Qml QGrapicsObject type in QGraphicsScene

[pkj]

In Qt4.8 we can use to Qml to create QGraphicsObject as described in the documentation as :http://doc.qt.io/qt-4.8/qml-integration.html#adding-qml-widgets-to-a-qgraphicsscene

QGraphicsScene* scene = myExistingGraphicsScene();
 QDeclarativeEngine *engine = new QDeclarativeEngine;
 QDeclarativeComponent component(engine, QUrl::fromLocalFile("myqml.qml"));
 QGraphicsObject *object =
     qobject_cast<QGraphicsObject *>(component.create());
 scene->addItem(object);

QGraphicsScene* scene = myExistingGraphicsScene();
 QDeclarativeEngine *engine = new QDeclarativeEngine;
 QDeclarativeComponent component(engine, QUrl::fromLocalFile("myqml.qml"));
 QGraphicsObject *object =
     qobject_cast<QGraphicsObject *>(component.create());
 scene->addItem(object);

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I want the type() of QGraphicsItem in the QGraphicsObject i get from the factory function of QDeclarativeComponent to be set to something different from the default 'User' set in QGraphicsItem.
As described in the docs here http://doc.qt.io/qt-4.8/qgraphicsitem.html#type I need to subclass the QgraphicsItem.
If I go ahead and do something like

class QmlObject : public QGraphicsObject{
 Q_OBJECT
public:
enum {Type = TypeMyType;}//TypeMyType = UserType+1;
int type() const { return Type; }
QmlObject ();
}
 
QmlObject :: QmlObject () : QGraphicsObject() 
{
QGraphicsScene* scene = myExistingGraphicsScene();
 QDeclarativeEngine *engine = new QDeclarativeEngine;
 QDeclarativeComponent component(engine, QUrl::fromLocalFile("myqml.qml"));
 QGraphicsObject *object =
     qobject_cast<QGraphicsObject *>(component.create());
 scene->addItem(object);
//DEAD END HERE, can't change the embedded QGraphicsObject already initialized.
}

class QmlObject : public QGraphicsObject{
 Q_OBJECT
public:
enum {Type = TypeMyType;}//TypeMyType = UserType+1;
int type() const { return Type; }
QmlObject ();
}

QmlObject :: QmlObject () : QGraphicsObject() 
{
QGraphicsScene* scene = myExistingGraphicsScene();
 QDeclarativeEngine *engine = new QDeclarativeEngine;
 QDeclarativeComponent component(engine, QUrl::fromLocalFile("myqml.qml"));
 QGraphicsObject *object =
     qobject_cast<QGraphicsObject *>(component.create());
 scene->addItem(object);
//DEAD END HERE, can't change the embedded QGraphicsObject already initialized.
}

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So if I go ahead by this route, since QObject is not copyable by Q_DISABLE_COPY, there is no way left for me to subclass it. And if I can't subclass it, I can't set the type of QGraphicsItem to something other than User.
AnyIdea how to go ahead and set the type of the QGraphicsItem?

[wysota]

You are trying to do something weird. The docs you mention are related to something completely different, there is no subclassing there. It is possible to do what you want but in a different way -- subclass QGraphicsObject to return your new type, then create a QML component using QDeclarativeEngine instance, then cast the resulting object to QGraphicsObject or QDeclarativeItem and set it as a child of your custom graphics object. Then just make sure the child always occupies the whole area of its parent (you can use QGraphicsLayout for this).

[pkj]

cast the resulting object to QGraphicsObject or QDeclarativeItem and set it as a child of your custom graphics object. Then just make sure the child always occupies the whole area of its parent (you can use QGraphicsLayout for this).

http://doc.qt.io/qt-4.8/QGraphicsLayout only work for items which inherit http://doc.qt.io/qt-4.8/QGraphicsLayoutItem. QGraphicsWidget does that. But not QDeclarativeItem. So I cannot use QGraphicsLayout. Is there another way in which the wrapper object for the QDeclarativeItem has a layout?

[wysota]

Then monitor the size yourself and resize the child when the parent changes size.