Touchscreen

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If you ever tried to set up a touchscreen device in linux, you might have noticed that it's either working out of the box (besides some calibration) or is very tedious, especially when it is not supported by the kernel.

Introduction

This article assumes that your touchscreen device is supported by the kernel (e.g. by the usbtouchscreen module). That means there exists a /dev/input/event* node for your device. Check out

less /proc/bus/input/devices

to see if your device is listed or try

cat /dev/input/event? # replace ? with the event numbers

for every of your event nodes while touching the display. If you found the corresponding node, it's likely that you will be able to get the device working.

Available X11 drivers

There are a lot of touchscreen input drivers for X11 out there. The most common ones are in the extra repository:

Less common drivers, not contained in the repository, are:

  • xf86-input-magictouch
  • xf86-input-mutouch
  • xf86-input-plpevtch
  • xf86-input-palmax

Proprietary drivers exist for some devices (e.g.: xf86-input-egalaxAUR), but it's recommended to try the open source drivers first.

Depending on your touchscreen device choose an appropriate driver. Again, evdev is likely to be the default if your touchscreen "just works."

evdev drivers

Calibration

Install xinput_calibratorAUR (AUR). Then, run xinput_calibrator and follow the instructions.

Using a touchscreen in a multi-head setup

To use multiple displays (some of which are touchscreens), you need to tell Xorg the mapping between the touch surface and the screen.

This can be done very easily with xinput:

Take for example the setup of having a wacom tablet and an external monitor. When we type xrandr we get a list of our two displays:

$ xrandr
Screen 0: minimum 320 x 200, current 2944 x 1080, maximum 8192 x 8192
LVDS1 connected 1024x768+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
   1024x768       60.0*+
   800x600        60.3     56.2  
   640x480        59.9  
VGA1 connected 1920x1080+1024+0 (normal left inverted right x axis y axis) 477mm x 268mm
   1920x1080      60.0*+
   1600x1200      60.0  
   1680x1050      60.0  
   1680x945       60.0  

You see we have two displays here. LVDS1 and VGA1. LVDS1 is the display internal to the tablet, and VGA1 is the external monitor. We wish to map our stylus input to LVDS1. So we have to find the ID of the stylus input:

 $ xinput --list
⎡ Virtual core pointer                    	id=2	[master pointer  (3)]
⎜   ↳ Virtual core XTEST pointer              	id=4	[slave  pointer  (2)]
⎜   ↳ QUANTA OpticalTouchScreen               	id=9	[slave  pointer  (2)]
⎜   ↳ TPPS/2 IBM TrackPoint                   	id=11	[slave  pointer  (2)]
⎜   ↳ Serial Wacom Tablet WACf004 stylus      	id=13	[slave  pointer  (2)]
⎜   ↳ Serial Wacom Tablet WACf004 eraser      	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)]
    ↳ Sleep Button                            	id=8	[slave  keyboard (3)]
    ↳ AT Translated Set 2 keyboard            	id=10	[slave  keyboard (3)]
    ↳ ThinkPad Extra Buttons                  	id=12	[slave  keyboard (3)]

We see that we have two stylus inputs who's ID's are 13 and 14. We now need to simply map our inputs to our output like so:

xinput --map-to-output 13 LVDS1
xinput --map-to-output 14 LVDS1

Touchegg

Touchegg is a multitouch gesture program, that runs as a user in the background, and adds multitouch support to window managers.