Qt Quick Widgets Example

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#include <QQuickWidget>
#include <QQuickItem>
#include <QQmlError>
#include <QtWidgets>
#include "fbitem.h"

static bool optMultipleSample = false;
static bool optCoreProfile = false;

class MainWindow : public QMainWindow {
    Q_OBJECT
public:
    MainWindow();

private slots:
    void quickWidgetStatusChanged(QQuickWidget::Status);
    void sceneGraphError(QQuickWindow::SceneGraphError error, const QString &message);
    void grabFramebuffer();
    void renderToPixmap();
    void grabToImage();
    void createQuickWidgetsInTabs(QMdiArea *mdiArea);

private:
    QQuickWidget *m_quickWidget;
};

MainWindow::MainWindow()
   : m_quickWidget(new QQuickWidget)
{
    QSurfaceFormat format;
    if (optCoreProfile) {
        format.setVersion(4, 4);
        format.setProfile(QSurfaceFormat::CoreProfile);
    }
    if (optMultipleSample)
        format.setSamples(4);
    m_quickWidget->setFormat(format);

    QMdiArea *centralWidget = new QMdiArea;

    QLCDNumber *lcd = new QLCDNumber;
    lcd->display(1337);
    lcd->setMinimumSize(250,100);
    centralWidget->addSubWindow(lcd);

    QUrl source("qrc:quickwidget/rotatingsquare.qml");

    connect(m_quickWidget, &QQuickWidget::statusChanged,
            this, &MainWindow::quickWidgetStatusChanged);
    connect(m_quickWidget, &QQuickWidget::sceneGraphError,
            this, &MainWindow::sceneGraphError);
    m_quickWidget->resize(300,300);
    m_quickWidget->setResizeMode(QQuickWidget::SizeRootObjectToView );
    m_quickWidget->setSource(source);

    centralWidget->addSubWindow(m_quickWidget);

    setCentralWidget(centralWidget);

    QMenu *fileMenu = menuBar()->addMenu(tr("&File"));
    fileMenu->addAction(tr("Grab framebuffer"), this, &MainWindow::grabFramebuffer);
    fileMenu->addAction(tr("Render to pixmap"), this, &MainWindow::renderToPixmap);
    fileMenu->addAction(tr("Grab via grabToImage"), this, &MainWindow::grabToImage);
    fileMenu->addAction(tr("Quit"), qApp, &QCoreApplication::quit);

    QMenu *windowMenu = menuBar()->addMenu(tr("&Window"));
    windowMenu->addAction(tr("Add tab widget"), this,
                          [this, centralWidget] { createQuickWidgetsInTabs(centralWidget); });
}

void MainWindow::createQuickWidgetsInTabs(QMdiArea *mdiArea)
{
    QTabWidget *tabWidget = new QTabWidget;

    const QSize size(400, 400);

    QQuickWidget *w = new QQuickWidget;
    w->resize(size);
    w->setResizeMode(QQuickWidget::SizeRootObjectToView);
    w->setSource(QUrl("qrc:quickwidget/rotatingsquaretab.qml"));

    tabWidget->addTab(w, tr("Plain Quick content"));

    w = new QQuickWidget;
    w->resize(size);
    w->setResizeMode(QQuickWidget::SizeRootObjectToView);
    w->setSource(QUrl("qrc:quickwidget/customgl.qml"));

    tabWidget->addTab(w, tr("Custom OpenGL drawing"));

    mdiArea->addSubWindow(tabWidget);
    tabWidget->show();
}

void MainWindow::quickWidgetStatusChanged(QQuickWidget::Status status)
{
    if (status == QQuickWidget::Error) {
        QStringList errors;
        const auto widgetErrors = m_quickWidget->errors();
        for (const QQmlError &error : widgetErrors)
            errors.append(error.toString());
        statusBar()->showMessage(errors.join(QStringLiteral(", ")));
    }
}

void MainWindow::sceneGraphError(QQuickWindow::SceneGraphError, const QString &message)
{
     statusBar()->showMessage(message);
}

template<class T> void saveToFile(QWidget *parent, T *saveable)
{
    QFileDialog fd(parent);
    fd.setAcceptMode(QFileDialog::AcceptSave);
    fd.setDefaultSuffix("png");
    fd.selectFile("test.png");
    if (fd.exec() == QDialog::Accepted)
        saveable->save(fd.selectedFiles().first());
}

void MainWindow::grabFramebuffer()
{
    QImage image = m_quickWidget->grabFramebuffer();
    saveToFile(this, &image);
}

void MainWindow::renderToPixmap()
{
    QPixmap pixmap(m_quickWidget->size());
    m_quickWidget->render(&pixmap);
    saveToFile(this, &pixmap);
}

void MainWindow::grabToImage()
{
    QFileDialog fd(this);
    fd.setAcceptMode(QFileDialog::AcceptSave);
    fd.setDefaultSuffix("png");
    fd.selectFile("test_grabToImage.png");
    if (fd.exec() == QDialog::Accepted) {
        QMetaObject::invokeMethod(m_quickWidget->rootObject(), "performLayerBasedGrab",
                                  Q_ARG(QVariant, fd.selectedFiles().first()));
    }
}

int main(int argc, char **argv)
{
    QApplication app(argc, argv);

    QCoreApplication::setApplicationName("Qt QQuickWidget Example");
    QCoreApplication::setOrganizationName("QtProject");
    QCoreApplication::setApplicationVersion(QT_VERSION_STR);
    QCommandLineParser parser;
    parser.setApplicationDescription(QCoreApplication::applicationName());
    parser.addHelpOption();
    parser.addVersionOption();
    QCommandLineOption multipleSampleOption("multisample", "Multisampling");
    parser.addOption(multipleSampleOption);
    QCommandLineOption coreProfileOption("coreprofile", "Use core profile");
    parser.addOption(coreProfileOption);

    parser.process(app);

    optMultipleSample = parser.isSet(multipleSampleOption);
    optCoreProfile = parser.isSet(coreProfileOption);

    qmlRegisterType<FbItem>("QuickWidgetExample", 1, 0, "FbItem");

    MainWindow mainWindow;
    mainWindow.show();

    return app.exec();
}

#include "main.moc"