Refactored Observer/ObserverNodePath and DatabasePager to improve their robustness.

include/osg/ObserverNodePath

@@ -15,17 +15,16 @@
 #define OSG_OBSERVERNODEPATH 1
 
 #include <osg/Node>
-#include <osg/Observer>
-#include <osg/ref_ptr>
-#include <list>
+#include <osg/observer_ptr>
+#include <vector>
 
 namespace osg {
 
-typedef std::list< osg::ref_ptr<osg::Node> > RefNodePath;
+typedef std::vector< osg::ref_ptr<osg::Node> > RefNodePath;
 
 /** ObserverNodePath is an observer class for tracking changes to a NodePath,
   * that automatically invalidates it when nodes are deleted.*/
-class OSG_EXPORT ObserverNodePath : public osg::Observer
+class OSG_EXPORT ObserverNodePath
 {
     public:
         ObserverNodePath();
@@ -38,9 +37,6 @@ class OSG_EXPORT ObserverNodePath : public osg::Observer
 
         ObserverNodePath& operator = (const ObserverNodePath& rhs);
 
-        bool valid() const { return _valid; }
-
-
         /** get the NodePath from the first parental chain back to root, plus the specified node.*/
         void setNodePathTo(osg::Node* node);
 
@@ -61,21 +57,18 @@ class OSG_EXPORT ObserverNodePath : public osg::Observer
 
         bool empty() const
         {
-            if (!_valid) return true;
-            OpenThreads::ScopedLock<OpenThreads::Mutex> lock(*getObserverMutex());
+            OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_mutex);
             return _nodePath.empty();
         }
 
     protected:
 
         void _setNodePath(const osg::NodePath& nodePath);
-
         void _clearNodePath();
 
-        virtual bool objectUnreferenced(void* ptr);
-
-        osg::NodePath                   _nodePath;
-        bool                            _valid;
+        typedef std::vector< osg::observer_ptr<osg::Node> > ObsNodePath;
+        mutable OpenThreads::Mutex      _mutex;
+        ObsNodePath                     _nodePath;
 };
 
 }