Add template specialization of QMetaType for QObject derived pointers.

This makes it possible to do things like

QVariant::fromValue(new SomeObject);

without first using Q_DECLARE_METATYPE(Something*)

This functionality was originally part of
http://codereview.qt-project.org/#change,11710 but was rejected
because the functionality was based on specialization of
QVariant::fromValue which could be dangerous.

This new implementation doesn't have such danger.

Change-Id: I83fe941b6984be54469bc6b9191f6eacaceaa036
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@nokia.com>
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>

2 files changed, 32 insertions, 0 deletions

diff --git a/tests/auto/corelib/kernel/qmetatype/tst_qmetatype.cpp b/tests/auto/corelib/kernel/qmetatype/tst_qmetatype.cpp
index f8403f11a1..572ecc9ba8 100644
--- a/tests/auto/corelib/kernel/qmetatype/tst_qmetatype.cpp
+++ b/tests/auto/corelib/kernel/qmetatype/tst_qmetatype.cpp
@@ -100,12 +100,29 @@ private slots:
 
 struct Foo { int i; };
 
+
+class CustomQObject : public QObject
+{
+    Q_OBJECT
+public:
+    CustomQObject(QObject *parent = 0)
+      : QObject(parent)
+    {
+    }
+};
+
+class CustomNonQObject {};
+
 void tst_QMetaType::defined()
 {
     QCOMPARE(int(QMetaTypeId2<QString>::Defined), 1);
     QCOMPARE(int(QMetaTypeId2<Foo>::Defined), 0);
     QCOMPARE(int(QMetaTypeId2<void*>::Defined), 1);
     QCOMPARE(int(QMetaTypeId2<int*>::Defined), 0);
+    QVERIFY(QMetaTypeId2<CustomQObject*>::Defined);
+    QVERIFY(!QMetaTypeId2<CustomQObject>::Defined);
+    QVERIFY(!QMetaTypeId2<CustomNonQObject>::Defined);
+    QVERIFY(!QMetaTypeId2<CustomNonQObject*>::Defined);
 }
 
 struct Bar
diff --git a/tests/auto/corelib/kernel/qvariant/tst_qvariant.cpp b/tests/auto/corelib/kernel/qvariant/tst_qvariant.cpp
index ccdab17668..5aa1389b65 100644
--- a/tests/auto/corelib/kernel/qvariant/tst_qvariant.cpp
+++ b/tests/auto/corelib/kernel/qvariant/tst_qvariant.cpp
@@ -2541,9 +2541,24 @@ public:
 };
 Q_DECLARE_METATYPE(CustomQObjectDerived*)
 
+class CustomQObjectDerivedNoMetaType : public CustomQObject {
+    Q_OBJECT
+public:
+    CustomQObjectDerivedNoMetaType(QObject *parent = 0) : CustomQObject(parent) {}
+};
+
 void tst_QVariant::qvariant_cast_QObject_derived()
 {
     {
+        CustomQObjectDerivedNoMetaType *object = new CustomQObjectDerivedNoMetaType(this);
+        QVariant data = QVariant::fromValue(object);
+        QVERIFY(data.userType() == qMetaTypeId<CustomQObjectDerivedNoMetaType*>());
+        QCOMPARE(data.value<QObject *>(), object);
+        QCOMPARE(data.value<CustomQObjectDerivedNoMetaType *>(), object);
+        QCOMPARE(data.value<CustomQObject *>(), object);
+        QVERIFY(data.value<CustomQWidget*>() == 0);
+    }
+    {
         CustomQObjectDerived *object = new CustomQObjectDerived(this);
         QVariant data = QVariant::fromValue(object);