File: Scanner.py

package info (click to toggle)
onboard 1.4.1-5
  • links: PTS, VCS
  • area: main
  • in suites: bookworm, bullseye
  • size: 31,548 kB
  • sloc: python: 29,215; cpp: 5,965; ansic: 5,735; xml: 1,026; sh: 163; makefile: 39
file content (1080 lines) | stat: -rw-r--r-- 31,506 bytes parent folder | download | duplicates (4)
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
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
# -*- coding: utf-8 -*-

# Copyright © 2011-2013 Gerd Kohlberger <lowfi@chello.at>
# Copyright © 2012-2014, 2016 marmuta <marmvta@gmail.com>
#
# This file is part of Onboard.
#
# Onboard 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 3 of the License, or
# (at your option) any later version.
#
# Onboard 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, see <http://www.gnu.org/licenses/>.

from __future__ import division, print_function, unicode_literals

import sys
import logging
from functools import cmp_to_key

from Onboard.Config      import Config
from Onboard.XInput      import XIDeviceManager, XIEventType, XIEventMask
from Onboard.WindowUtils import show_new_device_dialog
from Onboard.Timer       import Timer

logger = logging.getLogger(__name__)
config = Config()

"""
Methods and terminology from:
 - Colven, Judge, 2006: Switch access to technology. A comprehensive guide.
 - GOK: The GNOME On-screen Keyboard.
"""

class Chunker(object):
    """
    Abstract base class for all chunker objects.

    Organizes keys into groups and provides methods
    to travers and highlight them.

    Hierarchy:
      Chunker --> FlatChunker --> GroupChunker
                              --> GridChunker
    """

    def __init__(self):
        logger.debug("Chunker.__init__()")

        """ Hierarchy of keys (list). """
        self._chunks = None

        """ The index of the active chunk. """
        self._index = 0

        """ The number of chunks at the current level. """
        self._length = 0

        """ A stack of (index, len) tuples. """
        self._path = []

        """ Number of times the current level has been scanned. """
        self.cycles = 0

    def __del__(self):
        logger.debug("Chunker.__del__()")

    def chunk(self, layout, layer):
        """
        Abstract: Split the keys on a layer into chunks.
        """
        raise NotImplementedError()

    def get_current_object(self):
        """
        Get the list or key the chunker points to.
        """
        level = self._chunks

        for p in self._path:
            index = p[0]
            level = level[index]

        return level[self._index]

    def _highlight_rec(self, obj, hl, keys):
        """
        Recursively sets the highlight on all keys below obj.
        """
        if isinstance(obj, list):
            for o in obj:
                self._highlight_rec(o, hl, keys)
        else:
            if hl != obj.scanned:
                obj.scanned = hl
                keys.append(obj)

    def highlight(self, hl, root=None):
        """
        Highlight or clear the current chunk.
        """
        keys = []

        if not root:
            root = self.get_current_object()

        self._highlight_rec(root, hl, keys)

        return keys

    def highlight_all(self, hl):
        """
        Highlight or clear all chunks.
        """
        return self.highlight(hl, self._chunks)

    def next(self):
        """
        Move to the next chunk on the current level.
        """
        next = (self._index + 1) % self._length

        if next < self._index:
            self.cycles += 1

        self._index = next

    def previous(self):
        """
        Move to the previous chunk on the current level.
        """
        prev = (self._index - 1) % self._length

        if prev > self._index:
            self.cycles += 1

        self._index = prev

    def can_ascend(self):
        """
        Whether the chunker can move a level up in the hierarchy.
        """
        return len(self._path) != 0

    def ascend(self):
        """
        Move one level up in the hierarchy.
        """
        if self.can_ascend():
            self._index, self._length = self._path.pop()
            self.cycles = 0
            return True

        return False

    def can_descend(self):
        """
        Whether the chunker can move a level down in the hierarchy.
        """
        return isinstance(self.get_current_object(), list)

    def descend(self):
        """
        Move one level down in the hierarchy.
        - Skips levels that have only one element.
        """
        obj = self.get_current_object()

        while isinstance(obj, list):
            self._path.append((self._index, self._length))
            self._index = 0
            self._length = len(obj)
            self.cycles = 0

            if self._length == 1:
                obj = obj[0]
                continue
            return True

