qtdeclarative/examples/quick/imageresponseprovider/imageresponseprovider.cpp

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#include <qqmlextensionplugin.h>

#include <qqmlengine.h>
#include <qquickimageprovider.h>
#include <QDebug>
#include <QImage>
#include <QThreadPool>

class AsyncImageResponse : public QQuickImageResponse, public QRunnable
{
    public:
        AsyncImageResponse(const QString &id, const QSize &requestedSize)
         : m_id(id), m_requestedSize(requestedSize)
        {
            setAutoDelete(false);
        }

        QQuickTextureFactory *textureFactory() const
        {
            return QQuickTextureFactory::textureFactoryForImage(m_image);
        }

        void run()
        {
            m_image = QImage(50, 50, QImage::Format_RGB32);
            if (m_id == "slow") {
                qDebug() << "Slow, red, sleeping for 5 seconds";
                QThread::sleep(5);
                m_image.fill(Qt::red);
            } else {
                qDebug() << "Fast, blue, sleeping for 1 second";
                QThread::sleep(1);
                m_image.fill(Qt::blue);
            }
            if (m_requestedSize.isValid())
                m_image = m_image.scaled(m_requestedSize);

            emit finished();
        }

        QString m_id;
        QSize m_requestedSize;
        QImage m_image;
};

class AsyncImageProvider : public QQuickAsyncImageProvider
{
public:
    QQuickImageResponse *requestImageResponse(const QString &id, const QSize &requestedSize)
    {
        AsyncImageResponse *response = new AsyncImageResponse(id, requestedSize);
        pool.start(response);
        return response;
    }

private:
    QThreadPool pool;
};


class ImageProviderExtensionPlugin : public QQmlExtensionPlugin
{
    Q_OBJECT
    Q_PLUGIN_METADATA(IID QQmlExtensionInterface_iid)
public:
    void registerTypes(const char *uri)
    {
        Q_UNUSED(uri);
    }

    void initializeEngine(QQmlEngine *engine, const char *uri)
    {
        Q_UNUSED(uri);
        engine->addImageProvider("async", new AsyncImageProvider);
    }

};

#include "imageresponseprovider.moc"