Web   ·   Wiki   ·   Activities   ·   Blog   ·   Lists   ·   Chat   ·   Meeting   ·   Bugs   ·   Git   ·   Translate   ·   Archive   ·   People   ·   Donate
summaryrefslogtreecommitdiffstats
path: root/toolkitfix/activity/activity.py
blob: cffd12eeabe24b1f5b37ec61f222daf725e97ed2 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
"""Base class for activities written in Python

This is currently the only definitive reference for what an
activity must do to participate in the Sugar desktop.

   A Basic Activity

All activities must implement a class derived from 'Activity' in this class.
The convention is to call it ActivitynameActivity, but this is not required as
the activity.info file associated with your activity will tell the sugar-shell
which class to start.

For example the most minimal Activity:


   from sugar.activity import activity

   class ReadActivity(activity.Activity):
        pass

To get a real, working activity, you will at least have to implement:
    __init__(), read_file() and write_file()

Aditionally, you will probably need a at least a Toolbar so you can have some
interesting buttons for the user, like for example 'exit activity'

See the methods of the Activity class below for more information on what you
will need for a real activity.

STABLE.
"""
# Copyright (C) 2006-2007 Red Hat, Inc.
# Copyright (C) 2007-2009 One Laptop Per Child
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2 of the License, or (at your option) any later version.
#
# This library 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
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the
# Free Software Foundation, Inc., 59 Temple Place - Suite 330,
# Boston, MA 02111-1307, USA.

import gettext
import logging
import os
import time
from hashlib import sha1
import traceback
import gconf

import gtk
import gobject
import dbus
import dbus.service
import cjson

from sugar import util
from sugar.presence import presenceservice
from sugar.activity.activityservice import ActivityService
from sugar.activity.namingalert import NamingAlert
from sugar.graphics import style
from sugar.graphics.window import Window
from sugar.graphics.alert import Alert
from sugar.graphics.icon import Icon
from sugar.datastore import datastore
from sugar.session import XSMPClient
from sugar import wm

from sugar.tutorius.services import ObjectStore

# support deprecated imports
from sugar.activity.widgets import ActivityToolbar, EditToolbar
from sugar.activity.widgets import ActivityToolbox

_ = lambda msg: gettext.dgettext('sugar-toolkit', msg)

SCOPE_PRIVATE = "private"
SCOPE_INVITE_ONLY = "invite"  # shouldn't be shown in UI, it's implicit
SCOPE_NEIGHBORHOOD = "public"

J_DBUS_SERVICE = 'org.laptop.Journal'
J_DBUS_PATH = '/org/laptop/Journal'
J_DBUS_INTERFACE = 'org.laptop.Journal'


class _ActivitySession(gobject.GObject):

    __gsignals__ = {
        'quit-requested': (gobject.SIGNAL_RUN_FIRST, gobject.TYPE_NONE, ([])),
        'quit': (gobject.SIGNAL_RUN_FIRST, gobject.TYPE_NONE, ([])),
    }

    def __init__(self):
        gobject.GObject.__init__(self)

        self._xsmp_client = XSMPClient()
        self._xsmp_client.connect('quit-requested',
            self.__sm_quit_requested_cb)
        self._xsmp_client.connect('quit', self.__sm_quit_cb)
        self._xsmp_client.startup()

        self._activities = []
        self._will_quit = []

    def register(self, activity):
        self._activities.append(activity)

    def unregister(self, activity):
        self._activities.remove(activity)

        if len(self._activities) == 0:
            logging.debug('Quitting the activity process.')
            gtk.main_quit()

    def will_quit(self, activity, will_quit):
        if will_quit:
            self._will_quit.append(activity)

            # We can quit only when all the instances agreed to
            for activity in self._activities:
                if activity not in self._will_quit:
                    return

            self._xsmp_client.will_quit(True)
        else:
            self._will_quit = []
            self._xsmp_client.will_quit(False)

    def __sm_quit_requested_cb(self, client):
        self.emit('quit-requested')

    def __sm_quit_cb(self, client):
        self.emit('quit')


class Activity(Window, gtk.Container):
    """This is the base Activity class that all other Activities derive from.
       This is where your activity starts.

