Do direct notification of backend nodeswip/refactor

Since aspect manager is now on main thread, we can directly update
backend nodes safely. Track nodes which have changed properties and
notify the backend nodes as part of the frame loop.
This avoid allocating and delivering many change messages.

To follow:
- implement on all nodes
- look at backend to frontend syncing
- figure out what to do with non property messages (components
  added/removed, commands, ...)

Change-Id: Ia0c442b0528e728c4324d168200bae021bc29266
Reviewed-by: Mike Krus <mike.krus@kdab.com>
Reviewed-by: Paul Lemire <paul.lemire@kdab.com>

5 files changed, 39 insertions, 59 deletions

diff --git a/src/core/nodes/qbackendnode.cpp b/src/core/nodes/qbackendnode.cpp
index f10bf5769..3eb1cd9f7 100644
--- a/src/core/nodes/qbackendnode.cpp
+++ b/src/core/nodes/qbackendnode.cpp
@@ -256,16 +256,16 @@ void QBackendNode::setEnabled(bool enabled) Q_DECL_NOTHROW
 void QBackendNode::sceneChangeEvent(const QSceneChangePtr &e)
 {
     Q_D(QBackendNode);
-    auto propertyChange = qSharedPointerCast<QPropertyUpdatedChange>(e);
 
     switch (e->type()) {
-        case PropertyUpdated: {
-            if (propertyChange->propertyName() == QByteArrayLiteral("enabled"))
-                d->m_enabled = propertyChange->value().toBool();
-            break;
-        }
-        default:
-            break;
+    case PropertyUpdated: {
+        auto propertyChange = qSharedPointerCast<QPropertyUpdatedChange>(e);
+        if (propertyChange->propertyName() == QByteArrayLiteral("enabled"))
+            d->m_enabled = propertyChange->value().toBool();
+        break;
+    }
+    default:
+        break;
     }
 }
 
diff --git a/src/core/nodes/qcomponent.cpp b/src/core/nodes/qcomponent.cpp
index f67989b1e..2fe3c8094 100644
--- a/src/core/nodes/qcomponent.cpp
+++ b/src/core/nodes/qcomponent.cpp
@@ -73,7 +73,7 @@ void QComponentPrivate::addEntity(QEntity *entity)
         m_scene->addEntityForComponent(m_id, entity->id());
     }
 
-    const auto componentAddedChange = QComponentAddedChangePtr::create(q, entity);
+    const auto componentAddedChange = QComponentAddedChangePtr::create(q, entity);  // TODOSYNC notify backend directly
     notifyObservers(componentAddedChange);
     Q_EMIT q->addedToEntity(entity);
 }
@@ -86,7 +86,7 @@ void QComponentPrivate::removeEntity(QEntity *entity)
 
     m_entities.removeAll(entity);
 
-    const auto componentRemovedChange = QComponentRemovedChangePtr::create(q, entity);
+    const auto componentRemovedChange = QComponentRemovedChangePtr::create(q, entity);  // TODOSYNC notify backend directly
     notifyObservers(componentRemovedChange);
     Q_EMIT q->removedFromEntity(entity);
 }
diff --git a/src/core/nodes/qentity.cpp b/src/core/nodes/qentity.cpp
index 1d16e828e..a1f7d2859 100644
--- a/src/core/nodes/qentity.cpp
+++ b/src/core/nodes/qentity.cpp
@@ -105,7 +105,7 @@ void QEntityPrivate::removeDestroyedComponent(QComponent *comp)
     Q_Q(QEntity);
 
     if (m_changeArbiter) {
-        const auto componentRemovedChange = QComponentRemovedChangePtr::create(q, comp);
+        const auto componentRemovedChange = QComponentRemovedChangePtr::create(q, comp);  // TODOSYNC notify backend directly
         notifyObservers(componentRemovedChange);
     }
 
@@ -187,7 +187,7 @@ void QEntity::addComponent(QComponent *comp)
     d->registerPrivateDestructionHelper(comp, &QEntityPrivate::removeDestroyedComponent);
 
     if (d->m_changeArbiter) {
-        const auto componentAddedChange = QComponentAddedChangePtr::create(this, comp);
+        const auto componentAddedChange = QComponentAddedChangePtr::create(this, comp);     // TODOSYNC notify backend directly
         d->notifyObservers(componentAddedChange);
     }
     static_cast<QComponentPrivate *>(QComponentPrivate::get(comp))->addEntity(this);
diff --git a/src/core/nodes/qnode.cpp b/src/core/nodes/qnode.cpp
index 900c3f8ce..45d58bd8c 100644
--- a/src/core/nodes/qnode.cpp
+++ b/src/core/nodes/qnode.cpp
@@ -385,48 +385,13 @@ void QNodePrivate::unregisterNotifiedProperties()
 
 void QNodePrivate::propertyChanged(int propertyIndex)
 {
+    Q_UNUSED(propertyIndex);
+
     // Bail out early if we can to avoid the cost below
     if (m_blockNotifications)
         return;
 
