Introduce UnrefQueue to handle the deleting of no longer needed objects in the background thread

components/sceneutil/unrefqueue.cpp

@@ -0,0 +1,46 @@
+#include "unrefqueue.hpp"
+
+#include <osg/Object>
+//#include <osg/Timer>
+//#include <iostream>
+
+#include <components/sceneutil/workqueue.hpp>
+
+namespace SceneUtil
+{
+
+    class UnrefWorkItem : public SceneUtil::WorkItem
+    {
+    public:
+        std::vector<osg::ref_ptr<osg::Object> > mObjects;
+
+        virtual void doWork()
+        {
+            //osg::Timer timer;
+            //size_t objcount = mObjects.size();
+            mObjects.clear();
+            //std::cout << "cleared " << objcount << " objects in " << timer.time_m() << std::endl;
+        }
+    };
+
+    UnrefQueue::UnrefQueue()
+    {
+        mWorkItem = new UnrefWorkItem;
+    }
+
+    void UnrefQueue::push(osg::Object *obj)
+    {
+        mWorkItem->mObjects.push_back(obj);
+    }
+
+    void UnrefQueue::flush(SceneUtil::WorkQueue *workQueue)
+    {
+        if (mWorkItem->mObjects.empty())
+            return;
+
+        workQueue->addWorkItem(mWorkItem);
+
+        mWorkItem = new UnrefWorkItem;
+    }
+
+}