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Treat pointers to QObject derived types in QVariant specially.

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It is possible to do this for example:

QVariant v = QVariant::fromValue<MyCustomQObject*>();
QObject *object = v.value<QObject*>();

This means that if a QVariant contains a pointer to a QObject
derived type, third parties can extract a QObject* and use its
properties without knowing the concrete type.

This is a source compatible change.

Change-Id: Iee9a9437e99cc2f40d1a4bfea47275482ef7161f
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@nokia.com>
This commit is contained in:
Stephen Kelly 2011-12-30 13:18:24 +01:00 committed by Qt by Nokia
parent e85c0862d9
commit ae85d7c965
2 changed files with 156 additions and 14 deletions
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72
src/corelib/kernel/qvariant.h
View File

@ -49,6 +49,7 @@
#include <QtCore/qmap.h>
#include <QtCore/qhash.h>
#include <QtCore/qstring.h>
#include <QtCore/qobject.h>
QT_BEGIN_HEADER
@ -88,6 +89,39 @@ inline QVariant qVariantFromValue(const T &);
template<typename T>
inline T qvariant_cast(const QVariant &);
namespace QtPrivate {
template <typename Derived, typename Argument, typename ReturnType>
struct ObjectInvoker
{
static ReturnType invoke(Argument a)
{
return Derived::object(a);
}
};
template <typename Derived, typename Argument, typename ReturnType>
struct MetaTypeInvoker
{
static ReturnType invoke(Argument a)
{
return Derived::metaType(a);
}
};
template <typename Derived, typename T, typename Argument, typename ReturnType, bool = IsPointerToTypeDerivedFromQObject<T>::Value>
struct TreatAsQObjectBeforeMetaType : ObjectInvoker<Derived, Argument, ReturnType>
{
};
template <typename Derived, typename T, typename Argument, typename ReturnType>
struct TreatAsQObjectBeforeMetaType<Derived, T, Argument, ReturnType, false> : MetaTypeInvoker<Derived, Argument, ReturnType>
{
};
template<typename T> struct QVariantValueHelper;
}
class Q_CORE_EXPORT QVariant
{
public:
@ -375,14 +409,15 @@ protected:
#ifndef QT_NO_DEBUG_STREAM
friend Q_CORE_EXPORT QDebug operator<<(QDebug, const QVariant &);
#endif
Private d;
#ifndef Q_NO_TEMPLATE_FRIENDS
template<typename T>
friend inline T qvariant_cast(const QVariant &);
template<typename T> friend struct QtPrivate::QVariantValueHelper;
protected:
#else
public:
#endif
Private d;
void create(int type, const void *copy);
bool cmp(const QVariant &other) const;
bool convert(const int t, void *ptr) const;
@ -481,18 +516,35 @@ inline bool operator!=(const QVariant &v1, const QVariantComparisonHelper &v2)
}
#endif
namespace QtPrivate {
template<typename T>
struct QVariantValueHelper : TreatAsQObjectBeforeMetaType<QVariantValueHelper<T>, T, const QVariant &, T>
{
static T metaType(const QVariant &v)
{
const int vid = qMetaTypeId<T>(static_cast<T *>(0));
if (vid == v.userType())
return *reinterpret_cast<const T *>(v.constData());
if (vid < int(QMetaType::User)) {
T t;
if (v.convert(QVariant::Type(vid), &t))
return t;
}
return T();
}
#ifndef QT_NO_QOBJECT
static T object(const QVariant &v)
{
return qobject_cast<T>(QMetaType::typeFlags(v.userType()) & QMetaType::PointerToQObject ? v.d.data.o : 0);
}
#endif
};
}
#ifndef QT_MOC
template<typename T> inline T qvariant_cast(const QVariant &v)
{
const int vid = qMetaTypeId<T>(static_cast<T *>(0));
if (vid == v.userType())
return *reinterpret_cast<const T *>(v.constData());
if (vid < int(QMetaType::User)) {
T t;
if (v.convert(vid, &t))
return t;
}
return T();
return QtPrivate::QVariantValueHelper<T>::invoke(v);
}
template<> inline QVariant qvariant_cast<QVariant>(const QVariant &v)