    To get a working Activity:
        0. Derive your Activity from this class:
                class MyActivity(activity.Activity):
                    ...

        1. implement an __init__() method for your Activity class.

           Use your init method to create your own ActivityToolbar which will
           contain some standard buttons:
                toolbox = activity.ActivityToolbox(self)

           Add extra Toolbars to your toolbox.

           You should setup Activity sharing here too.

           Finaly, your Activity may need some resources which you can claim
           here too.

           The __init__() method is also used to make the distinction between
           being resumed from the Journal, or starting with a blank document.

        2. Implement read_file() and write_file()
           Most activities revolve around creating and storing Journal entries.
           For example, Write: You create a document, it is saved to the
           Journal and then later you resume working on the document.

           read_file() and write_file() will be called by sugar to tell your
           Activity that it should load or save the document the user is
           working on.

        3. Implement our Activity Toolbars.
           The Toolbars are added to your Activity in step 1 (the toolbox), but
           you need to implement them somewhere. Now is a good time.

           There are a number of standard Toolbars. The most basic one, the one
           your almost absolutely MUST have is the ActivityToolbar. Without
           this, you're not really making a proper Sugar Activity (which may be
           okay, but you should really stop and think about why not!) You do
           this with the ActivityToolbox(self) call in step 1.

           Usually, you will also need the standard EditToolbar. This is the
           one which has the standard copy and paste buttons. You need to
           derive your own EditToolbar class from sugar.EditToolbar:
                class EditToolbar(activity.EditToolbar):
                    ...

           See EditToolbar for the methods you should implement in your class.

           Finaly, your Activity will very likely need some activity specific
           buttons and options you can create your own toolbars by deriving a
           class from gtk.Toolbar:
                class MySpecialToolbar(gtk.Toolbar):
                    ...

        4. Use your creativity. Make your Activity something special and share
           it with your friends!

    Read through the methods of the Activity class below, to learn more about
    how to make an Activity work.

    Hint: A good and simple Activity to learn from is the Read activity. To
    create your own activity, you may want to copy it and use it as a template.
    """

    __gtype_name__ = 'SugarActivity'

    __gsignals__ = {
        'shared': (gobject.SIGNAL_RUN_FIRST, gobject.TYPE_NONE, ([])),
        'joined': (gobject.SIGNAL_RUN_FIRST, gobject.TYPE_NONE, ([])),
    }

    def __init__(self, handle, create_jobject=True):
        """Initialise the Activity

        handle -- sugar.activity.activityhandle.ActivityHandle
            instance providing the activity id and access to the
            presence service which *may* provide sharing for this
            application

        create_jobject -- boolean
            define if it should create a journal object if we are
            not resuming

        Side effects:

            Sets the gdk screen DPI setting (resolution) to the
            Sugar screen resolution.

            Connects our "destroy" message to our _destroy_cb
            method.

            Creates a base gtk.Window within this window.

            Creates an ActivityService (self._bus) servicing
            this application.

        Usage:
            If your Activity implements __init__(), it should call
            the base class __init()__ before doing Activity specific things.

