[Interest] Language and translator : Learning and questions

[Nicholas Yue]

Hi,

  Over the past week, I have been getting alot of help from this list and
have learnt alot from the knowledgeable people on the list.

  Here is a summary of my attempt to create a test app (as a QMainWindow),
loading a *.ui file directly and creating the UI on the fly and handling
the language switching.

  My code works as far as I know but I do have two questions:
  (1) The way I am handling the language/translator switch/change, is that
the correct way ? Any unforeseen resource leak ?
  (2) I see some examples where a translator is removed before installing a
new one, I comment that away and it still works, is there some issue
lurking in the background that will cause a crash later ?

  The full project is here
https://github.com/nyue/QtQuestions/tree/main/Qt5/language_change/mainwindow

HEADER
=======

#pragma once


#include <QMainWindow>

#include <QCheckBox>

#include <QLabel>

#include <QComboBox>

#include <QTranslator>

#include <QCoreApplication>

#include <QSharedPointer>

#include <QVector>


class MainWindow : public QMainWindow

{

	// NOTICE THIS MACRO

    Q_OBJECT

    //

    typedef QSharedPointer<QTranslator> TranslatorShdPtr;

    struct abc {

        QString name;

        QString bcp47;

        TranslatorShdPtr translator;

    };

    typedef QVector<abc> LanguageTranslatorVecContainer;

public:

    MainWindow(QWidget *parent = 0);

private:

	QCheckBox* ui_checkBox;

	QLabel* ui_label;

    QComboBox* ui_languageComboBox;

    QTranslator ui_translator;

    QLabel* ui_iconLabel;

    LanguageTranslatorVecContainer _ltc;

private:

    void retranslateUi();

private slots:

    void handleLanguageChange(int index);

};


SOURCE
=======

#include "MainWindow.h"

#include <QVBoxLayout>

#include <QDebug>

#include <QUiLoader>

#include <QFile>

#include <QDir>

#include <QDirIterator>

#include <QWidget>

#include <QApplication>


QString extract_bcp47(const QString language_file_path) {

    QStringList dotSplit = language_file_path.split(".");

    QString nameWithBCP47 = dotSplit[dotSplit.size()-2];

    QStringList underscoreSplit = nameWithBCP47.split("_");

    QString bcp47 = underscoreSplit[underscoreSplit.size()-1];

    return bcp47;

}


MainWindow::MainWindow(QWidget *parent)

    : QMainWindow(parent)

{

    QUiLoader loader;

    QFile file(":/designer/mainwindow.ui");

    file.open(QFile::ReadOnly);

    QWidget *widget = loader.load(&file, parent);

    loader.setTranslationEnabled(true);

    file.close();

    setCentralWidget(widget);


    // Build language drop down menu

    {

        ui_languageComboBox = findChild<QComboBox*>("comboBox");

        Q_ASSERT(ui_languageComboBox);

        connect(ui_languageComboBox, SIGNAL(currentIndexChanged(int)),
this, SLOT(handleLanguageChange(int)));


        // Find available languages


        // https://stackoverflow.com/questions/28463090/how-to-iterate-through-only-certain-type-of-files-using-qdiriterator#28463194

        QDirIterator it(QString(":/language/.qm"), QStringList() <<
"*.qm", QDir::Files, QDirIterator::Subdirectories);

        while (it.hasNext()) {

            QString item = it.next();

            QString language = extract_bcp47(item);

            QLocale locale(language);

            /*

            qDebug() << item;

            qDebug() << "bcp47 " << language;

            qDebug() << "countryToString " <<
QLocale::countryToString(locale.country());

            qDebug() << "languageToString " <<
QLocale::languageToString(locale.language());

            */


            // Create a translator for each language found

            TranslatorShdPtr t(new QTranslator);

            if (t->load(item))

            {

                struct abc
stuff{QLocale::languageToString(locale.language()),language,t};

                _ltc.push_back(stuff);

            }


        }


        // Iterate the languages found to build the drop down list

        QVectorIterator<struct abc> ii(_ltc);

        while (ii.hasNext()) {

            struct abc s = ii.next();

            // qDebug() << s.name << ": " << s.translator;

            // qDebug() << "s.name " << s.name;

            ui_languageComboBox->addItem(s.name,s.name);

        }


        // Default to English

        int index = ui_languageComboBox->findData("English");

        if ( index != -1 ) { // -1 for not found

            ui_languageComboBox->setCurrentIndex(index);

        }


    }


    ui_iconLabel = findChild<QLabel*>("iconLabel");

    Q_ASSERT(ui_iconLabel);

    QIcon languageIcon;

    languageIcon.addFile(":/icons/Font_Awesome_5_solid_language.svg");

    // languageIcon.addFile(":/icons/wl.png");

    QPixmap iconPixmap = languageIcon.pixmap(32);

    ui_iconLabel->setPixmap(iconPixmap);

    ui_iconLabel->resize(iconPixmap.width(),iconPixmap.height());


}



void MainWindow::handleLanguageChange(int index)

{

    QString langFile =
QString(":/language/.qm/mlc_%1.qm").arg(_ltc[index].bcp47);

    if (ui_translator.load(langFile)) {

        // qApp->removeTranslator(&ui_translator);

        bool installed = qApp->installTranslator(&ui_translator);

        if (installed) {

            this->retranslateUi();

        }

    }

}


void MainWindow::retranslateUi()

{

    ui_label = findChild<QLabel*>("label");

    if (ui_label)

        ui_label->setText(QCoreApplication::translate("MainWindow",
"Hello", nullptr));

}



Cheers
-- 
Nicholas Yue
Graphics - Arnold, Alembic, RenderMan, OpenGL, HDF5
Custom Dev - C++ porting, OSX, Linux, Windows
http://au.linkedin.com/in/nicholasyue
https://vimeo.com/channels/naiadtools
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