Fix Entity parenting hierarchy

When the initial Entity backend node hierarchy is created it skips over
any non-entity nodes to ensure that Entities are only parented to
other Entities. Calling QNode::setParent breaks this when reparenting
Entities to non-entity nodes.

Fix by sending a new "parentEntityUpdated" property update that backend
Entity nodes listen for. They keep the id of their new parent and flag
the need to rebuild the entity hierarchy.  This triggers a new job to
clear the children and parents of every backend Entity, then rebuilds
the hierarchy using the stored parent ID in each Entity. This is much
more forgiving of creation/parenting ordering issues and shouldn't be
less performant because any Entity reparent was previously marking
everything dirty anyway.

Add a new test from QTBUG-73905 that creates 4 cylinders and manipulates
the parents in different ways.

Add a new test to tst_nodes to reparent a QEntity to a QNode and ensure
the entity finds it's correct QEntity parent.

Add a new test to tst_entity to ensure backend nodes correctly handle
the new parenting events.

Task-number: QTBUG-73905
Change-Id: Iab0203947d89bbed2868b3629fbde879675fe568
Reviewed-by: Paul Lemire <paul.lemire@kdab.com>

1 files changed, 67 insertions, 0 deletions

diff --git a/tests/auto/core/nodes/tst_nodes.cpp b/tests/auto/core/nodes/tst_nodes.cpp
index 3f7fb4a75..193d88c83 100644
--- a/tests/auto/core/nodes/tst_nodes.cpp
+++ b/tests/auto/core/nodes/tst_nodes.cpp
@@ -81,6 +81,7 @@ private slots:
     void removingChildEntitiesFromNode();
 
     void checkConstructionSetParentMix(); // QTBUG-60612
+    void checkParentingQEntityToQNode(); // QTBUG-73905
     void checkConstructionWithParent();
     void checkConstructionWithNonRootParent(); // QTBUG-73986
     void checkConstructionAsListElement();
@@ -1079,6 +1080,72 @@ void tst_Nodes::checkConstructionSetParentMix()
     QCOMPARE(lastEvent->addedNodeId(), subTreeRoot->id());
 }
 
+void tst_Nodes::checkParentingQEntityToQNode()
+{
+    // GIVEN
+    ObserverSpy spy;
+    Qt3DCore::QScene scene;
+    QScopedPointer<MyQNode> root(new MyQNode());
+
+    // WHEN
+    root->setArbiterAndScene(&spy, &scene);
+    root->setSimulateBackendCreated(true);
+
+    // THEN
+    QVERIFY(Qt3DCore::QNodePrivate::get(root.data())->scene() != nullptr);
+
+    // WHEN
+    auto subTreeRoot = new Qt3DCore::QEntity(root.data());
+    auto childEntity = new Qt3DCore::QEntity(subTreeRoot);
+    auto childNode = new Qt3DCore::QNode(subTreeRoot);
+
+    // THEN
+    QCoreApplication::processEvents();
+
+    // Ensure first event is subTreeRoot creation
+    const Qt3DCore::QNodeCreatedChangeBasePtr firstEvent = spy.events.takeFirst().change().dynamicCast<Qt3DCore::QNodeCreatedChangeBase>();
+    QVERIFY(!firstEvent.isNull());
+    QCOMPARE(firstEvent->subjectId(), subTreeRoot->id());
+    QCOMPARE(firstEvent->parentId(), root->id());
+
+    // Ensure 2nd event is childEntity creation
+    const Qt3DCore::QNodeCreatedChangeBasePtr secondEvent = spy.events.takeFirst().change().dynamicCast<Qt3DCore::QNodeCreatedChangeBase>();
+    QVERIFY(!secondEvent.isNull());
+    QCOMPARE(secondEvent->subjectId(), childEntity->id());
+    QCOMPARE(secondEvent->parentId(), subTreeRoot->id());
+
+    // Ensure 3rd event is childNode creation
+    const Qt3DCore::QNodeCreatedChangeBasePtr thirdEvent = spy.events.takeFirst().change().dynamicCast<Qt3DCore::QNodeCreatedChangeBase>();
+    QVERIFY(!thirdEvent.isNull());
+    QCOMPARE(thirdEvent->subjectId(), childNode->id());
+    QCOMPARE(thirdEvent->parentId(), subTreeRoot->id());
+
+
+    // WHEN we reparent the childEntity to the childNode (QNode)
+
+    spy.events.clear();
+    childEntity->setParent(childNode);
+    // THEN we should get
+    // - one child removed change for childEntity->subTreeRoot,
+    // - one child added change for childEntity->childNode,
+    // - and one property updated event specifying the correct QEntity parent (subTreeRoot)
+    QCOMPARE(spy.events.size(), 3);
+
+    const auto removedEvent = spy.events.takeFirst().change().dynamicCast<Qt3DCore::QPropertyNodeRemovedChange>();
+    QVERIFY(!removedEvent.isNull());
+    QCOMPARE(removedEvent->subjectId(), subTreeRoot->id());
+
+    const auto addedEvent = spy.events.takeFirst().change().dynamicCast<Qt3DCore::QPropertyNodeAddedChange>();
+    QVERIFY(!addedEvent.isNull());
+    QCOMPARE(addedEvent->subjectId(), childNode->id());
+
+    const auto parentChangeEvent = spy.events.takeFirst().change().dynamicCast<Qt3DCore::QPropertyUpdatedChange>();
+    QVERIFY(!parentChangeEvent.isNull());
+    QCOMPARE(parentChangeEvent->subjectId(), childEntity->id());
+    QCOMPARE(parentChangeEvent->propertyName(), "parentEntityUpdated");
+    QCOMPARE(parentChangeEvent->value().value<Qt3DCore::QNodeId>(), subTreeRoot->id());
+}
+
 void tst_Nodes::checkConstructionWithParent()
 {
     // GIVEN