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+/****************************************************************************
+**
+** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
+** This file is part of the documentation of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:FDL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the Technology Preview License Agreement accompanying
+** this package.
+**
+** GNU Free Documentation License
+** Alternatively, this file may be used under the terms of the GNU Free
+** Documentation License version 1.3 as published by the Free Software
+** Foundation and appearing in the file included in the packaging of this
+** file.
+**
+** If you have questions regarding the use of this file, please contact
+** Nokia at qt-info@nokia.com.
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+/*!
+    \example linguist/arrowpad
+    \title Arrow Pad Example
+
+    This example is a slightly more involved and introduces a key \e
+    {Qt Linguist} concept: "contexts". It also shows how to use two
+    or more languages.
+
+    \image linguist-arrowpad_en.png
+
+    We will use two translations, French and Dutch, although there is no
+    effective limit on the number of possible translations that can be used
+    with an application. The relevant lines of \c arrowpad.pro are
+
+    \snippet examples/linguist/arrowpad/arrowpad.pro 0
+    \codeline
+    \snippet examples/linguist/arrowpad/arrowpad.pro 1
+
+    Run \c lupdate; it should produce two identical message files
+    \c arrowpad_fr.ts and \c arrowpad_nl.ts. These files will contain all the source
+    texts marked for translation with \c tr() calls and their contexts.
+
+    See the \l{Qt Linguist manual} for more information about
+    translating Qt application.
+
+    \section1 Line by Line Walkthrough
+
+    In \c arrowpad.h we define the \c ArrowPad subclass which is a
+    subclass of QWidget. In the screenshot above, the central
+    widget with the four buttons is an \c ArrowPad.
+
+    \snippet examples/linguist/arrowpad/arrowpad.h 0
+    \snippet examples/linguist/arrowpad/arrowpad.h 1
+    \snippet examples/linguist/arrowpad/arrowpad.h 2
+
+    When \c lupdate is run it not only extracts the source texts but it
+    also groups them into contexts. A context is the name of the class in
+    which the source text appears. Thus, in this example, "ArrowPad" is a
+    context: it is the context of the texts in the \c ArrowPad class. 
+    The \c Q_OBJECT macro defines \c tr(x) in \c ArrowPad like this:
+
+    \snippet doc/src/snippets/code/doc_src_examples_arrowpad.cpp 0
+
+    Knowing which class each source text appears in enables \e {Qt
+    Linguist} to group texts that are logically related together, e.g.
+    all the text in a dialog will have the context of the dialog's class
+    name and will be shown together. This provides useful information for
+    the translator since the context in which text appears may influence how
+    it should be translated. For some translations keyboard
+    accelerators may need to be changed and having all the source texts in a
+    particular context (class) grouped together makes it easier for the
+    translator to perform any accelerator changes without introducing
+    conflicts.
+
+    In \c arrowpad.cpp we implement the \c ArrowPad class.
+
+    \snippet examples/linguist/arrowpad/arrowpad.cpp 0
+    \snippet examples/linguist/arrowpad/arrowpad.cpp 1
+    \snippet examples/linguist/arrowpad/arrowpad.cpp 2
+    \snippet examples/linguist/arrowpad/arrowpad.cpp 3
+
+    We call \c ArrowPad::tr() for each button's label since the labels are
+    user-visible text.
+
+    \image linguist-arrowpad_en.png
+
+    \snippet examples/linguist/arrowpad/mainwindow.h 0
+    \snippet examples/linguist/arrowpad/mainwindow.h 1
+
+    In the screenshot above, the whole window is a \c MainWindow.
+    This is defined in the \c mainwindow.h header file. Here too, we
+    use \c Q_OBJECT, so that \c MainWindow will become a context in
+    \e {Qt Linguist}.
+
+    \snippet examples/linguist/arrowpad/mainwindow.cpp 0
+
+    In the implementation of \c MainWindow, \c mainwindow.cpp, we create
+    an instance of our \c ArrowPad class.
+
+    \snippet examples/linguist/arrowpad/mainwindow.cpp 1
+
+    We also call \c MainWindow::tr() twice, once for the action and
+    once for the shortcut.
