[SOLVED] [Qt Translations] using += lrelease and += embed_translations

Michael Uplawski · 03-26-2023, 03:38 AM

Good morning.

I do not understand the documentation of the qmake config-variables, nor the use of QM_FILES_RESOURCE_PREFIX, cannot see, how those translations under /usr/share/Qt[n]/translations are found by the respective applications, and have no clue about how I get my *.qm files read by my own application.

Here are the pertinent excerpts from my project. These are not working.

upsslideshow.pro

Code:

QM_FILES_RESOURCE_PREFIX = "/usr/share/upsslideshow"

CONFIG += lrelease 
CONFIG += embed_translations
(...)
TRANSLATIONS += upsslideshow_fr_FR.ts \
                upsslideshow_de_DE.ts

main.cpp

Code:

QTranslator translator;
  QString locale = QLocale::system().name();
  [[maybe_unused]]  bool isso = translator.load(QString("upsslideshow_") + locale);
  a.installTranslator(&translator);

I have moved the .qm files all over the place but the only way to make them available to the executable, had been to store them along the program, in the same directory. Each modification of my *.pro file had been followed by make distclean;qmake.
Anyway, I cannot see that QM_FILES_RESOURCE_PREFIX were honored anywhere, at least not in the generated Makefile.

For 15 years, I have not considered it necessary to produce translations for this program; I may just as well continue this way.

The only translation mechanism that satisfies me today, is my own, for the Ruby-language. No big deal, I would have said... but I am probably wrong.

Thank you for any hints.

Cheerio.

Edit: In the Qt-forum several responses are given to similar questions. Apart from imitating the code-examples, given there, and then to hope for the best, I see no way of taking benefit from these discussions, either. The procedures are illogical and the descriptions cryptic. I will not code something that I do not understand.

Michael Uplawski · 03-26-2023, 04:32 AM

Side-note: as I can imagine xslt-processing the *.ts files into a C++ header-file, can you imagine problems with the idea?

Side-note 2: YAML. Do you have experience with a YAML library for C++ ? This could be easier to integrate than a header-file, but may slow down the execution, as I cannot conditionally instantiate locale-specific translators.., I guess.

teckk · 03-26-2023, 03:19 PM

Examples:

https://doc.qt.io/qt-5/qtranslator.html

Code:

QTranslator* translator = new QTranslator();
if (translator->load("myfile.qm", "/path/to/folder/with/qm/files")) {
    app.installTranslator(translator);
}

https://doc.qt.io/qt-5/resources.html

Code:

QTranslator* translator = new QTranslator();
if (translator->load("myfile.qm", ":/resources/translations")) {
    app.installTranslator(translator);
}

Code:

if(!QFile::exists("myfile.qm"))
    qWarning("failed-no file");

https://wiki.qt.io/How_to_create_a_m...ge_application

teckk · 03-26-2023, 03:30 PM

Example pro file

Code:

TEMPLATE = app
TARGET = pdfviewer
QT += core gui widgets pdfwidgets

SOURCES += \
    main.cpp \
    mainwindow.cpp \
    pageselector.cpp \
    zoomselector.cpp

HEADERS += \
    mainwindow.h \
    pageselector.h \
    zoomselector.h

FORMS += \
    mainwindow.ui

RESOURCES += \
    resources.qrc
    
TRANSLATIONS += \
    languages/translation_en.ts \
    languages/translation_fr.ts \
    languages/translation_ru.ts

target.path = $$[QT_INSTALL_EXAMPLES]/pdfwidgets/pdfviewer
INSTALLS += target

Michael Uplawski · 03-27-2023, 01:55 AM

Quote:

Originally Posted by teckk

(...)
TRANSLATIONS += \
languages/translation_en.ts \
languages/translation_fr.ts \
languages/translation_ru.ts

target.path = $$[QT_INSTALL_EXAMPLES]/pdfwidgets/pdfviewer
INSTALLS += target[/code]

I have not advanced any further, but consent to discuss the examples.
1) the directory “languages” is a top level object in the project? Like in

Code:

--------------
/home/user/projects/pdfviewer
     src
     languages
     lib

(...)
---------------

2) :resources, from your second code example, is what and where?

3) There is no translation embedded in your examples. I ignore, thus, the detail which should help me advance with my own project. Maybe comment the code in this way, I do not yet get it.

More questions to follow.

Michael Uplawski · 03-27-2023, 06:45 AM

... and

I discover that qmake has produced another file that I have never heard of, qmake_qmake_qm_files.qrc. Content:

Code:

<!DOCTYPE RCC><RCC version="1.0">
<qresource prefix="[see below]">
<file alias="upsslideshow_fr_FR.qm">/home/michael/prog/upsslideshow/.qm/upsslideshow_fr_FR.qm</file>
<file alias="upsslideshow_de_DE.qm">/home/michael/prog/upsslideshow/.qm/upsslideshow_de_DE.qm</file>
</qresource>
</RCC>

Nothing I did not know, myself. Maybe someone knows what this file is supposed to do and why it does not help me.

THE GENERATIONS TO COME, HEAR ME
Edit: qmake_qmake_qm_files.qrc is a default resource file, when nothing else is set (nothing *.qrc in the project file).

And: Solved
The ominous path in the second argument to Translator.load() is a resource path. You can define your own, but if you choose to embed translations in your program, this path does not need to point at an existing directory: It depends on the content of the *.qrc file:

Code:

qresource prefix="i18n">

This is from the automatically generated default resource file, when none is named in the project-file. The prefix “i18n” will serve as parameter to Translator.load():

Code:

[[maybe_unused]]  bool isso = translator.load(QString("upsslideshow_") + locale, ":i18n");

The remainder of the configuration is made only in the project-file *.pro:

Code:

CONFIG += lrelease 
CONFIG += embed_translations
TRANSLATIONS += upsslideshow_fr_FR.ts \
                upsslideshow_de_DE.ts

You need *no* Prefixes other than i18n in the main.cpp (where the QTranslator is instantiated) and no file-paths whatsoever. lrelease will compile *.qm files to te directory “.qm” that is referenced in the default resource-file and the prefix i18n is enough to find it there.

Run qmake and make. Additional *.cpp- and *.h files will be generated, containing the translations, then compiled and linked in the executable.

Big Mess, but it works now.

Big mess in the documentation and all the discussions that I have found,

Michael Uplawski · 03-29-2023, 11:59 AM

New Web-Page:
Qt: Embedding Translations
Blog