Is Xvnc a X exension or X driver?

[Zhang, Xing Z]

Hi experts:
	I am looking into code of tigervnc, the Xvnc contains a vnc X server which seems a X driver or extension ( it locates at tigervnc-1.0.1/unix/xserver/hw/vnc). 
	Could anyone point me a programming howto followed by above implementation?
	I gone through documentations on X.org, but didn't find programming manual of such a extension/driver.
	Thank you.
	


Zhang Xin(Wing)
Intel(SSG/OTC) ShangHai China