Make QPropertyBindingPrivate accessible to QtQml

QtQml needs the private just for one detail which nobody else should
need it for: Tracking additional dependencies and marking the binding as
dirty. Exporting the private requires hiding some variables and
providing accessors, to compile with MSVC - including the removal of
QVarLengthArray usage. Upside: The binding structure shrinks by 8 bytes
and the encapsulation makes it a little easier to change things without
breaking declarative, ... in the unlikely event ;-)

Also remove setDirty() from the public API as it's not needed by QtQml
and using it is dangerous, because it means that there's a risk of
somebody keeping a reference (count) to the untyped binding from within
the binding closure, which introduces a memory leak.

Change-Id: I43bd56f4bdf218efb54fa23e2d627ad3acfafeb5
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 9 insertions, 15 deletions

diff --git a/src/corelib/kernel/qproperty.cpp b/src/corelib/kernel/qproperty.cpp
index 2dbe8b6310..18580fa756 100644
--- a/src/corelib/kernel/qproperty.cpp
+++ b/src/corelib/kernel/qproperty.cpp
@@ -53,7 +53,7 @@ QPropertyBase::QPropertyBase(QPropertyBase &&other, void *propertyDataPtr)
     QPropertyBasePointer d{this};
     d.setFirstObserver(nullptr);
     if (auto binding = d.bindingPtr())
-        binding->propertyDataPtr = propertyDataPtr;
+        binding->setProperty(propertyDataPtr);
 }
 
 void QPropertyBase::moveAssign(QPropertyBase &&other, void *propertyDataPtr)
@@ -73,7 +73,7 @@ void QPropertyBase::moveAssign(QPropertyBase &&other, void *propertyDataPtr)
     std::swap(d_ptr, other.d_ptr);
 
     if (auto binding = d.bindingPtr())
-        binding->propertyDataPtr = propertyDataPtr;
+        binding->setProperty(propertyDataPtr);
 
     d.setFirstObserver(observer.ptr);
 
@@ -111,10 +111,10 @@ QUntypedPropertyBinding QPropertyBase::setBinding(const QUntypedPropertyBinding
         newBinding.data()->ref.ref();
         d_ptr = (d_ptr & FlagMask) | reinterpret_cast<quintptr>(newBinding.data());
         d_ptr |= BindingBit;
-        newBinding->dirty = true;
-        newBinding->propertyDataPtr = propertyDataPtr;
+        newBinding->setDirty(true);
+        newBinding->setProperty(propertyDataPtr);
         if (observer)
-            observer.prependToBinding(newBinding.data());
+            newBinding->prependObserver(observer);
     } else {
         d_ptr &= ~BindingBit;
     }
@@ -175,11 +175,10 @@ static thread_local BindingEvaluationState *currentBindingEvaluationState = null
 
 BindingEvaluationState::BindingEvaluationState(QPropertyBindingPrivate *binding)
     : binding(binding)
-    , dependencyObservers(&binding->dependencyObservers)
 {
     previousState = currentBindingEvaluationState;
     currentBindingEvaluationState = this;
-    dependencyObservers->clear();
+    binding->clearDependencyObservers();
 }
 
 BindingEvaluationState::~BindingEvaluationState()
@@ -222,8 +221,7 @@ void QPropertyBase::registerWithCurrentlyEvaluatingBinding() const
 
     QPropertyBasePointer d{this};
 
-    currentState->dependencyObservers->append(QPropertyObserver());
-    QPropertyObserverPointer dependencyObserver{&(*currentState->dependencyObservers)[currentState->dependencyObservers->size() - 1]};
+    QPropertyObserverPointer dependencyObserver = currentState->binding->allocateDependencyObserver();
     dependencyObserver.setBindingToMarkDirty(currentState->binding);
     dependencyObserver.observeProperty(d);
 }
@@ -263,6 +261,8 @@ QPropertyObserver::~QPropertyObserver()
     d.unlink();
 }
 
+QPropertyObserver::QPropertyObserver() = default;
+
 QPropertyObserver::QPropertyObserver(QPropertyObserver &&other)
 {
     std::swap(bindingToMarkDirty, other.bindingToMarkDirty);
@@ -351,12 +351,6 @@ void QPropertyObserverPointer::observeProperty(QPropertyBasePointer property)
     property.addObserver(ptr);
 }
 
-void QPropertyObserverPointer::prependToBinding(QPropertyBindingPrivate *binding)
-{
-    ptr->prev = const_cast<QPropertyObserver **>(&binding->firstObserver.ptr);
-    binding->firstObserver = *this;
-}
-
 QPropertyBindingError::QPropertyBindingError(Type type)
 {
     if (type != NoError) {