Youou!!! I managed to make a python script that gives me back the pressure on a new virtual device :-D Now I can use it with Gimp/Krita/... The only remaining part to do is to write a proper C driver and load it directly in the kernel... If you have some idea let me know!
Proof:
So the idea of the script is to read the input from the event file of the graphics tablet, and then create the good events (no more BTN_LEFT, but BTN_TOUCH instead... see my other question/answer here for more details).
To run the script (see below), save it under combine_both.py, and make it executable/install deps:
$ chmod +x combine_both.py
$ sudo pip3 install libevdev
Then, check out the available input devices:
$ xinput list
This should give you several entries, among them one entry like
VEIKK.INC A30 Mouse id=12 [slave pointer (2)]
Note the id (noted as <id veikk> later), as well as the id of the virtual core pointer <id core>:
Virtual core pointer id=2 [master pointer (3)]
Then, you need to know which /dev/input/eventX file to pick, the easiest is to run sudo evtest and read the name of the file corresponding to the VEIKK.INC A30 Mouse. Then run the script with this file in argument like in:
sudo ./combine_both.py /dev/input/event7
This script should output stuff when you try to click/move on the device. Moreover xinput list should also list this device with name Tablet alone Pen (0) with an id <id fake tablet>, and xinput test <id fake tablet> should give you something like (note the 3 columns for x/y/pressure):
$ xinput test 21
[...]
motion a[0]=4151295 a[1]=4151295 a[2]=241
motion a[0]=4060671 a[1]=4060671 a[2]=226
motion a[0]=3969535 a[1]=3969535 a[2]=211
motion a[0]=3878399 a[1]=3878399 a[2]=196
motion a[0]=3787775 a[1]=3787775 a[2]=181
motion a[0]=3696639 a[1]=3696639 a[2]=166
motion a[0]=3605503 a[1]=3605503 a[2]=151
motion a[0]=3514879 a[1]=3514879 a[2]=137
motion a[0]=3423743 a[1]=3423743 a[2]=122
motion a[0]=3332607 a[1]=3332607 a[2]=107
motion a[0]=3241983 a[1]=3241983 a[2]=92
motion a[0]=3150847 a[1]=3150847 a[2]=77
motion a[0]=3059711 a[1]=3059711 a[2]=62
motion a[0]=2969087 a[1]=2969087 a[2]=47
motion a[0]=2877951 a[1]=2877951 a[2]=32
motion a[0]=2650623 a[1]=2650623 a[2]=17
button release 1
Now, to make it work with Gimp/Krita, you want to disable the real mouse (otherwise you have conflicts between the real and fake tablet), with
xinput float <id veikk>
and when you are done you can reattach the real device with
xinput reattach <id veikk> <id core>
In gimp, don't forget to setup Tablet alone Pen (0) with mode=screen in Edit/input devices, and make sure the real tablet VEIKK.INC A30 Mouse is disabled. Finally, chose a good dynamic, like Pencil Generic to test!
Enjoy! (and I'll let you know if I write the C driver at some points)
Script:
#!/usr/bin/env python3
import sys
import libevdev
import datetime
import time
def print_capabilities(l):
v = l.driver_version
print("Input driver version is {}.{}.{}".format(v >> 16, (v >> 8) & 0xff, v & 0xff))
id = l.id
print("Input device ID: bus {:#x} vendor {:#x} product {:#x} version {:#x}".format(
id["bustype"],
id["vendor"],
id["product"],
id["version"],
))
print("Input device name: {}".format(l.name))
print("Supported events:")
for t, cs in l.evbits.items():
print(" Event type {} ({})".format(t.value, t.name))
for c in cs:
if t in [libevdev.EV_LED, libevdev.EV_SND, libevdev.EV_SW]:
v = l.value[c]
print(" Event code {} ({}) state {}".format(c.value, c.name, v))
else:
print(" Event code {} ({})".format(c.value, c.name))
if t == libevdev.EV_ABS:
a = l.absinfo[c]
print(" {:10s} {:6d}".format('Value', a.value))
print(" {:10s} {:6d}".format('Minimum', a.minimum))
print(" {:10s} {:6d}".format('Maximum', a.maximum))
print(" {:10s} {:6d}".format('Fuzz', a.fuzz))
print(" {:10s} {:6d}".format('Flat', a.flat))
print(" {:10s} {:6d}".format('Resolution', a.resolution))
print("Properties:")
for p in l.properties:
print(" Property type {} ({})".format(p.value, p.name))
def print_event(e):
print("Event: time {}.{:06d}, ".format(e.sec, e.usec), end='')
if e.matches(libevdev.EV_SYN):
if e.matches(libevdev.EV_SYN.SYN_MT_REPORT):
print("++++++++++++++ {} ++++++++++++".format(e.code.name))
elif e.matches(libevdev.EV_SYN.SYN_DROPPED):
print(">>>>>>>>>>>>>> {} >>>>>>>>>>>>".format(e.code.name))
else:
print("-------------- {} ------------".format(e.code.name))
else:
print("type {:02x} {} code {:03x} {:20s} value {:4d}".format(e.type.value, e.type.name, e.code.value, e.code.name, e.value))
class Tablet():
def __init__(self, tablet_name):
self.tablet_name = tablet_name
def __enter__(self):
self.dev = libevdev.Device()
self.dev.name = "Tablet alone"
