[Spice-devel] [Qemu-devel] paravirtual mouse/tablet

[Alexander Graf]

On 14.01.2011, at 17:31, Gerd Hoffmann wrote:

>  Hi,
> 
>>>> For a simple tablet pressure and index would just be 0.
>>> 
>>> For a simple tablet pressure would be MAX and index would be 0. But yes, I like the idea :).
>> 
>> 0 for non-presses of course :). Sorry
> 
> Right ;)
> 
> There are three cases:
> 
> (1) no pressure supported (i.e. your mouse moving around in the vnc
>    window and qemu reporting this as tablet coordinates).
> (2) just pen/finger present/not present supported.  pressure jumps
>    between 0 and max (and we can make max == 1 in that case).

Phew - that's one of the bits where touchpads and tablets behave differently IIUC. For touchpads, pressing means movement happens. For tablets, pressing means an actual press, as if you would press your pencil on a sheet of paper. So for tablets, pressure==1 basically means click.

Now the thing is that multitouch gestures might take non-click pressure into account for their calculations. So we need pressure for movements on touchpads, but with tablets, we only need pressure when clicks happen. For everyone else, clicks would just be a button press.

Tricky.


Alex