QML: Allow namespaces as extensions to types

This way we can access the enums of namespaces as properties of the
primary type. This is achieved by:

1. Making enums of extended types available in the base type
2. Allowing the extension to be specified as plain metaObject rather
   than as type name.
3. Refraining from creating the extension if the create function does
   not exist.

The goal of this is to declare the Qt namespace in a civilized way, but
will also help with cleaning up the QtQuick value types and their enums.

Change-Id: I13399741d30ce38d1bff753cfa1b11e72ccfbf6a
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 19 insertions, 6 deletions

diff --git a/src/qml/qml/qqml.h b/src/qml/qml/qqml.h
index be482c5277..9118b42390 100644
--- a/src/qml/qml/qqml.h
+++ b/src/qml/qml/qqml.h
@@ -119,6 +119,13 @@
     template<typename T, typename... Args> \
     friend void QML_REGISTER_TYPES_AND_REVISIONS(const char *uri, int versionMajor, QList<int> *);
 
+#define QML_EXTENDED_NAMESPACE(EXTENDED_NAMESPACE) \
+    Q_CLASSINFO("QML.Extended", #EXTENDED_NAMESPACE) \
+    static constexpr const QMetaObject *qmlExtendedNamespace() { return &EXTENDED_NAMESPACE::staticMetaObject; } \
+    template<class, class> friend struct QML_PRIVATE_NAMESPACE::QmlExtendedNamespace; \
+    template<typename T, typename... Args> \
+    friend void QML_REGISTER_TYPES_AND_REVISIONS(const char *uri, int versionMajor, QList<int> *);
+
 #define QML_FOREIGN(FOREIGN_TYPE) \
     Q_CLASSINFO("QML.Foreign", #FOREIGN_TYPE) \
     using QmlForeignType = FOREIGN_TYPE; \
@@ -792,25 +799,30 @@ struct QmlTypeAndRevisionsRegistration;
 
 template<class T, class Resolved, class Extended>
 struct QmlTypeAndRevisionsRegistration<T, Resolved, Extended, false, false> {
-    static void registerTypeAndRevisions(const char *uri, int versionMajor, QList<int> *qmlTypeIds)
+    static void registerTypeAndRevisions(const char *uri, int versionMajor, QList<int> *qmlTypeIds,
+                                         const QMetaObject *extension)
     {
         QQmlPrivate::qmlRegisterTypeAndRevisions<Resolved, Extended>(
-                    uri, versionMajor, QQmlPrivate::StaticMetaObject<T>::staticMetaObject(), qmlTypeIds);
+                    uri, versionMajor, QQmlPrivate::StaticMetaObject<T>::staticMetaObject(),
+                    qmlTypeIds, extension);
     }
 };
 
 template<class T, class Resolved>
 struct QmlTypeAndRevisionsRegistration<T, Resolved, void, true, false> {
-    static void registerTypeAndRevisions(const char *uri, int versionMajor, QList<int> *qmlTypeIds)
+    static void registerTypeAndRevisions(const char *uri, int versionMajor, QList<int> *qmlTypeIds,
+                                         const QMetaObject *)
     {
         QQmlPrivate::qmlRegisterSingletonAndRevisions<Resolved>(
-                    uri, versionMajor, QQmlPrivate::StaticMetaObject<T>::staticMetaObject(), qmlTypeIds);
+                    uri, versionMajor, QQmlPrivate::StaticMetaObject<T>::staticMetaObject(),
+                    qmlTypeIds);
     }
 };
 
 template<class T, class Resolved>
 struct QmlTypeAndRevisionsRegistration<T, Resolved, void, false, true> {
-    static void registerTypeAndRevisions(const char *uri, int versionMajor, QList<int> *qmlTypeIds)
+    static void registerTypeAndRevisions(const char *uri, int versionMajor, QList<int> *qmlTypeIds,
+                                         const QMetaObject *)
     {
         const int id = qmlRegisterInterface<Resolved>(uri, versionMajor);
         if (qmlTypeIds)
@@ -830,7 +842,8 @@ void qmlRegisterTypesAndRevisions(const char *uri, int versionMajor, QList<int>
             typename QQmlPrivate::QmlExtended<T>::Type,
             QQmlPrivate::QmlSingleton<T>::Value,
             QQmlPrivate::QmlInterface<T>::Value>
-            ::registerTypeAndRevisions(uri, versionMajor, qmlTypeIds);
+            ::registerTypeAndRevisions(uri, versionMajor, qmlTypeIds,
+                                       QQmlPrivate::QmlExtendedNamespace<T>::metaObject());
     qmlRegisterTypesAndRevisions<Args...>(uri, versionMajor, qmlTypeIds);
 }