        """
        Window.__init__(self)

        ObjectStore().activity = self

        if os.environ.has_key('SUGAR_ACTIVITY_ROOT'):
            # If this activity runs inside Sugar, we want it to take all the
            # screen. Would be better if it was the shell to do this, but we
            # haven't found yet a good way to do it there.
            screen = gtk.gdk.screen_get_default()
            screen.connect('size-changed', self.__screen_size_changed_cb)
            self._adapt_window_to_screen()

        # process titles will only show 15 characters
        # but they get truncated anyway so if more characters
        # are supported in the future we will get a better view
        # of the processes
        proc_title = "%s <%s>" % (get_bundle_name(), handle.activity_id)
        util.set_proc_title(proc_title)

        self.connect('realize', self.__realize_cb)
        self.connect('delete-event', self.__delete_event_cb)

        self._active = False
        self._activity_id = handle.activity_id
        self._pservice = presenceservice.get_instance()
        self.shared_activity = None
        self._share_id = None
        self._join_id = None
        self._updating_jobject = False
        self._closing = False
        self._quit_requested = False
        self._deleting = False
        self._max_participants = 0
        self._invites_queue = []
        self._jobject = None
        self._read_file_called = False

        self._session = _get_session()
        self._session.register(self)
        self._session.connect('quit-requested',
                              self.__session_quit_requested_cb)
        self._session.connect('quit', self.__session_quit_cb)

        accel_group = gtk.AccelGroup()
        self.set_data('sugar-accel-group', accel_group)
        self.add_accel_group(accel_group)

        self._bus = ActivityService(self)
        self._owns_file = False

        share_scope = SCOPE_PRIVATE

        if handle.object_id:
            self._jobject = datastore.get(handle.object_id)
            self.set_title(self._jobject.metadata['title'])

            if self._jobject.metadata.has_key('share-scope'):
                share_scope = self._jobject.metadata['share-scope']

        # handle activity share/join
        mesh_instance = self._pservice.get_activity(self._activity_id,
                                                    warn_if_none=False)
        logging.debug("*** Act %s, mesh instance %r, scope %s",
                      self._activity_id, mesh_instance, share_scope)
        if mesh_instance is not None:
            # There's already an instance on the mesh, join it
            logging.debug("*** Act %s joining existing mesh instance %r",
                          self._activity_id, mesh_instance)
            self.shared_activity = mesh_instance
            self.shared_activity.connect('notify::private',
                                         self.__privacy_changed_cb)
            self._join_id = self.shared_activity.connect("joined",
                                                         self.__joined_cb)
            if not self.shared_activity.props.joined:
                self.shared_activity.join()
            else:
                self.__joined_cb(self.shared_activity, True, None)
        elif share_scope != SCOPE_PRIVATE:
            logging.debug('*** Act %s no existing mesh instance, but used to '
                'be shared, will share', self._activity_id)
            # no existing mesh instance, but activity used to be shared, so
            # restart the share
            if share_scope == SCOPE_INVITE_ONLY:
                self.share(private=True)
            elif share_scope == SCOPE_NEIGHBORHOOD:
                self.share(private=False)
            else:
                logging.debug('Unknown share scope %r', share_scope)

        if handle.object_id is None and create_jobject:
            logging.debug('Creating a jobject.')
            self._jobject = datastore.create()
            title = _('%s Activity') % get_bundle_name()
            self._jobject.metadata['title'] = title
            self.set_title(self._jobject.metadata['title'])
            self._jobject.metadata['title_set_by_user'] = '0'
            self._jobject.metadata['activity'] = self.get_bundle_id()
            self._jobject.metadata['activity_id'] = self.get_id()
            self._jobject.metadata['keep'] = '0'
            self._jobject.metadata['preview'] = ''
            self._jobject.metadata['share-scope'] = SCOPE_PRIVATE
            if self.shared_activity is not None:
                icon_color = self.shared_activity.props.color
            else:
                client = gconf.client_get_default()
                icon_color = client.get_string('/desktop/sugar/user/color')
            self._jobject.metadata['icon-color'] = icon_color

            self._jobject.file_path = ''
            # Cannot call datastore.write async for creates:
            # https://dev.laptop.org/ticket/3071
            datastore.write(self._jobject)

    def get_active(self):
        return self._active

    def set_active(self, active):
        if self._active != active:
            self._active = active
            if not self._active and self._jobject:
                self.save()

    active = gobject.property(
        type=bool, default=False, getter=get_active, setter=set_active)

    def get_max_participants(self):
        return self._max_participants

    def set_max_participants(self, participants):
        self._max_participants = participants

    max_participants = gobject.property(
            type=int, default=0, getter=get_max_participants,
            setter=set_max_participants)

    def get_id(self):
        """Returns the activity id of the current instance of your activity.

