sugar-toolkit-gtk3/services/presence/buddy.py

850 lines
29 KiB
Python

"""An "actor" on the network, whether remote or local"""
# Copyright (C) 2007, Red Hat, Inc.
# Copyright (C) 2007, Collabora Ltd.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
import os
import gobject
import dbus, dbus.service
from ConfigParser import ConfigParser, NoOptionError
from sugar import env, profile, util
import logging
import random
_BUDDY_PATH = "/org/laptop/Sugar/Presence/Buddies/"
_BUDDY_INTERFACE = "org.laptop.Sugar.Presence.Buddy"
_OWNER_INTERFACE = "org.laptop.Sugar.Presence.Buddy.Owner"
class NotFoundError(dbus.DBusException):
"""Raised when a given actor is not found on the network"""
def __init__(self):
dbus.DBusException.__init__(self)
self._dbus_error_name = _PRESENCE_INTERFACE + '.NotFound'
class DBusGObjectMetaclass(dbus.service.InterfaceType, gobject.GObjectMeta): pass
class DBusGObject(dbus.service.Object, gobject.GObject): __metaclass__ = DBusGObjectMetaclass
_PROP_NICK = "nick"
_PROP_KEY = "key"
_PROP_ICON = "icon"
_PROP_CURACT = "current-activity"
_PROP_COLOR = "color"
_PROP_OWNER = "owner"
_PROP_VALID = "valid"
class Buddy(DBusGObject):
"""Person on the network (tracks properties and shared activites)
The Buddy is a collection of metadata describing a particular
actor/person on the network. The Buddy object tracks a set of
activities which the actor has shared with the presence service.
Buddies have a "valid" property which is used to flag Buddies
which are no longer reachable. That is, a Buddy may represent
a no-longer reachable target on the network.
The Buddy emits GObject events that the PresenceService uses
to track changes in its status.
Attributes:
_activities -- dictionary mapping activity ID to
activity.Activity objects
handles -- dictionary mapping telepresence client to
"handle" (XXX what's that)
"""
__gsignals__ = {
'validity-changed': (gobject.SIGNAL_RUN_FIRST, gobject.TYPE_NONE,
([gobject.TYPE_BOOLEAN])),
'property-changed': (gobject.SIGNAL_RUN_FIRST, gobject.TYPE_NONE,
([gobject.TYPE_PYOBJECT])),
'icon-changed': (gobject.SIGNAL_RUN_FIRST, gobject.TYPE_NONE,
([gobject.TYPE_PYOBJECT]))
}
__gproperties__ = {
_PROP_KEY : (str, None, None, None,
gobject.PARAM_READWRITE | gobject.PARAM_CONSTRUCT_ONLY),
_PROP_ICON : (object, None, None, gobject.PARAM_READWRITE),
_PROP_NICK : (str, None, None, None, gobject.PARAM_READWRITE),
_PROP_COLOR : (str, None, None, None, gobject.PARAM_READWRITE),
_PROP_CURACT : (str, None, None, None, gobject.PARAM_READWRITE),
_PROP_VALID : (bool, None, None, False, gobject.PARAM_READABLE),
_PROP_OWNER : (bool, None, None, False, gobject.PARAM_READABLE)
}
def __init__(self, bus_name, object_id, **kwargs):
"""Initialize the Buddy object
bus_name -- DBUS object bus name (identifier)
object_id -- the activity's unique identifier
kwargs -- used to initialize the object's properties
constructs a DBUS "object path" from the _BUDDY_PATH
and object_id
"""
if not bus_name:
raise ValueError("DBus bus name must be valid")
if not object_id or not isinstance(object_id, int):
raise ValueError("object id must be a valid number")
self._bus_name = bus_name
self._object_id = object_id
self._object_path = _BUDDY_PATH + str(self._object_id)
dbus.service.Object.__init__(self, self._bus_name, self._object_path)
self._activities = {} # Activity ID -> Activity
self._activity_sigids = {}
self.handles = {} # tp client -> handle
self._valid = False
self._owner = False