### NB: all the following information needs to be enabled
### in order to recognize the device as a tablet.
# Say that the device will send "absolute" values
self.dev.enable(libevdev.INPUT_PROP_DIRECT)
# Say that we are using the pen (not the erasor), and should be set to 1 when we are at proximity to the device.
# See http://www.infradead.org/~mchehab/kernel_docs_pdf/linux-input.pdf page 9 (=13) and guidelines page 12 (=16), or the https://github.com/linuxwacom/input-wacom/blob/master/4.5/wacom_w8001.c (rdy=proximity)
self.dev.enable(libevdev.EV_KEY.BTN_TOOL_PEN)
self.dev.enable(libevdev.EV_KEY.BTN_TOOL_RUBBER)
# Click
self.dev.enable(libevdev.EV_KEY.BTN_TOUCH)
# Press button 1 on pen
self.dev.enable(libevdev.EV_KEY.BTN_STYLUS)
# Press button 2 on pen, see great doc
self.dev.enable(libevdev.EV_KEY.BTN_STYLUS2)
# Send absolute X coordinate
self.dev.enable(libevdev.EV_ABS.ABS_X,
libevdev.InputAbsInfo(minimum=0, maximum=32767, resolution=100))
# Send absolute Y coordinate
self.dev.enable(libevdev.EV_ABS.ABS_Y,
libevdev.InputAbsInfo(minimum=0, maximum=32767, resolution=100))
# Send absolute pressure
self.dev.enable(libevdev.EV_ABS.ABS_PRESSURE,
libevdev.InputAbsInfo(minimum=0, maximum=8191))
# Use to confirm that we finished to send the informations
# (to be sent after every burst of information, otherwise
# the kernel does not proceed the information)
self.dev.enable(libevdev.EV_SYN.SYN_REPORT)
# Report buffer overflow
self.dev.enable(libevdev.EV_SYN.SYN_DROPPED)
self.uinput = self.dev.create_uinput_device()
print("New device at {} ({})".format(self.uinput.devnode, self.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. And it
# will never be detected in the futur ;-)
time.sleep(1)
# self.simulate_first_click()
self.reset_state()
return self
def __exit__(self, type, value, traceback):
pass
def reset_state(self):
self.is_away = True
self.is_touching = False
self.pressed_button_1 = False
self.pressed_button_2 = False
self.lastmodif = datetime.datetime.now()
def send_events(self, events, is_away=False):
self.lastmodif = datetime.datetime.now()
self.is_away = is_away
self.uinput.send_events(events)
def simulate_first_click(self):
"""Useful only the first time to make sure
xinput detected the input"""
# Reports that the PEN is close to the surface
# Important to make sure xinput can detect (and list)
# the pen. Otherwise, it won't write anything in gimp.
self.uinput.send_events([
libevdev.InputEvent(libevdev.EV_KEY.BTN_TOUCH,
value=0),
libevdev.InputEvent(libevdev.EV_KEY.BTN_TOOL_PEN,
value=1),
libevdev.InputEvent(libevdev.EV_SYN.SYN_REPORT,
value=0),
])
