Re: [Qemu-devel] [SDL] Problem with mouse grabbing

[Gregory Alexander <yakovlev@grandecom.net>]

Jim C. Brown wrote:
> On Sun, Apr 25, 2004 at 06:45:08PM -0500, Greg Alexander wrote:
> 
>>QEMU Needs to grab the mouse because it emulates a real mouse, instead 
>>of using a pseudo-mouse driver.
> 
> 
> I don't follow you here. How would using a pseudo-mouse driver fix it?

A pseudo-mouse driver for the guest OS would position the guest mouse 
pointer at the position of the host mouse pointer within the VNC window, 
instead of using relative mouse movements and pretending to be a real 
mouse to the guest OS.

>>As a result, mouse scaling will always be a problem, since all the user 
>>has to do is change the mouse scaling in the host OS to cause problems 
>>with the tracking (the scaling problem you noticed.) 
> 
> 
> There must be some way to detect this. If we did know what the mouse scaling
> was, this should be easy to compensate for.

If you have that much access to the guest OS, why not just write the 
pseudo-mouse driver?  Of course, there's also the option of adding a 
"dumb" scaling option to the emulated mouse that is user configurable.

>>That's not to 
>>mention if the mouse came in somewhere different from where it left. 
>>There's nothing to cause the emulated mouse pointer to move to the 
>>position where the real one entered the QEMU window.
>>
> 
> 
> It does for me, actually. And I didn't deliberately change any code to make it
> do this, either. It seems to be a side effect.

I guess if the scaling is accurate and it interprets moving off the 
screen and then moving back in at another location as a movement from 
where it left to where it came in, that would take care of the leaving 
and reentering problems.

GREG