Send events to a virtual input device

Instead of sending mouse move and click events to the system’s main
device, create a separate virtual input device that registers itself as
a Wacom tablet. Most importantly, this enables pressure and tilt
sensitivity which is picked up by programs such as GIMP or Krita.

Because this uses the `libevdev` library that is only supported on
Linux, this commit breaks compatibility with Windows and (probably)
macOS.

Furthermore, because creating virtual input devices is restricted to
root, the script must now be run with `sudo`. Failing to do so will most
likely trigger a permission error.

CLI changes
-----------

* Drop the `--orientation` flag. Orientation of the device can now be
configured just like any other Wacom device using `xinput`:

```
xinput --set-prop "reMarkable tablet stylus" "Wacom Rotation" <orientation>
```

where `<orientation>` is one of 0 (for “right” orientation), 1 (for
“portrait” orientation), 2 (for “left” orientation) or 3 (for “reversed
portrait” orientation).

* Drop the `--monitor` flag. This can also be configured using `xinput`
instead:

```
xinput --map-to-output "reMarkable tablet stylus" <output>
```

where `<output>` is the name of an output currently connected to the
device, as listed by `xrandr` (e.g. LVDS1).

* Drop the `--offset` flag. This didn’t seem to be used anywhere in the
code.

* Drop the `--threshold` flag. The pressure threshold required to
trigger a click event can be configured using `xinput`:

```
xinput --set-prop "reMarkable tablet stylus" "Wacom Pressure Threshold" 1000
```

where `1000` can be replaced by an arbitrary pressure threshold. On my
machine, the default seems to be 26. The pressure profile (mapping the
actual pressure put on the stylus to the pressure actually received by
the drawing programs) can also be adjusted using the following prop:

```
xinput --set-prop "reMarkable tablet stylus" "Wacom Pressurecurve" 50 0
100 50
```

Dependencies changes
--------------------

Replaced dependency pynput with libevdev (which requires that libevdev
is present on the system). Dropped dependency `screeninfo` because
assigning the input to a monitor is no longer done through this program.

remarkable_mouse/remarkable_mouse.py

@@ -8,61 +8,99 @@ import os
 import sys
 import struct
 from getpass import getpass
+
+import libevdev
 import paramiko
-from screeninfo import get_monitors
-from pynput.mouse import Button, Controller
-
-# evtype_sync = 0
-# evtype_key = 1
-e_type_abs = 3
-
-# evcode_stylus_distance = 25
-# evcode_stylus_xtilt = 26
-# evcode_stylus_ytilt = 27
-e_code_stylus_xpos = 1
-e_code_stylus_ypos = 0
-e_code_stylus_pressure = 24
-# evcode_finger_xpos = 53
-# evcode_finger_ypos = 54
-# evcode_finger_pressure = 58
-
-stylus_width = 15725
-stylus_height = 20951
-# finger_width = 767
-# finger_height = 1023
-
-mouse = Controller()
+
 logging.basicConfig(format='%(message)s')
 log = logging.getLogger(__name__)
 
