Enable middle click emulation with xinput

middle-click-emu-enable.py

#!/usr/bin/python

# This small script will enable middle click emulation for all pointing
# devices available. For some reason GNOME does not expose any option at all
# for middle click emulation so the only way to enable it is through the
# `xinput` program, which must be installed for the script to work


from subprocess import check_output, check_call
import re

MID_EMU_ENABLED_RE = "Middle Emulation Enabled"
POINTER_RE = ".*slave\s+pointer.*"

if __name__ == "__main__":
    # Get all the XInput devices
    raw_list = check_output('/usr/bin/xinput').decode()
    pid = []

    for p in raw_list.split("\n"):
        dev = re.split("\t+", p)
        if len(dev) > 2:
            # Check if device is a pointer but not the XTEST device
            # if it's a pointer add it to the list
            if re.match(POINTER_RE, dev[2]) and not "XTEST" in dev[0]:
                pid.append(int(dev[1].split("=")[1]))

    for pointer in pid:
        # Request all available properties for the pointer
        raw_props = check_output(['/usr/bin/xinput',
            'list-props',
            str(pointer)]).decode()
        # Traverse through the properties
        for prop in raw_props.split("\n"):
            # Check if this property is the Middle Click Emulation but not
            # the default one, i.e.
            # THIS
            # 	libinput Middle Emulation Enabled (300):	0
            # NOT THIS
            #   libinput Middle Emulation Enabled Default (301):	0
            if (MID_EMU_ENABLED_RE in prop) and not ("Default" in prop):
                id_match = re.match('.*\((\d+)\).*', prop)
                prop_id = int(id_match.group(1))
                try:
                    # Set the middle click emulation property to 1
                    # thus enabling it!
                    check_call(['/usr/bin/xinput',
                        'set-int-prop',
                        str(pointer),
                        str(prop_id), '8', '1'])
                except CalledProcessError as exc:
                    print("Failed to enable middle click emulation",
                          "for pointing device id=%d" % pointer)