self._key = None
self._icon = ''
self._current_activity = None
self._nick = None
self._color = None
if not kwargs.get(_PROP_KEY):
raise ValueError("key required")
_ALLOWED_INIT_PROPS = [_PROP_NICK, _PROP_KEY, _PROP_ICON, _PROP_CURACT, _PROP_COLOR]
for (key, value) in kwargs.items():
if key not in _ALLOWED_INIT_PROPS:
logging.debug("Invalid init property '%s'; ignoring..." % key)
del kwargs[key]
gobject.GObject.__init__(self, **kwargs)
def do_get_property(self, pspec):
"""Retrieve current value for the given property specifier
pspec -- property specifier with a "name" attribute
"""
if pspec.name == _PROP_KEY:
return self._key
elif pspec.name == _PROP_ICON:
return self._icon
elif pspec.name == _PROP_NICK:
return self._nick
elif pspec.name == _PROP_COLOR:
return self._color
elif pspec.name == _PROP_CURACT:
if not self._current_activity:
return None
if not self._activities.has_key(self._current_activity):
return None
return self._current_activity
elif pspec.name == _PROP_VALID:
return self._valid
elif pspec.name == _PROP_OWNER:
return self._owner
def do_set_property(self, pspec, value):
"""Set given property
pspec -- property specifier with a "name" attribute
value -- value to set
emits 'icon-changed' signal on icon setting
calls _update_validity on all calls
"""
if pspec.name == _PROP_ICON:
if str(value) != self._icon:
self._icon = str(value)
self.IconChanged(self._icon)
self.emit('icon-changed', self._icon)
elif pspec.name == _PROP_NICK:
self._nick = value
elif pspec.name == _PROP_COLOR:
self._color = value
elif pspec.name == _PROP_CURACT:
self._current_activity = value
elif pspec.name == _PROP_KEY:
self._key = value
self._update_validity()
# dbus signals
@dbus.service.signal(_BUDDY_INTERFACE,
signature="ay")
def IconChanged(self, icon_data):
"""Generates DBUS signal with icon_data"""
@dbus.service.signal(_BUDDY_INTERFACE,
signature="o")
def JoinedActivity(self, activity_path):
"""Generates DBUS signal when buddy joins activity
activity_path -- DBUS path to the activity object
"""
@dbus.service.signal(_BUDDY_INTERFACE,
signature="o")
def LeftActivity(self, activity_path):
"""Generates DBUS signal when buddy leaves activity
activity_path -- DBUS path to the activity object
"""
@dbus.service.signal(_BUDDY_INTERFACE,
signature="a{sv}")
def PropertyChanged(self, updated):
"""Generates DBUS signal when buddy's property changes
updated -- updated property-set (dictionary) with the
Buddy's property (changed) values. Note: not the
full set of properties, just the changes.
"""
# dbus methods
@dbus.service.method(_BUDDY_INTERFACE,
in_signature="", out_signature="ay")
def GetIcon(self):
"""Retrieve Buddy's icon data
returns empty string or dbus.ByteArray
"""
if not self.props.icon:
return ""
return dbus.ByteArray(self.props.icon)
@dbus.service.method(_BUDDY_INTERFACE,
in_signature="", out_signature="ao")
def GetJoinedActivities(self):
"""Retrieve set of Buddy's joined activities (paths)
returns list of dbus service paths for the Buddy's joined
activities
"""
acts = []
for act in self.get_joined_activities():
if act.props.valid:
acts.append(act.object_path())
return acts
@dbus.service.method(_BUDDY_INTERFACE,
in_signature="", out_signature="a{sv}")
def GetProperties(self):
"""Retrieve set of Buddy's properties
returns dictionary of
nick : str(nickname)
owner : bool( whether this Buddy is an owner??? )
XXX what is the owner flag for?
key : str(public-key)
color: Buddy's icon colour
XXX what type?
