Support querying indirect extensions for a given object

Introduce a private version of qmlExtendedObject() that returns an
index-based extension (where 0 represents an extension on the leaf type
and N represents a (N - 1)th base type's extension)

Teach QQmlProxyMetaObject to distinguish different extension proxies.
Its custom metaCall can now query up to 128 extensions (should be enough
for the user needs)

Change-Id: I5520a1e84501f1f9fe6a8e77d8269009a12c255c
Reviewed-by: Maximilian Goldstein <max.goldstein@qt.io>
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

1 files changed, 7 insertions, 2 deletions

diff --git a/src/qml/qml/qqml.cpp b/src/qml/qml/qqml.cpp
index 728250dcf2..3c9f930eb9 100644
--- a/src/qml/qml/qqml.cpp
+++ b/src/qml/qml/qqml.cpp
@@ -151,6 +151,11 @@ QObject *qmlAttachedPropertiesObject(QObject *object, QQmlAttachedPropertiesFunc
 
 QObject *qmlExtendedObject(QObject *object)
 {
+    return QQmlPrivate::qmlExtendedObject(object, 0);
+}
+
+QObject *QQmlPrivate::qmlExtendedObject(QObject *object, int index)
+{
     if (!object)
         return nullptr;
 
@@ -161,8 +166,8 @@ QObject *qmlExtendedObject(QObject *object)
 
     const int id = d->metaObject->metaCall(
                 object, QMetaObject::CustomCall,
-                QQmlProxyMetaObject::ExtensionObjectId, &result);
-    if (id != QQmlProxyMetaObject::ExtensionObjectId)
+                QQmlProxyMetaObject::extensionObjectId(index), &result);
+    if (id != QQmlProxyMetaObject::extensionObjectId(index))
         return nullptr;
 
     return static_cast<QObject *>(result);