[Qemu-devel] Re: [PATCH] Support VNC PointerTypeChange psuedo-encoding

[Daniel P. Berrange]

On Fri, Jan 05, 2007 at 09:30:32PM -0600, Anthony Liguori wrote:
> The following patch adds support to the VNC server for the 
> PointerTypeChange.  This is a new encoding I've defined specifically for 
> virtualization.  It allows a VNC client to support a server that has a 
> relative mouse (such as a PS/2 mouse in QEMU).  If you're familiar with 
> the mouse being offset in a VNC session, this patch is the proper way to 
> address that.
> 
> This extension is documented at http://tocm.wikidot.com/pointertypechange
> 
> It uses a type that I've reserved in the latest RFB spec.
> 
> Currently, the only client that supports this encoding is my PoC client 
> available at http://hg.codemonkey.ws/vnc-gui.  I've also talked to Dan 
> Berrange, the virt-manager maintainer, and I believe he plans on 
> supporting this extension in virt-manager too.  Once QEMU supports the 
> encoding, I suspect some of the other more popular VNC clients will 
> considering also supporting it.

Yes, I will be implementing this extension in virt-manager, since its the
only approach to mouse pointer sanity which is portable across different
guest OS. Client-end code to make use of this extension is quite simple,
so I expect regular VNC clients could easily add support for it. For those
not familiar with VNC protocol, its worth noting that this extension is
'opt-in' - ie current default mouse pointer handling is unchanged, unless
the VNC client explicitly asks for it to be turned on.

That all said, if you've configured QEMU to use one of the pointer devices
which does absolute co-ordinates correctly (ie the graphics tables), then
you don't want to turn on this extension. ie. If you can get absolute coords
going through the whole stack Local Desktop -> VNC Client -> QEMU -> Guest OS
-> Guest Desktop, then that is the perfect approach because it doesn't
require you to do a local cursor-grab.

Regards,
Dan.
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