current-activity: Buddy's current activity_id, or
"" if no current activity
"""
props = {}
props[_PROP_NICK] = self.props.nick
props[_PROP_OWNER] = self.props.owner
props[_PROP_KEY] = self.props.key
props[_PROP_COLOR] = self.props.color
if self.props.current_activity:
props[_PROP_CURACT] = self.props.current_activity
else:
props[_PROP_CURACT] = ""
return props
# methods
def object_path(self):
"""Retrieve our dbus.ObjectPath object"""
return dbus.ObjectPath(self._object_path)
def _activity_validity_changed_cb(self, activity, valid):
"""Join or leave the activity when its validity changes"""
if valid:
self.JoinedActivity(activity.object_path())
else:
self.LeftActivity(activity.object_path())
def add_activity(self, activity):
"""Add an activity to the Buddy's set of activities
activity -- activity.Activity instance
calls JoinedActivity
"""
actid = activity.props.id
if self._activities.has_key(actid):
return
self._activities[actid] = activity
# join/leave activity when it's validity changes
sigid = activity.connect("validity-changed", self._activity_validity_changed_cb)
self._activity_sigids[actid] = sigid
if activity.props.valid:
self.JoinedActivity(activity.object_path())
def remove_activity(self, activity):
"""Remove the activity from the Buddy's set of activities
activity -- activity.Activity instance
calls LeftActivity
"""
actid = activity.props.id
if not self._activities.has_key(actid):
return
activity.disconnect(self._activity_sigids[actid])
del self._activity_sigids[actid]
del self._activities[actid]
if activity.props.valid:
self.LeftActivity(activity.object_path())
def get_joined_activities(self):
"""Retrieves list of still-valid activity objects"""
acts = []
for act in self._activities.values():
acts.append(act)
return acts
def set_properties(self, properties):
"""Set the given set of properties on the object
properties -- set of property values to set
if no change, no events generated
if change, generates property-changed and
calls _update_validity
"""
changed = False
changed_props = {}
if _PROP_NICK in properties.keys():
nick = properties[_PROP_NICK]
if nick != self._nick:
self._nick = nick
changed_props[_PROP_NICK] = nick
changed = True
if _PROP_COLOR in properties.keys():
color = properties[_PROP_COLOR]
if color != self._color:
self._color = color
changed_props[_PROP_COLOR] = color
changed = True
if _PROP_CURACT in properties.keys():
curact = properties[_PROP_CURACT]
if curact != self._current_activity:
self._current_activity = curact
changed_props[_PROP_CURACT] = curact
changed = True
if not changed or not len(changed_props.keys()):
return
# Try emitting PropertyChanged before updating validity
# to avoid leaking a PropertyChanged signal before the buddy is
# actually valid the first time after creation
if self._valid:
self.PropertyChanged(changed_props)
self.emit('property-changed', changed_props)
self._update_validity()
def _update_validity(self):
"""Check whether we are now valid
validity is True if color, nick and key are non-null
emits validity-changed if we have changed validity
"""
try:
old_valid = self._valid
if self._color and self._nick and self._key:
self._valid = True
else:
self._valid = False
if old_valid != self._valid:
self.emit("validity-changed", self._valid)
except AttributeError:
self._valid = False
class GenericOwner(Buddy):
"""Common functionality for Local User-like objects
The TestOwner wants to produce something *like* a
ShellOwner, but with randomised changes and the like.
This class provides the common features for a real
local owner and a testing one.
"""
__gtype_name__ = "GenericOwner"
__gproperties__ = {
'registered' : (bool, None, None, False, gobject.PARAM_READWRITE | gobject.PARAM_CONSTRUCT),
'server' : (str, None, None, None, gobject.PARAM_READABLE | gobject.PARAM_CONSTRUCT),
'key-hash' : (str, None, None, None, gobject.PARAM_READABLE | gobject.PARAM_CONSTRUCT)
}
def __init__(self, ps, bus_name, object_id, **kwargs):
"""Initialize the GenericOwner instance
ps -- presenceservice.PresenceService object
bus_name -- DBUS object bus name (identifier)
object_id -- the activity's unique identifier
kwargs -- used to initialize the object's properties
calls Buddy.__init__
"""
self._ps = ps
self._server = 'olpc.collabora.co.uk'
self._key_hash = None
self._registered = False
if kwargs.has_key("server"):
self._server = kwargs["server"]
del kwargs["server"]
if kwargs.has_key("key_hash"):
self._key_hash = kwargs["key_hash"]
del kwargs["key_hash"]
if kwargs.has_key("registered"):
self._registered = kwargs["registered"]
del kwargs["registered"]
Buddy.__init__(self, bus_name, object_id, **kwargs)
self._owner = True
def get_registered(self):
"""Retrieve whether owner has registered with presence server"""
return self._registered
def get_server(self):
"""Retrieve presence server (XXX url??)"""
return self._server
def get_key_hash(self):
"""Retrieve the user's private-key hash"""
return self._key_hash
def set_registered(self, registered):
"""Customisation point: handle the registration of the owner"""
raise RuntimeError("Subclasses must implement")
class ShellOwner(GenericOwner):
"""Representation of the local-machine owner using Sugar's Shell
The ShellOwner uses the Sugar Shell's dbus services to
register for updates about the user's profile description.
