> I vote for the Synaptics PS/2 touchpad emulation. From the Linux 
> kernel source, it does not seem difficult.
>
> Another topic is the keycode conversions. Even with SDL, a solution 
> like bochs or rdesktop (with an option to give the host keyboard 
> mapping) is needed. That's why I did not merge the various patch 
> submitted to 'improve' the SDL keyboard emulation.
>
It looks like the Synaptics emulation would require an additional driver 
on the Windows side, but Linux/X should support it (and detect it) 
natively.  I wonder how hard it is to write a mouse (or mouse filter 
driver) for Windows to support this sort of device. 

Two other possiblities might be to use the host/guest interface, or to 
implement USB support and create a HID mouse driver with absolute 
positioning support.

Matt.