# Says that the pen it out of range of the tablet. Useful
# to make sure you can move your mouse, and to avoid
# strange things during the first draw.
self.uinput.send_events([
libevdev.InputEvent(libevdev.EV_KEY.BTN_TOUCH,
value=0),
libevdev.InputEvent(libevdev.EV_KEY.BTN_TOOL_PEN,
value=0),
libevdev.InputEvent(libevdev.EV_SYN.SYN_REPORT,
value=0),
])
def send_state_no_pos(self, is_away=False):
self.lastmodif = datetime.datetime.now()
self.is_away = is_away
print("Away: {}, Touching: {}".format(self.is_away, self.is_touching))
self.uinput.send_events([
libevdev.InputEvent(libevdev.EV_KEY.BTN_TOUCH,
value=1 if self.is_touching else 0),
libevdev.InputEvent(libevdev.EV_KEY.BTN_TOOL_PEN,
value=1 if not self.is_away else 0),
libevdev.InputEvent(libevdev.EV_KEY.BTN_STYLUS,
value=1 if self.pressed_button_1 else 0),
libevdev.InputEvent(libevdev.EV_KEY.BTN_STYLUS2,
value=1 if self.pressed_button_2 else 0),
libevdev.InputEvent(libevdev.EV_SYN.SYN_REPORT,
value=0),
])
def touch_press(self):
self.is_touching = True
self.send_state_no_pos()
def touch_release(self):
self.is_touching = False
self.send_state_no_pos()
def button_1_press(self):
self.pressed_button_1 = True
self.send_state_no_pos()
def button_1_release(self):
self.pressed_button_1 = False
self.send_state_no_pos()
def button_2_press(self):
self.pressed_button_2 = True
self.send_state_no_pos()
def button_2_release(self):
self.pressed_button_2 = False
self.send_state_no_pos()
def move_x(self, abs_x):
self.send_events([
libevdev.InputEvent(libevdev.EV_ABS.ABS_X,
value=abs_x),
libevdev.InputEvent(libevdev.EV_SYN.SYN_REPORT,
value=0),
])
def move_y(self, abs_y):
self.send_events([
libevdev.InputEvent(libevdev.EV_ABS.ABS_Y,
value=abs_y),
libevdev.InputEvent(libevdev.EV_SYN.SYN_REPORT,
value=0),
])
def change_pressure(self, pressure):
self.send_events([
libevdev.InputEvent(libevdev.EV_ABS.ABS_PRESSURE,
value=pressure),
libevdev.InputEvent(libevdev.EV_SYN.SYN_REPORT,
value=0),
])
def handle_event(self, e):
if e.matches(libevdev.EV_ABS.ABS_PRESSURE):
self.change_pressure(e.value)
elif e.matches(libevdev.EV_ABS.ABS_X):
self.move_x(e.value)
elif e.matches(libevdev.EV_ABS.ABS_Y):
self.move_y(e.value)
elif e.matches(libevdev.EV_KEY.BTN_LEFT):
if e.value == 1:
self.touch_press()
else:
self.touch_release()
elif e.matches(libevdev.EV_SYN.SYN_REPORT):
pass
else:
print("Unkown event:")
print_event(e)
def main(args):
path = args[1]
try:
with Tablet("Tablet alone") as tablet:
### Read the events from real graphics tablet
with open(path, "rb") as fd:
l = libevdev.Device(fd)
print_capabilities(l)
print("################################\n"
"# Waiting for events #\n"
"################################")
while True:
try:
ev = l.events()
for e in ev:
print_event(e)
tablet.handle_event(e)
except libevdev.EventsDroppedException:
for e in l.sync():
print_event(e)
tablet.handle_event(e)
except KeyboardInterrupt:
pass
except IOError as e:
import errno
if e.errno == errno.EACCES:
print("Insufficient permissions to access {}".format(path))
elif e.errno == errno.ENOENT:
print("Device {} does not exist".format(path))
else:
raise e
except OSError as e:
print(e)
if __name__ == "__main__":
if len(sys.argv) != 2:
print("Usage: sudo {} /dev/input/eventX".format(sys.argv[0]))
print(" $ sudo evtest")
print("can help you to know which file to use.")
sys.exit(1)
main(sys.argv)
Best Answer
Running Linux (Ubuntu or Debian)
If it runs Android, it has Linux drivers, since Android runs on a Linux kernel. However Google maintains its own forked version of the Linux kernel source, and not all drivers have been ported back. There is no official Ubuntu distribution for ARM, but there are people working on an informal ARM port. That page lists OMAP chips but not Tegra. There is a Tegra porting effort (for the Toshiba AC100) as well, but it's not completely working. If you don't find what you're looking for, try Debian, which officially supports ARM (but doesn't support recent tablets out-of-the-box either).
On a tablet, a problem you'll run into is the touchscreen. Touchscreen support on Linux is still work in progress.
If you manage to get all the hardware working, most open-source applications will be just one
apt-get installaway. Forget about running any closed-source PC application.Running an official Linux-based tablet OS
If you have a choice of tablets, consider looking for a model sold with Maemo or MeeGo. Maemo was only released on a few high-end phones, none that qualifies as a proper tablet as far as I know. Maemo tablets have been announced. Beware that the future of Maemo and MeeGo is uncertain since Nokia is no longer actively supporting them.
Maemo and MeeGo are actual Linux systems, with a custom X-based GUI. Most common Linux programs will run on them, and may either be one
apt-getorzyppercommand away, or may require recompiling.Running Android
Android is based on a Linux kernel, but it lacks a few kernel features, and the userland is completely different. The advantage of Android is that it'll have all the drivers you need. The main downsides are that it's difficult to find Android applications that are meant for offline work, and that the user interface is intended for small screens with only full-screen windows. Nonetheless, you can install many development tools on Android, including BusyBox (basic command-line tools), scripting languages (Perl, Python, Lua, Ruby, ...), but GUI applications are a problem since Android doesn't use X. You'll need to find an Android editor that suits you, and so on.