QChangeArbiter/QPostMan: batch frontend changes

- Updated unit tests
- Added QAbstractPostman and QAbstractArbiter as they are more than
  QObserverInterfaces but still need to be easily testable.

Change-Id: I0fc2ce48031eecc9bf893798650ef68e9d7d8bb7
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>

1 files changed, 29 insertions, 0 deletions

diff --git a/src/core/qpostman.cpp b/src/core/qpostman.cpp
index bd91def10..b7e7904d7 100644
--- a/src/core/qpostman.cpp
+++ b/src/core/qpostman.cpp
@@ -39,6 +39,7 @@
 #include <Qt3DCore/qscenepropertychange.h>
 #include <Qt3DCore/qbackendscenepropertychange.h>
 #include <Qt3DCore/private/qscene_p.h>
+#include <Qt3DCore/private/qlockableobserverinterface_p.h>
 #include <Qt3DCore/qnode.h>
 #include <Qt3DCore/private/qnode_p.h>
 
@@ -57,6 +58,7 @@ public:
 
     Q_DECLARE_PUBLIC(QPostman)
     QScene *m_scene;
+    std::vector<QSceneChangePtr> m_batch;
 };
 
 QPostman::QPostman(QObject *parent)
@@ -84,6 +86,23 @@ void QPostman::sceneChangeEvent(const QSceneChangePtr &e)
     notifyFrontendNode.invoke(this, Q_ARG(QSceneChangePtr, e));
 }
 
+/*!
+ * This will start or append \a change to a batch of changes from frontend
+ * nodes. Once the batch is complete, when the event loop returns, the batch is
+ * sent to the QChangeArbiter to notify the backend aspects.
+ */
+void QPostman::notifyBackend(const QSceneChangePtr &change)
+{
+    // If batch in progress
+    // add change
+    // otherwise start batch
+    // by calling a queued slot
+    Q_D(QPostman);
+    if (d->m_batch.empty())
+        QMetaObject::invokeMethod(this, "submitChangeBatch", Qt::QueuedConnection);
+    d->m_batch.push_back(change);
+}
+
 void QPostman::notifyFrontendNode(const QSceneChangePtr &e)
 {
     Q_D(QPostman);
@@ -95,6 +114,16 @@ void QPostman::notifyFrontendNode(const QSceneChangePtr &e)
     }
 }
 
+void QPostman::submitChangeBatch()
+{
+    Q_D(QPostman);
+    QLockableObserverInterface *arbiter = Q_NULLPTR;
+    if (d->m_scene && (arbiter = d->m_scene->arbiter()) != Q_NULLPTR) {
+        arbiter->sceneChangeEventWithLock(d->m_batch);
+        d->m_batch.clear();
+    }
+}
+
 } //Qt3D
 
 QT_END_NAMESPACE