Add a QBindingStorage class

QBindingStorage is a class that can store a set of binding objects
for the properties of a QObject. This will get used to reduce the
memory overhead of the property system when adding bindable properties
to QObject based classes.

The binding storage has a pointer to the TLS entry containing the
currently evaluating binding. Like that we avoid repeated TLS
lookups and reduce the overhead of the property system to one
pointer lookup and one compare for the case that properties
aren't being used.

Each QObject now owns one binding storage object, that can be used to
store binding data for properties that members of the QObject.

Change-Id: I27427c03c2ba281f072e074be96147bdbcaac246
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 21 insertions, 0 deletions

diff --git a/src/corelib/kernel/qproperty.h b/src/corelib/kernel/qproperty.h
index 85bdfdcd56..bb89dbf94f 100644
--- a/src/corelib/kernel/qproperty.h
+++ b/src/corelib/kernel/qproperty.h
@@ -721,6 +721,27 @@ public:
     }
 };
 
+struct QBindingStatus;
+
+struct QBindingStorageData;
+class Q_CORE_EXPORT QBindingStorage
+{
+    mutable QBindingStorageData *d = nullptr;
+    QBindingStatus *bindingStatus = nullptr;
+
+    template<typename Class, typename T, auto Offset, auto Setter>
+    friend class QObjectCompatProperty;
+public:
+    QBindingStorage();
+    ~QBindingStorage();
+
+    bool isEmpty() { return !d; }
+
+    void maybeUpdateBindingAndRegister(const QUntypedPropertyData *data) const;
+    QtPrivate::QPropertyBindingData *bindingData(const QUntypedPropertyData *data) const;
+    QtPrivate::QPropertyBindingData *bindingData(QUntypedPropertyData *data, bool create);
+};
+
 QT_END_NAMESPACE
 
 #endif // QPROPERTY_H