-# mouse state
-LIFTED = 0
-PRESSED = 1
-
-
-# remap wacom coordinates in various orientations
-def fit(x, y, stylus_width, stylus_height, monitor, orientation):
-
-    if orientation == 'vertical':
-        y = stylus_height - y
-    elif orientation == 'right':
-        x, y = y, x
-        stylus_width, stylus_height = stylus_height, stylus_width
-    elif orientation == 'left':
-        x, y = stylus_height - y, stylus_width - x
-        stylus_width, stylus_height = stylus_height, stylus_width
-
-    ratio_width, ratio_height = monitor.width / stylus_width, monitor.height / stylus_height
-    scaling = ratio_width if ratio_width > ratio_height else ratio_height
-
-    return (
-        scaling * (x - (stylus_width - monitor.width / scaling) / 2),
-        scaling * (y - (stylus_height - monitor.height / scaling) / 2)
+# Maximum value that can be reported by the Wacom driver for the X axis
+MAX_ABS_X = 20967
+
+# Maximum value that can be reported by the Wacom driver for the Y axis
+MAX_ABS_Y = 15725
+
+def create_local_device():
+    """
+    Create a virtual input device on this host that has the same
+    characteristics as a Wacom tablet.
+
+    :returns: virtual input device
+    """
+    device = libevdev.Device()
+
+    # Set device properties to emulate those of Wacom tablets
+    device.name = 'reMarkable tablet'
+    device.id = {
+        'bustype': 24,
+        'vendor': 1386,
+        'product': 0,
+        'version': 54
+    }
+
+    # Enable buttons supported by the digitizer
+    device.enable(libevdev.EV_KEY.BTN_TOOL_PEN)
+    device.enable(libevdev.EV_KEY.BTN_TOOL_RUBBER)
+    device.enable(libevdev.EV_KEY.BTN_TOUCH)
+    device.enable(libevdev.EV_KEY.BTN_STYLUS)
+    device.enable(libevdev.EV_KEY.BTN_STYLUS2)
+
+    # Enable position, tilt, distance and pressure change events
+    device.enable(
+        libevdev.EV_ABS.ABS_X,
+        libevdev.InputAbsInfo(
+            minimum=0,
+            maximum=MAX_ABS_X
+        )
+    )
+    device.enable(
+        libevdev.EV_ABS.ABS_Y,
+        libevdev.InputAbsInfo(
+            minimum=0,
+            maximum=MAX_ABS_Y
+        )
+    )
+    device.enable(
+        libevdev.EV_ABS.ABS_PRESSURE,
+        libevdev.InputAbsInfo(
+            minimum=0,
+            maximum=4095
+        )
+    )
+    device.enable(
+        libevdev.EV_ABS.ABS_DISTANCE,
+        libevdev.InputAbsInfo(
+            minimum=0,
+            maximum=255
+        )
+    )
+    device.enable(
+        libevdev.EV_ABS.ABS_TILT_X,
+        libevdev.InputAbsInfo(
+            minimum=-9000,
+            maximum=9000
         )
+    )
+    device.enable(
+        libevdev.EV_ABS.ABS_TILT_Y,
+        libevdev.InputAbsInfo(
+            minimum=-9000,
+            maximum=9000
+        )
+    )
+
+    return device.create_uinput_device()
 
+def open_remote_device(args, file='/dev/input/event0'):
+    """
+    Open a remote input device via SSH.
 
-def open_eventfile(args, file='/dev/input/event0'):
-    """ssh to reMarkable and open event0"""
+    :param args: command-line arguments
+    :param file: path to the input device on the device
+    :returns: read-only stream of input events
+    """
+    log.info("Connecting to input '{}' on '{}'".format(file, args.address))
 
     if args.key is not None:
         password = None
@@ -94,90 +132,76 @@ def open_eventfile(args, file='/dev/input/event0'):
         pkey=pkey,
         look_for_keys=False
     )
-    print("Connected to {}".format(args.address))
 
     # Start reading events
     _, stdout, _ = client.exec_command('cat ' + file)
 
     return stdout
 
+def pipe_device(args, remote_device, local_device):
+    """
+    Pipe events from a remote device to a local device.
 
-def read_tablet(args):
-    """Loop forever and map evdev events to mouse"""
-
-    state = LIFTED
-    new_x = new_y = False
-
-    monitor = get_monitors()[args.monitor]
-    log.debug('Chose monitor: {}'.format(monitor))
-
-    stdout = open_eventfile(args)
+    :param args: command-line arguments
+    :param remote_device: stream of events to read from
+    :param local_device: local virtual device to write events to
+    """
+    # While debug mode is active, we log events grouped together between
+    # SYN_REPORT events. Pending events for the next log are stored here
+    pending_events = []
 