98
tests/auto/corelib/kernel/qvariant/tst_qvariant.cpp
View File

@ -83,11 +83,22 @@ Q_DECLARE_METATYPE(QFont)
Q_DECLARE_METATYPE(QColor)
Q_DECLARE_METATYPE(QKeySequence)
class CustomNonQObject;
class tst_QVariant : public QObject
{
Q_OBJECT
public:
tst_QVariant(QObject *parent = 0)
: QObject(parent), customNonQObjectPointer(0)
{
}
private slots:
void cleanupTestCase();
void constructor();
void copy_constructor();
void isNull();
@ -176,6 +187,7 @@ private slots:
void qvariant_cast_QObject_data();
void qvariant_cast_QObject();
void qvariant_cast_QObject_derived();
void toLocale();
@ -275,6 +287,9 @@ private:
void dataStream_data(QDataStream::Version version);
void loadQVariantFromDataStream(QDataStream::Version version);
void saveQVariantFromDataStream(QDataStream::Version version);
CustomNonQObject *customNonQObjectPointer;
QVector<QObject*> objectPointerTestData;
};
Q_DECLARE_METATYPE(QDate)
@ -2452,20 +2467,63 @@ void tst_QVariant::invalidQColor() const
QVERIFY(!qvariant_cast<QColor>(va).isValid());
}
void tst_QVariant::qvariant_cast_QObject_data() {
class CustomQObject : public QObject {
Q_OBJECT
public:
CustomQObject(QObject *parent = 0) : QObject(parent) {}
};
class CustomQWidget : public QWidget {
Q_OBJECT
public:
CustomQWidget(QWidget *parent = 0) : QWidget(parent) {}
};
Q_DECLARE_METATYPE(CustomQObject*)
Q_DECLARE_METATYPE(CustomQWidget*)
class CustomNonQObject { };
Q_DECLARE_METATYPE(CustomNonQObject)
Q_DECLARE_METATYPE(CustomNonQObject*)
void tst_QVariant::cleanupTestCase()
{
delete customNonQObjectPointer;
qDeleteAll(objectPointerTestData);
}
void tst_QVariant::qvariant_cast_QObject_data()
{
QTest::addColumn<QVariant>("data");
QTest::addColumn<bool>("success");
QObject *obj = new QObject(this);
QObject *obj = new QObject;
obj->setObjectName(QString::fromLatin1("Hello"));
QTest::newRow("from QObject") << QVariant(QMetaType::QObjectStar, &obj) << true;
QTest::newRow("from QObject2") << QVariant::fromValue(obj) << true;
QTest::newRow("from String") << QVariant(QLatin1String("1, 2, 3")) << false;
QTest::newRow("from int") << QVariant((int) 123) << false;
QWidget *widget = new QWidget;
widget->setObjectName(QString::fromLatin1("Hello"));
QTest::newRow("from QWidget") << QVariant::fromValue(widget) << true;
CustomQObject *customObject = new CustomQObject(this);
customObject->setObjectName(QString::fromLatin1("Hello"));
QTest::newRow("from Derived QObject") << QVariant::fromValue(customObject) << true;
CustomQWidget *customWidget = new CustomQWidget;
customWidget->setObjectName(QString::fromLatin1("Hello"));
QTest::newRow("from Derived QWidget") << QVariant::fromValue(customWidget) << true;
QTest::newRow("from custom Object") << QVariant::fromValue(CustomNonQObject()) << false;
// Deleted in cleanupTestCase.
customNonQObjectPointer = new CustomNonQObject;
QTest::newRow("from custom ObjectStar") << QVariant::fromValue(customNonQObjectPointer) << false;
// Deleted in cleanupTestCase.
objectPointerTestData.push_back(obj);
objectPointerTestData.push_back(widget);
objectPointerTestData.push_back(customObject);
objectPointerTestData.push_back(customWidget);
}
void tst_QVariant::qvariant_cast_QObject() {
void tst_QVariant::qvariant_cast_QObject()
{
QFETCH(QVariant, data);
QFETCH(bool, success);
@ -2476,6 +2534,38 @@ void tst_QVariant::qvariant_cast_QObject() {
}
}
class CustomQObjectDerived : public CustomQObject {
Q_OBJECT
public:
CustomQObjectDerived(QObject *parent = 0) : CustomQObject(parent) {}
};
Q_DECLARE_METATYPE(CustomQObjectDerived*)
void tst_QVariant::qvariant_cast_QObject_derived()
{
{
CustomQObjectDerived *object = new CustomQObjectDerived(this);
QVariant data = QVariant::fromValue(object);
QVERIFY(data.userType() == qMetaTypeId<CustomQObjectDerived*>());
QCOMPARE(data.value<QObject *>(), object);
QCOMPARE(data.value<CustomQObjectDerived *>(), object);
QCOMPARE(data.value<CustomQObject *>(), object);
QVERIFY(data.value<CustomQWidget*>() == 0);
}
{
CustomQWidget customWidget;
QWidget *widget = &customWidget;
QVariant data = QVariant::fromValue(widget);
QVERIFY(data.userType() == QMetaType::QWidgetStar);
QCOMPARE(data.value<QObject*>(), widget);
QCOMPARE(data.value<QWidget*>(), widget);
QCOMPARE(data.value<CustomQWidget*>(), widget);
}
}
Q_DECLARE_METATYPE(qint8);
void tst_QVariant::convertToQUint8() const