        return False

    def up(self):
        """
        Abstract: Move to key above the current.
        """
        raise NotImplementedError()

    def down(self):
        """
        Abstract: Move to key below the current.
        """
        raise NotImplementedError()

    def get_key(self):
        """
        Get the current key.
        Returns None if the object is a list.
        """
        obj = self.get_current_object()

        if not isinstance(obj, list):
            return obj

        return None

    def reset(self):
        """
        Set the chunker to its initial state.
        """
        self.cycles  = 0
        self._index  = 0
        self._length = len(self._chunks)
        self._path   = []

    def is_reset(self):
        """
        Is the chunker in its initial state.
        """
        return not self._index and \
               not self.cycles and \
               not len(self._path)


class FlatChunker(Chunker):
    """
    Chunks a layer based on key location.
    """
    def compare_keys(self, a, b):
        """
        Sort keys by y and then x position
        """
        rect_a = a.get_border_rect().int()
        rect_b = b.get_border_rect().int()

        y = rect_a.y - rect_b.y
        if y != 0:
            return y

        return rect_a.x - rect_b.x

    def chunk(self, layout, layer):
        """
        Create a list of scannable keys and sort it.
        """
        self._chunks = [k for k in layout.iter_layer_keys(layer) \
                        if k.is_path_scannable()]
        self._chunks.extend([k for k in layout.iter_layer_keys(None) \
                             if k.is_path_scannable()])
        self._chunks.sort(key=cmp_to_key(self.compare_keys))
        self._length = len(self._chunks)


class GroupChunker(FlatChunker):
    """
    Chunks a layer based on priority and key location.
    """
    def compare_keys(self, a, b):
        """
        Sort keys by priority and location.
        """
        p = a.get_path_scan_priority() - b.get_path_scan_priority()
        if p != 0:
            return p

        return super(GroupChunker, self).compare_keys(a, b)

    def chunk(self, layout, layer):
        """
        Create a nested list of keys.
        """
        last_priority = None
        last_y = None
        chunks = []

        # populates 'self._chunks' with a flat sorted list of keys
        # using the compare_keys method of this class
        super(GroupChunker, self).chunk(layout, layer)

        # creates a new nested chunk list with the following layout:
        # A list of 'priority groups' where each members is a
        # list of 'scan rows' in which each member is a key.
        for key in self._chunks:
            scan_priority = key.get_path_scan_priority()
            if scan_priority != last_priority:
                last_priority = scan_priority
                last_y = None
                group = []
                chunks.append(group)

            rect = key.get_border_rect().int()
            if rect.y != last_y:
                last_y = rect.y
                row = []
                group.append(row)

            row.append(key)

        # if all keys are in the same group, remove the group
        if len(chunks) == 1:
            chunks = chunks[0]

        self._chunks = chunks
        self._length = len(self._chunks)


class GridChunker(FlatChunker):
    """
    Chunks a layer into rows of keys.
    """
    def chunk(self, layout, layer):
        """
        Create a nested list of keys.
        """
        last_x = sys.maxsize
        chunks = []

        # populates 'self._chunks' with a flat sorted list of keys
        super(GridChunker, self).chunk(layout, layer)

        for key in self._chunks:
            rect = key.get_border_rect().int()
            if rect.x < last_x:
                row = []
                chunks.append(row)
            last_x = rect.x
            row.append(key)

        self._chunks = chunks
        self._length = len(self._chunks)

    def _select_neighbour(self, key, direction):
        if key is None:
            return

        kc = key.get_border_rect().get_center()
        min_x = sys.float_info.max

        self.ascend()
        direction()

        for idx, obj in enumerate(self.get_current_object()):
            oc = obj.get_border_rect().get_center()
            dx = abs(kc[0] - oc[0])
            if dx < min_x:
                min_x = dx
                neighbour = idx

        self.descend()
        self._index = neighbour

    def up(self):
        self._select_neighbour(self.get_key(), self.previous)

    def down(self):
        self._select_neighbour(self.get_key(), self.next)


class ScanMode(Timer):
    """
    Abstract base class for all scanning modes.

    Specifies how the scanner moves between chunks of keys
    and when to activate them. Scan mode subclasses define
    a set of actions they support and the base class translates
    input device events into scan actions.

