From 78e0e72eb5ec2c5b107523b8af48fdedd599bba7 Mon Sep 17 00:00:00 2001
From: Olivier Goffart <ogoffart@woboq.com>
Date: Sun, 3 Aug 2014 14:56:34 +0200
Subject: Let QMetaType know which types are Q_GADGET

This is required so we can take a QVariant and detect that it contains a
Q_GADGET and then use method like QMetaType::metaObject and QMetaProperty::write
with the QVariant::data

Change-Id: I3603692e4e84426e10bf59949e3def3ea4947bec
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
---
 src/corelib/kernel/qmetatype.cpp | 22 ++++++++++++++++++----
 src/corelib/kernel/qmetatype.h   | 22 +++++++++++++++++++---
 src/corelib/kernel/qobjectdefs.h |  1 +
 3 files changed, 38 insertions(+), 7 deletions(-)

(limited to 'src/corelib')

diff --git a/src/corelib/kernel/qmetatype.cpp b/src/corelib/kernel/qmetatype.cpp
index 63f181cdac..ee86867249 100644
--- a/src/corelib/kernel/qmetatype.cpp
+++ b/src/corelib/kernel/qmetatype.cpp
@@ -283,10 +283,11 @@ struct DefinedTypesFilter {
     \value MovableType An instance of a type having this attribute can be safely moved by memcpy.
     \omitvalue SharedPointerToQObject
     \omitvalue IsEnumeration
-    \omitvalue PointerToQObject
+    \value PointerToQObject This type is a pointer to a derived of QObject
     \omitvalue WeakPointerToQObject
     \omitvalue TrackingPointerToQObject
     \omitvalue WasDeclaredAsMetaType
+    \value IsGadget This type is a Q_GADGET and it's corresponding QMetaObject can be accessed with QMetaType::metaObject Since 5.5.
 */
 
 /*!
@@ -363,8 +364,19 @@ struct DefinedTypesFilter {
 
 /*!
     \fn const QMetaObject *QMetaType::metaObject() const
-    \since 5.0
-    \internal
+    \since 5.5
+
+    return a QMetaObject relative to this type.
+
+    If the type is a pointer type to a subclass of QObject, flags contains
+    QMetaType::PointerToQObject and this function returns the corresponding QMetaObject. This can
+    be used to in combinaison with QMetaObject::construct to create QObject of this type.
+
+    If the type is a Q_GADGET, flags contains QMetaType::IsGadget, and this function returns its
+    QMetaObject.  This can be used to retrieve QMetaMethod and QMetaProperty and use them on a
+    pointer of this type. (given by QVariant::data for example)
+
+    \sa QMetaType::metaObjectForType(), QMetaType::flags()
 */
 
 /*!
@@ -2025,7 +2037,9 @@ private:
 /*!
     \since 5.0
 
-    Returns QMetaObject of a given \a type, if the \a type is a pointer to type derived from QObject.
+    returns QMetaType::metaObject for \a type
+
+    \sa metaObject()
 */
 const QMetaObject *QMetaType::metaObjectForType(int type)
 {
diff --git a/src/corelib/kernel/qmetatype.h b/src/corelib/kernel/qmetatype.h
index 947bf77796..dc7e7e0395 100644
--- a/src/corelib/kernel/qmetatype.h
+++ b/src/corelib/kernel/qmetatype.h
@@ -1,6 +1,7 @@
 /****************************************************************************
 **
 ** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
+** Copyright (C) 2014 Olivier Goffart <ogoffart@woboq.com>
 ** Contact: http://www.qt-project.org/legal
 **
 ** This file is part of the QtCore module of the Qt Toolkit.
@@ -435,7 +436,8 @@ public:
         SharedPointerToQObject = 0x20,
         WeakPointerToQObject = 0x40,
         TrackingPointerToQObject = 0x80,
-        WasDeclaredAsMetaType = 0x100
+        WasDeclaredAsMetaType = 0x100,
+        IsGadget = 0x200
     };
     Q_DECLARE_FLAGS(TypeFlags, TypeFlag)
 
@@ -1335,14 +1337,27 @@ namespace QtPrivate
         enum { Value = sizeof(checkType(static_cast<T*>(0))) == sizeof(yes_type) };
     };
 
-    template<typename T, bool = IsPointerToTypeDerivedFromQObject<T>::Value>
+    template<typename T>
+    struct IsGadgetHelper
+    {
+        template<typename X> static typename X::QtGadgetHelper *checkType(X*);
+        static char checkType(void*);
+        enum { Value = sizeof(checkType(static_cast<T*>(0))) == sizeof(void*)  };
+    };
+
+    template<typename T, typename Enable = void>
     struct MetaObjectForType
     {
         static inline const QMetaObject *value() { return 0; }
     };
 
     template<typename T>
-    struct MetaObjectForType<T*, /* isPointerToTypeDerivedFromQObject = */ true>
+    struct MetaObjectForType<T*, typename QEnableIf<IsPointerToTypeDerivedFromQObject<T*>::Value>::Type>
+    {
+        static inline const QMetaObject *value() { return &T::staticMetaObject; }
+    };
+    template<typename T>
+    struct MetaObjectForType<T, typename QEnableIf<IsGadgetHelper<T>::Value>::Type>
     {
         static inline const QMetaObject *value() { return &T::staticMetaObject; }
     };
@@ -1553,6 +1568,7 @@ namespace QtPrivate {
                      | (IsWeakPointerToTypeDerivedFromQObject<T>::Value ? QMetaType::WeakPointerToQObject : 0)
                      | (IsTrackingPointerToTypeDerivedFromQObject<T>::Value ? QMetaType::TrackingPointerToQObject : 0)
                      | (Q_IS_ENUM(T) ? QMetaType::IsEnumeration : 0)
+                     | (IsGadgetHelper<T>::Value ? QMetaType::IsGadget : 0)
              };
     };
 
diff --git a/src/corelib/kernel/qobjectdefs.h b/src/corelib/kernel/qobjectdefs.h
index 38ee31b250..a495bce7ec 100644
--- a/src/corelib/kernel/qobjectdefs.h
+++ b/src/corelib/kernel/qobjectdefs.h
@@ -159,6 +159,7 @@ private: \
 #define Q_GADGET \
 public: \
     static const QMetaObject staticMetaObject; \
+    typedef void QtGadgetHelper; \
 private: \
     Q_DECL_HIDDEN_STATIC_METACALL static void qt_static_metacall(QObject *, QMetaObject::Call, int, void **);
 #endif // QT_NO_META_MACROS
-- 
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