Pass a pointer to the property data into the method evaluating a binding

Make it possible to evaluate the binding but write the result into
a different memory location. This will help support compat properties,
where the setter does a lot of additional work.

Change-Id: Ib60220eb629e3dcb5c0d7004b693e92290dfabe5
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

src/corelib/kernel/qproperty.cpp

@@ -88,7 +88,7 @@ void QPropertyBindingPrivate::markDirtyAndNotifyObservers()
         staticObserverCallback(propertyDataPtr);
 }
 
-bool QPropertyBindingPrivate::evaluateIfDirtyAndReturnTrueIfValueChanged()
+bool QPropertyBindingPrivate::evaluateIfDirtyAndReturnTrueIfValueChanged(const QUntypedPropertyData *data)
 {
     if (!dirty)
         return false;
@@ -113,10 +113,13 @@ bool QPropertyBindingPrivate::evaluateIfDirtyAndReturnTrueIfValueChanged()
 
     bool changed = false;
 
+    Q_ASSERT(propertyDataPtr == data);
+    QUntypedPropertyData *mutable_data = const_cast<QUntypedPropertyData *>(data);
+
     if (hasBindingWrapper) {
         changed = staticBindingWrapper(metaType, propertyDataPtr, evaluationFunction);
     } else {
-        changed = evaluationFunction(metaType, propertyDataPtr);
+        changed = evaluationFunction(metaType, mutable_data);
     }
 
     dirty = false;
@@ -300,13 +303,13 @@ QPropertyBindingPrivate *QPropertyBindingPrivate::currentlyEvaluatingBinding()
     return currentBindingEvaluationState ? currentBindingEvaluationState->binding : nullptr;
 }
 
-void QPropertyBindingData::evaluateIfDirty() const
+void QPropertyBindingData::evaluateIfDirty(const QUntypedPropertyData *property) const
 {
     QPropertyBindingDataPointer d{this};
     QPropertyBindingPrivate *binding = d.bindingPtr();
     if (!binding)
         return;
-    binding->evaluateIfDirtyAndReturnTrueIfValueChanged();
+    binding->evaluateIfDirtyAndReturnTrueIfValueChanged(property);
 }
 
 void QPropertyBindingData::removeBinding()
@@ -452,7 +455,7 @@ void QPropertyObserverPointer::notify(QPropertyBindingPrivate *triggeringBinding
             if (!knownIfPropertyChanged && triggeringBinding) {
                 knownIfPropertyChanged = true;
 
-                propertyChanged = triggeringBinding->evaluateIfDirtyAndReturnTrueIfValueChanged();
+                propertyChanged = triggeringBinding->evaluateIfDirtyAndReturnTrueIfValueChanged(propertyDataPtr);
             }
             if (!propertyChanged)
                 return;
@@ -1446,6 +1449,7 @@ struct QBindingStoragePrivate
 QBindingStorage::QBindingStorage()
 {
     currentlyEvaluatingBinding = &currentBindingEvaluationState;
+    Q_ASSERT(currentlyEvaluatingBinding);
 }
 
 QBindingStorage::~QBindingStorage()
@@ -1455,6 +1459,7 @@ QBindingStorage::~QBindingStorage()
 
 void QBindingStorage::maybeUpdateBindingAndRegister(const QUntypedPropertyData *data) const
 {
+    Q_ASSERT(currentlyEvaluatingBinding);
     QUntypedPropertyData *dd = const_cast<QUntypedPropertyData *>(data);
     auto storage = *currentlyEvaluatingBinding ?
                 QBindingStoragePrivate(d).getAndCreate(dd) :
@@ -1462,7 +1467,7 @@ void QBindingStorage::maybeUpdateBindingAndRegister(const QUntypedPropertyData *
     if (!storage)
         return;
     if (auto *binding = storage->binding())
-        binding->evaluateIfDirtyAndReturnTrueIfValueChanged();
+        binding->evaluateIfDirtyAndReturnTrueIfValueChanged(const_cast<QUntypedPropertyData *>(data));
     storage->registerWithCurrentlyEvaluatingBinding();
 }
 

src/corelib/kernel/qproperty.h

@@ -67,7 +67,7 @@ template <typename T>
 class QPropertyData : public QUntypedPropertyData
 {
 protected:
-    T val = T();
+    mutable T val = T();
 private:
     class DisableRValueRefs {};
 protected:
@@ -341,7 +341,7 @@ public:
     parameter_type value() const
     {
         if (d.hasBinding())
-            d.evaluateIfDirty();
+            d.evaluateIfDirty(this);
         d.registerWithCurrentlyEvaluatingBinding();
         return this->val;
     }

src/corelib/kernel/qproperty_p.h

@@ -230,7 +230,7 @@ public:
     void unlinkAndDeref();
 
     void markDirtyAndNotifyObservers();
-    bool evaluateIfDirtyAndReturnTrueIfValueChanged();
+    bool evaluateIfDirtyAndReturnTrueIfValueChanged(const QUntypedPropertyData *data);
 
     static QPropertyBindingPrivate *get(const QUntypedPropertyBinding &binding)
     { return binding.d.data(); }

src/corelib/kernel/qpropertyprivate.h

@@ -87,10 +87,9 @@ class Q_CORE_EXPORT QPropertyBindingData
     // notification later when the value changes.
     mutable quintptr d_ptr = 0;
     friend struct QT_PREPEND_NAMESPACE(QPropertyBindingDataPointer);
+    Q_DISABLE_COPY(QPropertyBindingData)
 public:
     QPropertyBindingData() = default;
-    Q_DISABLE_COPY(QPropertyBindingData)
-    QPropertyBindingData(QPropertyBindingData &&other) = delete;
     QPropertyBindingData(QPropertyBindingData &&other, QUntypedPropertyData *propertyDataPtr);
     QPropertyBindingData &operator=(QPropertyBindingData &&other) = delete;
     ~QPropertyBindingData();
@@ -105,7 +104,7 @@ public:
                                        QPropertyBindingWrapper guardCallback = nullptr);
     QPropertyBindingPrivate *binding() const;
 
-    void evaluateIfDirty() const;
+    void evaluateIfDirty(const QUntypedPropertyData *property) const;
     void removeBinding();
 
     void registerWithCurrentlyEvaluatingBinding() const;