- Qt 5.15
- Qt Quick Demo - Photo Surface
- Qt 5.15.17 Reference Documentation

# 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>
     #ifdef REQUEST_PERMISSIONS_ON_ANDROID
     #include <QtAndroid>

     bool requestStoragePermission() {
         using namespace QtAndroid;

         QString permission = QStringLiteral("android.permission.WRITE_EXTERNAL_STORAGE");
         const QHash<QString, PermissionResult> results = requestPermissionsSync(QStringList({permission}));
         if (!results.contains(permission) || results[permission] == PermissionResult::Denied) {
             qWarning() << "Couldn't get permission: " << permission;
             return false;
         }

         return true;
     }
     #endif

     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
     #ifdef REQUEST_PERMISSIONS_ON_ANDROID
         if (!requestStoragePermission())
             return -1;
     #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();
     }