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, 16 insertions, 3 deletions

diff --git a/src/render/renderers/opengl/renderer/renderer.cpp b/src/render/renderers/opengl/renderer/renderer.cpp
index 4b70710f2..a023b82f9 100644
--- a/src/render/renderers/opengl/renderer/renderer.cpp
+++ b/src/render/renderers/opengl/renderer/renderer.cpp
@@ -198,6 +198,7 @@ Renderer::Renderer(QRenderAspect::RenderType type)
     , m_sendTextureChangesToFrontendJob(Render::GenericLambdaJobPtr<std::function<void ()>>::create([this] { sendTextureChangesToFrontend(); }, JobTypes::SendTextureChangesToFrontend))
     , m_introspectShaderJob(Render::GenericLambdaJobPtr<std::function<void ()>>::create([this] { reloadDirtyShaders(); }, JobTypes::DirtyShaderGathering))
     , m_syncTextureLoadingJob(Render::GenericLambdaJobPtr<std::function<void ()>>::create([] {}, JobTypes::SyncTextureLoading))
+    , m_updateEntityHierarchyJob(Render::UpdateEntityHierarchyJobPtr::create())
     , m_ownedContext(false)
     , m_offscreenHelper(nullptr)
     #if QT_CONFIG(qt3d_profile_jobs)
@@ -210,6 +211,9 @@ Renderer::Renderer(QRenderAspect::RenderType type)
     if (m_renderThread)
         m_renderThread->waitForStart();
 
+    m_worldTransformJob->addDependency(m_updateEntityHierarchyJob);
+    m_updateEntityLayersJob->addDependency(m_updateEntityHierarchyJob);
+
     // Create jobs to update transforms and bounding volumes
     // We can only update bounding volumes once all world transforms are known
     m_updateWorldBoundingVolumeJob->addDependency(m_worldTransformJob);
@@ -299,6 +303,7 @@ void Renderer::setNodeManagers(NodeManagers *managers)
     m_updateMeshTriangleListJob->setManagers(m_nodesManager);
     m_filterCompatibleTechniqueJob->setManager(m_nodesManager->techniqueManager());
     m_updateEntityLayersJob->setManager(m_nodesManager);
+    m_updateEntityHierarchyJob->setManager(m_nodesManager);
 }
 
 void Renderer::setServices(QServiceLocator *services)
@@ -1665,14 +1670,17 @@ QVector<Qt3DCore::QAspectJobPtr> Renderer::renderBinJobs()
 
     // Add jobs
     const bool entitiesEnabledDirty = dirtyBitsForFrame & AbstractRenderer::EntityEnabledDirty;
-    if (entitiesEnabledDirty) {
+    const bool entityHierarchyNeedsToBeRebuilt = dirtyBitsForFrame & AbstractRenderer::EntityHierarchyDirty;
+    if (entitiesEnabledDirty || entityHierarchyNeedsToBeRebuilt) {
         renderBinJobs.push_back(m_updateTreeEnabledJob);
         // This dependency is added here because we clear all dependencies
         // at the start of this function.
         m_calculateBoundingVolumeJob->addDependency(m_updateTreeEnabledJob);
+        m_calculateBoundingVolumeJob->addDependency(m_updateEntityHierarchyJob);
     }
 
-    if (dirtyBitsForFrame & AbstractRenderer::TransformDirty) {
+    if (dirtyBitsForFrame & AbstractRenderer::TransformDirty ||
+        dirtyBitsForFrame & AbstractRenderer::EntityHierarchyDirty) {
         renderBinJobs.push_back(m_worldTransformJob);
         renderBinJobs.push_back(m_updateWorldBoundingVolumeJob);
         renderBinJobs.push_back(m_updateShaderDataTransformJob);
@@ -1685,6 +1693,7 @@ QVector<Qt3DCore::QAspectJobPtr> Renderer::renderBinJobs()
     }
 
     if (dirtyBitsForFrame & AbstractRenderer::GeometryDirty ||
+        dirtyBitsForFrame & AbstractRenderer::EntityHierarchyDirty ||
         dirtyBitsForFrame & AbstractRenderer::TransformDirty) {
         renderBinJobs.push_back(m_expandBoundingVolumeJob);
     }
@@ -1722,11 +1731,15 @@ QVector<Qt3DCore::QAspectJobPtr> Renderer::renderBinJobs()
     // Layer cache is dependent on layers, layer filters (hence FG structure
     // changes) and the enabled flag on entities
     const bool frameGraphDirty = dirtyBitsForFrame & AbstractRenderer::FrameGraphDirty;
-    const bool layersDirty = dirtyBitsForFrame & AbstractRenderer::LayersDirty;
+    const bool layersDirty = dirtyBitsForFrame & AbstractRenderer::LayersDirty || entityHierarchyNeedsToBeRebuilt;
     const bool layersCacheNeedsToBeRebuilt = layersDirty || entitiesEnabledDirty || frameGraphDirty;
     const bool materialDirty = dirtyBitsForFrame & AbstractRenderer::MaterialDirty;
     const bool materialCacheNeedsToBeRebuilt = materialDirty || frameGraphDirty;
 
+    // Rebuild Entity Hierarchy if dirty
+    if (entityHierarchyNeedsToBeRebuilt)
+        renderBinJobs.push_back(m_updateEntityHierarchyJob);
+
     // Rebuild Entity Layers list if layers are dirty
     if (layersDirty)
         renderBinJobs.push_back(m_updateEntityLayersJob);