ChangeArbiter/SceneChange: use id as change subject

Instead of having a QNode* or QObservable as the subject of a change, we use
it's unique NodeId instead. That will prevent the ChangeArbiter from trying to
distribute changes by looking at a QNode/QObservable id when the
QNode/QObservable might have been destroyed in the meantime.

Change-Id: Ia419d5b841434fd65522c8c65de552089cfe97cf
Task-number: QTBUG-44628
Reviewed-by: Laszlo Agocs <laszlo.agocs@theqtcompany.com>
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>

1 files changed, 4 insertions, 5 deletions

diff --git a/src/core/qchangearbiter.cpp b/src/core/qchangearbiter.cpp
index 86ddc7d72..1d111d642 100644
--- a/src/core/qchangearbiter.cpp
+++ b/src/core/qchangearbiter.cpp
@@ -124,8 +124,7 @@ void QChangeArbiter::distributeQueueChanges(QChangeQueue *changeQueue)
         switch (change->observableType()) {
 
         case QSceneChange::Observable: {
-            QObservableInterface *subject = change->subject().m_observable;
-            QNodeId nodeId = m_scene->nodeIdFromObservable(subject);
+            const QNodeId nodeId = change->subjectId();
             if (m_nodeObservations.contains(nodeId)) {
                 QObserverList &observers = m_nodeObservations[nodeId];
                 Q_FOREACH (const QObserverPair&observer, observers) {
@@ -139,9 +138,9 @@ void QChangeArbiter::distributeQueueChanges(QChangeQueue *changeQueue)
         }
 
         case QSceneChange::Node: {
-            QNode *subject = change->subject().m_node;
-            if (m_nodeObservations.contains(subject->id())) {
-                QObserverList &observers = m_nodeObservations[subject->id()];
+            const QNodeId nodeId = change->subjectId();
+            if (m_nodeObservations.contains(nodeId)) {
+                QObserverList &observers = m_nodeObservations[nodeId];
                 Q_FOREACH (const QObserverPair&observer, observers) {
                     if ((change->type() & observer.first))
                         observer.second->sceneChangeEvent(change);