-    const auto toBackendValue = [](const QVariant &data) -> QVariant
-    {
-        if (data.canConvert<QNode*>()) {
-            QNode *node = data.value<QNode*>();
-
-            // Ensure the node and all ancestors have issued their node creation changes.
-            // We can end up here if a newly created node with a parent is immediately set
-            // as a property on another node. In this case the deferred call to
-            // _q_postConstructorInit() will not have happened yet as the event
-            // loop will still be blocked. We need to do this for all ancestors,
-            // since the subtree of this node otherwise can end up on the backend
-            // with a reference to a non-existent parent.
-            if (node)
-                QNodePrivate::get(node)->_q_ensureBackendNodeCreated();
-
-            const QNodeId id = node ? node->id() : QNodeId();
-            return QVariant::fromValue(id);
-        }
-
-        return data;
-    };
-
-    Q_Q(QNode);
-
-    const QMetaProperty property = q->metaObject()->property(propertyIndex);
-
-    const QVariant data = property.read(q);
-
-    if (data.type() == QVariant::List) {
-        QSequentialIterable iterable = data.value<QSequentialIterable>();
-        QVariantList variants;
-        variants.reserve(iterable.size());
-        for (const auto &v : iterable)
-            variants.append(toBackendValue(v));
-        notifyPropertyChange(property.name(), variants);
-    } else {
-        notifyPropertyChange(property.name(), toBackendValue(data));
-    }
+    update();
 }
 
 /*!
@@ -498,8 +463,13 @@ void QNodePrivate::addEntityComponentToScene(QNode *root)
 // Called in the main thread by QScene -> following QEvent::childAdded / addChild
 void QNodePrivate::setArbiter(QLockableObserverInterface *arbiter)
 {
-    if (m_changeArbiter && m_changeArbiter != arbiter)
+    if (m_changeArbiter && m_changeArbiter != arbiter) {
         unregisterNotifiedProperties();
+
+        // Remove node from dirtyFrontendNodeList on old arbiter
+        Q_Q(QNode);
+        m_changeArbiter->removeDirtyFrontEndNode(q);
+    }
     m_changeArbiter = static_cast<QAbstractArbiter *>(arbiter);
     if (m_changeArbiter)
         registerNotifiedProperties();
@@ -626,26 +596,26 @@ QScene *QNodePrivate::scene() const
  */
 void QNodePrivate::notifyPropertyChange(const char *name, const QVariant &value)
 {
+    Q_UNUSED(name);
+    Q_UNUSED(value);
+
     // Bail out early if we can to avoid operator new
     if (m_blockNotifications)
         return;
 
-    auto e = QPropertyUpdatedChangePtr::create(m_id);
-    e->setPropertyName(name);
-    e->setValue(value);
-    notifyObservers(e);
+    update();
 }
 
 void QNodePrivate::notifyDynamicPropertyChange(const QByteArray &name, const QVariant &value)
 {
+    Q_UNUSED(name);
+    Q_UNUSED(value);
+
     // Bail out early if we can to avoid operator new
     if (m_blockNotifications)
         return;
 
-    auto e = QDynamicPropertyUpdatedChangePtr::create(m_id);
-    e->setPropertyName(name);
-    e->setValue(value);
-    notifyObservers(e);
+    update();
 }
 
 /*!
@@ -704,6 +674,14 @@ void QNodePrivate::updatePropertyTrackMode()
     }
 }
 
+void QNodePrivate::update()
+{
+    if (m_changeArbiter) {
+        Q_Q(QNode);
+        m_changeArbiter->addDirtyFrontEndNode(q);
+    }
+}
+
 /*!
     \internal
  */
diff --git a/src/core/nodes/qnode_p.h b/src/core/nodes/qnode_p.h
index 511a0e562..990c2caeb 100644
--- a/src/core/nodes/qnode_p.h
+++ b/src/core/nodes/qnode_p.h
@@ -89,6 +89,8 @@ public:
     void insertTree(QNode *treeRoot, int depth = 0);
     void updatePropertyTrackMode();
 
+    void update();
+
     Q_DECLARE_PUBLIC(QNode)
 
     // For now this just protects access to the m_changeArbiter.