source: trunk/doc/src/examples/trollprint.qdoc@ 846

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/*!
    \example linguist/trollprint
    \title Troll Print Example

    Troll Print is an example application that lets the user choose
    printer settings. It comes in two versions: English and
    Portuguese.

    \image linguist-trollprint_10_en.png

    We've included a translation file, \c trollprint_pt.ts, which contains some
    Portuguese translations for this example.

    We will consider two releases of the same application: Troll Print
    1.0 and 1.1. We will learn to reuse the translations created for one
    release in a subsequent release. (In this tutorial, you need to edit
    some source files. It's probably best to copy all the files to a new
    temporary directory and work from there.)

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

    \section1 Line by Line Walkthrough

    The \c PrintPanel class is defined in \c printpanel.h.

    \snippet examples/linguist/trollprint/printpanel.h 0

    \c PrintPanel is a QWidget. It needs the \c Q_OBJECT macro for \c
    tr() to work properly.

    The implementation file is \c printpanel.cpp.

    \snippet examples/linguist/trollprint/printpanel.cpp 0

    Some of the code is commented out in Troll Print 1.0; you will
    uncomment it later, for Troll Print 1.1.

    \snippet examples/linguist/trollprint/printpanel.cpp 1
    \snippet examples/linguist/trollprint/printpanel.cpp 2

    Notice the two occurrences of \c tr("Enabled") and of \c
    tr("Disabled") in PrintPanel. Since both "Enabled"s and "Disabled"s
    appear in the same context \e {Qt Linguist} will only display one
    occurrence of each and will use the same translations for the
    duplicates that it doesn't display. Whilst this is a useful
    timesaver, in some languages, such as Portuguese, the second
    occurrence requires a separate translation. We will see how \e {Qt
    Linguist} can be made to display all the occurrences for separate
    translation shortly.

    The header file for \c MainWindow, \c mainwindow.h, contains no
    surprises. In the implementation, \c mainwindow.cpp, we have some
    user-visible source texts that must be marked for translation.

    \snippet examples/linguist/trollprint/mainwindow.cpp 0

    We must translate the window title.

    \snippet examples/linguist/trollprint/mainwindow.cpp 1
    \snippet examples/linguist/trollprint/mainwindow.cpp 3

    We also need to translate the actions and menus. Note that the
    two argument form of \c tr() is used for the keyboard
    accelerator, "Ctrl+Q", since the second argument is the only clue
    the translator has to indicate what function that accelerator
    will perform.

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

    The \c main() function in \c main.cpp is the same as the one in
    the \l{linguist/arrowpad}{Arrow Pad} example. In particular, it
    chooses a translation file based on the current locale.

    \section1 Running Troll Print 1.0 in English and in Portuguese

    We will use the translations in the \c trollprint_pt.ts file that is provided.

    Set the \c LANG environment variable to \c pt, and then run \c
    trollprint. You should still see the English version. Now run \c
    lrelease, e.g. \c {lrelease trollprint.pro}, and then run the
    example again. Now you should see the Portuguese edition (Troll
    Imprimir 1.0):

    \image linguist-trollprint_10_pt_bad.png

    Whilst the translation has appeared correctly, it is in fact wrong. In
    good Portuguese, the second occurrence of "Enabled" should be
    "Ativadas", not "Ativado" and the ending for the second translation of
    "Disabled" must change similarly too.

    If you open \c trollprint_pt.ts using \e {Qt Linguist}, you will see that
    there is just one occurrence of "Enabled" and of "Disabled" in the
    translation source file, even though there are two of each in the
    source code. This is because \e {Qt Linguist} tries to minimize the
    translator's work by using the same translation for duplicate source
    texts. In cases such as this where an identical translation is wrong,
    the programmer must disambiguate the duplicate occurrences. This is
    easily achieved by using the two argument form of \c tr().

    We can easily determine which file must be changed because the
    translator's "context" is in fact the class name for the class where
    the texts that must be changed appears. In this case the file is \c
    printpanel.cpp, where there are four lines to change. Add the
    second argument "two-sided" in the appropriate \c tr() calls to the
    first pair of radio buttons:

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

    and add the second argument "colors" in the appropriate \c tr() calls
    for the second pair of radio buttons:

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

    Now run \c lupdate and open \c trollprint_pt.ts with \e {Qt Linguist}. You
    should now see two changes.

    First, the translation source file now contains \e three "Enabled",
    "Disabled" pairs. The first pair is marked "(obs.)" signifying that they
    are obsolete. This is because these texts appeared in \c tr() calls that
    have been replaced by new calls with two arguments. The second pair has
    "two-sided" as their comment, and the third pair has "colors" as their
    comment. The comments are shown in the \gui {Source text and comments}
    area in \e {Qt Linguist}.

