Be able to read and write properties to Q_GADGET

Change-Id: Ic12f465d31459748ca08ac8c457fd61a5773e2e2
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>

src/corelib/kernel/qmetaobject.cpp

@@ -2969,6 +2969,49 @@ bool QMetaProperty::reset(QObject *object) const
         QMetaObject::metacall(object, QMetaObject::ResetProperty, idx + mobj->propertyOffset(), argv);
     return true;
 }
+/*!
+    \since 5.5
+
+    Reads the property's value from the given \a gadget. Returns the value
+    if it was able to read it; otherwise returns an invalid variant.
+
+    This function should only be used if this is a property of a Q_GADGET
+*/
+QVariant QMetaProperty::readOnGadget(const void *gadget) const
+{
+    Q_ASSERT(priv(mobj->d.data)->flags & PropertyAccessInStaticMetaCall && mobj->d.static_metacall);
+    return read(reinterpret_cast<const QObject*>(gadget));
+}
+
+/*!
+    \since 5.5
+
+    Writes \a value as the property's value to the given \a gadget. Returns
+    true if the write succeeded; otherwise returns \c false.
+
+    This function should only be used if this is a property of a Q_GADGET
+*/
+bool QMetaProperty::writeOnGadget(void *gadget, const QVariant &value) const
+{
+    Q_ASSERT(priv(mobj->d.data)->flags & PropertyAccessInStaticMetaCall && mobj->d.static_metacall);
+    return write(reinterpret_cast<QObject*>(gadget), value);
+}
+
+/*!
+    \since 5.5
+
+    Resets the property for the given \a gadget with a reset method.
+    Returns \c true if the reset worked; otherwise returns \c false.
+
+    Reset methods are optional; only a few properties support them.
+
+    This function should only be used if this is a property of a Q_GADGET
+*/
+bool QMetaProperty::resetOnGadget(void *gadget) const
+{
+    Q_ASSERT(priv(mobj->d.data)->flags & PropertyAccessInStaticMetaCall && mobj->d.static_metacall);
+    return reset(reinterpret_cast<QObject*>(gadget));
+}
 
 /*!
     Returns \c true if this property can be reset to a default value; otherwise

src/corelib/kernel/qmetaobject.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.
@@ -237,6 +238,10 @@ public:
     bool write(QObject *obj, const QVariant &value) const;
     bool reset(QObject *obj) const;
 
+    QVariant readOnGadget(const void *gadget) const;
+    bool writeOnGadget(void *gadget, const QVariant &value) const;
+    bool resetOnGadget(void *gadget) const;
+
     bool hasStdCppSet() const;
     inline bool isValid() const { return isReadable(); }
     inline const QMetaObject *enclosingMetaObject() const { return mobj; }

tests/auto/corelib/kernel/qmetaproperty/tst_qmetaproperty.cpp

@@ -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 test suite of the Qt Toolkit.
@@ -50,6 +51,7 @@ private slots:
     void hasStdCppSet();
     void isConstant();
     void isFinal();
+    void gadget();
 
 public:
     enum EnumType { EnumType1 };
@@ -103,5 +105,32 @@ void tst_QMetaProperty::isFinal()
     QVERIFY(!prop.isFinal());
 }
 
+class MyGadget {
+    Q_GADGET
+    Q_PROPERTY(QString value READ getValue WRITE setValue RESET resetValue)
+public:
+    QString m_value;
+    void setValue(const QString &value) { m_value = value; }
+    QString getValue() { return m_value; }
+    void resetValue() { m_value = QLatin1Literal("reset"); }
+};
+
+void tst_QMetaProperty::gadget()
+{
+    const QMetaObject *mo = &MyGadget::staticMetaObject;
+    QMetaProperty valueProp = mo->property(mo->indexOfProperty("value"));
+    QVERIFY(valueProp.isValid());
+    {
+        MyGadget g;
+        QString hello = QLatin1Literal("hello");
+        QVERIFY(valueProp.writeOnGadget(&g, hello));
+        QCOMPARE(g.m_value, QLatin1String("hello"));
+        QCOMPARE(valueProp.readOnGadget(&g), QVariant(hello));
+        QVERIFY(valueProp.resetOnGadget(&g));
+        QCOMPARE(valueProp.readOnGadget(&g), QVariant(QLatin1String("reset")));
+    }
+}
+
+
 QTEST_MAIN(tst_QMetaProperty)
 #include "tst_qmetaproperty.moc"