languagechooser.cpp Example File

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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);
 }