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Qt Linguist Manual: Release Manager

Two tools are provided for the release manager, lupdate and lrelease. These tools can process qmake project files, or operate directly on the file system.

Qt Project Files

The easiest method to use lupdate and lrelease is by specifing a .pro Qt project file. There must be an entry in the TRANSLATIONS section of the project file for each language that is additional to the native language. A typical entry looks like this:

 TRANSLATIONS = arrowpad_fr.ts \

Using a locale within the translation file name is useful for determining which language to load at runtime. This is explained in the Programmers chapter.

An example of a complete .pro file with four translation source files:

 HEADERS         = main-dlg.h \
 SOURCES         = main-dlg.cpp \
                   options-dlg.cpp \
 FORMS           = search-dlg.ui
 TRANSLATIONS    = superapp_dk.ts \
                   superapp_fi.ts \
                   superapp_no.ts \
 CODECFORTR      = ISO-8859-5

QTextCodec::setCodecForTr() makes it possible to choose a 8-bit encoding for literal strings that appear within tr() calls. This is useful for applications whose source language is, for example, Chinese or Japanese. If no encoding is set, tr() uses Latin1.

If you do use the QTextCodec::codecForTr() mechanism in your application, Qt Linguist needs you to set the CODECFORTR entry in the .pro file as well. For example:

 CODECFORTR      = ISO-8859-5

Also, if your compiler uses a different encoding for its runtime system as for its source code and you want to use non-ASCII characters in string literals, you will need to set the CODECFORSRC. For example:


Microsoft Visual Studio 2005 .NET appears to be the only compiler for which this is necessary. However, if you want to write portable code, we recommend that you avoid non-ASCII characters in your source files. You can still specify non-ASCII characters portably using escape sequences, for example:

 label->setText(tr("F\374r \310lise"));


Usage: lupdate myproject.pro

lupdate is a command line tool that finds the translatable strings in the specified source, header and Qt Designer interface files, and produces or updates .ts translation files. The files to process and the files to update can be set at the command line, or provided in a .pro file specified as an command line argument. The produced translation files are given to the translator who uses Qt Linguist to read the files and insert the translations.

Companies that have their own translators in-house may find it useful to run lupdate regularly, perhaps monthly, as the application develops. This will lead to a fairly low volume of translation work spread evenly over the life of the project and will allow the translators to support a number of projects simultaneously.

Companies that hire in translators as required may prefer to run lupdate only a few times in the application's life cycle, the first time might be just before the first test phase. This will provide the translator with a substantial single block of work and any bugs that the translator detects may easily be included with those found during the initial test phase. The second and any subsequent lupdate runs would probably take place during the final beta phase.

The TS file format is a simple human-readable XML format that can be used with version control systems if required. lupdate can also process Localization Interchange File Format (XLIFF) format files; files in this format typically have file names that end with the .xlf suffix.

Pass the -help option to lupdate to obtain the list of supported options:

     lupdate [options] [project-file]
     lupdate [options] [source-file|path]... -ts ts-files
     -help  Display this information and exit.
            Drop all obsolete strings.
     -extensions <ext>[,<ext>]...
            Process files with the given extensions only.
            The extension list must be separated with commas, not with whitespace.
            Default: 'ui,c,c++,cc,cpp,cxx,ch,h,h++,hh,hpp,hxx'.
            Only include plural form messages.
            Do not explain what is being done.
            Display the version of lupdate and exit.

Qt Linguist is also able to import and export XLIFF files. See the Translators section for more information.


Usage: lrelease myproject.pro

lrelease is a command line tool that produces QM files out of TS files. The QM file format is a compact binary format that is used by the localized application. It provides extremely fast lookups for translations. The TS files lrelease processes can be specified at the command line, or given indirectly by a Qt .pro project file.

This tool is run whenever a release of the application is to be made, from initial test version through to final release version. If the QM files are not created, e.g. because an alpha release is required before any translation has been undertaken, the application will run perfectly well using the text the programmers placed in the source files. Once the QM files are available the application will detect them and use them automatically.

Note that lrelease will only incorporate translations that are marked as "finished". Otherwise the original text will be used instead.

Pass the -help option to lrelease to obtain the list of supported options:

     lrelease [options] project-file
     lrelease [options] ts-files [-qm qm-file]
     -help  Display this information and exit
            Compress the QM files
            Do not include unfinished translations
            If the translated text is the same as
            the source text, do not include the message
            Do not explain what is being done
            Display the version of lrelease and exit

Missing Translations

Both lupdate and lrelease may be used with TS translation source files which are incomplete. Missing translations will be replaced with the native language phrases at runtime.

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