        The activity id is sort-of-like the unix process id (PID). However,
        unlike PIDs it is only different for each new instance (with
        create_jobject = True set) and stays the same everytime a user
        resumes an activity. This is also the identity of your Activity to
        other XOs for use when sharing.
        """
        return self._activity_id

    def get_bundle_id(self):
        """Returns the bundle_id from the activity.info file"""
        return os.environ['SUGAR_BUNDLE_ID']

    def set_canvas(self, canvas):
        """Sets the 'work area' of your activity with the canvas of your
        choice.

        One commonly used canvas is gtk.ScrolledWindow
        """
        Window.set_canvas(self, canvas)
        if not self._read_file_called:
            canvas.connect('map', self.__canvas_map_cb)

    def __screen_size_changed_cb(self, screen):
        self._adapt_window_to_screen()

    def _adapt_window_to_screen(self):
        screen = gtk.gdk.screen_get_default()
        self.set_geometry_hints(None,
                                screen.get_width(), screen.get_height(),
                                screen.get_width(), screen.get_height(),
                                screen.get_width(), screen.get_height(),
                                1, 1, 1, 1)

    def __session_quit_requested_cb(self, session):
        self._quit_requested = True

        if not self._prepare_close():
            session.will_quit(self, False)
        elif not self._updating_jobject:
            session.will_quit(self, True)

    def __session_quit_cb(self, client):
        self._complete_close()

    def __canvas_map_cb(self, canvas):
        logging.debug('Activity.__canvas_map_cb')
        if self._jobject and self._jobject.file_path and \
                not self._read_file_called:
            self.read_file(self._jobject.file_path)
            self._read_file_called = True
        canvas.disconnect_by_func(self.__canvas_map_cb)

    def __jobject_create_cb(self):
        pass

    def __jobject_error_cb(self, err):
        logging.debug('Error creating activity datastore object: %s', err)

    def get_activity_root(self):
        """ FIXME: Deprecated. This part of the API has been moved
        out of this class to the module itself

        Returns a path for saving Activity specific preferences, etc.

        Returns a path to the location in the filesystem where the activity can
        store activity related data that doesn't pertain to the current
        execution of the activity and thus cannot go into the DataStore.

        Currently, this will return something like
        ~/.sugar/default/MyActivityName/

        Activities should ONLY save settings, user preferences and other data
        which isn't specific to a journal item here. If (meta-)data is in
        anyway specific to a journal entry, it MUST be stored in the DataStore.
        """
        if os.environ.has_key('SUGAR_ACTIVITY_ROOT') and \
           os.environ['SUGAR_ACTIVITY_ROOT']:
            return os.environ['SUGAR_ACTIVITY_ROOT']
        else:
            return '/'

    def read_file(self, file_path):
        """
        Subclasses implement this method if they support resuming objects from
        the journal. 'file_path' is the file to read from.

        You should immediately open the file from the file_path, because the
        file_name will be deleted immediately after returning from read_file().
        Once the file has been opened, you do not have to read it immediately:
        After you have opened it, the file will only be really gone when you
        close it.

        Although not required, this is also a good time to read all meta-data:
        the file itself cannot be changed externally, but the title,
        description and other metadata['tags'] may change. So if it is
        important for you to notice changes, this is the time to record the
        originals.
        """
        raise NotImplementedError

    def write_file(self, file_path):
        """
        Subclasses implement this method if they support saving data to objects
        in the journal. 'file_path' is the file to write to.

        If the user did make changes, you should create the file_path and save
        all document data to it.

