Qt Quick Demo - Photo Surface

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 #ifdef QT_WIDGETS_LIB
 #include <QtWidgets/QApplication>
 #else
 #include <QtGui/QGuiApplication>
 #endif
 #include <QtQml/QQmlApplicationEngine>
 #include <QtQml/QQmlContext>
 #include <QtQuick/QQuickWindow>
 #include <QtGui/QImageReader>
 #include <QtCore/QCommandLineParser>
 #include <QtCore/QCommandLineOption>
 #include <QtCore/QDebug>
 #include <QtCore/QDir>
 #include <QtCore/QMimeDatabase>
 #include <QtCore/QStandardPaths>
 #include <QtCore/QUrl>

 static QStringList imageNameFilters()
 {
     QStringList result;
     QMimeDatabase mimeDatabase;
     const auto supportedMimeTypes = QImageReader::supportedMimeTypes();
     for (const QByteArray &m : supportedMimeTypes) {
         const auto suffixes = mimeDatabase.mimeTypeForName(m).suffixes();
         for (const QString &suffix : suffixes)
             result.append(QLatin1String("*.") + suffix);
     }
     return result;
 }

 int main(int argc, char* argv[])
 {
     // The reason to use QApplication is that QWidget-based dialogs
     // are the native dialogs on Qt-based platforms like KDE,
     // but they cannot be instantiated if this is a QGuiApplication.
 #ifdef QT_WIDGETS_LIB
     QApplication app(argc, argv);
 #else
     QGuiApplication app(argc, argv);
 #endif

     QQuickWindow::setDefaultAlphaBuffer(true);

     QCoreApplication::setApplicationName(QStringLiteral("Photosurface"));
     QCoreApplication::setOrganizationName(QStringLiteral("QtProject"));
     QCoreApplication::setApplicationVersion(QLatin1String(QT_VERSION_STR));
     QCommandLineParser parser;
     parser.setApplicationDescription(QStringLiteral("Qt Quick Demo - Photo Surface"));
     parser.addHelpOption();
     parser.addVersionOption();
     parser.addPositionalArgument(QStringLiteral("directory"),
                                  QStringLiteral("The image directory or URL to show."));
     parser.process(app);

     QUrl initialUrl;
     if (!parser.positionalArguments().isEmpty()) {
         initialUrl = QUrl::fromUserInput(parser.positionalArguments().first(),
                                          QDir::currentPath(), QUrl::AssumeLocalFile);
         if (!initialUrl.isValid()) {
             qWarning().nospace() << "Invalid argument: \""
                 << parser.positionalArguments().first() << "\": " << initialUrl.errorString();
             return 1;
         }
     }

     const QStringList nameFilters = imageNameFilters();

     QQmlApplicationEngine engine;
     QQmlContext *context = engine.rootContext();

     QUrl picturesLocationUrl = QUrl::fromLocalFile(QDir::homePath());
     const QStringList picturesLocations = QStandardPaths::standardLocations(QStandardPaths::PicturesLocation);
     if (!picturesLocations.isEmpty()) {
         picturesLocationUrl = QUrl::fromLocalFile(picturesLocations.first());
         if (initialUrl.isEmpty()
             && !QDir(picturesLocations.first()).entryInfoList(nameFilters, QDir::Files).isEmpty()) {
             initialUrl = picturesLocationUrl;
         }
     }

     context->setContextProperty(QStringLiteral("contextPicturesLocation"), picturesLocationUrl);
     context->setContextProperty(QStringLiteral("contextInitialUrl"), initialUrl);
     context->setContextProperty(QStringLiteral("contextImageNameFilters"), nameFilters);

     engine.load(QUrl("qrc:///photosurface.qml"));
     if (engine.rootObjects().isEmpty())
         return -1;

     return app.exec();
 }