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How to map external touch screen to ignore laptop in multimonitor setup?

rated 0 times [ 1] [ 0] / answers: 1 / hits: 1435 / 2 Years ago, wed, december 1, 2021, 5:16:03

Kubuntu 20.04 with extended display. Laptop screen has no touch. External screen is a touchscreen. When touching the center of the external screen, the mouse points at the border between two screens. It's calculated as if the touchscreen's width is the width of both screens together.

How can I make the touchscreen fit only the external screen? Also, it's a portable screen. So I would like to make the change permanent between disconnects.

sza@sza-Lenovo-ThinkBook-15-IIL:~$ xinput

⎡ Virtual core pointer                          id=2    [master pointer  (3)]

⎜   ↳ Virtual core XTEST pointer                id=4    [slave  pointer  (2)]

⎜   ↳ Logitech M705                             id=12   [slave  pointer  (2)]

⎜   ↳ Logitech K750                             id=13   [slave  pointer  (2)]

⎜   ↳ G2Touch Multi-Touch by G2TSP              id=9    [slave  pointer  (2)]

⎜   ↳ Elan Touchpad                             id=14   [slave  pointer  (2)]

⎣ Virtual core keyboard                         id=3    [master keyboard (2)]

    ↳ Virtual core XTEST keyboard               id=5    [slave  keyboard (3)]

    ↳ Power Button                              id=6    [slave  keyboard (3)]

    ↳ Video Bus                                 id=7    [slave  keyboard (3)]

    ↳ Power Button                              id=8    [slave  keyboard (3)]

    ↳ Integrated Camera: Integrated C           id=11   [slave  keyboard (3)]

    ↳ Ideapad extra buttons                     id=15   [slave  keyboard (3)]

    ↳ AT Translated Set 2 keyboard              id=16   [slave  keyboard (3)]

    ↳ Logitech K750                             id=17   [slave  keyboard (3)]



sza@sza-Lenovo-ThinkBook-15-IIL:~$ xinput list-props 9

Device 'G2Touch Multi-Touch by G2TSP':

        Device Enabled (172):   1

        Coordinate Transformation Matrix (174): 1.000000, 0.000000, 0.000000, 0.000000, 1.000000, 0.000000, 0.000000, 0.000000, 1.000000

        libinput Calibration Matrix (312):      1.000000, 0.000000, 0.000000, 0.000000, 1.000000, 0.000000, 0.000000, 0.000000, 1.000000

        libinput Calibration Matrix Default (313):      1.000000, 0.000000, 0.000000, 0.000000, 1.000000, 0.000000, 0.000000, 0.000000, 1.000000

        libinput Send Events Modes Available (295):     1, 0

        libinput Send Events Mode Enabled (296):        0, 0

        libinput Send Events Mode Enabled Default (297):        0, 0

        Device Node (298):      "/dev/input/event4"

        Device Product ID (299):        10900, 22093



sza@sza-Lenovo-ThinkBook-15-IIL:~$ xrandr

Screen 0: minimum 320 x 200, current 3840 x 1080, maximum 16384 x 16384

eDP-1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 344mm x 194mm

   1920x1080     60.06*+  60.01    59.97    59.96    59.93  

   ...

DP-1 connected 1920x1080+1920+0 (normal left inverted right x axis y axis) 344mm x 195mm

   1920x1080     60.00*+  50.00    59.94    30.00    29.97  

   ...

HDMI-1 disconnected (normal left inverted right x axis y axis)

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diket

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1 Year ago

answered 2 Years ago ideobedi · Accepted Answer

You may find the following xinput option to be of interest:

--map-to-output device crtc

    Restricts  the  movements  of  the absolute device to the RandR

    crtc. The output name must match a currently  connected  output

    (see  xrandr(1)).  If  the  NVIDIA binary driver is detected or

    RandR 1.2 or later is not available, a Xinerama output  may  be

    specified as "HEAD-N", with N being the Xinerama screen number.

    This option has no effect on relative devices.

Based on info you've provided, the following command may do what you need:

xinput --map-to-output "G2Touch Multi-Touch by G2TSP" DP-1

If this command does what you want, you can set up udev to run it whenever the touch screen is connected. However, xinput will not work when called directly because udev is a system service that runs outside of X. It's necessary to create a watcher script inside of X that udev can notify.

Install inotify-tools.

Create the watcher script. Set it up to run after the user has logged into X. This can be done via the display manager or desktop environment, depending on whether you want the script running for all users or select users.

#!/usr/bin/env bash

inotifywait -m /tmp |

   while read path action file; do

      if [[ "$file" =~ touchscreen-attach ]] ; then

         [[ "$action" = "OPEN" ]] &&

            sleep 1 &&

            xinput --map-to-output "G2Touch Multi-Touch by G2TSP" DP-1

      fi

   done

Use lsusb to get the device id of the touch screen. It will be in the form idVendor:idProduct (eg, 2a94:564d).

Create a file /etc/udev/rules.d/10-touchscreen.rules:

ACTION=="add", SUBSYSTEM=="usb", ATTRS{idVendor}=="2a94", ATTRS{idProduct}=="564d", RUN+="touch /tmp/touchscreen-attach"

See also:

How to execute a shellscript when I plug-in a USB-device

How to use inotifywait to watch a directory for creation of files of a specific extension

JackDaniels points out that KDE has input settings associated with Graphic Tablets. They work for my Wacom tablet, but not my laptop touch screen. If this works with your external touch screen, it would be much easier to set up than what I've described above.