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/*!

    \example linguist/hellotr

    \title Hello tr() Example

    This example is a small Hello World program with a Latin translation. The

    screenshot below shows the English version.

    \image linguist-hellotr_en.png

    See the \l{Qt Linguist manual} for more information about

    translating Qt application.

    \section1 Line by Line Walkthrough

    \snippet examples/linguist/hellotr/main.cpp 0

    This line includes the definition of the QTranslator class. 

    Objects of this class provide translations for user-visible text.

    \snippet examples/linguist/hellotr/main.cpp 5

    Creates a QTranslator object without a parent.

    \snippet examples/linguist/hellotr/main.cpp 6

    Tries to load a file called \c hellotr_la.qm (the \c .qm file extension is

    implicit) that contains Latin translations for the source texts used in

    the program. No error will occur if the file is not found.

    \snippet examples/linguist/hellotr/main.cpp 7

    Adds the translations from \c hellotr_la.qm to the pool of translations used

    by the program.

    \snippet examples/linguist/hellotr/main.cpp 8

    Creates a push button that displays "Hello world!". If \c hellotr_la.qm

    was found and contains a translation for "Hello world!", the

    translation appears; if not, the source text appears.

    All classes that inherit QObject have a \c tr() function. Inside

    a member function of a QObject class, we simply write \c tr("Hello

    world!") instead of \c QPushButton::tr("Hello world!") or \c

    QObject::tr("Hello world!").

    \section1 Running the Application in English

    Since we haven't made the translation file \c hellotr_la.qm, the source text

    is shown when we run the application:

    \image linguist-hellotr_en.png

    \section1 Creating a Latin Message File

    The first step is to create a project file, \c hellotr.pro, that lists

    all the source files for the project. The project file can be a qmake

    project file, or even an ordinary makefile. Any file that contains

    \snippet examples/linguist/hellotr/hellotr.pro 0

    \snippet examples/linguist/hellotr/hellotr.pro 1

    will work. \c TRANSLATIONS specifies the message files we want to

    maintain. In this example, we just maintain one set of translations,

    namely Latin.

    Note that the file extension is \c .ts, not \c .qm. The \c .ts

    translation source format is designed for use during the

    application's development. Programmers or release managers run

    the \c lupdate program to generate and update TS files with

    the source text that is extracted from the source code.

    Translators read and update the TS files using \e {Qt

    Linguist} adding and editing their translations.

    The TS format is human-readable XML that can be emailed directly

    and is easy to put under version control. If you edit this file

    manually, be aware that the default encoding for XML is UTF-8, not

    Latin1 (ISO 8859-1). One way to type in a Latin1 character such as

    '\oslash' (Norwegian o with slash) is to use an XML entity:

    "\ø". This will work for any Unicode 4.0 character.

    Once the translations are complete the \c lrelease program is used to

    convert the TS files into the QM Qt message file format. The

    QM format is a compact binary format designed to deliver very

    fast lookup performance. Both \c lupdate and \c lrelease read all the

    project's source and header files (as specified in the HEADERS and

    SOURCES lines of the project file) and extract the strings that

    appear in \c tr() function calls.

    \c lupdate is used to create and update the message files (\c hellotr_la.ts

    in this case) to keep them in sync with the source code. It is safe to

    run \c lupdate at any time, as \c lupdate does not remove any

    information. For example, you can put it in the makefile, so the TS

    files are updated whenever the source changes.

    Try running \c lupdate right now, like this:

    \snippet doc/src/snippets/code/doc_src_examples_hellotr.qdoc 0

    (The \c -verbose option instructs \c lupdate to display messages that

    explain what it is doing.) You should now have a file \c hellotr_la.ts in

    the current directory, containing this:

    \snippet doc/src/snippets/code/doc_src_examples_hellotr.qdoc 1

    You don't need to understand the file format since it is read and

    updated using tools (\c lupdate, \e {Qt Linguist}, \c lrelease).

    \section1 Translating to Latin with Qt Linguist

    We will use \e {Qt Linguist} to provide the translation, although

    you can use any XML or plain text editor to enter a translation into a

    TS file.

    To start \e {Qt Linguist}, type

    \snippet doc/src/snippets/code/doc_src_examples_hellotr.qdoc 2

    You should now see the text "QPushButton" in the top left pane.

    Double-click it, then click on "Hello world!" and enter "Orbis, te

    saluto!" in the \gui Translation pane (the middle right of the

    window). Don't forget the exclamation mark!

    Click the \gui Done checkbox and choose \gui File|Save from the

    menu bar. The TS file will no longer contain

    \snippet doc/src/snippets/code/doc_src_examples_hellotr.qdoc 3

    but instead will have

    \snippet doc/src/snippets/code/doc_src_examples_hellotr.qdoc 4

    \section1 Running the Application in Latin

    To see the application running in Latin, we have to generate a QM

    file from the TS file. Generating a QM file can be achieved

    either from within \e {Qt Linguist} (for a single TS file), or

    by using the command line program \c lrelease which will produce one

    QM file for each of the TS files listed in the project file.

    Generate \c hellotr_la.qm from \c hellotr_la.ts by choosing

    \gui File|Release from \e {Qt Linguist}'s menu bar and pressing

    \gui Save in the file save dialog that pops up. Now run the \c hellotr

    program again. This time the button will be labelled "Orbis, te

    saluto!".

    \image linguist-hellotr_la.png

*/