QParameter: add bookkeeping of QNode values

Change-Id: I0a7334907e4b34df6955fb24832958b674d7b62b
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>

3 files changed, 48 insertions, 4 deletions

diff --git a/src/core/nodes/qnode_p.h b/src/core/nodes/qnode_p.h
index c203b342f..73893cc1e 100644
--- a/src/core/nodes/qnode_p.h
+++ b/src/core/nodes/qnode_p.h
@@ -108,13 +108,13 @@ public:
     static void nodePtrDeleter(QNode *q);
 
     template<typename Caller, typename NodeType>
-    using DestructionFunction = void (Caller::*)(NodeType *);
+    using DestructionFunctionPointer = void (Caller::*)(NodeType *);
 
     template<typename Caller, typename NodeType, typename PropertyType>
-    void registerDestructionHelper(NodeType *, DestructionFunction<Caller, NodeType>, PropertyType);
+    void registerDestructionHelper(NodeType *, DestructionFunctionPointer<Caller, NodeType>, PropertyType);
 
     template<typename Caller, typename NodeType>
-    void registerDestructionHelper(NodeType *node, DestructionFunction<Caller, NodeType> func, NodeType *&)
+    void registerDestructionHelper(NodeType *node, DestructionFunctionPointer<Caller, NodeType> func, NodeType *&)
     {
         // If the node is destoyed, we make sure not to keep a dangling pointer to it
         Q_Q(QNode);
@@ -123,7 +123,7 @@ public:
     }
 
     template<typename Caller, typename NodeType>
-    void registerDestructionHelper(NodeType *node, DestructionFunction<Caller, NodeType> func, QVector<NodeType*> &)
+    void registerDestructionHelper(NodeType *node, DestructionFunctionPointer<Caller, NodeType> func, QVector<NodeType*> &)
     {
         // If the node is destoyed, we make sure not to keep a dangling pointer to it
         Q_Q(QNode);
@@ -131,6 +131,19 @@ public:
         m_destructionConnections.insert(node, QObject::connect(node, &QNode::nodeDestroyed, f));
     }
 
+    template<typename Caller, typename ValueType>
+    using DestructionFunctionValue = void (Caller::*)(const ValueType&);
+
+    template<typename Caller, typename NodeType, typename ValueType>
+    void registerDestructionHelper(NodeType *node, DestructionFunctionValue<Caller, ValueType> func, NodeType *&,
+                                   const ValueType &resetValue)
+    {
+        // If the node is destoyed, we make sure not to keep a dangling pointer to it
+        Q_Q(QNode);
+        auto f = [q, func, resetValue]() { (static_cast<Caller *>(q)->*func)(resetValue); };
+        m_destructionConnections.insert(node, QObject::connect(node, &QNode::nodeDestroyed, f));
+    }
+
     void unregisterDestructionHelper(QNode *node)
     {
         QObject::disconnect(m_destructionConnections.take(node));
diff --git a/src/render/materialsystem/qparameter.cpp b/src/render/materialsystem/qparameter.cpp
index 2b2dd29d5..afaf42158 100644
--- a/src/render/materialsystem/qparameter.cpp
+++ b/src/render/materialsystem/qparameter.cpp
@@ -288,12 +288,21 @@ void QParameter::setValue(const QVariant &dv)
     Q_D(QParameter);
     if (d->m_value != dv) {
 
+        QNode *oldNodeValue = d->m_value.value<QNode *>();
+        if (oldNodeValue != nullptr)
+            d->unregisterDestructionHelper(oldNodeValue);
+
         // In case node values are declared inline
         QNode *nodeValue = dv.value<QNode *>();
         if (nodeValue != nullptr && !nodeValue->parent())
             nodeValue->setParent(this);
 
         d->setValue(dv);
+
+        // Ensures proper bookkeeping
+        if (nodeValue != nullptr)
+            d->registerDestructionHelper(nodeValue, &QParameter::setValue, nodeValue, QVariant());
+
         emit valueChanged(dv);
     }
 }
diff --git a/tests/auto/render/qparameter/tst_qparameter.cpp b/tests/auto/render/qparameter/tst_qparameter.cpp
index f124af809..d5957db27 100644
--- a/tests/auto/render/qparameter/tst_qparameter.cpp
+++ b/tests/auto/render/qparameter/tst_qparameter.cpp
@@ -249,6 +249,28 @@ private Q_SLOTS:
 
     }
 
+    void checkBookeeping()
+    {
+        // GIVEN
+        Qt3DRender::QParameter parameter;
+        QSignalSpy spy(&parameter, SIGNAL(valueChanged(QVariant)));
+
+        {
+            // WHEN
+            QScopedPointer<Qt3DCore::QNode> node(new Qt3DCore::QNode());
+            parameter.setValue(QVariant::fromValue(node.data()));
+
+            // THEN
+            QCOMPARE(spy.count(), 1);
+            QCOMPARE(parameter.value(), QVariant::fromValue(node.data()));
+            spy.clear();
+        }
+
+        // THEN
+        QCOMPARE(spy.count(), 1);
+        QCOMPARE(parameter.value(), QVariant());
+    }
+
 };
 
 QTEST_MAIN(tst_QParameter)