"""
__gtype_name__ = "ShellOwner"
_SHELL_SERVICE = "org.laptop.Shell"
_SHELL_OWNER_INTERFACE = "org.laptop.Shell.Owner"
_SHELL_PATH = "/org/laptop/Shell"
def __init__(self, ps, bus_name, object_id, test=False):
"""Initialize the ShellOwner instance
ps -- presenceservice.PresenceService object
bus_name -- DBUS object bus name (identifier)
object_id -- the activity's unique identifier
test -- ignored
Retrieves initial property values from the profile
module. Loads the buddy icon from file as well.
XXX note: no error handling on that
calls GenericOwner.__init__
"""
server = profile.get_server()
key_hash = profile.get_private_key_hash()
registered = profile.get_server_registered()
key = profile.get_pubkey()
nick = profile.get_nick_name()
color = profile.get_color().to_string()
icon_file = os.path.join(env.get_profile_path(), "buddy-icon.jpg")
f = open(icon_file, "r")
icon = f.read()
f.close()
GenericOwner.__init__(self, ps, bus_name, object_id, key=key, nick=nick,
color=color, icon=icon, server=server, key_hash=key_hash,
registered=registered)
self._bus = dbus.SessionBus()
self._bus.add_signal_receiver(self._name_owner_changed_handler,
signal_name="NameOwnerChanged",
dbus_interface="org.freedesktop.DBus")
# Connect to the shell to get notifications on Owner object
# property changes
try:
self._connect_to_shell()
except dbus.DBusException:
pass
def set_registered(self, value):
"""Handle notification that we have been registered"""
if value:
profile.set_server_registered()
def _name_owner_changed_handler(self, name, old, new):
"""Handle DBUS notification of a new / renamed service
Watches for the _SHELL_SERVICE, i.e. the Sugar Shell,
and registers with it if we have not yet registered
with it (using _connect_to_shell).
"""
if name != self._SHELL_SERVICE:
return
if (old and len(old)) and (not new and not len(new)):
# shell went away
self._shell_owner = None
elif (not old and not len(old)) and (new and len(new)):
# shell started
self._connect_to_shell()
def _connect_to_shell(self):
"""Connect to the Sugar Shell service to watch for events
Connects the various XChanged events on the Sugar Shell
service to our _x_changed_cb methods.
"""
obj = self._bus.get_object(self._SHELL_SERVICE, self._SHELL_PATH)
self._shell_owner = dbus.Interface(obj, self._SHELL_OWNER_INTERFACE)
self._shell_owner.connect_to_signal('IconChanged', self._icon_changed_cb)
self._shell_owner.connect_to_signal('ColorChanged', self._color_changed_cb)
self._shell_owner.connect_to_signal('NickChanged', self._nick_changed_cb)
self._shell_owner.connect_to_signal('CurrentActivityChanged',
self._cur_activity_changed_cb)
def _icon_changed_cb(self, icon):
"""Handle icon change, set property to generate event"""
self.props.icon = icon
def _color_changed_cb(self, color):
"""Handle color change, set property to generate event"""
props = {_PROP_COLOR: color}
self.set_properties(props)
def _nick_changed_cb(self, nick):
"""Handle nickname change, set property to generate event"""
props = {_PROP_NICK: nick}
self.set_properties(props)
def _cur_activity_changed_cb(self, activity_id):
"""Handle current-activity change, set property to generate event
Filters out local activities (those not in self.activites)
because the network users can't join those activities, so
the activity_id shared will be None in those cases...
"""
if not self._activities.has_key(activity_id):
# This activity is local-only
activity_id = None
props = {_PROP_CURACT: activity_id}
self.set_properties(props)
class TestOwner(GenericOwner):
"""Class representing the owner of the machine. This test owner
changes random attributes periodically."""
