Touchscreens (mutouch) & multiple heads

[Michael Smith]

Peter Hutterer wrote:
> On Fri, Apr 15, 2011 at 12:11:09PM -0400, Michael Smith wrote:
>> Hi,
>>
>> I have an Intel 915GM with two heads, each 800x600. One head feeds a
>> touchscreen using the mutouch driver. Touchscreen input is being
>> scaled by the total screen dimensions (1600x600), rather than just
>> the 800x600 part of the display that is connected to the
>> touchscreen.

>> Where is the right place to add a way to override the screen width
>> used for converting raw coordinates? Or is there already a way to do
>> this?
> 
> http://www.x.org/wiki/XInputCoordinateTransformationMatrixUsage
> run-time only though

Thanks! I ended up doing something similar by fiddling with negative 
MinY/MaxY values.

It's encouraging to know I'm not the only one with this use case (i.e. 
Wacom tablet users also solve the same problem).

The transformation matrix may be a decent way to implement this 
internally, but as a user interface it's pretty awful - it would be nice 
to have a knob that says input device X is associated with the bounds of 
screen Y so you don't have to manually recalculate your matrix if you 
dynamically add or remove a screen or change a resolution.

Mike