QNode: _q_postConstructorInit set scene on whole subtree

_q_postConstrutorInit is called in a deferred invocation when constructing a
Node with a parent. If several nodes are created that way, the
_q_postConstructorInit call from the node which parents the other will
actually build the node creation changes for the whole subtree and incidently
prevent the _q_postConstructorInit invocation for the children to do anything
(including setting the scene). Therefore _q_postConstructorInit should set the
scene on all the Node it will be creating creation changes for.

Change-Id: I07d4e80675758b9701cc941881f1faaa1c89af4b
Task-number: QTBUG-69352
Reviewed-by: Svenn-Arne Dragly <svenn-arne.dragly@qt.io>
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>

1 files changed, 8 insertions, 3 deletions

diff --git a/src/core/nodes/qnode.cpp b/src/core/nodes/qnode.cpp
index ff7a1b2ce..9c069f936 100644
--- a/src/core/nodes/qnode.cpp
+++ b/src/core/nodes/qnode.cpp
@@ -188,9 +188,14 @@ void QNodePrivate::_q_postConstructorInit()
     if (!parentNode)
         return;
 
-
-    if (m_scene)
-        m_scene->addObservable(q); // Sets the m_changeArbiter to that of the scene
+    // Set the scene on this node and all children it references so that all
+    // children have a scene set since notifyCreationChanges will set
+    // m_hasBackendNode to true for all children, which would prevent them from
+    // ever having their scene set
+    if (m_scene) {
+        QNodeVisitor visitor;
+        visitor.traverse(q, parentNode->d_func(), &QNodePrivate::setSceneHelper);
+    }
 
     // Let the backend know we have been added to the scene
     notifyCreationChange();