        Additionally, you should also write any metadata needed to resume your
        activity. For example, the Read activity saves the current page and
        zoom level, so it can display the page.

        Note: Currently, the file_path *WILL* be different from the one you
        received in file_read(). Even if you kept the file_path from
        file_read() open until now, you must still write the entire file to
        this file_path.
        """
        raise NotImplementedError

    def __save_cb(self):
        logging.debug('Activity.__save_cb')
        self._updating_jobject = False
        if self._quit_requested:
            self._session.will_quit(self, True)
        elif self._closing:
            self._complete_close()

    def __save_error_cb(self, err):
        logging.debug('Activity.__save_error_cb')
        self._updating_jobject = False
        if self._quit_requested:
            self._session.will_quit(self, False)
        if self._closing:
            self._show_keep_failed_dialog()
            self._closing = False
        logging.debug('Error saving activity object to datastore: %s', err)

    def _cleanup_jobject(self):
        if self._jobject:
            if self._owns_file and os.path.isfile(self._jobject.file_path):
                logging.debug('_cleanup_jobject: removing %r',
                    self._jobject.file_path)
                os.remove(self._jobject.file_path)
            self._owns_file = False
            self._jobject.destroy()
            self._jobject = None

    def get_preview(self):
        """Returns an image representing the state of the activity. Generally
        this is what the user is seeing in this moment.

        Activities can override this method, which should return a str with the
        binary content of a png image with a width of 300 and a height of 225
        pixels.
        """
        if self.canvas is None or not hasattr(self.canvas, 'get_snapshot'):
            return None
        pixmap = self.canvas.get_snapshot((-1, -1, 0, 0))

        width, height = pixmap.get_size()
        pixbuf = gtk.gdk.Pixbuf(gtk.gdk.COLORSPACE_RGB, 0, 8, width, height)
        pixbuf = pixbuf.get_from_drawable(pixmap, pixmap.get_colormap(),
                                          0, 0, 0, 0, width, height)
        pixbuf = pixbuf.scale_simple(style.zoom(300), style.zoom(225),
                                     gtk.gdk.INTERP_BILINEAR)

        preview_data = []

        def save_func(buf, data):
            data.append(buf)

        pixbuf.save_to_callback(save_func, 'png', user_data=preview_data)
        preview_data = ''.join(preview_data)

        return preview_data

    def _get_buddies(self):
        if self.shared_activity is not None:
            buddies = {}
            for buddy in self.shared_activity.get_joined_buddies():
                if not buddy.props.owner:
                    buddy_id = sha1(buddy.props.key).hexdigest()
                    buddies[buddy_id] = [buddy.props.nick, buddy.props.color]
            return buddies
        else:
            return {}

    def save(self):
        """Request that the activity is saved to the Journal.

        This method is called by the close() method below. In general,
        activities should not override this method. This method is part of the
        public API of an Acivity, and should behave in standard ways. Use your
        own implementation of write_file() to save your Activity specific data.
        """

        if self._jobject is None:
            logging.debug('Cannot save, no journal object.')
            return

        logging.debug('Activity.save: %r', self._jobject.object_id)

        if self._updating_jobject:
            logging.info('Activity.save: still processing a previous request.')
            return

        buddies_dict = self._get_buddies()
        if buddies_dict:
            self.metadata['buddies_id'] = cjson.encode(buddies_dict.keys())
            self.metadata['buddies'] = cjson.encode(self._get_buddies())

        preview = self.get_preview()
        if preview is not None:
            self.metadata['preview'] = dbus.ByteArray(preview)

        file_path = os.path.join(self.get_activity_root(), 'instance',
                                 '%i' % time.time())
        try:
            self.write_file(file_path)
        except NotImplementedError:
            logging.debug('Activity.write_file is not implemented.')
        else:
            if os.path.exists(file_path):
                self._owns_file = True
                self._jobject.file_path = file_path

        # Cannot call datastore.write async for creates:
        # https://dev.laptop.org/ticket/3071
        if self._jobject.object_id is None:
            datastore.write(self._jobject, transfer_ownership=True)
        else:
            self._updating_jobject = True
            datastore.write(self._jobject,
                    transfer_ownership=True,
                    reply_handler=self.__save_cb,
                    error_handler=self.__save_error_cb)

    def copy(self):
        """Request that the activity 'Keep in Journal' the current state
           of the activity.

