QObjectCompatProperty: Add support for custom getters

Add additional template argument to QObjectCompatProperty to specify
a custom getter. This may be useful for classes like
QAbstractProxyModelPrivate the need to customize property getters.

Task-number: QTBUG-89655
Change-Id: I34fe4bdebbbf1446aff60bd20a946454607f52d5
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

3 files changed, 31 insertions, 11 deletions

diff --git a/src/corelib/kernel/qproperty.h b/src/corelib/kernel/qproperty.h
index 4358182c25..f653d78fb6 100644
--- a/src/corelib/kernel/qproperty.h
+++ b/src/corelib/kernel/qproperty.h
@@ -956,7 +956,7 @@ class Q_CORE_EXPORT QBindingStorage
     mutable QBindingStorageData *d = nullptr;
     QBindingStatus *bindingStatus = nullptr;
 
-    template<typename Class, typename T, auto Offset, auto Setter, auto Signal>
+    template<typename Class, typename T, auto Offset, auto Setter, auto Signal, auto Getter>
     friend class QObjectCompatProperty;
     friend class QObjectPrivate;
     friend class QtPrivate::QPropertyBindingData;
diff --git a/src/corelib/kernel/qproperty_p.h b/src/corelib/kernel/qproperty_p.h
index 0e01026d54..cc080ff82b 100644
--- a/src/corelib/kernel/qproperty_p.h
+++ b/src/corelib/kernel/qproperty_p.h
@@ -447,13 +447,14 @@ namespace QtPrivate {
     void Q_CORE_EXPORT initBindingStatusThreadId();
 }
 
-template<typename Class, typename T, auto Offset, auto Setter, auto Signal=nullptr>
+template<typename Class, typename T, auto Offset, auto Setter, auto Signal = nullptr,
+         auto Getter = nullptr>
 class QObjectCompatProperty : public QPropertyData<T>
 {
     template<typename Property, typename>
     friend class QtPrivate::QBindableInterfaceForProperty;
 
-    using ThisType = QObjectCompatProperty<Class, T, Offset, Setter, Signal>;
+    using ThisType = QObjectCompatProperty<Class, T, Offset, Setter, Signal, Getter>;
     using SignalTakesValue = std::is_invocable<decltype(Signal), Class, T>;
     Class *owner()
     {
@@ -486,6 +487,14 @@ class QObjectCompatProperty : public QPropertyData<T>
             && QtPrivate::isPropertyInBindingWrapper(this);
     }
 
+    inline static T getPropertyValue(const QUntypedPropertyData *d) {
+        auto prop = static_cast<const ThisType *>(d);
+        if constexpr (std::is_null_pointer_v<decltype(Getter)>)
+            return prop->value();
+        else
+            return (prop->owner()->*Getter)();
+    }
+
 public:
     using value_type = typename QPropertyData<T>::value_type;
     using parameter_type = typename QPropertyData<T>::parameter_type;
@@ -596,7 +605,7 @@ public:
         }
         if constexpr (!std::is_null_pointer_v<decltype(Signal)>) {
             if constexpr (SignalTakesValue::value)
-                (owner()->*Signal)(value());
+                (owner()->*Signal)(getPropertyValue(this));
             else
                 (owner()->*Signal)();
         }
@@ -650,15 +659,16 @@ private:
 };
 
