Regulate your screen brightness live with a simple zenity slider. Made this script because the built-in slider in Manjaro's task bar doesn't work on my older iMac and I don't want to put too much effort into fixing it. Based on this script: https://gist.github.com/ViktorNova/a13c6613dd365b2c67b0 NOTE: Check line 60 for window positioning

brightness.py

#!/usr/bin/python3

import sys, subprocess, os, time
from subprocess import PIPE, Popen
from threading  import Thread
from queue import Queue, Empty
import atexit

dir_path = os.path.dirname(os.path.realpath(__file__))
lockfile=os.path.join(dir_path, '.brightness-lock~')
def createlock():
    with open(lockfile, 'w') as fp: 
        pass
def removelock():
    os.remove(lockfile)

if os.path.isfile(lockfile):
    exit(1)

createlock()
atexit.register(removelock)

def enqueue_output(out, queue):
    for line in iter(out.readline, b''):
        queue.put(line)
    out.close()

def popen_stdout(args):
    with open(os.devnull, 'w') as devnull:
        p = Popen(args, stdout=subprocess.PIPE, stderr=devnull)
        p.wait()
        if p.returncode == 1: raise Exception()
        return p.communicate()[0]

def set_brightness(opval):
    int_val = int(opval)
    with open(brightness_file, 'w') as fh:
        fh.write("%d" % int_val)

brightness_files = [
    "/sys/class/backlight/radeon_bl0/brightness",
    "/sys/class/backlight/radeon_bl1/brightness",
]

low = 1
high = 255
window_title = 'Screen Brightness'

index = 0
while index < len(brightness_files):
    try:
        brightness_file = brightness_files[index]
        curr = int(popen_stdout(["cat",brightness_file]).strip())
    except Exception: index += 1
    else: break

if index >= len(brightness_files):
    raise Exception("None of the brightness files exist: %s" %
        ', '.join(brightness_files))

p_wmctrl_init = Popen('wmctrl -R "%s"' % (window_title), shell=True)

p = Popen([
    "zenity","--scale","--print-partial", "--value=%d" % curr,
    "--title",window_title,"--text","","--min-value=%d" % low,
    "--max-value=%d" % high, "--step=1"
], stdout=PIPE, close_fds=True)
q = Queue()
t = Thread(target=enqueue_output, args=(p.stdout, q))
t.daemon = True
t.start()

retcode=1
while retcode != 0:
    p_wmctrl = Popen('wmctrl -r "%s" -R "%s" -e 0,1452,0,-1,-1' \
        % (window_title,window_title), shell=True)
    time.sleep(.025)
    p_wmctrl.wait()
    retcode=p_wmctrl.returncode

while True:
    try: 
        line = q.get_nowait()
    except Empty:
        if not t.is_alive():
            p.wait()
            if p.returncode == 1:
                set_brightness(curr)
            break
    else:
        set_brightness(line)