QT_TR_NOOP does not get recognized from lupdate

sandro4912

I have this code:

#include <QApplication>
#include <QMessageBox>
#include <QTranslator>

int main(int argc, char **argv)
{
    QApplication app{argc, argv};

    QTranslator translator;
    translator.load("noop_de_DE");
    app.installTranslator(&translator);

    QVector<QString>texts = {
        QT_TRANSLATE_NOOP("main", "URL"),
        QT_TRANSLATE_NOOP("main", "Title"),
        QT_TRANSLATE_NOOP("main", "Publisher")
    };

    QVector<QString>texts2 = {
        QT_TR_NOOP("This is a very special string."),
        QT_TR_NOOP("And this is just as special")};

    QMessageBox::information( nullptr,
         qApp->translate("main",texts[2].toStdString().c_str()),
         qApp->translate(nullptr,texts2[1].toStdString().c_str()) );
}

If I run lupdate only the strings in QT_TRANSLATE_NOOP get added to the translation file. WHY QT_TR_NOOP is not recognized?

It gives tr() cannot be called without context for the lines with QT_TR_NOOP

Also it says in the help that qApp->translate() is obsolete bur does not mention whats the alternative in QT5.

Christian Ehrlicher

See https://doc.qt.io/qt-5/i18n-source-translation.html#using-qt-tr-noop-and-qt-translate-noop-in-c
For QT_TR_NOOP you need a context (= class derived from QObject) where you define your strings to translate. So since you don't have a class here the correct way is to use QT_TRANSLATE_NOOP
And why do you store your untranslated strings as QString at all? Simple char* would be enough and would save you the strange toStdString().c_str() stuff (which should be replaced to toUtf8().constData() if really needed...)

sandro4912

well i have it from an example in QT4 which looks like this:

#include <QApplication>

#include <QMessageBox>

#include <QTranslator>

int main( int argc, char **argv )
{
  QApplication app( argc, argv );
  
  QTranslator translator;
  translator.load( "noop_sv_SE" );
  app.installTranslator( &translator );
  
  char *texts[] = { QT_TRANSLATE_NOOP("main","URL"),
                    QT_TRANSLATE_NOOP("main","Title"),
                    QT_TRANSLATE_NOOP("main","Publisher") };
                    
  char *texts2[] = { QT_TR_NOOP( "This is a very special string."),
                     QT_TR_NOOP( "And this is just as special.") };
  
  QMessageBox::information( 0, qApp->translate("main",texts[2]), qApp->translate(0,texts2[1]) );

  return 0;
}

I turn on c++17 compilation in the project. Than i get complains that in C++11 to convert from char* to string literals is not allowed. Also in this example code QT_TR_NOOP is used and seems to work. But its based on a old QT4 version.

Christian Ehrlicher

Because your char strings must be const -> const char *texts[].
QT_TR_NOOP can't work - see documentation.