 namespace QtPrivate {
-template<typename Class, typename Ty, auto Offset, auto Setter, auto Signal>
-class QBindableInterfaceForProperty<QObjectCompatProperty<Class, Ty, Offset, Setter, Signal>, std::void_t<Class>>
+template<typename Class, typename Ty, auto Offset, auto Setter, auto Signal, auto Getter>
+class QBindableInterfaceForProperty<
+        QObjectCompatProperty<Class, Ty, Offset, Setter, Signal, Getter>, std::void_t<Class>>
 {
-    using Property = QObjectCompatProperty<Class, Ty, Offset, Setter, Signal>;
+    using Property = QObjectCompatProperty<Class, Ty, Offset, Setter, Signal, Getter>;
     using T = typename Property::value_type;
 public:
     static constexpr QBindableInterface iface = {
         [](const QUntypedPropertyData *d, void *value) -> void
-        { *static_cast<T*>(value) = static_cast<const Property *>(d)->value(); },
+        { *static_cast<T*>(value) = Property::getPropertyValue(d); },
         [](QUntypedPropertyData *d, const void *value) -> void
         {
             (static_cast<Property *>(d)->owner()->*Setter)(*static_cast<const T*>(value));
@@ -668,7 +678,7 @@ public:
         [](QUntypedPropertyData *d, const QUntypedPropertyBinding &binding) -> QUntypedPropertyBinding
         { return static_cast<Property *>(d)->setBinding(static_cast<const QPropertyBinding<T> &>(binding)); },
         [](const QUntypedPropertyData *d, const QPropertyBindingSourceLocation &location) -> QUntypedPropertyBinding
-        { return Qt::makePropertyBinding([d]() -> T { return static_cast<const Property *>(d)->value(); }, location); },
+        { return Qt::makePropertyBinding([d]() -> T { return Property::getPropertyValue(d); }, location); },
         [](const QUntypedPropertyData *d, QPropertyObserver *observer) -> void
         { observer->setSource(static_cast<const Property *>(d)->bindingData()); },
         []() { return QMetaType::fromType<T>(); }
@@ -717,6 +727,16 @@ public:
             QObjectCompatProperty<Class, Type, Class::_qt_property_##name##_offset, setter,        \
                                   signal>(value);
 
+#define QT_OBJECT_COMPAT_PROPERTY_WITH_ARGS_7(Class, Type, name, setter, signal, getter, value) \
+    static constexpr size_t _qt_property_##name##_offset() { \
+        QT_WARNING_PUSH QT_WARNING_DISABLE_INVALID_OFFSETOF \
+        return offsetof(Class, name); \
+        QT_WARNING_POP \
+    } \
+    QObjectCompatProperty<Class, Type, Class::_qt_property_##name##_offset, setter, signal, getter>\
+        name = QObjectCompatProperty<Class, Type, Class::_qt_property_##name##_offset, setter,     \
+                                     signal, getter>(value);
+
 #define Q_OBJECT_COMPAT_PROPERTY_WITH_ARGS(...) \
     QT_WARNING_PUSH QT_WARNING_DISABLE_INVALID_OFFSETOF \
     QT_OVERLOADED_MACRO(QT_OBJECT_COMPAT_PROPERTY_WITH_ARGS, __VA_ARGS__) \
diff --git a/src/corelib/kernel/qpropertyprivate.h b/src/corelib/kernel/qpropertyprivate.h
index d3f384748a..fec69f3a72 100644
--- a/src/corelib/kernel/qpropertyprivate.h
+++ b/src/corelib/kernel/qpropertyprivate.h
@@ -61,7 +61,7 @@ QT_BEGIN_NAMESPACE
 
 class QBindingStorage;
 
-template<typename Class, typename T, auto Offset, auto Setter, auto Signal>
+template<typename Class, typename T, auto Offset, auto Setter, auto Signal, auto Getter>
 class QObjectCompatProperty;
 
 namespace QtPrivate {
@@ -263,7 +263,7 @@ class Q_CORE_EXPORT QPropertyBindingData
     friend class QT_PREPEND_NAMESPACE(QQmlPropertyBinding);
     friend struct QT_PREPEND_NAMESPACE(QPropertyDelayedNotifications);
 
-    template<typename Class, typename T, auto Offset, auto Setter, auto Signal>
+    template<typename Class, typename T, auto Offset, auto Setter, auto Signal, auto Getter>
     friend class QT_PREPEND_NAMESPACE(QObjectCompatProperty);
 
     Q_DISABLE_COPY(QPropertyBindingData)