#!/usr/bin/env python

# Build a multi screen wallpaper

# First argument is the directory where the wallpapers can be
# found. We use xinerama to know the dimension of each screen.

import sys
import os
import re
import random
import string
import subprocess
import optparse

import xcb
import xcb.xproto
import xcb.xinerama

import Image

parser = optparse.OptionParser()
parser.add_option("-d", "--directory", dest="directory", default=".",
                   help="search for images in DIRECTORY", metavar="DIRECTORY")
parser.add_option("-t", "--target", dest="target", default="background.jpg",
                   help="write background to FILE", metavar="FILE")
parser.add_option("-c", "--crop", dest="crop", action="store_true",
                  help="crop image instead of centering them")
options, args = parser.parse_args()

assert not args, "No additional arguments are accepted"

background = None

# Get display size
display = xcb.connect()
root = display.get_setup().roots[0]
background = Image.new('RGB', (root.width_in_pixels, root.height_in_pixels))

# Query xinerama (not randr since the query is longer)
try:
    xinerama = display(xcb.xinerama.key)
except xcb.ExtensionException:
    xinerama = None
if not xinerama or not xinerama.IsActive().reply().state:
    screens = [(background.size[0], background.size[1], 0, 0)]
else:
    screens = [(screen.width, screen.height, screen.x_org, screen.y_org)
               for screen in xinerama.QueryScreens().reply().screen_info]
screens.sort(key=lambda screen: -screen[0]*screen[1])

# Get as many random image as we have screens
images = []
for root, _, files in os.walk(os.path.join(options.directory)):
    for i in files:
        if string.lower(os.path.splitext(i)[1]) in ('.jpg',
                                                    '.jpeg',
                                                    '.png'):
            images.append(os.path.join(root, i))
images = random.sample(images,
                       len(screens) + \
                           random.randint(0, 3)) # Randomly favor larger images
images = [Image.open(os.path.join(options.directory,
                                  image)) for image in images]
images.sort(key=lambda image: -image.size[0]*image.size[1])

for index in range(len(screens)):
    x, y, offsetx, offsety = screens[index]
    image = images[index]

    # Find the right size for the screen
    imx, imy = x, image.size[1]*x/image.size[0]
    if (options.crop and imy < y) or (not options.crop and imy > y):
        imx, imy = image.size[0]*y/image.size[1], y
    image = image.resize((imx, imy), Image.CUBIC)
    if options.crop:
        image = image.crop(((imx-x)/2, (imy-y)/2,
                            imx-(imx-x)/2, imy-(imy-y)/2))

    # Include it
    if options.crop:
        background.paste(image, (offsetx, offsety))
    else:
        background.paste(image, ((x-imx)/2 + offsetx,
                                 (y-imy)/2 + offsety))

# Save
assert background, "Don't know the size of the display area"
background.save(options.target)