Shared node bookkeeping

Any time a property references a QNode there is a risk that the node gets
destroyed and then the property is left pointing to a dangling pointer.

To handle such cases, setters of such properties are able to use a helper
that internally connect QObject::destroyed signal to a setter removal method.

Change-Id: I42428c851d0e3d2d88ab0cf6a5b75605334ec648
Task-number: QTBUG-53456
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/src/render/frontend/qrendersettings.cpp b/src/render/frontend/qrendersettings.cpp
index a6e4a99eb..b0a409275 100644
--- a/src/render/frontend/qrendersettings.cpp
+++ b/src/render/frontend/qrendersettings.cpp
@@ -110,9 +110,18 @@ void QRenderSettings::setActiveFrameGraph(QFrameGraphNode *activeFrameGraph)
     if (d->m_activeFrameGraph == activeFrameGraph)
         return;
 
+    if (d->m_activeFrameGraph)
+        d->unregisterDestructionHelper(d->m_activeFrameGraph);
+
     if (activeFrameGraph != nullptr && !activeFrameGraph->parent())
         activeFrameGraph->setParent(this);
+
     d->m_activeFrameGraph = activeFrameGraph;
+
+    // Ensures proper bookkeeping
+    if (d->m_activeFrameGraph)
+        d->registerDestructionHelper(d->m_activeFrameGraph, &QRenderSettings::setActiveFrameGraph, d->m_activeFrameGraph);
+
     emit activeFrameGraphChanged(activeFrameGraph);
 }