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, 11 insertions, 0 deletions

diff --git a/src/corelib/kernel/qobject.h b/src/corelib/kernel/qobject.h
index d1a0c3562c..21081fa569 100644
--- a/src/corelib/kernel/qobject.h
+++ b/src/corelib/kernel/qobject.h
@@ -62,6 +62,7 @@
 QT_BEGIN_NAMESPACE
 
 
+class QBindingStorage;
 class QEvent;
 class QTimerEvent;
 class QChildEvent;
@@ -371,6 +372,8 @@ public:
     bool setProperty(const char *name, const QVariant &value);
     QVariant property(const char *name) const;
     QList<QByteArray> dynamicPropertyNames() const;
+    QBindingStorage *bindingStorage();
+    const QBindingStorage *bindingStorage() const;
 #endif // QT_NO_PROPERTIES
 
 Q_SIGNALS:
@@ -457,6 +460,14 @@ inline T qobject_cast(const QObject *object)
 template <class T> inline const char * qobject_interface_iid()
 { return nullptr; }
 
+inline const QBindingStorage *qGetBindingStorage(const QObject *o)
+{
+    return o->bindingStorage();
+}
+inline QBindingStorage *qGetBindingStorage(QObject *o)
+{
+    return o->bindingStorage();
+}
 
 #if defined(Q_CLANG_QDOC)
 #  define Q_DECLARE_INTERFACE(IFace, IId)