Yrurtj

I would like to simulate a graphics tablet (like wacom's ones) from a script. The "good" way to proceed seems to use libevent that is an abstract layer above uinput. So I tried to write a script that sends some event like EV_ABS.ABS_X or EV_ABS.ABS_PRESSURE, using the python library of libevent. Unfortunately, when I use Krita/Gimp/... to test it, the line that it draws does not change it's shape depending on the pressure, and xinput test-xi2 does not display any pressure event. Any idea why?

Thanks!

Steps to reproduce

Execute the code below:

sudo pip3 install libevdev

chmod +x ./simulate_graphics_tablet.py

sudo ./simulate_graphics_tablet.py

Then you have 30 seconds to:

• either run xinput list and then xinput test-xi2 <number of Tablet alone>
  


• or open Gimp, go to 'Edit/Input device' and configure the device 'Tablet alone' to 'Screen', save and close the pop up,create a new file (Ctrl-N), Zoom and press 'tab' to have a drawing surface covering most of the screen. Switch to brush using 'p' key, by making sure the brush is set to Pressure size.

What I get: a uniform line, and on xinput I don't have any reference to pressure and I just have things like:

EVENT type 17 (RawMotion)

    device: 11 (11)

    detail: 0

    flags: 

    valuators:

          0: 29897.54 (29897.54)

          1: 29897.54 (29897.54)

What I expect: a line whose size is not constatn (the script increase the pressure linearly), or to see some pressure-related events on xinput.

#!/usr/bin/env python3

import sys

import libevdev

import time



def main(args):

    dev = libevdev.Device()

    dev.name = "Tablet alone"

    dev.enable(libevdev.EV_ABS.ABS_X,

               libevdev.InputAbsInfo(minimum=0, maximum=32767))

    dev.enable(libevdev.EV_ABS.ABS_Y,

               libevdev.InputAbsInfo(minimum=0, maximum=32767))

    dev.enable(libevdev.EV_ABS.ABS_Z,

               libevdev.InputAbsInfo(minimum=0, maximum=8191))

    # dev.enable(libevdev.EV_ABS.ABS_0B,

    #            libevdev.InputAbsInfo(minimum=0, maximum=8191))

    # dev.enable(libevdev.EV_ABS.ABS_DISTANCE,

    #            libevdev.InputAbsInfo(minimum=0, maximum=8191))

    dev.enable(libevdev.EV_ABS.ABS_PRESSURE,

               libevdev.InputAbsInfo(minimum=0, maximum=8191))

    dev.enable(libevdev.EV_MSC.MSC_SCAN)

    dev.enable(libevdev.EV_KEY.KEY_P)

    dev.enable(libevdev.EV_KEY.BTN_LEFT)

    dev.enable(libevdev.EV_KEY.BTN_RIGHT)

    dev.enable(libevdev.EV_KEY.BTN_MIDDLE)

    dev.enable(libevdev.EV_KEY.BTN_TOUCH)

    dev.enable(libevdev.EV_SYN.SYN_REPORT)

    dev.enable(libevdev.EV_SYN.SYN_CONFIG)

    dev.enable(libevdev.EV_SYN.SYN_MT_REPORT)

    dev.enable(libevdev.EV_SYN.SYN_DROPPED)

    dev.enable(libevdev.EV_SYN.SYN_04)

    dev.enable(libevdev.EV_SYN.SYN_05)

    dev.enable(libevdev.EV_SYN.SYN_06)

    dev.enable(libevdev.EV_SYN.SYN_07)

    dev.enable(libevdev.EV_SYN.SYN_08)

    dev.enable(libevdev.EV_SYN.SYN_09)

    dev.enable(libevdev.EV_SYN.SYN_0A)

    dev.enable(libevdev.EV_SYN.SYN_0B)

    dev.enable(libevdev.EV_SYN.SYN_0C)

    dev.enable(libevdev.EV_SYN.SYN_0D)

    dev.enable(libevdev.EV_SYN.SYN_0E)

    dev.enable(libevdev.EV_SYN.SYN_MAX)

    try:

        uinput = dev.create_uinput_device()

        print("New device at {} ({})".format(uinput.devnode, uinput.syspath))

        # Sleep for a bit so udev, libinput, Xorg, Wayland, ...

        # all have had a chance to see the device and initialize

        # it. Otherwise the event will be sent by the kernel but

        # nothing is ready to listen to the device yet.

        print("Waiting 30s to let you:")

        print("1) open Gimp")

        print("2) Go to 'Edit/Input device' and configure the device 'Tablet alone' to 'Screen'.")

        print("3) Save and close the pop up")

        print("4) Create a new file (Ctrl-N)")

        print("5) Zoom and press 'tab' to have a drawing surface coverint most of the screen.")

        print("6) Switch to brush using 'p' key.")

        time.sleep(30)



        pc = 0

        direc = +1

        already_pressed_one = False

        # uinput.send_events([

        #     libevdev.InputEvent(libevdev.EV_KEY.KEY_P, 1),

        #     libevdev.InputEvent(libevdev.EV_SYN.SYN_REPORT, 0),

        # ])

        # time.sleep(0.1)

        # uinput.send_events([

        #     libevdev.InputEvent(libevdev.EV_KEY.KEY_P, 0),

        #     libevdev.InputEvent(libevdev.EV_SYN.SYN_REPORT, 0),

        # ])

        for i in range(250):

            pc_ = pc/100

            val_x = int(pc_*10000 + (1-pc_)*17767)

            val_y = int(pc_*5000 + (1-pc_)*22767)

            val_pres = int(pc_*10 + (1-pc_)*6000)

            print("Will send: x={}, y={}, press={} (pc={})".format(

                val_x,

                val_y,

                val_pres,

                pc))

            uinput.send_events([

                libevdev.InputEvent(libevdev.EV_ABS.ABS_PRESSURE, val_pres),

                libevdev.InputEvent(libevdev.EV_ABS.ABS_X, val_y),

                libevdev.InputEvent(libevdev.EV_ABS.ABS_Y, val_y),

                libevdev.InputEvent(libevdev.EV_SYN.SYN_REPORT, 0),

            ])

            pc += direc

            if not already_pressed_one:

                print("Press!")

                uinput.send_events([

                    libevdev.InputEvent(libevdev.EV_KEY.BTN_LEFT, 1),

                    libevdev.InputEvent(libevdev.EV_SYN.SYN_REPORT, 0),

                ])                

                already_pressed_one = True

            if pc >= 100 or pc <=0 :

                print("Release click.")

                uinput.send_events([

                    libevdev.InputEvent(libevdev.EV_KEY.BTN_LEFT, 0),

                    libevdev.InputEvent(libevdev.EV_SYN.SYN_REPORT, 0),

                ])

                if pc >= 100:

                    pc = 100

                    direc = -1

                if pc <= 0:

                    pc = 0

                    direc = +1

                time.sleep(10)

                print("Press!")

                uinput.send_events([

                    libevdev.InputEvent(libevdev.EV_KEY.BTN_LEFT, 1),

                    libevdev.InputEvent(libevdev.EV_SYN.SYN_REPORT, 0),

                ])

                already_pressed_one = True

            time.sleep(0.1)



    except KeyboardInterrupt:

        pass

    except OSError as e:

        print(e)





if __name__ == "__main__":

    if len(sys.argv) > 2:

        print("Usage: {}")

        sys.exit(1)

    main(sys.argv)

EDIT:
I tried to play with ABS_KEY.BTN_TOOL_PEN as explained here, but I don't know why the second I enable it it stops being detected by xinput list:

dev.enable(libevdev.EV_KEY.BTN_TOOL_PEN)