    Second, the translation text "Ativado" and "Desativado" have been
    automatically used as translations for the new "Enabled" and "Disabled"
    texts, again to minimize the translator's work. Of course in this case
    these are not correct for the second occurrence of each word, but they
    provide a good starting point.

    Change the second "Ativado" into "Ativadas" and the second
    "Desativado" into "Desativadas", then save and quit. Run \c lrelease
    to obtain an up-to-date binary \c trollprint_pt.qm file, and run Troll Print
    (or rather Troll Imprimir).

    \image linguist-trollprint_10_pt_good.png

    The second argument to \c tr() calls, called "comments" in \e {Qt
    Linguist}, distinguish between identical source texts that occur in
    the same context (class). They are also useful in other cases to give
    clues to the translator, and in the case of Ctrl key accelerators are
    the only means of conveying the function performed by the accelerator to
    the translator.

    An additional way of helping the translator is to provide information on
    how to navigate to the particular part of the application that contains
    the source texts they must translate. This helps them see the context
    in which the translation appears and also helps them to find and test
    the translations. This can be achieved by using a \c TRANSLATOR comment
    in the source code:

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

    Try adding these comments to some source files, particularly to
    dialog classes, describing the navigation necessary to reach the
    dialogs. You could also add them to the example files, e.g. \c
    mainwindow.cpp and \c printpanel.cpp are appropriate files. Run \c
    lupdate and then start \e {Qt Linguist} and load in \c trollprint_pt.ts.
    You should see the comments in the \gui {Source text and comments} area
    as you browse through the list of source texts.

    Sometimes, particularly with large programs, it can be difficult for
    the translator to find their translations and check that they're
    correct. Comments that provide good navigation information can save
    them time:

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

    \section1 Troll Print 1.1

    We'll now prepare release 1.1 of Troll Print. Start your favorite text
    editor and follow these steps:

    \list
    \o Uncomment the two lines that create a QLabel with the text
         "\<b\>TROLL PRINT\</b\>" in \c printpanel.cpp.
    \o Word-tidying: Replace "2-sided" by "Two-sided" in \c printpanel.cpp.
    \o Replace "1.0" with "1.1" everywhere it occurs in \c mainwindow.cpp.
    \o Update the copyright year to 1999-2000 in \c mainwindow.cpp.
    \endlist

    (Of course the version number and copyright year would be consts or
    #defines in a real application.)

    Once finished, run \c lupdate, then open \c trollprint_pt.ts in \e {Qt
    Linguist}. The following items are of special interest:

    \list
    \o \c MainWindow
         \list
         \o Troll Print 1.0 - marked "(obs.)", obsolete
         \o About Troll Print 1.0 - marked "(obs.)", obsolete
         \o Troll Print 1.0. Copyright 1999 Software, Inc. -
       marked obsolete
         \o Troll Print 1.1 - automatically translated as
       "Troll Imprimir 1.1"
         \o About Troll Print 1.1 - automatically translated as
       "Troll Imprimir 1.1"
         \o Troll Print 1.1. Copyright 1999-2000 Software,
       Inc. - automatically translated as "Troll Imprimir 1.1.
       Copyright 1999-2000 Software, Inc."
         \endlist
    \o \c PrintPanel
         \list
         \o 2-sided - marked "(obs.)", obsolete
         \o \<b\>TROLL PRINT\</b\> - unmarked, i.e. untranslated
         \o Two-sided - unmarked, i.e. untranslated.
         \endlist
    \endlist

    Notice that \c lupdate works hard behind the scenes to make revisions
    easier, and it's pretty smart with numbers.

    Go over the translations in \c MainWindow and mark these as "done".
    Translate "\<b\>TROLL PRINT\</b\>" as "\<b\>TROLL IMPRIMIR\</b\>".
    When you're translating "Two-sided", press the \gui {Guess Again}
    button to translate "Two-sided", but change the "2" into "Dois".

    Save and quit, then run \c lrelease. The Portuguese version
    should look like this:

    \image linguist-trollprint_11_pt.png

    Choose \gui{Ajuda|Sobre} (\gui{Help|About}) to see the about box.

    If you choose \gui {Ajuda|Sobre Qt} (\gui {Help|About Qt}), you'll get
    an English dialog. Oops! Qt itself needs to be translated. See
    \l{Internationalization with Qt} for details.

    Now set \c LANG=en to get the original English version:

    \image linguist-trollprint_11_en.png
*/