From b20c7df63aec36cb3cb871e4b898b0e684dcb59a Mon Sep 17 00:00:00 2001
From: Simon Hausmann <simon.hausmann@qt.io>
Date: Thu, 30 Apr 2020 08:34:42 +0200
Subject: [PATCH] Remove QPropertyMemberChangeHandler again

Adding support for a static notifier within QProperty itself - through a
QProperty "sister" class - is more efficient in terms of memory
consumption and run-time performance.

The MemberChangeHandler permanently takes up at least three pointers,
while the notified properties only cost one pointer in the binding.

Change-Id: Ia1a8c2b66f1f3c2fe13ae0ad9f12cdb6bdcc35ef
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>
---
 src/corelib/kernel/qproperty.h                | 23 -------------------
 .../kernel/qproperty/tst_qproperty.cpp        | 20 ----------------
 2 files changed, 43 deletions(-)

diff --git a/src/corelib/kernel/qproperty.h b/src/corelib/kernel/qproperty.h
index 5ba4d2eda7c..de08a71349e 100644
--- a/src/corelib/kernel/qproperty.h
+++ b/src/corelib/kernel/qproperty.h
@@ -731,28 +731,6 @@ QPropertyChangeHandler<Functor> QNotifiedProperty<T, Callback, ValueGuard>::subs
     return onValueChanged(f);
 }
 
-template <auto propertyMember, auto callbackMember>
-struct QPropertyMemberChangeHandler;
-
-template<typename Class, typename PropertyType, PropertyType Class::* PropertyMember, void(Class::*Callback)()>
-struct QPropertyMemberChangeHandler<PropertyMember, Callback> : public QPropertyObserver
-{
-    QPropertyMemberChangeHandler(Class *obj)
-        : QPropertyObserver(notify)
-    {
-        setSource(obj->*PropertyMember);
-    }
-
-    static void notify(QPropertyObserver *, void *propertyDataPtr)
-    {
-        // memberOffset is the offset of the QProperty<> member within the class. We get the absolute address
-        // of that member and subtracting the relative offset gives us the address of the class instance.
-        const size_t memberOffset = reinterpret_cast<size_t>(&(static_cast<Class *>(nullptr)->*PropertyMember));
-        Class *obj = reinterpret_cast<Class *>(reinterpret_cast<char *>(propertyDataPtr) - memberOffset);
-        (obj->*Callback)();
-    }
-};
-
 template<typename T>
 class QPropertyAlias : public QPropertyObserver
 {
@@ -892,7 +870,6 @@ public:
         return aliasedProperty<T>() != nullptr;
     }
 };
-
 QT_END_NAMESPACE
 
 #endif // QPROPERTY_H
diff --git a/tests/auto/corelib/kernel/qproperty/tst_qproperty.cpp b/tests/auto/corelib/kernel/qproperty/tst_qproperty.cpp
index 53d361ca267..cafc1932574 100644
--- a/tests/auto/corelib/kernel/qproperty/tst_qproperty.cpp
+++ b/tests/auto/corelib/kernel/qproperty/tst_qproperty.cpp
@@ -67,7 +67,6 @@ private slots:
     void settingPropertyValueDoesRemoveBinding();
     void genericPropertyBinding();
     void genericPropertyBindingBool();
-    void staticChangeHandler();
     void setBindingFunctor();
     void multipleObservers();
     void propertyAlias();
@@ -661,25 +660,6 @@ void tst_QProperty::genericPropertyBindingBool()
     QVERIFY(property.value());
 }
 
-struct ItemType
-{
-    QProperty<int> x;
-    QVector<int> observedValues;
-    void xChanged() {
-        observedValues << x.value();
-    }
-    QPropertyMemberChangeHandler<&ItemType::x, &ItemType::xChanged> test{this};
-};
-
-void tst_QProperty::staticChangeHandler()
-{
-    ItemType t;
-    t.x = 42;
-    t.x = 100;
-    QVector<int> values{42, 100};
-    QCOMPARE(t.observedValues, values);
-}
-
 void tst_QProperty::setBindingFunctor()
 {
     QProperty<int> property;