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GRWU - Gnome RSS Wallpaper Updater

UPDATE: Project in GitHub

Because I wanted to make some updates to this tool, I found it more convenient to move the project to GitHub. Here's the link: https://github.com/lietu/grwu/

Further updates will happen there, and only there.

What is this?

I was using the NASA image of the day RSS feed to dynamically update the wallpaper on my Windows desktops and realized I wasn't doing that on my linux desktops (which are running Gnome 3). I checked quickly and it looked like there were no existing tools for this, so I rolled my own.

grwu.py

Put the contents below to a file called "grwu.py" and place that file anywhere you want.

#!/usr/bin/env python
#
# GRWU - Gnome RSS Wallpaper Updater
#
# Reads an RSS feed, picks an image out of it, downloads it and updates your
# gnome background image with that image. It is very much possible that this
# only works with the NASA image of the day feed format.
#
# Recommend using with crontab (run "crontab -e" to edit it), add e.g.:
#
# 30 * * * * export $(xargs -n 1 -0 echo </proc/$(pidof gnome-session)/environ | grep -Z DBUS_SESSION_BUS_ADDRESS=); python /path/to/grwu.py "http://url.to/feed.rss"
#
#
# Distributed with the "New BSD License":
# ---------------------------------------
#
# Copyright (c) 2014, Janne Enberg
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
#   * Redistributions of source code must retain the above copyright notice,
#     this list of conditions and the following disclaimer.
#   * Redistributions in binary form must reproduce the above copyright
#     notice, this list of conditions and the following disclaimer in the
#     documentation and/or other materials provided with the distribution.
#   * Neither the name of grwu nor the names of its contributors
#     may be used to endorse or promote products derived from this software
#     without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
# POSSIBILITY OF SUCH DAMAGE.
#

import os
import sys
import zlib
import urllib2
import xml.etree.ElementTree as ET
from random import choice
from tempfile import NamedTemporaryFile
from subprocess import call


# Read this many bytes of HTTP responses per iteration
READ_BLOCK_SIZE = 1024 * 8

# Default RSS feed url
rssUrl = "http://www.nasa.gov/rss/dyn/image_of_the_day.rss"

# Path to store wallpapers in
tempPath = '/tmp/gnome-wallpaper-updater/'

# Set to True to NOT delete all old files after update
keepFiles = False

# Shush, don't output anything
quiet = True


class WallpaperUpdater(object):

    def __init__(self, quiet):
        self.quiet = quiet

    def log(self, message):
        if not self.quiet:
            print(message)

    def update(self, rssUrl, storeDir, keepFiles):
        """Update wallpaper from RSS feed"""

        # Check that our path exists
        if not os.path.isdir(storeDir):
            os.makedirs(storeDir)

        # Get the new wallpaper image
        path = self._get_wallpaper(rssUrl, storeDir)

        # Update it as the wallpaper
        self._set_wallpaper(path)

        # Clean up if needed
        if not keepFiles:
            self._clean_dir(storeDir, [path])

    def _get_wallpaper(self, rssUrl, storeDir):
        """Download new wallpaper and return full path to file"""

        uri = self._get_wallpaper_uri(rssUrl, storeDir)
        return self._load_uri(uri, storeDir)

    def _get_wallpaper_uri(self, rssUrl, storeDir):
        """Pick the wallpaper image to use from the RSS feed"""

        return choice(self._get_wallpaper_uris(rssUrl, storeDir))

    def _get_wallpaper_uris(self, rssUrl, storeDir):
        """Get a list of image URIs in the RSS feed"""

        uris = []
        root = self._load_rss(rssUrl, storeDir)
        for enc in root.iter('enclosure'):
            if enc.attrib["type"].startswith("image/"):
                uris.append(enc.attrib["url"])

        self.log("Found {} images in feed".format(str(len(uris))))

        return uris

    def _load_rss(self, rssUrl, storeDir):
        """Load XML for the RSS, returns root node"""

        filename = self._load_uri(rssUrl, storeDir)
        root = ET.parse(filename).getroot()
        os.remove(filename)

        return root

    def _load_uri(self, uri, storeDir):
        """Load URI contents, handle gzip, save to file"""

        self.log("Loading " + uri)
        request = urllib2.Request(uri)
        request.add_header('Accept-Encoding', 'gzip')
        response = urllib2.urlopen(request)
        encoding = response.headers.get('content-encoding', '')

        isGZipped = encoding.find('gzip') >= 0

        filename = uri.split('/')[-1].split('#')[0].split('?')[0]
        extension = filename.split('.')[-1]

        tmp = NamedTemporaryFile(
            suffix='.'+extension,
            dir=storeDir,
            delete=False
        )

        d = zlib.decompressobj(16 + zlib.MAX_WBITS)
        while True:
            data = response.read(READ_BLOCK_SIZE)
            if not data:
                break

            if isGZipped:
                data = d.decompress(data)

            tmp.file.write(data)

        return tmp.name

    def _set_wallpaper(self, filename):
        """Update gnome wallpaper"""

        self.log("Updating background to " + filename)
        call([
            "gsettings", "set", "org.gnome.desktop.background", "picture-uri",
            "file://" + filename
        ])

    def _clean_dir(self, path, exclude):
        """Remove all but excluded contents in given path"""

        for root, dirs, filenames in os.walk(path):
            for f in filenames:
                fullpath = os.path.join(path, f)
                if not fullpath in exclude:
                    os.remove(fullpath)


if __name__ == "__main__":
    if len(sys.argv) == 2:
        rssUrl = sys.argv[1]

    wu = WallpaperUpdater(quiet)
    wu.update(rssUrl, tempPath, keepFiles)

Usage

python /path/to/grwu.py [url]

If no URL is given it defaults to NASA image of the day feed, which honestly is probably the only one giving supported format RSS. I checked a few other "picture of the day" RSS feeds and they seem to be quite random in how they provide the links to the images, and didn't bother supporting them.

Recommended usage is that you add a line in your crontab (run "crontab -e" to edit it) to periodically update your wallpaper, e.g. to update it every 30 minutes add:

30 * * * * export $(xargs -n 1 -0 echo </proc/$(pidof gnome-session)/environ | grep -Z DBUS_SESSION_BUS_ADDRESS=); python /path/to/grwu.py [url]

That horrible export command at the front is needed because the idiots behind the linux desktop development came up with DBUS and are now using it for everything. It pulls the DBUS session address for your running gnome session out of the environment of the running process and exports it to the cron environment before running the script.

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Copyright © 2014 Janne Enberg. All rights reserved.