Allow retrieval of interface IId from class type.

This method is necessary for QML to support Qt interfaces, but probably
shouldn't be used otherwise.

Reviewed-by: Roberto Raggi

2 files changed, 21 insertions, 0 deletions

diff --git a/src/corelib/kernel/qobject.h b/src/corelib/kernel/qobject.h
index 1fb216b..4715626 100644
--- a/src/corelib/kernel/qobject.h
+++ b/src/corelib/kernel/qobject.h
@@ -379,6 +379,9 @@ inline QList<T> qFindChildren(const QObject *o, const QRegExp &re)
 #endif // Q_MOC_RUN
 
 
+template <class T> inline const char * qobject_interface_iid() 
+{ return 0; }
+
 template <class T> inline T qobject_cast_helper(QObject *object, T)
 { return static_cast<T>(((T)0)->staticMetaObject.cast(object)); }
 
@@ -395,6 +398,8 @@ inline T qobject_cast(const QObject *object)
 
 #ifndef Q_MOC_RUN
 #  define Q_DECLARE_INTERFACE(IFace, IId) \
+    template <> inline const char *qobject_interface_iid<IFace *>() \
+    { return IId; } \
     template <> inline IFace *qobject_cast_helper<IFace *>(QObject *object, IFace *) \
     { return (IFace *)(object ? object->qt_metacast(IId) : 0); } \
     template <> inline IFace *qobject_cast_helper<IFace *>(const QObject *object, IFace *) \
@@ -458,8 +463,13 @@ inline T qobject_cast(const QObject *object)
 }
 
 
+template <class T> inline const char * qobject_interface_iid() 
+{ return 0; }
+
 #ifndef Q_MOC_RUN
 #  define Q_DECLARE_INTERFACE(IFace, IId) \
+    template <> inline const char *qobject_interface_iid<IFace *>() \
+    { return IId; } \
     template <> inline IFace *qobject_cast<IFace *>(QObject *object) \
     { return reinterpret_cast<IFace *>((object ? object->qt_metacast(IId) : 0)); } \
     template <> inline IFace *qobject_cast<IFace *>(const QObject *object) \
diff --git a/tests/auto/qobject/tst_qobject.cpp b/tests/auto/qobject/tst_qobject.cpp
index 4f25af6..3df83d7 100644
--- a/tests/auto/qobject/tst_qobject.cpp
+++ b/tests/auto/qobject/tst_qobject.cpp
@@ -118,6 +118,7 @@ private slots:
     void connectToSender();
     void qobjectConstCast();
     void uniqConnection();
+    void interfaceIid();
 protected:
 };
 
@@ -2887,5 +2888,15 @@ void tst_QObject::uniqConnection()
     delete r2;
 }
 
+void tst_QObject::interfaceIid()
+{
+    QCOMPARE(QByteArray(qobject_interface_iid<Foo::Bleh *>()), 
+             QByteArray(Bleh_iid));
+    QCOMPARE(QByteArray(qobject_interface_iid<Foo::Bar *>()), 
+             QByteArray("com.qtest.foobar"));
+    QCOMPARE(QByteArray(qobject_interface_iid<FooObject *>()), 
+             QByteArray());
+}
+
 QTEST_MAIN(tst_QObject)
 #include "tst_qobject.moc"