#!/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 os
import random
import string
import optparse
import tempfile

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))
images = [Image.open(image) for image in images]
print("wallpaper: {}".format(" + ".join(
    ["`%s`" % x.filename[(len(options.directory) + 1):]
     for x in images])))

# Link chosen wallpapers
for idx, image in enumerate(images):
    target = "{}.{}".format(options.target, idx)
    if os.path.lexists(target):
        os.remove(target)
    os.symlink(os.path.abspath(image.filename), target)

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"
with tempfile.NamedTemporaryFile(
        delete=False,
        dir=os.path.dirname(os.path.realpath(options.target))) as tmp:
    background.save(tmp, "png")
    os.rename(tmp.name, options.target)