Print out changes to evdev multitouch state

state.py

#!/usr/bin/env python3

import sys
import libevdev

AXES = {
    'ABS_MT_TRACKING_ID': libevdev.EV_ABS.ABS_MT_TRACKING_ID,
    'ABS_MT_POSITION_X':  libevdev.EV_ABS.ABS_MT_POSITION_X,
    'ABS_MT_POSITION_Y':  libevdev.EV_ABS.ABS_MT_POSITION_Y
}

def slot_state(slot):
    return { k:slot[v] for (k,v) in AXES.items() }

def slot_states(device):
    return [ slot_state(s) for s in device.slots ]

def print_states(states):
    for state in states:
        trk_id = state['ABS_MT_TRACKING_ID']
        x = state['ABS_MT_POSITION_X']
        y = state['ABS_MT_POSITION_Y']
        print(f"{trk_id}: {x}, {y}")

def active_contacts(device):
    return [ x for x in slot_states(device) if x['ABS_MT_TRACKING_ID'] != -1 ]

def slot_status(device):
    return [ 'X' if x['ABS_MT_TRACKING_ID'] != -1 else '.' for x in slot_states(device) ]

def print_update(device):
    active = [ x['ABS_MT_TRACKING_ID'] for x in active_contacts(device) ]
    count = len(active)
    status = slot_status(device)
    print(f" >> {''.join(status)} ({count} active contacts: {active}) {' '*30}")
    #print(active)

def monitor_contact_count(device):
    while True:
        print_update(device)
        for e in device.events():
            if not e.matches(libevdev.EV_SYN.SYN_REPORT):
                continue
            print_update(device)

def main(args):
    if len(args) != 2:
        print(f"Usage: {args[0]} <file>")
        return
    fd = open(args[1], 'rb')
    device = libevdev.Device(fd)
    #print_slot_states(active_contacts(device))
    monitor_contact_count(device)

if __name__ == "__main__":
    main(sys.argv)