Is Xvnc a X exension or X driver?

Zhang, Xing Z xing.z.zhang at
Mon Apr 19 18:34:50 PDT 2010

Thank You Alan, you point out me a direction for study.
> (I've cc'ed xorg-devel, since this is really much more of a developer topic than
>  a user topic.)
> Zhang, Xing Z wrote:
> > 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).
> VNC includes an X extension, but Xvnc itself is an X server using the hw/vnc
> layer.   Originally X support for different hardware was delivered by having a
> different DDX layer for each, resulting in multiple different X servers and
> changing X servers to use different types.   In the current code, the
> hw/xfree86
> layer provides a common DDX layer for many types of hardware with loadable
> driver modules for each type, but there are still other DDX layers for other
> types of X server, such as Xvnc, Xvfb & Xnest, as well as the kdrive DDX layer
> which supports multiple har

Does hw/xfree86 layer allow people write a virtual server like Xvnc? Or we 
should switch back to old DDX layer?

dware types using the older model of per-hardware
> X server binaries.
> > 	Could anyone point me a programming howto followed by above
> implementation?
> > 	I gone through documentations on, but didn't find programming
> manual of such a extension/driver.
> There isn't a lot of up-to-date documentation on X server internals - not many
> people are interested in spending the huge amounts of time required to write a
> programming manual that less than 100 people will ever read.
> Documents that do exist (though not necessarily completely up-to-date):
>  * Definition of the Porting Layer for the X v11 Sample Server:
>    html:
>    pdf:
>  * The X Window System Server, Elias Israel, Erik Fortune,
> 	Digital Press, ISBN 1-55558-096-3, 1993.
>    (X11R5 era, though some basic concepts are still unchanged)
> --
> 	-Alan Coopersmith-        alan.coopersmith at
> 	 Oracle Solaris Platform Engineering: X Window System

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