#!/usr/bin/env python

# Change brightness incrementally using xrandr

# since the older XF86VidModeSetGammaRamp() method no longer works.

# Usage: xbright [val|+val|-val]

# val is floating point and can go from 0 to 1 (or maybe higher?)

import sys, os

# There is an xrandr library for python:

# from Xlib import X, display

# from Xlib.ext import randr

# but it has no documentation and no examples, so rather than spending

# 2 days trying to figure out the API from reading the entire source,

# I can spend 10 minutes and parse output from /usr/bin/xrandr instead:

import subprocess

XRANDR = "/usr/bin/xrandr"

def get_brightness():

# xrandr --verbose | grep -i brightness

proc = subprocess.Popen([XRANDR, "--verbose"],

shell=False, stdout=subprocess.PIPE)

s = proc.communicate()[0]

if not s:

print("No output from xrandr --verbose!")

sys.exit(1)

monitor = None

for line in s.split('\n'):

line = line.strip()

words = line.split()

if len(words) > 1 and words[1] == "connected":

monitor = words[0]

elif line.startswith("Brightness: "):

if not monitor:

print("Warning: couldn't tell which monitor to use")

return (float(line[12:]), monitor)

print("No Brightness line in xrandr --verbose!")

sys.exit(1)

def set_brightness(new_brightness):

args = [ XRANDR ]

if monitor:

args.append("--output")

args.append(monitor)

args.append("--brightness")

args.append(str(new_brightness))

subprocess.call(args)

def Usage():

print("Usage: %s [b | +b | -b]" % os.path.basename(sys.argv[0]))

sys.exit(1)

if __name__ == "__main__":

# We need to call cur_brightness even if we're setting an absolute

# brightness, because we need to get the relevant monitor.

cur_brightness, monitor = get_brightness()

if len(sys.argv) <= 1:

print("Currently brightness is %.1f on monitor %s\n" % (cur_brightness,

monitor))

Usage()

if sys.argv[1][0] == '-':

b = cur_brightness - float(sys.argv[1][1:])

if b < 0: b = 0

elif sys.argv[1][0] == '+':

b = cur_brightness + float(sys.argv[1][1:])

if b > 1: b = 1

else:

b = float(sys.argv[1])

set_brightness(b)