QML: Allow singleton types to be extended

It seems we never stated that singletons can not be extended in our
documentation. Therefore this is technically a bug fix and doesn't need
separate documentation.

Change-Id: I7877289bd5a52ecf709f80ba1975137981ec65f0
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 14 insertions, 2 deletions

diff --git a/src/qml/qml/qqmlprivate.h b/src/qml/qml/qqmlprivate.h
index 4fcfd65c09..19072f0751 100644
--- a/src/qml/qml/qqmlprivate.h
+++ b/src/qml/qml/qqmlprivate.h
@@ -526,6 +526,10 @@ namespace QQmlPrivate
 
         const QMetaObject *instanceMetaObject;
         QMetaType typeId;
+
+        QObject *(*extensionObjectCreate)(QObject *);
+        const QMetaObject *extensionMetaObject;
+
         QTypeRevision revision;
     };
 
@@ -540,6 +544,10 @@ namespace QQmlPrivate
         const QMetaObject *classInfoMetaObject;
 
         QMetaType typeId;
+
+        QObject *(*extensionObjectCreate)(QObject *);
+        const QMetaObject *extensionMetaObject;
+
         QVector<int> *qmlTypeIds;
     };
 
@@ -752,10 +760,10 @@ namespace QQmlPrivate
         }
     };
 
-    template<typename T>
+    template<typename T, typename E>
     void qmlRegisterSingletonAndRevisions(const char *uri, int versionMajor,
                                           const QMetaObject *classInfoMetaObject,
-                                          QVector<int> *qmlTypeIds)
+                                          QVector<int> *qmlTypeIds, const QMetaObject *extension)
     {
         RegisterSingletonTypeAndRevisions api = {
             0,
@@ -769,6 +777,10 @@ namespace QQmlPrivate
             classInfoMetaObject,
 
             QmlMetaType<T>::self(),
+
+            ExtendedType<E>::createParent,
+            extension ? extension : ExtendedType<E>::staticMetaObject(),
+
             qmlTypeIds
         };