Как правильно использовать QWidget в QML?

/* qmlwidget.h */

#include <QQuickPaintedItem>
#include <QPushButton>

class QmlWidget : public QQuickPaintedItem
{
    Q_OBJECT

public:
    explicit QmlWidget(QQuickItem* parent = 0);
    void paint(QPainter* painter);

private:
    QPushButton* w;
};

/* qmlwidget.cpp */

#include "qmlwidget.h"

QmlWidget::QmlWidget(QQuickItem* parent) :
    QQuickPaintedItem(parent)
{
    w = new QPushButton;
}

void QmlWidget::paint(QPainter *painter) {
    w->render(painter);
}

/* main.cpp */

#include <QQmlApplicationEngine>
#include <QApplication>
#include "qmlwidget.h"

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    qmlRegisterType<QmlWidget>("QmlWidget",1,0,"QmlWidget");
    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
    return app.exec();
}

/* main.qml */

import QtQuick 2.6
import QtQuick.Window 2.2
import QmlWidget 1.0

Window {
    visible: true
    width: 640
    height: 320

    QmlWidget {
        anchors.fill: parent
    }
}