right
+    side of the menu bar. Try running the application with various
+    styles and see the results:
+
+    \snippet doc/src/snippets/code/doc_src_examples_application.qdoc 0
+
+    Let's now review the toolbars:
+
+    \snippet examples/mainwindows/application/mainwindow.cpp 30
+
+    Creating toolbars is very similar to creating menus. The same
+    actions that we put in the menus can be reused in the toolbars.
+
+    \snippet examples/mainwindows/application/mainwindow.cpp 32
+    \snippet examples/mainwindows/application/mainwindow.cpp 33
+
+    QMainWindow::statusBar() returns a pointer to the main window's
+    QStatusBar widget. Like with \l{QMainWindow::menuBar()}, the
+    widget is automatically created the first time the function is
+    called.
+
+    \snippet examples/mainwindows/application/mainwindow.cpp 34
+    \snippet examples/mainwindows/application/mainwindow.cpp 36
+
+    The \c readSettings() function is called from the constructor to
+    load the user's preferences and other application settings. The
+    QSettings class provides a high-level interface for storing
+    settings permanently on disk. On Windows, it uses the (in)famous
+    Windows registry; on Mac OS X, it uses the native XML-based
+    CFPreferences API; on Unix/X11, it uses text files.
+
+    The QSettings constructor takes arguments that identify your
+    company and the name of the product. This ensures that the
+    settings for different applications are kept separately.
+
+    We use QSettings::value() to extract the value of the "pos" and
+    "size" settings. The second argument to QSettings::value() is
+    optional and specifies a default value for the setting if there
+    exists none. This value is used the first time the application is
+    run.
+
+    When restoring the position and size of a window, it's important
+    to call QWidget::resize() before QWidget::move(). The reason why
+    is given in the \l{Window Geometry} overview.
+
+    \snippet examples/mainwindows/application/mainwindow.cpp 37
+    \snippet examples/mainwindows/application/mainwindow.cpp 39
+
+    The \c writeSettings() function is called from \c closeEvent().
+    Writing settings is similar to reading them, except simpler. The
+    arguments to the QSettings constructor must be the same as in \c
+    readSettings().
+
+    \snippet examples/mainwindows/application/mainwindow.cpp 40
+    \snippet examples/mainwindows/application/mainwindow.cpp 41
+
+    The \c maybeSave() function is called to save pending changes. If
+    there are pending changes, it pops up a QMessageBox giving the
+    user to save the document. The options are QMessageBox::Yes,
+    QMessageBox::No, and QMessageBox::Cancel. The \gui{Yes} button is
+    made the default button (the button that is invoked when the user
+    presses \key{Return}) using the QMessageBox::Default flag; the
+    \gui{Cancel} button is made the escape button (the button that is
+    invoked when the user presses \key{Esc}) using the
+    QMessageBox::Escape flag.
+
+    The \c maybeSave() function returns \c true in all cases, except
+    when the user clicks \gui{Cancel}. The caller must check the
+    return value and stop whatever it was doing if the return value
+    is \c false.
+
+    \snippet examples/mainwindows/application/mainwindow.cpp 42
+    \snippet examples/mainwindows/application/mainwindow.cpp 43
+
+    In \c loadFile(), we use QFile and QTextStream to read in the
+    data. The QFile object provides access to the bytes stored in a
+    file.
+
+    We start by opening the file in read-only mode. The QFile::Text
+    flag indicates that the file is a text file, not a binary file.
+    On Unix and Mac OS X, this makes no difference, but on Windows,
+    it ensures that the "\\r\\n" end-of-line sequence is converted to
+    "\\n" when reading.
+
+    If we successfully opened the file, we use a QTextStream object
+    to read in the data. QTextStream automatically converts the 8-bit
+    data into a Unicode QString and supports various encodings. If no
+    encoding is specified, QTextStream assumes the file is written
+    using the system's default 8-bit encoding (for example, Latin-1;
+    see QTextCodec::codecForLocale() for details).
+
+    Since the call to QTextStream::readAll() might take some time, we
+    set the cursor to be Qt::WaitCursor for the entire application
+    while it goes on.
+
+    At the end, we call the private \c setCurrentFile() function,
+    which we'll cover in a moment, and we display the string "File
+    loaded" in the status bar for 2 seconds (2000 milliseconds).
+
+    \snippet examples/mainwindows/application/mainwindow.cpp 44
+    \snippet examples/mainwindows/application/mainwindow.cpp 45
+
+    Saving a file is very similar to loading one. Here, the
+    QFile::Text flag ensures that on Windows, "\\n" is converted into
+    "\\r\\n" to conform to the Windows convension.
+
+    \snippet examples/mainwindows/application/mainwindow.cpp 46
+    \snippet examples/mainwindows/application/mainwindow.cpp 47
+
+    The \c setCurrentFile() function is called to reset the state of
+    a few variables when a file is loaded or saved, or when the user
+    starts editing a new file (in which case \c fileName is empty).
+    We update the \c curFile variable, clear the
+    QTextDocument::modified flag and the associated \c
+    QWidget:windowModified flag, and update the window title to
+    contain the new file name (or \c untitled.txt).
+
+    The \c strippedName() function call around \c curFile in the
+    QWidget::setWindowTitle() call shortens the file name to exclude
+    the path. Here's the function:
+
+    \snippet examples/mainwindows/application/mainwindow.cpp 48
+    \snippet examples/mainwindows/application/mainwindow.cpp 49
+
+    \section1 The main() Function
+
+    The \c main() function for this application is typical of
+    applications that contain one main window:
+
+    \snippet examples/mainwindows/application/main.cpp 0
+
+    \section1 The Resource File
+
+    As you will probably recall, for some of the actions, we
+    specified icons with file names starting with \c{:} and mentioned
+    that such file names aren't ordinary file names, but path in the
+    executable's stored resources. These resources are compiled
+
+    The resources associated with an application are specified in a
+    \c .qrc file, an XML-based file format that lists files on the
+    disk. Here's the \c application.qrc file that's used by the
+    Application example:
+
+    \quotefile mainwindows/application/application.qrc
+
+    The \c .png files listed in the \c application.qrc file are files
+    that are part of the Application example's source tree. Paths are
+    relative to the directory where the \c application.qrc file is
+    located (the \c mainwindows/application directory).
+
+    The resource file must be mentioned in the \c application.pro
+    file  so that \c qmake knows about it:
+
+    \snippet examples/mainwindows/application/application.pro 0
+
+    \c qmake will produce make rules to generate a file called \c
+    qrc_application.cpp that is linked into the application. This
+    file contains all the data for the images and other resources as
+    static C++ arrays of compressed binary data. See
+    \l{resources.html}{The Qt Resource System} for more information
+    about resources.
+*/