Store the QMetaObject with the QMetaType.

This will allow conversion between pointers to compatible QObject
derived types.

Change-Id: I19e08934571fb3f1b91e594892214041fe5f6a11
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@nokia.com>

3 files changed, 98 insertions, 7 deletions

diff --git a/src/corelib/kernel/qmetatype.cpp b/src/corelib/kernel/qmetatype.cpp
index e1cebc453d..ea079fa712 100644
--- a/src/corelib/kernel/qmetatype.cpp
+++ b/src/corelib/kernel/qmetatype.cpp
@@ -286,6 +286,7 @@ static const struct { const char * typeName; int typeNameLength; int type; } typ
 
 Q_CORE_EXPORT const QMetaTypeInterface *qMetaTypeGuiHelper = 0;
 Q_CORE_EXPORT const QMetaTypeInterface *qMetaTypeWidgetsHelper = 0;
+Q_CORE_EXPORT const QMetaObject *qMetaObjectWidgetsHelper = 0;
 
 class QCustomTypeInfo : public QMetaTypeInterface
 {
@@ -496,6 +497,7 @@ int QMetaType::registerNormalizedType(const NS(QByteArray) &normalizedTypeName,
             inf.destructor = destructor;
             inf.size = size;
             inf.flags = flags;
+            inf.metaObject = metaObject;
             idx = ct->size() + User;
             ct->append(inf);
             return idx;
@@ -1521,6 +1523,51 @@ QMetaType::TypeFlags QMetaType::typeFlags(int type)
     return static_cast<QMetaType::TypeFlags>(QMetaTypeSwitcher::switcher<quint32>(flags, type, 0));
 }
 
+#ifndef QT_BOOTSTRAPPED
+namespace {
+class MetaObject
+{
+public:
+    MetaObject(const int type)
+        : m_type(type)
+    {}
+    template<typename T>
+    const QMetaObject *delegate(const T*) { return QtPrivate::MetaObjectForType<T>::value(); }
+    const QMetaObject *delegate(const void*) { return 0; }
+    const QMetaObject *delegate(const QMetaTypeSwitcher::UnknownType*) { return 0; }
+    const QMetaObject *delegate(const QMetaTypeSwitcher::NotBuiltinType*) { return customMetaObject(m_type); }
+private:
+    const int m_type;
+    static const QMetaObject *customMetaObject(const int type)
+    {
+        const QVector<QCustomTypeInfo> * const ct = customTypes();
+        if (Q_UNLIKELY(!ct || type < QMetaType::User))
+            return 0;
+        QReadLocker locker(customTypesLock());
+        if (Q_UNLIKELY(ct->count() <= type - QMetaType::User))
+            return 0;
+        return ct->at(type - QMetaType::User).metaObject;
+    }
+};
+}  // namespace
+#endif
+
+/*!
+    \since 5.0
+
+    Returns QMetaObject of a given \a type, if the \a type is a pointer to type derived from QObject.
+*/
+const QMetaObject *QMetaType::metaObjectForType(int type)
+{
+#ifndef QT_BOOTSTRAPPED
+    MetaObject mo(type);
+    return QMetaTypeSwitcher::switcher<const QMetaObject*>(mo, type, 0);
+#else
+    Q_UNUSED(type);
+    return 0;
+#endif
+}
+
 /*!
     \fn int qRegisterMetaType(const char *typeName)
     \relates QMetaType
@@ -1710,7 +1757,7 @@ QMetaType QMetaType::typeInfo(const int type)
                                  , typeInfo.info.size
                                  , typeInfo.info.flags
                                  , type
-                                 , 0)
+                                 , typeInfo.info.metaObject)
                 : QMetaType(UnknownType);
 }
 
@@ -1809,4 +1856,20 @@ QMetaType::TypeFlags QMetaType::flagsExtended() const
     return 0;
 }
 
+const QMetaObject *QMetaType::metaObjectExtended() const
+{
+    return 0;
+}
+
+
+namespace QtPrivate
+{
+const QMetaObject *metaObjectForQWidget()
+{
+    if (!qMetaTypeWidgetsHelper)
+        return 0;
+    return qMetaObjectWidgetsHelper;
+}
+}
+
 QT_END_NAMESPACE
diff --git a/src/corelib/kernel/qmetatype.h b/src/corelib/kernel/qmetatype.h
index fa0726adfa..a42333fbf8 100644
--- a/src/corelib/kernel/qmetatype.h
+++ b/src/corelib/kernel/qmetatype.h
@@ -196,7 +196,7 @@ class Q_CORE_EXPORT QMetaType {
                          ConstructEx = 0x4, DestructEx = 0x8,
                          NameEx = 0x10, SizeEx = 0x20,
                          CtorEx = 0x40, DtorEx = 0x80,
-                         FlagsEx = 0x100
+                         FlagsEx = 0x100, MetaObjectEx = 0x200
                        };
 public:
 #ifndef Q_QDOC
@@ -290,6 +290,7 @@ public:
     static const char *typeName(int type);
     static int sizeOf(int type);
     static TypeFlags typeFlags(int type);
+    static const QMetaObject *metaObjectForType(int type);
     static bool isRegistered(int type);
     static void *create(int type, const void *copy = 0);
 #if QT_DEPRECATED_SINCE(5, 0)
@@ -312,6 +313,7 @@ public:
     inline bool isRegistered() const;
     inline int sizeOf() const;
     inline TypeFlags flags() const;
+    inline const QMetaObject *metaObject() const;
 
