Qt 5.11 | Qt Quick | C++ Extensions: Image Response Provider Example | imageresponseprovider.cpp Example File

Qt 5.11.3 Reference Documentation

# imageresponseprovider.cpp Example File

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 override
              {
                  return QQuickTextureFactory::textureFactoryForImage(m_image);
              }

              void run() override
              {
                  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) override
          {
              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) override
          {
              Q_UNUSED(uri);
          }

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

      };

      #include "imageresponseprovider.moc"