__gtype_name__ = "TestOwner"
def __init__(self, ps, bus_name, object_id, test_num):
self._cp = ConfigParser()
self._section = "Info"
self._test_activities = []
self._test_cur_act = ""
self._change_timeout = 0
self._cfg_file = os.path.join(env.get_profile_path(), 'test-buddy-%d' % test_num)
(pubkey, privkey, registered) = self._load_config()
if not pubkey or not len(pubkey) or not privkey or not len(privkey):
(pubkey, privkey) = _get_new_keypair(test_num)
if not pubkey or not privkey:
raise RuntimeError("Couldn't get or create test buddy keypair")
self._save_config(pubkey, privkey, registered)
privkey_hash = util.printable_hash(util._sha_data(privkey))
nick = _get_random_name()
from sugar.graphics import xocolor
color = xocolor.XoColor().to_string()
icon = _get_random_image()
logging.debug("pubkey is %s" % pubkey)
GenericOwner.__init__(self, ps, bus_name, object_id, key=pubkey, nick=nick,
color=color, icon=icon, registered=registered, key_hash=privkey_hash)
self._ps.connect('connection-status', self._ps_connection_status_cb)
def _share_reply_cb(self, actid, object_path):
activity = self._ps.internal_get_activity(actid)
if not activity or not object_path:
logging.debug("Couldn't find activity %s even though it was shared." % actid)
return
logging.debug("Shared activity %s (%s)." % (actid, activity.props.name))
self._test_activities.append(activity)
def _share_error_cb(self, actid, err):
logging.debug("Error sharing activity %s: %s" % (actid, str(err)))
def _ps_connection_status_cb(self, ps, connected):
if not connected:
return
if not len(self._test_activities):
# Share some activities
actid = util.unique_id("Activity 1")
callbacks = (lambda *args: self._share_reply_cb(actid, *args),
lambda *args: self._share_error_cb(actid, *args))
atype = "org.laptop.WebActivity"
properties = {"foo": "bar"}
self._ps._share_activity(actid, atype, "Wembley Stadium", properties, callbacks)
actid2 = util.unique_id("Activity 2")
callbacks = (lambda *args: self._share_reply_cb(actid2, *args),
lambda *args: self._share_error_cb(actid2, *args))
atype = "org.laptop.WebActivity"
properties = {"baz": "bar"}
self._ps._share_activity(actid2, atype, "Maine Road", properties, callbacks)
# Change a random property ever 10 seconds
if self._change_timeout == 0:
self._change_timeout = gobject.timeout_add(10000, self._update_something)
def set_registered(self, value):
if value:
self._registered = True
def _load_config(self):
if not os.path.exists(self._cfg_file):
return (None, None, False)
if not self._cp.read([self._cfg_file]):
return (None, None, False)
if not self._cp.has_section(self._section):
return (None, None, False)
try:
pubkey = self._cp.get(self._section, "pubkey")
privkey = self._cp.get(self._section, "privkey")
registered = self._cp.get(self._section, "registered")
return (pubkey, privkey, registered)
except NoOptionError:
pass
return (None, None, False)
def _save_config(self, pubkey, privkey, registered):
# Save config again
if not self._cp.has_section(self._section):
self._cp.add_section(self._section)
self._cp.set(self._section, "pubkey", pubkey)
self._cp.set(self._section, "privkey", privkey)
self._cp.set(self._section, "registered", registered)
f = open(self._cfg_file, 'w')
self._cp.write(f)
f.close()
def _update_something(self):
it = random.randint(0, 10000) % 4
if it == 0:
self.props.icon = _get_random_image()
elif it == 1:
from sugar.graphics import xocolor
props = {_PROP_COLOR: xocolor.XoColor().to_string()}
self.set_properties(props)
elif it == 2:
props = {_PROP_NICK: _get_random_name()}
self.set_properties(props)
elif it == 3:
actid = ""
idx = random.randint(0, len(self._test_activities))
# if idx == len(self._test_activites), it means no current
# activity
if idx < len(self._test_activities):
activity = self._test_activities[idx]
actid = activity.props.id
props = {_PROP_CURACT: actid}
self.set_properties(props)
return True
def _hash_private_key(self):
"""Unused method to has a private key, see profile"""
self.privkey_hash = None
key_path = os.path.join(env.get_profile_path(), 'owner.key')
try:
f = open(key_path, "r")
lines = f.readlines()
f.close()
except IOError, e:
logging.error("Error reading private key: %s" % e)
return
key = ""
for l in lines:
l = l.strip()
if l.startswith("-----BEGIN DSA PRIVATE KEY-----"):
continue
if l.startswith("-----END DSA PRIVATE KEY-----"):
continue
key += l
if not len(key):
logging.error("Error parsing public key.")
