From Wang Rui, "The file attached includes two new features for the serialization IO functionality. First, custom serializer version control should work now, just by defining a new REGISTER_CUSTOM_OBJECT_WRAPPER macro. For example:

// A custom class
namespace CustomDomain {

class MyGroup : public osg::Group
{
public:
    META_Node( CustomDomain, MyGroup );

    void setMyName( const std::string& n );
    const std::string& getMyName() const;

    void setMyID( int id );
    int getMyID() const;

    ...
};

}

// The serialization wrapper using a custom domain name
REGISTER_CUSTOM_OBJECT_WRAPPER( MyDomain,
                                CustomDomain_MyGroup,
                                new CustomDomain::MyGroup,
                                CustomDomain::MyGroup,
                                "osg::Object osg::Node osg::Group CustomDomain::MyGroup" )
{
    ADD_STRING_SERIALIZER( MyName, std::string() );
    {
        UPDATE_TO_VERSION_SCOPED( 1 );  // Updated for a new domain version
        ADD_INT_SERIALIZER( MyID, 0 );
    }
}

Save the class instance as follows:
osgDB::writeNodeFile( *myGroup, "serializer_test.osgt", new osgDB::Options("CustomDomains=MyDomain:1") );

The output file will include the domain version definition and all the class data, and can be read back. We can also force setting the domain version by the CustomDomains option while reading the saved files. If we save the class instance without any options, MyID will be ignored because the default domain version is 0.

This may help third-party libraries like osgEarth to maintain their own serializers without regarding to the OSG soversion changes.

Another feature added is a more robust binary format, which in fact adds a size-offset at each block's beginning. When there are problems or unsupported data types while reading, we can now directly jump to the block end indicated by the offset value. So a .osgb file will automatically ignore bad data and read remains as normal (at present it will fail at all). This feature will not break the backward compatibility, and can be disabled by setting "RobustBinaryFormat=false" while writing out.

Hope these changes can work smoothly with present and future community projects. Maybe we should also consider have an osgserializer example to test and demonstrate all things we can do now."