     while True:
-        _, _, e_type, e_code, e_value = struct.unpack('2IHHi', stdout.read(16))
-
-        if e_type == e_type_abs:
-
-            # handle x direction
-            if e_code == e_code_stylus_xpos:
-                log.debug(e_value)
-                x = e_value
-                new_x = True
-
-            # handle y direction
-            if e_code == e_code_stylus_ypos:
-                log.debug('\t{}'.format(e_value))
-                y = e_value
-                new_y = True
-
-            # handle draw
-            if e_code == e_code_stylus_pressure:
-                log.debug('\t\t{}'.format(e_value))
-                if e_value > args.threshold:
-                    if state == LIFTED:
-                        log.info('PRESS')
-                        state = PRESSED
-                        mouse.press(Button.left)
-                else:
-                    if state == PRESSED:
-                        log.info('RELEASE')
-                        state = LIFTED
-                        mouse.release(Button.left)
+        e_time, e_millis, e_type, e_code, e_value = struct.unpack('2IHHi', remote_device.read(16))
+        e_bit = libevdev.evbit(e_type, e_code)
+        event = libevdev.InputEvent(e_bit, value=e_value)
 
+        local_device.send_events([event])
 
-            # only move when x and y are updated for smoother mouse
-            if new_x and new_y:
-                mapped_x, mapped_y = fit(x, y, stylus_width, stylus_height, monitor, args.orientation)
-                mouse.move(
-                    monitor.x + mapped_x - mouse.position[0],
-                    monitor.y + mapped_y - mouse.position[1]
+        if args.debug:
+            if e_bit == libevdev.EV_SYN.SYN_REPORT:
+                event_repr = ', '.join(
+                    '{} = {}'.format(
+                        event.code.name,
+                        event.value
+                    ) for event in pending_events
                 )
-                new_x = new_y = False
+                log.debug('{}.{:0>6} - {}'.format(e_time, e_millis, event_repr))
+                pending_events = []
+            else:
+                pending_events += [event]
 
 def main():
-
     try:
         parser = argparse.ArgumentParser(description="use reMarkable tablet as a mouse input")
-        parser.add_argument('--orientation', default='left', choices=['vertical', 'left', 'right'])
-        parser.add_argument('--monitor', default=0, type=int, metavar='NUM', help="monitor to use")
-        parser.add_argument('--offset', default=(0, 0), type=int, metavar=('x', 'y'), nargs=2, help="offset mapped region on monitor")
         parser.add_argument('--debug', action='store_true', default=False, help="enable debug messages")
         parser.add_argument('--key', type=str, metavar='PATH', help="ssh private key")
         parser.add_argument('--password', default=None, type=str, help="ssh password")
         parser.add_argument('--address', default='10.11.99.1', type=str, help="device address")
-        parser.add_argument('--threshold', default=1000, type=int, help="stylus pressure threshold (default 1000)")
 
         args = parser.parse_args()
 
         if args.debug:
-            print('Debugging enabled...')
             logging.getLogger('').setLevel(logging.DEBUG)
             log.setLevel(logging.DEBUG)
+            log.info('Debugging enabled...')
+        else:
+            logging.getLogger('').setLevel(logging.INFO)
+            log.setLevel(logging.INFO)
 
-        read_tablet(args)
+        try:
+            local_device = create_local_device()
+            log.info("Created virtual input device '{}'".format(local_device.devnode))
+        except PermissionError:
+            log.error('Insufficient permissions for creating a virtual input device')
+            log.error('Make sure you run this program as root')
+            sys.exit(1)
+
+        remote_device = open_remote_device(args)
+        pipe_device(args, remote_device, local_device)
     except KeyboardInterrupt:
         pass
-
+    except EOFError:
+        pass
 
 if __name__ == '__main__':
     main()

setup.py

@@ -20,8 +20,7 @@ setup(
     },
     install_requires=[
         'paramiko',
-        'screeninfo',
-        'pynput'
+        'libevdev'
     ],
     classifiers=[
         "Programming Language :: Python :: 3",