Introduced CMake option OSG_PROVIDE_READFILE option that defaults to ON, but when switched to OFF disables the building of the osgDB::read*File() methods,

forcing users to use osgDB::readRef*File() methods.  The later is preferable as it closes a potential threading bug when using paging databases in conjunction
with the osgDB::Registry Object Cache.  This threading bug occurs when one thread gets an object from the Cache via an osgDB::read*File() call where only
a pointer to the object is passed back, so taking a reference to the object is delayed till it gets reassigned to a ref_ptr<>, but at the same time another
thread calls a flush of the Object Cache deleting this object as it's referenceCount is now zero.  Using osgDB::readREf*File() makes sure the a ref_ptr<> is
passed back and the referenceCount never goes to zero.

To ensure the OSG builds when OSG_PROVIDE_READFILE is to OFF the many cases of osgDB::read*File() usage had to be replaced with a ref_ptr<> osgDB::readRef*File()
usage.  The avoid this change causing lots of other client code to be rewritten to handle the use of ref_ptr<> in place of C pointer I introduced a serious of
templte methods in various class to adapt ref_ptr<> to the underly C pointer to be passed to old OSG API's, example of this is found in include/osg/Group:

    bool addChild(Node* child); // old method which can only be used with a Node*

    tempalte<class T> bool addChild(const osg::ref_ptr<T>& child) { return addChild(child.get()); } // adapter template method

These changes together cover 149 modified files, so it's a large submission. This extent of changes are warrent to make use of the Object Cache
and multi-threaded loaded more robust.



git-svn-id: http://svn.openscenegraph.org/osg/OpenSceneGraph/branches/OpenSceneGraph-3.4@15165 16af8721-9629-0410-8352-f15c8da7e697

examples/osgsimplifier/osgsimplifier.cpp

@@ -26,10 +26,10 @@
 class KeyboardEventHandler : public osgGA::GUIEventHandler
 {
 public:
-    
+
     KeyboardEventHandler(unsigned int& flag) : _flag(flag)
     {}
-    
+
     virtual bool handle(const osgGA::GUIEventAdapter& ea,osgGA::GUIActionAdapter&)
     {
         switch(ea.getEventType())
@@ -65,7 +65,7 @@ int main( int argc, char **argv )
 
     // use an ArgumentParser object to manage the program arguments.
     osg::ArgumentParser arguments(&argc,argv);
-    
+
     // set up the usage document, in case we need to print out how to use this program.
     arguments.getApplicationUsage()->setApplicationName(arguments.getApplicationName());
     arguments.getApplicationUsage()->setDescription(arguments.getApplicationName()+" examples illustrates simplification of triangle meshes.");
@@ -73,7 +73,7 @@ int main( int argc, char **argv )
     arguments.getApplicationUsage()->addCommandLineOption("-h or --help","Display this information");
     arguments.getApplicationUsage()->addCommandLineOption("--ratio <ratio>","Specify the sample ratio","0.5]");
     arguments.getApplicationUsage()->addCommandLineOption("--max-error <error>","Specify the maximum error","4.0");
-    
+
 
     float sampleRatio = 0.5f;
     float maxError = 4.0f;
@@ -99,18 +99,18 @@ int main( int argc, char **argv )
     }
 
     // read the scene from the list of file specified commandline args.
-    osg::ref_ptr<osg::Node> loadedModel = osgDB::readNodeFiles(arguments);
-  
+    osg::ref_ptr<osg::Node> loadedModel = osgDB::readRefNodeFiles(arguments);
+
     // if not loaded assume no arguments passed in, try use default mode instead.
-    if (!loadedModel) loadedModel = osgDB::readNodeFile("dumptruck.osgt");
-    
+    if (!loadedModel) loadedModel = osgDB::readRefNodeFile("dumptruck.osgt");
+
     // if no model has been successfully loaded report failure.
-    if (!loadedModel) 
+    if (!loadedModel)
     {
         std::cout << arguments.getApplicationName() <<": No data loaded" << std::endl;
         return 1;
     }
-    
+
     //loadedModel->accept(simplifier);
 
     unsigned int keyFlag = 0;
@@ -133,29 +133,29 @@ int main( int argc, char **argv )
     {
         // fire off the cull and draw traversals of the scene.
         viewer.frame();
-    
+
         if (keyFlag == 1 || keyFlag == 2)
         {
             if (keyFlag == 1) ratio *= multiplier;
             if (keyFlag == 2) ratio /= multiplier;
             if (ratio<minRatio) ratio=minRatio;
-            
+
             osgUtil::Simplifier simplifier(ratio, maxError);
 
             std::cout<<"Runing osgUtil::Simplifier with SampleRatio="<<ratio<<" maxError="<<maxError<<" ...";
             std::cout.flush();
-            
+
             osg::ref_ptr<osg::Node> root = (osg::Node*)loadedModel->clone(osg::CopyOp::DEEP_COPY_ALL);
 
             root->accept(simplifier);
-            
+
             std::cout<<"done"<<std::endl;
-            
+
             viewer.setSceneData(root.get());
             keyFlag = 0;
         }
     }
-    
+
     return 0;
 }