From Riccardo Corsi, introduced CameraManipulator::updateCamera() method that allows more Camera properties to be controlled by the CameraManipulator.

include/osgGA/CameraManipulator

@@ -87,6 +87,10 @@ class OSGGA_EXPORT CameraManipulator : public GUIEventHandler
         /** get the position of the manipulator as a inverse matrix of the manipulator, typically used as a model view matrix.*/
         virtual osg::Matrixd getInverseMatrix() const = 0;
 
+        /** update the camera for the current frame, typically called by the viewer classes. 
+            Default implementation simply set the camera view matrix. */
+        virtual void updateCamera(osg::Camera* camera) { camera->setViewMatrix(getInverseMatrix()); }
+
         /** Get the FusionDistanceMode. Used by SceneView for setting up stereo convergence.*/
         virtual osgUtil::SceneView::FusionDistanceMode getFusionDistanceMode() const { return osgUtil::SceneView::PROPORTIONAL_TO_SCREEN_DISTANCE; }
 

src/osgViewer/CompositeViewer.cpp

@@ -1159,7 +1159,8 @@ void CompositeViewer::updateTraversal()
             view->setFusionDistance( view->getCameraManipulator()->getFusionDistanceMode(),
                                     view->getCameraManipulator()->getFusionDistanceValue() );
             
-            view->getCamera()->setViewMatrix( view->getCameraManipulator()->getInverseMatrix());
+            view->getCameraManipulator()->updateCamera(view->getCamera());
+            
         }
         view->updateSlaves();
 

src/osgViewer/Viewer.cpp

@@ -1038,7 +1038,7 @@ void Viewer::updateTraversal()
         setFusionDistance( getCameraManipulator()->getFusionDistanceMode(),
                             getCameraManipulator()->getFusionDistanceValue() );
 
-        _camera->setViewMatrix(_cameraManipulator->getInverseMatrix());
+        _cameraManipulator->updateCamera(_camera);
     }
 
     updateSlaves();