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Date: Fri, 14 Jan 2011 16:13:29 +0100
From: Gerd Hoffmann <kraxel@redhat.com>
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Subject: Re: [Qemu-devel] paravirtual mouse/tablet
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To: Alexander Graf <agraf@suse.de>
Cc: spice-devel <spice-devel@lists.freedesktop.org>, Avi Kivity <avi@redhat.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>

   Hi,

> So it'd end up being (x,y,pressure) N times (I think 16 is fine for
> the foreseeable future).

I'd tend to extend MOVE to (x,y,pressure,index) and send N events with 
the same timestamp.  Needs to send only as many events as it finds 
fingers on the touchpad, i.e. usually just one or two, even if the 
protocol can easily handle alot more than 16 ;)

For a simple tablet pressure and index would just be 0.

> The details of what exactly that means
> should be figured out by the guest driver.

Agree.

> I'm not familiar with the hardware interface, but in order to support
> that the background interface must be a lot more complex than a
> simple button press.

Buttons events are for buttons.  Real ones, which apple lost ;)

Of course a tap on the trackpad is usually interpreted as mouse click. 
But that is the job of the guest OS, our virtual hardware doesn't care.

> But then again - how would we forward fine-grained scrolling to the
> guest if we only know that it's scrolling, but not what the actual
> presses on the touchpad looked like? Ugh.

There must be an interface to get (more or less) the raw touchpad data, 
for apps which want implement their own multitouch gestures?

cheers,
   Gerd