# hash it
key_hash = util._sha_data(key)
self.privkey_hash = util.printable_hash(key_hash)
def _extract_public_key(keyfile):
try:
f = open(keyfile, "r")
lines = f.readlines()
f.close()
except IOError, e:
logging.error("Error reading public key: %s" % e)
return None
# Extract the public key
magic = "ssh-dss "
key = ""
for l in lines:
l = l.strip()
if not l.startswith(magic):
continue
key = l[len(magic):]
break
if not len(key):
logging.error("Error parsing public key.")
return None
return key
def _extract_private_key(keyfile):
"""Get a private key from a private key file"""
# Extract the private key
try:
f = open(keyfile, "r")
lines = f.readlines()
f.close()
except IOError, e:
logging.error("Error reading private key: %s" % e)
return None
key = ""
for l in lines:
l = l.strip()
if l.startswith("-----BEGIN DSA PRIVATE KEY-----"):
continue
if l.startswith("-----END DSA PRIVATE KEY-----"):
continue
key += l
if not len(key):
logging.error("Error parsing private key.")
return None
return key
def _get_new_keypair(num):
"""Retrieve a public/private key pair for testing"""
# Generate keypair
privkeyfile = os.path.join("/tmp", "test%d.key" % num)
pubkeyfile = os.path.join("/tmp", 'test%d.key.pub' % num)
# force-remove key files if they exist to ssh-keygen doesn't
# start asking questions
try:
os.remove(pubkeyfile)
os.remove(privkeyfile)
except OSError:
pass
cmd = "ssh-keygen -q -t dsa -f %s -C '' -N ''" % privkeyfile
import commands
print "Generating new keypair..."
(s, o) = commands.getstatusoutput(cmd)
print "Done."
pubkey = privkey = None
if s != 0:
logging.error("Could not generate key pair: %d (%s)" % (s, o))
else:
pubkey = _extract_public_key(pubkeyfile)
privkey = _extract_private_key(privkeyfile)
try:
os.remove(pubkeyfile)
os.remove(privkeyfile)
except OSError:
pass
return (pubkey, privkey)
def _get_random_name():
"""Produce random names for testing"""
names = ["Liam", "Noel", "Guigsy", "Whitey", "Bonehead"]
return names[random.randint(0, len(names) - 1)]
def _get_random_image():
"""Produce a random image for display"""
import cairo, math, random, gtk
def rand():
return random.random()
SIZE = 200
s = cairo.ImageSurface(cairo.FORMAT_ARGB32, SIZE, SIZE)
cr = cairo.Context(s)
# background gradient
cr.save()
g = cairo.LinearGradient(0, 0, 1, 1)
g.add_color_stop_rgba(1, rand(), rand(), rand(), rand())
g.add_color_stop_rgba(0, rand(), rand(), rand(), rand())
cr.set_source(g)
cr.rectangle(0, 0, SIZE, SIZE);
cr.fill()
cr.restore()
# random path
cr.set_line_width(10 * rand() + 5)
cr.move_to(SIZE * rand(), SIZE * rand())
cr.line_to(SIZE * rand(), SIZE * rand())
cr.rel_line_to(SIZE * rand() * -1, 0)
cr.close_path()
cr.stroke()
# a circle
cr.set_source_rgba(rand(), rand(), rand(), rand())
cr.arc(SIZE * rand(), SIZE * rand(), 100 * rand() + 30, 0, 2 * math.pi)
cr.fill()
# another circle
cr.set_source_rgba(rand(), rand(), rand(), rand())
cr.arc(SIZE * rand(), SIZE * rand(), 100 * rand() + 30, 0, 2 * math.pi)
cr.fill()
def img_convert_func(buf, data):
data[0] += buf
return True
data = [""]
pixbuf = gtk.gdk.pixbuf_new_from_data(s.get_data(), gtk.gdk.COLORSPACE_RGB,
True, 8, s.get_width(), s.get_height(), s.get_stride())
pixbuf.save_to_callback(img_convert_func, "jpeg", {"quality": "90"}, data)
del pixbuf
return str(data[0])