[vbox-dev] mouse integration concept level overview?

Huihong Luo huisinro at yahoo.com
Tue Sep 6 10:25:27 PDT 2011

Hi Michael,
I noted that Windows additions (vboxmouse.sys and VBoxMouseNT.sys) doesn't perform any conversion from this 0-FFFF percentange coordinates, however X11 additions convert them to screen resolution. Does Windows happen to use the same measurement of 0-0xFFFF ?
Another thing is that the cursor shape at pointer disppears when moving out of vm guest window, does virtualbox perform some special task to make the curson not to appear? or the host simply reports some out of range positions to the guest. I was curious how this is handled.
- huihong

--- On Fri, 9/2/11, Michael Thayer <michael.thayer at oracle.com> wrote:

From: Michael Thayer <michael.thayer at oracle.com>
Subject: Re: [vbox-dev] mouse integration concept level overview?
To: "Huihong Luo" <huisinro at yahoo.com>
Cc: vbox-dev at virtualbox.org
Date: Friday, September 2, 2011, 1:47 PM

Hello Huihong,

On Thu, 2011-09-01 at 20:56 -0700, Huihong Luo wrote:
> I need to know a bit more about the mouse integration. Can someone explain in big picture on what happened when a mouse pointer is moving from host to the guest? once the mouse inside the guest window, host informs the guest about the mouse positions? etc.
> I need to get some ideas on this in order to implement the drag-and-drop feature for vbox. Right now, it's stuck when the mouse is dragged from host to vm, how the guest side knows about that. I need to press a key for now to tell the guest side, so the dnd isn't smooth yet. A good understanding on mouse integration would be very helpful.
> _______________________________________________ vbox-dev mailing list vbox-dev at virtualbox.org http://vbox.innotek.de/mailman/listinfo/vbox-dev

I'm afraid that this will be a quick-ish explanation for now.  When
absolute pointer reporting is enabled (see the VMMDevReq_GetMouseStatus
VMM device request) the current pointer position can be requested with
the VMMDevReqMousePointer request.  This is reported as a percentage of
the width and height (respectively) of the guest screen - expressed as a
value from 0 to 0xFFFF - or of the virtual desktop for multi-monitor
guests.  The host works out what percentage values correspond to the
position of the host pointer relative to the host window the machine is
running in, and the Additions report the position back to the guest in a
way that the guest OS can convert to the correct pixel offset.  The host
sends a VMM device event (basically an interrupt and a data word) when
absolute reporting is enabled or disabled and when new position data is

Hope that helps a bit.


ORACLE Deutschland B.V. & Co. KG   Michael Thayer
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