I18N Example

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#include <QtWidgets>

#include "languagechooser.h"
#include "mainwindow.h"

#if 0 // Used to be included in Qt4 for Q_WS_MAC
extern void qt_mac_set_menubar_merge(bool merge);

#endif

LanguageChooser::LanguageChooser(const QString& defaultLang, QWidget *parent)
    : QDialog(parent, Qt::WindowStaysOnTopHint)
{
    groupBox = new QGroupBox("Languages");

    QGridLayout *groupBoxLayout = new QGridLayout;

    QStringList qmFiles = findQmFiles();
    for (int i = 0; i < qmFiles.size(); ++i) {
        QCheckBox *checkBox = new QCheckBox(languageName(qmFiles[i]));
        qmFileForCheckBoxMap.insert(checkBox, qmFiles[i]);
        connect(checkBox,
                QOverload<bool>::of(&QCheckBox::toggled),
                this,
                &LanguageChooser::checkBoxToggled);
        if (languageMatch(defaultLang, qmFiles[i]))
                checkBox->setCheckState(Qt::Checked);
        groupBoxLayout->addWidget(checkBox, i / 2, i % 2);
    }
    groupBox->setLayout(groupBoxLayout);

    buttonBox = new QDialogButtonBox;

    showAllButton = buttonBox->addButton("Show All",
                                         QDialogButtonBox::ActionRole);
    hideAllButton = buttonBox->addButton("Hide All",
                                         QDialogButtonBox::ActionRole);

    connect(showAllButton, &QAbstractButton::clicked, this, &LanguageChooser::showAll);
    connect(hideAllButton, &QAbstractButton::clicked, this, &LanguageChooser::hideAll);

    QVBoxLayout *mainLayout = new QVBoxLayout;
    mainLayout->addWidget(groupBox);
    mainLayout->addWidget(buttonBox);
    setLayout(mainLayout);

#if 0 // Used to be included in Qt4 for Q_WS_MAC
    qt_mac_set_menubar_merge(false);
#endif

    setWindowTitle("I18N");
}

bool LanguageChooser::languageMatch(const QString& lang, const QString& qmFile)
{
    //qmFile: i18n_xx.qm
    const QString prefix = "i18n_";
    const int langTokenLength = 2; /*FIXME: is checking two chars enough?*/
    return qmFile.midRef(qmFile.indexOf(prefix) + prefix.length(), langTokenLength) == lang.leftRef(langTokenLength);
}

bool LanguageChooser::eventFilter(QObject *object, QEvent *event)
{
    if (event->type() == QEvent::Close) {
        MainWindow *window = qobject_cast<MainWindow *>(object);
        if (window) {
            QCheckBox *checkBox = mainWindowForCheckBoxMap.key(window);
            if (checkBox)
                checkBox->setChecked(false);
        }
    }
    return QWidget::eventFilter(object, event);
}

void LanguageChooser::closeEvent(QCloseEvent * /* event */)
{
    qApp->quit();
}

void LanguageChooser::checkBoxToggled()
{
    QCheckBox *checkBox = qobject_cast<QCheckBox *>(sender());
    MainWindow *window = mainWindowForCheckBoxMap[checkBox];
    if (!window) {
        QTranslator translator;
        translator.load(qmFileForCheckBoxMap[checkBox]);
        qApp->installTranslator(&translator);

        window = new MainWindow;
        window->setPalette(colorForLanguage(checkBox->text()));

        window->installEventFilter(this);
        mainWindowForCheckBoxMap.insert(checkBox, window);
    }
    window->setVisible(checkBox->isChecked());
}

void LanguageChooser::showAll()
{
    foreach (QCheckBox *checkBox, qmFileForCheckBoxMap.keys())
        checkBox->setChecked(true);
}

void LanguageChooser::hideAll()
{
    foreach (QCheckBox *checkBox, qmFileForCheckBoxMap.keys())
        checkBox->setChecked(false);
}

QStringList LanguageChooser::findQmFiles()
{
    QDir dir(":/translations");
    QStringList fileNames = dir.entryList(QStringList("*.qm"), QDir::Files,
                                          QDir::Name);
    QMutableStringListIterator i(fileNames);
    while (i.hasNext()) {
        i.next();
        i.setValue(dir.filePath(i.value()));
    }
    return fileNames;
}

QString LanguageChooser::languageName(const QString &qmFile)
{
    QTranslator translator;
    translator.load(qmFile);

    return translator.translate("MainWindow", "English");
}

QColor LanguageChooser::colorForLanguage(const QString &language)
{
    uint hashValue = qHash(language);
    int red = 156 + (hashValue & 0x3F);
    int green = 156 + ((hashValue >> 6) & 0x3F);
    int blue = 156 + ((hashValue >> 12) & 0x3F);
    return QColor(red, green, blue);
}