    Hierarchy:
        ScanMode --> AutoScan --> UserScan
                              --> OverScan
                 --> StepScan
                 --> DirectScan
    """

    """ Scan actions """
    ACTION_STEP       = 0
    ACTION_LEFT       = 1
    ACTION_RIGHT      = 2
    ACTION_UP         = 3
    ACTION_DOWN       = 4
    ACTION_ACTIVATE   = 5
    ACTION_STEP_START = 6
    ACTION_STEP_STOP  = 7
    ACTION_UNHANDLED  = 8

    """ Time between key activation flashes (in sec) """
    ACTIVATION_FLASH_INTERVAL = 0.1

    """ Number of key activation flashes """
    ACTIVATION_FLASH_COUNT = 4

    def __init__(self, redraw_callback, activate_callback):
        super(ScanMode, self).__init__()

        logger.debug("ScanMode.__init__()")

        """ Activation timer instance """
        self._activation_timer = Timer()

        """ Counter for key flash animation """
        self._flash = 0

        """ Callback for key redraws """
        self._redraw_callback = redraw_callback

        """ Callback for key activation """
        self._activate_callback = activate_callback

        """ A Chunker instance """
        self.chunker = None

    def __del__(self):
        logger.debug("ScanMode.__del__()")

    def map_actions(self, detail, pressed):
        """
        Abstract: Convert input events into scan actions.
        """
        raise NotImplementedError()

    def do_action(self, action):
        """
        Abstract: Handle scan actions.
        """
        raise NotImplementedError()

    def scan(self):
        """
        Abstract: Move between chunks.
        """
        raise NotImplementedError()

    def create_chunker(self):
        """
        Abstract: Create a chunker instance.
        """
        raise NotImplementedError()

    def init_position(self):
        """
        Virtual: Called if a new layer was set or a key activated.
        """
        pass

    def handle_event(self, event):
        """
        Translate device events into scan actions.
        """
        # Ignore events during key activation
        if self._activation_timer.is_running():
            return

        event_type = event.xi_type
        if event_type == XIEventType.ButtonPress:
            button_map = config.scanner.device_button_map
            action = self.map_actions(button_map, event.button, True)

        elif event_type == XIEventType.ButtonRelease:
            button_map = config.scanner.device_button_map
            action = self.map_actions(button_map, event.button, False)

        elif event_type == XIEventType.KeyPress:
            key_map = config.scanner.device_key_map
            action = self.map_actions(key_map, event.keyval, True)

        elif event_type == XIEventType.KeyRelease:
            key_map = config.scanner.device_key_map
            action = self.map_actions(key_map, event.keyval, False)

        else:
            action = self.ACTION_UNHANDLED

        if action != self.ACTION_UNHANDLED:
            self.do_action(action)

    def on_timer(self):
        """
        Override: Timer() callback.
        """
        return self.scan()

    def max_cycles_reached(self):
        """
        Check if the maximum number of scan cycles is reached.
        """
        return self.chunker.cycles >= config.scanner.cycles

    def set_layer(self, layout, layer):
        """
        Set the layer that should be scanned.
        """
        self.reset()
        self.chunker = self.create_chunker()
        self.chunker.chunk(layout, layer)
        self.init_position()

    def _on_activation_timer(self, key):
        """
        Timer callback: Flashes the key and finally activates it.
        """
        if self._flash > 0:
            key.scanned = not key.scanned
            self._flash -= 1
            self.redraw([key])
            return True
        else:
            self._activate_callback(key)
            self.init_position()
            return False

    def activate(self):
        """
        Activates a key and triggers feedback.
        """
        key = self.chunker.get_key()
        if not key:
            return

        if config.scanner.feedback_flash:
            self._flash = self.ACTIVATION_FLASH_COUNT
            self._activation_timer.start(self.ACTIVATION_FLASH_INTERVAL,
                                         self._on_activation_timer,
                                         key)
        else:
            self._activate_callback(key)
            self.init_position()

    def reset(self):
        """
        Stop scanning and clear all highlights.
        """
        if self.is_running():
            self.stop()

        if self.chunker:
            self.redraw(self.chunker.highlight_all(False))

    def redraw(self, keys=None):
        """
        Update individual keys or the entire keyboard.
        """
        self._redraw_callback(keys)

    def finalize(self):
        """
        Clean up the ScanMode instance.
        """
        self.reset()
        self._activation_timer = None


