qt_add_lrelease

Add targets to transform Qt Linguist .ts files into .qm files.

The command is defined in the LinguistTools component of the Qt6 package. Load the package with:

find_package(Qt6 REQUIRED COMPONENTS LinguistTools)

This command was introduced in Qt 6.2.

Synopsis

Since 6.7:

qt_add_lrelease(TS_FILES file1.ts [file2.ts ...]
                [LRELEASE_TARGET target-name]
                [EXCLUDE_FROM_ALL]
                [NO_GLOBAL_TARGET]
                [QM_FILES_OUTPUT_VARIABLE variable-name]
                [MERGE_QT_TRANSLATIONS]
                [QT_TRANSLATION_CATALOGS catalog1 [catalog2 ...]]
                [OPTIONS ...])

Since 6.2 (deprecated):

qt_add_lrelease(target TS_FILES file1.ts [file2.ts ...]
                [NO_TARGET_DEPENDENCY]
                [NO_GLOBAL_TARGET]
                [QM_FILES_OUTPUT_VARIABLE variable-name]
                [OPTIONS ...])

If versionless commands are disabled, use qt6_add_lrelease() instead. It supports the same set of arguments as this command.

Description

Creates a custom command to transform .ts files into .qm files with lrelease.

The execution of the custom command is driven by a custom target that is built by default. The name of that custom target defaults to ${PROJECT_NAME}_lrelease. Further calls of qt_add_lrelease will create target names with an increasing number appended. The custom target name can be specified with the LRELEASE_TARGET option.

The .ts files must be specified with the argument TS_FILES.

This function is designed to be used in conjunction with qt_add_lupdate. See also the convenience wrapper qt_add_translations.

Options

You can set additional OPTIONS that should be passed when lrelease is invoked. You can find possible options in the lrelease documentation.

By default, the .qm files will be placed in the current build directory (CMAKE_CURRENT_BINARY_DIR). To change this, you can set OUTPUT_LOCATION as a property of the source .ts file.

For example, with the following code, the .qm files are generated in a translations directory below the current build directory.

set_source_files_properties(app_en.ts app_de.ts
    PROPERTIES OUTPUT_LOCATION "${CMAKE_CURRENT_BINARY_DIR}/translations")

Processing Generated .qm Files

To further process the generated .qm files, for example to create install rules, qt_add_lrelease can store the paths of the .qm files in a variable. Pass QM_FILES_OUTPUT_VARIABLE <variable-name> to the function for that.

Build by Default

By default, the command creates a custom target that is added to the default build target. This ensures that the .qm files are always up-to-date when the project is built. This behavior can be turned off with the EXCLUDE_FROM_ALL argument. In this case, the user must build the ${PROJECT_NAME}_lrelease target manually.

Umbrella Target

In addition to the target ${target}_lrelease, an umbrella target release_translations is created. This target will build all ${target}_lrelease targets that were created with qt_add_lrelease.

Pass NO_GLOBAL_TARGET to qt_add_lrelease to prevent this behavior.

The name of this target can be overridden by setting the variable QT_GLOBAL_LRELEASE_TARGET before calling qt_add_lrelease.

Merging Qt-provided translations

Since Qt 6.9, you can merge the translations that are provided by Qt into application-specific .qm files. To do that, pass the MERGE_QT_TRANSLATIONS option to qt_add_translations. This will determine the Qt translation catalogs that belong to the modules used by your project and merge them into the .qm files that are produced by lrelease.

The Qt translation catalogs are determined by the find_package calls in the scope of your CMakeLists.txt where qt_add_translations is called. For example, the following sequence will merge the catalogs qtbase and qtmultimedia into your .qm files:

find_package(Qt6 COMPONENTS MultimediaWidgets)
...
qt_add_lrelease(
    TS_FILES myapp_de.ts myapp_fi.ts
    MERGE_QT_TRANSLATIONS
)

To explicitly specify the catalogs, use the QT_TRANSLATION_CATALOGS argument:

qt_add_lrelease(
    TS_FILES myapp_de.ts myapp_fi.ts
    MERGE_QT_TRANSLATIONS
    QT_TRANSLATION_CATALOGS qtbase qtmultimedia
)

If your project supports a language for which Qt doesn't offer its own translation, a warning will be issued at configure time. You can suppress this warning by setting the CMake variable QT_NO_MISSING_CATALOG_LANGUAGE_WARNING to ON.

Deprecated Command Signature

Older versions of qt_add_lrelease took a target as the first argument. This is still possible but deprecated.

Examples

Add the targets myapp_lrelease and release_translations for transforming the given .ts files into .qm files. Also, install the generated .qm files. The target myapp_lrelease is built by default.

project(myapp)
...
qt_add_lrelease(
    TS_FILES myapp_de.ts myapp_fr.ts
    QM_FILES_OUTPUT_VARIABLE qm_files
)
install(FILES ${qm_files} DESTINATION "translations")

You can specify the name of the created target by passing the LRELEASE_TARGET argument:

qt_add_lrelease(
    LRELEASE_TARGET create_myapp_qm_files
    TS_FILES myapp_de.ts myapp_fr.ts
    QM_FILES_OUTPUT_VARIABLE qm_files
)