Added OperationQueue class for future work on support thread pools that share

a single OpeationQueue.

include/osg/GraphicsThread

@@ -35,13 +35,13 @@ class RefBlock: virtual public osg::Referenced, public OpenThreads::Block
 };
 
 /** Base class for implementing graphics operations.*/
-struct Operation : virtual public Referenced
+class Operation : virtual public Referenced
 {
+    public:
         Operation(const std::string& name, bool keep):
             _name(name),
             _keep(keep) {}
 
-    virtual ~Operation() {}
 
         /** Set the human readable name of the operation.*/
         void setName(const std::string& name) { _name = name; }
@@ -61,10 +61,49 @@ struct Operation : virtual public Referenced
         /** Do the actual task of this operation.*/ 
         virtual void operator () (Object*) = 0;
 
+    protected:
+
+        virtual ~Operation() {}
+
         std::string _name;
         bool        _keep;
 };
 
+class OSG_EXPORT OperationQueue : public Referenced
+{
+    public:
+    
+        OperationQueue();
+        
+        RefBlock* getOperationsBlock() { return _operationsBlock.get(); }
+        
+        const RefBlock* getOperationsBlock() const { return _operationsBlock.get(); }
+
+        /** Add operation to end of OperationQueue, this will be 
+          * executed by the operation thread once this operation gets to the head of the queue.*/
+        void add(Operation* operation);
+        
+        /** Remove operation from OperationQueue.*/
+        void remove(Operation* operation);
+
+        /** Remove named operation from OperationQueue.*/
+        void remove(const std::string& name);
+
+        /** Remove all operations from OperationQueue.*/
+        void removeAllOperations();
+        
+    protected:
+
+        virtual ~OperationQueue();
+
+        typedef std::list< ref_ptr<Operation> > Operations;
+
+        OpenThreads::Mutex          _operationsMutex;
+        osg::ref_ptr<osg::RefBlock> _operationsBlock;
+        Operations _operations;
+
+};
+
 /** GraphicsThread is a helper class for running OpenGL GraphicsOperation within a single thread assigned to a specific GraphicsContext.*/
 class OSG_EXPORT OperationsThread : public Referenced, public OpenThreads::Thread
 {
@@ -110,13 +149,13 @@ class OSG_EXPORT OperationsThread : public Referenced, public OpenThreads::Threa
         
         observer_ptr<Object>   _parent;
 
-        typedef std::list< ref_ptr<Operation> > OperationQueue;
+        typedef std::list< ref_ptr<Operation> > Operations;
 
         bool                        _done;
 
         OpenThreads::Mutex          _operationsMutex;
         osg::ref_ptr<osg::RefBlock> _operationsBlock;
-        OperationQueue              _operations;
+        Operations                  _operations;
         osg::ref_ptr<Operation>     _currentOperation;
 
 };