Added osg::SyncSwapBuffersCallback to include/osg/GraphicsContext and support for enabling it to include/osg/DisplaySettings, and to the Viewer/CompositeViewer::realize() methods.

To enable the sync of swap buffers set the env var OSG_SYNC_SWAP_BUFFERS to ON or 1, to switch off set to OFF or 0.

One can also use the --sync command line option for application that pass on command line options to the osg::DisplaySettings::instance().


git-svn-id: http://svn.openscenegraph.org/osg/OpenSceneGraph/trunk@14456 16af8721-9629-0410-8352-f15c8da7e697

src/osgViewer/Viewer.cpp

@@ -544,6 +544,8 @@ void Viewer::realize()
     {
         osg::GraphicsContext* gc = *citr;
 
+        if (ds->getSyncSwapBuffers()) gc->setSwapCallback(new osg::SyncSwapBuffersCallback);
+
         // set the pool sizes, 0 the default will result in no GL object pools.
         gc->getState()->setMaxTexturePoolSize(maxTexturePoolSize);
         gc->getState()->setMaxBufferObjectPoolSize(maxBufferObjectPoolSize);