class AutoScan(ScanMode):
    """
    Automatic scan mode for 1 switch. Starts scanning on
    switch press and moves through a hierarchy of chunks.
    """
    def create_chunker(self):
        return GroupChunker()

    def map_actions(self, dev_map, detail, is_press):
        if is_press and detail in dev_map:
            return self.ACTION_STEP

        return self.ACTION_UNHANDLED

    def scan(self):
        self.redraw(self.chunker.highlight(False))
        self.chunker.next()

        if self.max_cycles_reached():
            self.chunker.reset()
            return False
        else:
            self.redraw(self.chunker.highlight(True))
            return True

    def do_action(self, action):
        if not self.is_running():
            # Start scanning
            self.redraw(self.chunker.highlight(True))
            self.start(config.scanner.interval)
        else:
            # Subsequent clicks
            self.stop()
            self.redraw(self.chunker.highlight(False))

            if self.chunker.descend():
                # Move one level down
                self.redraw(self.chunker.highlight(True))
                self.start(config.scanner.interval)
            else:
                # Activate
                self.activate()
                self.chunker.reset()


class UserScan(AutoScan):
    """
    Automatic scan mode for 1 switch. Like AutoScan but
    the scanner progresses only during switch press.
    """
    def map_actions(self, dev_map, detail, is_press):
        if detail in dev_map:
            if is_press:
                return self.ACTION_STEP_START
            else:
                return self.ACTION_STEP_STOP

        return self.ACTION_UNHANDLED

    def do_action(self, action):
        if action == self.ACTION_STEP_START:
            if not self.chunker.is_reset():
                # Every press except the initial
                self.redraw(self.chunker.highlight(False))
                self.chunker.descend()

            self.redraw(self.chunker.highlight(True))
            self.start(config.scanner.interval)

        elif action == self.ACTION_STEP_STOP:
            # Every release
            self.stop()
            if not self.chunker.can_descend():
                # Activate
                self.redraw(self.chunker.highlight(False))
                self.activate()
                self.chunker.reset()


class OverScan(AutoScan):
    """
    Automatic scan mode for 1 switch. Does fast forward
    scanning in a flat hierarchy with slow backtracking.
    """
    def __init__(self, redraw_callback, activate_callback):
        super(OverScan, self).__init__(redraw_callback, activate_callback)

        self._step = -1
        self._fast = True

    def create_chunker(self):
        return FlatChunker()

    def scan(self):
        self.redraw(self.chunker.highlight(False))
        if self._step > 0:
            # Backtrack
            self.chunker.previous()
            self._step -= 1
            self.redraw(self.chunker.highlight(True))
        else:
            # Fast forward
            self.chunker.next()

            if self.max_cycles_reached():
                # Abort
                self.chunker.reset()
                return False

            self.redraw(self.chunker.highlight(True))

            if not self._fast:
                self.stop()
                self.do_action(None)

        return True

    def do_action(self, action):
        if not self.is_running():
            # Start
            self._fast = True
            self._step = -1
            self.redraw(self.chunker.highlight(True))
            self.start(config.scanner.interval_fast)
        else:
            # Subsequent clicks
            if self._step >= 0:
                # Activate
                self.stop()
                self.redraw(self.chunker.highlight(False))
                self.activate()
                self.chunker.reset()
            else:
                # Backtrack
                self._step = config.scanner.backtrack
                self._fast = False
                self.chunker.cycles = 0
                self.start(config.scanner.interval)


class StepScan(ScanMode):
    """
    Directed scan mode for 2 switches.
    """
    def __init__(self, redraw_callback, activate_callback):
        super(StepScan, self).__init__(redraw_callback, activate_callback)

        self.swapped = False

    def create_chunker(self):
        return GroupChunker()

    def init_position(self):
        self.chunker.reset()
        self.redraw(self.chunker.highlight(True))

    def map_actions(self, dev_map, detail, is_press):
        if is_press and detail in dev_map:
            return dev_map[detail]

        return self.ACTION_UNHANDLED

    def get_alternate(self, action):
        if config.scanner.alternate and self.swapped:
            if action == self.ACTION_STEP:
                return self.ACTION_ACTIVATE
            else:
                return self.ACTION_STEP

