added in rB74518b28267e9b18199212fbaa3c689fa018d20c. No special bind/unbind needed for standalone viewer, so can just use a static stub in the display callback.
added in rB74518b28267e9b18199212fbaa3c689fa018d20c. No special bind/unbind needed for standalone viewer, so can just use a static stub in the display callback.