     inline void *create(const void *copy = 0) const;
     inline void destroy(void *data) const;
@@ -339,6 +341,7 @@ private:
     void dtor();
     uint sizeExtended() const;
     QMetaType::TypeFlags flagsExtended() const;
+    const QMetaObject *metaObjectExtended() const;
     void *createExtended(const void *copy = 0) const;
     void destroyExtended(void *data) const;
     void *constructExtended(void *where, const void *copy = 0) const;
@@ -355,7 +358,7 @@ private:
     uint m_typeFlags;
     uint m_extensionFlags;
     int m_typeId;
-    const QMetaObject *m_metaObject; // Placeholder for Qt 5.1 feature.
+    const QMetaObject *m_metaObject;
 };
 
 #undef QT_DEFINE_METATYPE_ID
@@ -466,12 +469,21 @@ namespace QtPrivate
     {
         static inline const QMetaObject *value() { return 0; }
     };
+
     template<typename T>
     struct MetaObjectForType<T*, /* isPointerToTypeDerivedFromQObject = */ true>
     {
         static inline const QMetaObject *value() { return &T::staticMetaObject; }
     };
 
+    Q_CORE_EXPORT const QMetaObject *metaObjectForQWidget();
+
+    template<>
+    struct MetaObjectForType<QWidget*, /* isPointerToTypeDerivedFromQObject = */ true>
+    {
+        static const QMetaObject *value() { return metaObjectForQWidget(); }
+    };
+
     template<typename T>
     struct IsSharedPointerToTypeDerivedFromQObject
     {
@@ -846,7 +858,7 @@ inline QMetaType::QMetaType(const ExtensionFlag extensionFlags, const QMetaTypeI
                             uint size,
                             uint theTypeFlags,
                             int typeId,
-                            const QMetaObject *metaObject)
+                            const QMetaObject *_metaObject)
     : m_creator(creator)
     , m_deleter(deleter)
     , m_saveOp(saveOp)
@@ -858,7 +870,7 @@ inline QMetaType::QMetaType(const ExtensionFlag extensionFlags, const QMetaTypeI
     , m_typeFlags(theTypeFlags)
     , m_extensionFlags(extensionFlags)
     , m_typeId(typeId)
-    , m_metaObject(metaObject)
+    , m_metaObject(_metaObject)
 {
     if (Q_UNLIKELY(isExtended(CtorEx) || typeId == QMetaType::Void))
         ctor(info);
@@ -924,6 +936,13 @@ inline QMetaType::TypeFlags QMetaType::flags() const
     return QMetaType::TypeFlags(m_typeFlags);
 }
 
+inline const QMetaObject *QMetaType::metaObject() const
+{
+    if (Q_UNLIKELY(isExtended(MetaObjectEx)))
+        return metaObjectExtended();
+    return m_metaObject;
+}
+
 QT_END_NAMESPACE
 
 
diff --git a/src/corelib/kernel/qmetatype_p.h b/src/corelib/kernel/qmetatype_p.h
index cffc45c988..126acde8fa 100644
--- a/src/corelib/kernel/qmetatype_p.h
+++ b/src/corelib/kernel/qmetatype_p.h
@@ -130,6 +130,7 @@ public:
     QMetaType::Destructor destructor;
     int size;
     quint32 flags; // same as QMetaType::TypeFlags
+    const QMetaObject *metaObject;
 };
 
 #ifndef QT_NO_DATASTREAM
@@ -147,6 +148,12 @@ public:
     QT_METATYPE_INTERFACE_INIT_EMPTY_DATASTREAM_IMPL(Type)
 #endif
 
+#ifndef QT_BOOTSTRAPPED
+#define METAOBJECT_DELEGATE(Type) (QtPrivate::MetaObjectForType<Type>::value())
+#else
+#define METAOBJECT_DELEGATE(Type) 0
+#endif
+
 #define QT_METATYPE_INTERFACE_INIT_IMPL(Type, DATASTREAM_DELEGATE) \
 { \
     /*creator*/(qMetaTypeCreateHelper<Type>), \
@@ -155,7 +162,8 @@ public:
     /*constructor*/(qMetaTypeConstructHelper<Type>), \
     /*destructor*/(qMetaTypeDestructHelper<Type>), \
     /*size*/(QTypeInfo<Type>::sizeOf), \
-    /*flags*/QtPrivate::QMetaTypeTypeFlags<Type>::Flags \
+    /*flags*/QtPrivate::QMetaTypeTypeFlags<Type>::Flags, \
+    /*metaObject*/METAOBJECT_DELEGATE(Type) \
 }
 
 
@@ -179,7 +187,8 @@ public:
     /*constructor*/ 0, \
     /*destructor*/ 0, \
     /*size*/ 0, \
-    /*flags*/ 0 \
+    /*flags*/ 0, \
+    /*metaObject*/ 0 \
 }
 
 namespace QtMetaTypePrivate {