        Activities should not override this method. Instead, like save() do any
        copy work that needs to be done in write_file()
        """
        logging.debug('Activity.copy: %r', self._jobject.object_id)
        self.save()
        self._jobject.object_id = None

    def __privacy_changed_cb(self, shared_activity, param_spec):
        if shared_activity.props.private:
            self._jobject.metadata['share-scope'] = SCOPE_INVITE_ONLY
        else:
            self._jobject.metadata['share-scope'] = SCOPE_NEIGHBORHOOD

    def __joined_cb(self, activity, success, err):
        """Callback when join has finished"""
        self.shared_activity.disconnect(self._join_id)
        self._join_id = None
        if not success:
            logging.debug('Failed to join activity: %s', err)
            return

        self.present()
        self.emit('joined')
        self.__privacy_changed_cb(self.shared_activity, None)

    def get_shared_activity(self):
        """Returns an instance of the shared Activity or None

        The shared activity is of type sugar.presence.activity.Activity
        """
        return self._shared_activity

    def get_shared(self):
        """Returns TRUE if the activity is shared on the mesh."""
        if not self.shared_activity:
            return False
        return self.shared_activity.props.joined

    def __share_cb(self, ps, success, activity, err):
        self._pservice.disconnect(self._share_id)
        self._share_id = None
        if not success:
            logging.debug('Share of activity %s failed: %s.',
                self._activity_id, err)
            return

        logging.debug('Share of activity %s successful, PS activity is %r.',
                      self._activity_id, activity)

        activity.props.name = self._jobject.metadata['title']

        self.shared_activity = activity
        self.shared_activity.connect('notify::private',
                self.__privacy_changed_cb)
        self.emit('shared')
        self.__privacy_changed_cb(self.shared_activity, None)

        self._send_invites()

    def _invite_response_cb(self, error):
        if error:
            logging.error('Invite failed: %s', error)

    def _send_invites(self):
        while self._invites_queue:
            buddy_key = self._invites_queue.pop()
            buddy = self._pservice.get_buddy(buddy_key)
            if buddy:
                self.shared_activity.invite(
                            buddy, '', self._invite_response_cb)
            else:
                logging.error('Cannot invite %s, no such buddy.', buddy_key)

    def invite(self, buddy_key):
        """Invite a buddy to join this Activity.

        Side Effects:
            Calls self.share(True) to privately share the activity if it wasn't
            shared before.
        """
        self._invites_queue.append(buddy_key)

        if (self.shared_activity is None
            or not self.shared_activity.props.joined):
            self.share(True)
        else:
            self._send_invites()

    def share(self, private=False):
        """Request that the activity be shared on the network.

        private -- bool: True to share by invitation only,
            False to advertise as shared to everyone.

        Once the activity is shared, its privacy can be changed by setting
        its 'private' property.
        """
        if self.shared_activity and self.shared_activity.props.joined:
            raise RuntimeError("Activity %s already shared." %
                               self._activity_id)
        verb = private and 'private' or 'public'
        logging.debug('Requesting %s share of activity %s.', verb,
            self._activity_id)
        self._share_id = self._pservice.connect("activity-shared",
                                                self.__share_cb)
        self._pservice.share_activity(self, private=private)

    def _show_keep_failed_dialog(self):
        alert = Alert()
        alert.props.title = _('Keep error')
        alert.props.msg = _('Keep error: all changes will be lost')

