Introduced a alternative implementation of observer_ptr<> that uses ObserverSet rather than an local WeakReference object.

src/osg/Observer.cpp

@@ -24,7 +24,8 @@ Observer::~Observer()
 {
 }
 
-ObserverSet::ObserverSet()
+ObserverSet::ObserverSet(const Referenced* observedObject):
+    _observedObject(const_cast<Referenced*>(observedObject))
 {
     //OSG_NOTICE<<"ObserverSet::ObserverSet() "<<this<<std::endl;
 }
@@ -37,19 +38,40 @@ ObserverSet::~ObserverSet()
 void ObserverSet::addObserver(Observer* observer)
 {
     //OSG_NOTICE<<"ObserverSet::addObserver("<<observer<<") "<<this<<std::endl;
-    OpenThreads::ScopedLock<OpenThreads::Mutex> lock(*getObserverSetMutex());
+    OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_mutex);
     _observers.insert(observer);
 }
 
 void ObserverSet::removeObserver(Observer* observer)
 {
     //OSG_NOTICE<<"ObserverSet::removeObserver("<<observer<<") "<<this<<std::endl;
-    OpenThreads::ScopedLock<OpenThreads::Mutex> lock(*getObserverSetMutex());
+    OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_mutex);
     _observers.erase(observer);
 }
 
+Referenced* ObserverSet::addRefLock()
+{
+    OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_mutex);
+
+    if (!_observedObject) return 0;
+
+    int refCount = _observedObject->ref();
+    if (refCount == 1)
+    {
+        // The object is in the process of being deleted, but our
+        // objectDeleted() method hasn't been run yet (and we're
+        // blocking it -- and the final destruction -- with our lock).
+        _observedObject->unref_nodelete();
+        return 0;
+    }
+
+    return _observedObject;
+}
+
 void ObserverSet::signalObjectDeleted(void* ptr)
 {
+    OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_mutex);
+
     for(Observers::iterator itr = _observers.begin();
         itr != _observers.end();
         ++itr)
@@ -57,4 +79,7 @@ void ObserverSet::signalObjectDeleted(void* ptr)
         (*itr)->objectDeleted(ptr);
     }
     _observers.clear();
+
+    // reset the observed object so that we know that it's now detached.
+    _observedObject = 0;
 }