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RE: [Xen-devel] [PATCH 1/3] Add Summagraphics Tablet emulation

  • To: "Keir Fraser" <Keir.Fraser@xxxxxxxxxxxx>
  • From: "Dugger, Donald D" <donald.d.dugger@xxxxxxxxx>
  • Date: Wed, 15 Mar 2006 17:36:47 -0800
  • Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Thu, 16 Mar 2006 01:37:55 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: AcZIjIRkYM1haZakSn22Jo8TlVcdUQADI0gQ
  • Thread-topic: [Xen-devel] [PATCH 1/3] Add Summagraphics Tablet emulation


Multiple problems:

1)  As you suspected, roundoff errors add up and cause problems.

2)  Cursor position.  The cursor is what's actually moved by the mouse
and there's no way to know where the cursor starts.  When you start X,
and at other times, the cursor is warped to the center of the screen and
there's no way for `qemu-dm' to know that this happened.

3)  Mouse accelleration.  This is the real problem, different cursor
handlers, think `gpm' and X, provide different mouse accellerations so
that there's no way to know how far the cursor actually moves based upon
the pointer movement.

I've not found a way to overcome all of these issues and, given that the
Summagraphics devices almost exactly matches what the VNC mouse is
providing, doing Summagraphics emulation is the simplest, most natural
solution for VNC.

Don Dugger
"Censeo Toto nos in Kansa esse decisse." - D. Gale
Ph: (303)440-1368 

>-----Original Message-----
>From: Keir Fraser [mailto:Keir.Fraser@xxxxxxxxxxxx] 
>Sent: Wednesday, March 15, 2006 4:56 PM
>To: Dugger, Donald D
>Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
>Subject: Re: [Xen-devel] [PATCH 1/3] Add Summagraphics Tablet emulation
>On 15 Mar 2006, at 23:22, Dugger, Donald D wrote:
>> Yes, the 3 patches are independent so you can apply them as you wish.
>> I'm not sure what your concern is about the touchpad patch.  
>There was
>> code to emulate a touchpad in the code but it was all wrong 
>and didn't
>> work, I basically had to re-do all of the touchpad code to 
>get this to
>> work.
>Why is it not possible to translate from absolute coordinates provided 
>by VNC into deltas required for PS/2 mouse emulation? Do you end up 
>with accumulating absolute error?
>  -- Keir

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