        cancel_icon = Icon(icon_name='dialog-cancel')
        alert.add_button(gtk.RESPONSE_CANCEL, _('Don\'t stop'), cancel_icon)

        stop_icon = Icon(icon_name='dialog-ok')
        alert.add_button(gtk.RESPONSE_OK, _('Stop anyway'), stop_icon)

        self.add_alert(alert)
        alert.connect('response', self._keep_failed_dialog_response_cb)

        self.present()

    def _keep_failed_dialog_response_cb(self, alert, response_id):
        self.remove_alert(alert)
        if response_id == gtk.RESPONSE_OK:
            self.close(skip_save=True)

    def can_close(self):
        """Activities should override this function if they want to perform
        extra checks before actually closing."""

        return True

    def _prepare_close(self, skip_save=False):
        if not skip_save:
            try:
                self.save()
            except:
                logging.info(traceback.format_exc())
                self._show_keep_failed_dialog()
                return False

        if self.shared_activity:
            self.shared_activity.leave()

        self._closing = True

        return True

    def _complete_close(self):
        self._cleanup_jobject()
        self.destroy()

        # Make the exported object inaccessible
        dbus.service.Object.remove_from_connection(self._bus)

        self._session.unregister(self)

    def close(self, skip_save=False):
        """Request that the activity be stopped and saved to the Journal

        Activities should not override this method, but should implement
        write_file() to do any state saving instead. If the application wants
        to control wether it can close, it should override can_close().
        """
        if not self.can_close():
            return

        if skip_save or self.metadata.get('title_set_by_user', '0') == '1':
            if not self._closing:
                if not self._prepare_close(skip_save):
                    return

            if not self._updating_jobject:
                self._complete_close()
        else:
            title_alert = NamingAlert(self, get_bundle_path())
            title_alert.set_transient_for(self.get_toplevel())
            title_alert.show()
            self.present()

    def __realize_cb(self, window):
        wm.set_bundle_id(window.window, self.get_bundle_id())
        wm.set_activity_id(window.window, str(self._activity_id))

    def __delete_event_cb(self, widget, event):
        self.close()
        return True

    def get_metadata(self):
        """Returns the jobject metadata or None if there is no jobject.

        Activities can set metadata in write_file() using:
            self.metadata['MyKey'] = "Something"

        and retrieve metadata in read_file() using:
            self.metadata.get('MyKey', 'aDefaultValue')

        Note: Make sure your activity works properly if one or more of the
        metadata items is missing. Never assume they will all be present.
        """
        if self._jobject:
            return self._jobject.metadata
        else:
            return None

    metadata = property(get_metadata, None)

    def handle_view_source(self):
        raise NotImplementedError

    def get_document_path(self, async_cb, async_err_cb):
        async_err_cb(NotImplementedError())

    def get_tutorials(self):
        return {}

    # DEPRECATED
    _shared_activity = property(lambda self: self.shared_activity, None)


_session = None


def _get_session():
    global _session

    if _session is None:
        _session = _ActivitySession()

    return _session


def get_bundle_name():
    """Return the bundle name for the current process' bundle"""
    return os.environ['SUGAR_BUNDLE_NAME']


def get_bundle_path():
    """Return the bundle path for the current process' bundle"""
    return os.environ['SUGAR_BUNDLE_PATH']


def get_activity_root():
    """Returns a path for saving Activity specific preferences, etc."""
    if os.environ.has_key('SUGAR_ACTIVITY_ROOT') and \
            os.environ['SUGAR_ACTIVITY_ROOT']:
        return os.environ['SUGAR_ACTIVITY_ROOT']
    else:
        raise RuntimeError("No SUGAR_ACTIVITY_ROOT set.")


def show_object_in_journal(object_id):
    bus = dbus.SessionBus()
    obj = bus.get_object(J_DBUS_SERVICE, J_DBUS_PATH)
    journal = dbus.Interface(obj, J_DBUS_INTERFACE)
    journal.ShowObject(object_id)