Added first version of the script.

Signed-off-by: Olivier Gayot <olivier.gayot@sigexec.com>

1 files changed, 129 insertions, 0 deletions

diff --git a/brightness.py b/brightness.py
new file mode 100755
index 0000000..0cebd00
--- /dev/null
+++ b/brightness.py
@@ -0,0 +1,129 @@
+#!/usr/bin/env python3
+
+'''
+brightness.py
+Usage:
+    brightness.py [show]
+    brightness.py set [--] <value>
+'''
+
+import re
+import sys
+import docopt
+
+backlight_prefix_path = '/sys/class/backlight/intel_backlight'
+
+
+def read_brightness():
+    '''
+    Return the current brightness value as reported by the driver.
+    '''
+    # We can use either the `brightness' file or `actual_brightness'.
+    # The differences are documented in the linux kernel tree at
+    # Documentation/sysfs-class-backlight.txt
+    # Briefly speaking, reading the `brigthness' file returns the
+    # brightness as reported by the driver whereas reading
+    # `actual_brigthess` returns the value queried directly from the
+    # hardware.
+    with open(backlight_prefix_path + '/brightness') as fd:
+        return int(fd.read())
+
+
+def read_max_brightness():
+    '''
+    Return the maximum brightness value that is supported.
+    '''
+    with open(backlight_prefix_path + '/max_brightness') as fd:
+        return int(fd.read())
+
+
+def print_current_brightness():
+    '''
+    Output the current brightness first as a value over the maximum
+    value, then as a percentage.
+    '''
+
+    max_brightness = read_max_brightness()
+    cur_brightness = read_brightness()
+
+    percentage_brightness = cur_brightness * 100 / max_brightness
+
+    output = 'Current brightness: {cur}/{max} ({percentage:.2f}%)'.format(
+        cur=cur_brightness, max=max_brightness,
+        percentage=percentage_brightness)
+
+    print(output)
+
+
+def set_current_brightness(value):
+    '''
+    Set the current brightness value according to the parameter.
+    The parameter can take multiple forms:
+    1) a number (e.g. 650);
+    2) a number followed by the '%' sign (e.g. 70%);
+    3) a number preceded by a '+' or '-' sign (e.g. +30);
+    4) a number number preceded by a '+' or '-' sign and followed by a '%' sign
+      (e.g. +10%).
+    '''
+
+    matches = re.fullmatch('([+-])?(\d+)(%)?', value)
+
+    if matches is None:
+        raise ValueError()
+
+    groups = matches.groups()
+    # The first group is either '+', '-' or None.
+    # The second group is a number.
+    # The third group is either '%' or None.
+    max_brightness = None
+    cur_brightness = None
+    new_brightness = None
+
+    # If we are going to increment / decrement the the value, we need to know
+    # what the current value is.
+    if groups[0] is not None:
+        cur_brightness = read_brightness()
+    # If we want to play around with percentage values, we need to know what
+    # the maximum value is.
+    if groups[2] is not None:
+        max_brightness = read_max_brightness()
+
+    # option 1)
+    if groups[0] is None and groups[2] is None:
+        new_brightness = int(groups[1])
+    # option 2)
+    elif groups[0] is None and groups[2] is not None:
+        new_brightness = round(int(groups[1]) * max_brightness / 100)
+    # option 3)
+    elif groups[0] is not None and groups[2] is None:
+        if groups[0] == '+':
+            new_brightness = cur_brightness + int(groups[1])
+        else:
+            new_brightness = cur_brightness - int(groups[1])
+    # option 4)
+    else:
+        delta = round(int(groups[1]) * max_brightness / 100)
+        if groups[0] == '+':
+            new_brightness = cur_brightness + delta
+        else:
+            new_brightness = cur_brightness - delta
+
+    with open(backlight_prefix_path + '/brightness', mode='w') as fd:
+        print(new_brightness, file=fd)
+
+
+def main(argv=None):
+    args = docopt.docopt(__doc__, version='1', argv=argv)
+
+    try:
+        if args['set']:
+            set_current_brightness(args['<value>'])
+        else:
+            print_current_brightness()
+
+    except ValueError as e:
+        raise docopt.DocoptExit(str(e))
+
+
+if __name__ == '__main__':
+    main()