xsetbg.py

   1 """Set a random background image (XWin)
   2
   3 Select a random image from a (list of) directory(s)
   4 and set it as the desktop wallpaper (display it in the root window)
   5 using xli program.
   6
   7 """
   8
   9 from fcntl import flock, LOCK_EX, LOCK_UN, LOCK_NB
  10 from datetime import timedelta
  11 import os
  12 import random
  13 import re
  14 import subprocess
  15 import sys
  16 from time import time
  17
  18 from xsetbg_conf import xsetbg_dir, xsetbg_conf
  19 from xsetbg_db import xsetbg_db
  20
  21 __all__ = ['change']
  22
  23
  24 def error(error_str):
  25     sys.exit("%s: Error: %s\n" % (sys.argv[0], error_str))
  26
  27
  28 if not xsetbg_db:
  29     error("No database found. Run rescan_fs.py. Abort.")
  30
  31 if xsetbg_db.select().count() == 0:
  32     error("No images found. Run rescan_fs.py. Abort.")
  33
  34
  35 # minimum time in seconds between background image changes
  36 if xsetbg_conf.has_option("xsetbg", "min_pause"):
  37     min_pause = xsetbg_conf.getint("xsetbg", "min_pause")
  38 else:
  39     min_pause = 60
  40
  41 borders = xsetbg_conf.get("xsetbg", "borders").split(',')
  42 if xsetbg_conf.has_option("xsetbg", "borders"):
  43     borders = [border.strip() for border in
  44                xsetbg_conf.get("xsetbg", "borders").split(',')]
  45 else:
  46     borders = ["darkcyan", "steelblue", "midnightblue"]
  47
  48 # minimum time in seconds between occurences of the same image
  49 if xsetbg_conf.has_option("xsetbg", "min_delay"):
  50     min_delay = xsetbg_conf.get("xsetbg", "min_delay")
  51
  52     # Borrowed from http://stackoverflow.com/a/2765366
  53     td_re = re.compile('(?:(?P<years>\d+)y)?'
  54                        '(?:(?P<months>\d+)m)?'
  55                        '(?:(?P<days>\d+)d)?'
  56                        '(?:T(?:(?P<hours>\d+)h)?'
  57                        '(?:(?P<minutes>\d+)m)?(?:(?P<seconds>\d+)s)?)?')
  58     td_dict = td_re.match(min_delay).groupdict(0)
  59     delta = timedelta(days=int(td_dict['days']) +
  60                       (int(td_dict['months']) * 30) +
  61                       (int(td_dict['years']) * 365),
  62                       hours=int(td_dict['hours']),
  63                       minutes=int(td_dict['minutes']),
  64                       seconds=int(td_dict['seconds']))
  65
  66     if delta:
  67         min_delay = delta.days * 24*3600 + delta.seconds
  68     else:
  69         min_delay = int(min_delay)
  70
  71 else:
  72     min_delay = 3600*24  # 24 hours
  73
  74
  75 if xsetbg_db.select(
  76         '(is_image = 1) AND (last_shown IS NULL OR last_shown < %d)' %
  77         (time() - min_delay)).count() == 0:
  78     error("No unshown images found. Run rescan_fs.py "
  79           "or decrease min_delay. Abort.")
  80
  81 fs_encoding = xsetbg_conf.get("images", "fs_encoding")
  82
  83
  84 def change(force=False):
  85     # Use the program's file as the lock file:
  86     # lock it to prevent two processes run in parallel.
  87     lock_file = open(os.path.join(xsetbg_dir, 'xsetbg.py'), 'r')
  88
  89     try:
  90         flock(lock_file, LOCK_EX | LOCK_NB)
  91     except IOError:  # already locked
  92         lock_file.close()
  93         return
  94
  95     try:
  96         timestamp = xsetbg_db.select(
  97             '(is_image = 1) AND (last_shown IS NOT NULL)',
  98             orderBy='-last_shown')[0].last_shown
  99         current_time = time()
 100
 101         if not force and timestamp is not None and \
 102                 current_time - timestamp < min_pause:
 103             # Too early to change background
 104             return
 105
 106         # Select a random image that has never been shown
 107         not_shown_select = xsetbg_db.select(
 108             '(is_image = 1) AND (last_shown IS NULL)')
 109         not_shown_count = not_shown_select.count()
 110         if not_shown_count:
 111             row = not_shown_select[random.randint(0, not_shown_count - 1)]
 112         else:
 113             old_shown_select = xsetbg_db.select(
 114                 '(is_image = 1) AND '
 115                 '(last_shown IS NOT NULL AND last_shown < %d)' %
 116                 current_time - min_delay)
 117             old_shown_count = old_shown_select.count()
 118             if old_shown_count:
 119                 row = old_shown_select[random.randint(0, old_shown_count - 1)]
 120             else:
 121                 error("No images to show found. Run rescan_fs.py "
 122                       "or decrease min_delay. Abort.")
 123
 124         program_options = ["xli", "-border", random.choice(borders),
 125                            "-center", "-onroot", "-quiet", "-zoom", "auto",
 126                            row.full_name.encode(fs_encoding)]
 127
 128         rc = subprocess.call(program_options)
 129         if rc:
 130             error("cannot execute xli!")
 131         else:
 132             row.last_shown = current_time
 133
 134     finally:
 135         # Unlock and close the lock file
 136         flock(lock_file, LOCK_UN)
 137         lock_file.close()