XInput: Tablet to screen coordinate translation

Magnus Vigerlöf Magnus.Vigerlof at
Wed Feb 28 10:54:55 PST 2007

On Wednesday 28 February 2007 02:02, Peter Hutterer wrote:
> On 28/02/2007, at 10:17 , Magnus Vigerlöf wrote:
> > So the coordinates that is sent on the first two axis (x & y) to
> > xf86PostXXXEvent must be converted into coordinates that will fit
> > the actual
> > screen resolution (provided first_valuator is 0)?
> True, that how it appears to me.
> > This conversion is something that the xf86PostXXXEvent-functions
> > seems to have
> > handled itself previously with a little help by the actual driver
> > (by calling
> > LocalDeviceRec->conversion_proc() from within xf86PostXXXEvent), so
> > it can
> > generate XInput events with the native (sub-pixel precision)
> > resolution for
> > that device which is independent of the screen and also core-events
> > that is
> > scaled to the screen resolution.
> >
> > I'm not sure I like the new way since it limits the value range the
> > driver may
> > report and also put the full responsibility of handling
> > notification of
> > screen resolution changes in the device driver for its device.
> just had a look at the old code, you're right. sounds reasonable to me.
> care to submit a patch?

If you can give me an advice on one little detail, sure...

The function pointers to the conversion routines are stored in a 
LocalDeviceRec structure, which isn't accessible in GetPointerEvents (I guess 
there's no desire in adding a dependency to hw/xfree/common/ from dix/, is 
there?). So I wonder what you think would be the best ('right') way of making 
these functions accessible to GPE (where they are needed as far as I can 

 - Defining additional parameters for the GPE method? (function/structure 
 - Moving the LocalDeviceRec struct into include/inputstr.h? This will pull a 
few other structs with it as well..

Or I split the GPE function into two functions. First create the XInput 
events, then translate the x/y coordinates and create the core events. That 
would place the call to the translation routines into the xf86PostXXXEvent 
where the LocalDeviceRec structure will be known.

Other ways to do it?


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