+
+    Note the use of \c tr() to support different keys in other
+    languages. "Ctrl+Q" is a good choice for Quit in English, but a
+    Dutch translator might want to use "Ctrl+A" (for Afsluiten) and a
+    German translator "Strg+E" (for Beenden). When using \c tr() for
+    \key Ctrl key accelerators, the two argument form should be used
+    with the second argument describing the function that the
+    accelerator performs.
+
+    Our \c main() function is defined in \c main.cpp as usual.
+
+    \snippet examples/linguist/arrowpad/main.cpp 2
+    \snippet examples/linguist/arrowpad/main.cpp 3
+
+    We choose which translation to use according to the current locale.
+    QLocale::system() can be influenced by setting the \c LANG
+    environment variable, for example. Notice that the use of a naming
+    convention that incorporates the locale for \c .qm message files,
+    (and TS files), makes it easy to implement choosing the
+    translation file according to locale.
+
+    If there is no QM message file for the locale chosen the original
+    source text will be used and no error raised.
+
+    \section1 Translating to French and Dutch
+
+    We'll begin by translating the example application into French. Start
+    \e {Qt Linguist} with \c arrowpad_fr.ts. You should get the seven source
+    texts ("\&Up", "\&Left", etc.) grouped in two contexts ("ArrowPad"
+    and "MainWindow").
+
+    Now, enter the following translations:
+
+    \list
+    \o \c ArrowPad
+         \list
+         \o \&Up - \&Haut
+         \o \&Left - \&Gauche
+         \o \&Right - \&Droite
+         \o \&Down - \&Bas
+         \endlist
+    \o \c MainWindow
+         \list
+         \o E\&xit - \&Quitter
+         \o Ctrl+Q - Ctrl+Q
+         \o \&File - \&Fichier
+         \endlist
+    \endlist
+
+    It's quickest to press \key{Alt+D} (which clicks the \gui {Done \& Next}
+    button) after typing each translation, since this marks the
+    translation as done and moves on to the next source text.
+
+    Save the file and do the same for Dutch working with \c arrowpad_nl.ts:
+
+    \list
+    \o \c ArrowPad
+         \list
+         \o \&Up - \&Omhoog
+         \o \&Left - \&Links
+         \o \&Right - \&Rechts
+         \o \&Down - Omlaa\&g
+         \endlist
+    \o \c MainWindow
+         \list
+         \o E\&xit - \&Afsluiten
+         \o Ctrl+Q - Ctrl+A
+         \o File - \&Bestand
+         \endlist
+    \endlist
+
+    We have to convert the \c tt1_fr.ts and \c tt1_nl.ts translation source
+    files into QM files. We could use \e {Qt Linguist} as we've done
+    before; however using the command line tool \c lrelease ensures that
+    \e all the QM files for the application are created without us
+    having to remember to load and \gui File|Release each one
+    individually from \e {Qt Linguist}.
+
+    Type
+
+    \snippet doc/src/snippets/code/doc_src_examples_arrowpad.qdoc 1
+
+    This should create both \c arrowpad_fr.qm and \c arrowpad_nl.qm. Set the \c
+    LANG environment variable to \c fr. In Unix, one of the two following
+    commands should work
+
+    \snippet doc/src/snippets/code/doc_src_examples_arrowpad.qdoc 2
+
+    In Windows, either modify \c autoexec.bat or run
+
+    \snippet doc/src/snippets/code/doc_src_examples_arrowpad.qdoc 3
+
+    When you run the program, you should now see the French version:
+
+    \image linguist-arrowpad_fr.png
+
+    Try the same with Dutch, by setting \c LANG=nl. Now the Dutch
+    version should appear:
+
+    \image linguist-arrowpad_nl.png
+
+    \section1 Exercises
+
+    Mark one of the translations in \e {Qt Linguist} as not done, i.e.
+    by unchecking the "done" checkbox; run \c lupdate, then \c lrelease,
+    then the example. What effect did this change have?
+
+    Set \c LANG=fr_CA (French Canada) and run the example program again. 
+    Explain why the result is the same as with \c LANG=fr.
+
+    Change one of the accelerators in the Dutch translation to eliminate the
+    conflict between \e \&Bestand and \e \&Boven.
+*/