Why multi-touch fail to work for multi-display?

Leslie Zhai xiangzhai83 at gmail.com
Tue Oct 22 10:03:13 CEST 2013

Hi Peter,

Thanks for your reply :)

Coordinate Transformation Matrix is so cool, my LeslieMT is too 
Even if LeslieMT is able to work, but it is not easy to configure the 
device path, for example, /dev/input/event3 might be changed when a 
Projected Capacitive touch screen USB device plug out/in or Linux box 

But it needs to read the device file descriptor to get 9 eGalax touch 
screen devices` (X, Y) value simultaneously, then recognize the proper 
gesture, so ugly and dull LeslieMT meets the "special" project requirement.

Best Regards,


> On Sat, Oct 19, 2013 at 11:31:08AM +0800, Leslie Zhai wrote:
>> Hi Xorg developers,
>> I use Projected Capacitive touch screen device
>> http://en.wikipedia.org/wiki/Touchscreen#Projected_capacitance
>> It can be pasted on the normal monitor, then it is able to touch, the
>> cursor
>> will move to the position where touched. It experienced like iphone and
>> other
>> single touch screen device.
>> But when I put multiple Projected Capacitive touch screen devices on
>> several
>> monitors, then touch some of them simultaneously, the cursor of X Window
>> was
>> only moving in the first monitor, even though it was able to move to other
>> monitors` display, it still failed to show the correct position.
> default behaviour is to map the device to the set of all monitors together.
> if you want to map a device to a specific montior you need to set the input
> transformation matrix.
> http://sourceforge.net/apps/mediawiki/linuxwacom/index.php?title=Dual_and_Multi-Monitor_Set_Up
> because output can change positions, size, orientation, etc. at any time
> there is no static (i.e. xorg.conf) option to configure this, it needs to be
> set at runtime.
> one matrix exists per device, so you can configure multiple touchscreens
> easily enough.
> Cheers,
>     Peter

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