        return action

    def do_action(self, action):
        if action == self.get_alternate(self.ACTION_STEP):
            self.redraw(self.chunker.highlight(False))
            self.chunker.next()
            if self.max_cycles_reached():
                self.init_position()
            else:
                self.redraw(self.chunker.highlight(True))
        else:
            self.redraw(self.chunker.highlight(False))
            self.swapped = not self.swapped
            if self.chunker.descend():
                self.redraw(self.chunker.highlight(True))
            else:
                self.activate()


class DirectScan(ScanMode):
    """
    Directed scan mode for 3 or 5 switches.
    """
    def create_chunker(self):
        return GridChunker()

    def init_position(self):
        self.chunker.descend()
        self.redraw(self.chunker.highlight(True))

    def map_actions(self, dev_map, detail, is_press):
        if is_press and detail in dev_map:
            return dev_map[detail]

        return self.ACTION_UNHANDLED

    def do_action(self, action):
        keys = self.chunker.highlight(False)

        if action == self.ACTION_LEFT:
            self.chunker.previous()
        elif action == self.ACTION_RIGHT:
            self.chunker.next()
        elif action == self.ACTION_UP:
            self.chunker.up()
        elif action == self.ACTION_DOWN:
            self.chunker.down()
        else:
            self.activate()

        keys.extend(self.chunker.highlight(True))
        self.redraw(keys)


class Scanner(object):
    """
    Main controller class for keyboard scanning. Manages
    ScanMode and ScanDevices objects and provides the
    public interface for the scanner.
    """

    """ Scan modes """
    MODE_AUTOSCAN  = 0
    MODE_OVERSCAN  = 1
    MODE_STEPSCAN  = 2
    MODE_DIRECTED3 = 3
    MODE_DIRECTED5 = 4

    def __init__(self, redraw_callback, activate_callback):
        logger.debug("Scanner.__init__()")

        """ A scan mode instance """
        self.mode = self._get_scan_mode(config.scanner.mode,
                                        redraw_callback,
                                        activate_callback)

        """ A scan device instance """
        self.device = ScanDevice(self.mode.handle_event)

        """ A keyboard layout """
        self.layout = None

        """ The active layer of the layout """
        self.layer = None

        config.scanner.mode_notify_add(self._mode_notify)
        config.scanner.user_scan_notify_add(self._user_scan_notify)

    def __del__(self):
        logger.debug("Scanner.__del__()")

    def _mode_notify(self, mode):
        """
        Callback for scanner.mode configuration changes.
        """
        rcb = self.mode._redraw_callback
        acb = self.mode._activate_callback

        self.mode.finalize()
        self.mode = self._get_scan_mode(mode, rcb, acb)
        self.mode.set_layer(self.layout, self.layer)

        self.device._event_handler = self.mode.handle_event

    def _user_scan_notify(self, user_scan):
        """
        Callback for scanner.user_scan configuration changes.
        """
        if config.scanner.mode == self.MODE_AUTOSCAN:
            self._mode_notify(config.scanner.mode)

    def _get_scan_mode(self, mode, redraw_callback, activate_callback):
        """
        Get the ScanMode instance for the current profile.
        """
        profiles = [ AutoScan, OverScan, StepScan, DirectScan ]

        if mode == self.MODE_AUTOSCAN and config.scanner.user_scan:
            return UserScan(redraw_callback, activate_callback)

        return profiles[mode](redraw_callback, activate_callback)

    def update_layer(self, layout, layer, force_update = False):
        """
        Notify the scanner about layer or layout changes.
        """
        changed = False

        if self.layout != layout:
            self.layout = layout
            changed = True

        if self.layer != layer:
            self.layer = layer
            changed = True

        if changed or force_update:
            self.mode.set_layer(self.layout, self.layer)

    def finalize(self):
        """
        Clean up all objects related to scanning.
        """
        config.scanner.mode_notify_remove(self._mode_notify)
        config.scanner.user_scan_notify_remove(self._user_scan_notify)
        self.device.finalize()
        self.mode.finalize()


class ScanDevice(object):
    """
    Input device manager class.

    Manages input devices on the system and deals with
    PnP related event. The actual press/release events
    are forwarded to a ScanMode instance.
    """

    """ Default device name (virtual core pointer) """
    DEFAULT_NAME = "Default"

    """ Device id's of the primary masters """
    DEFAULT_VCP_ID = 2
    DEFAULT_VCK_ID = 3

    """ Device name blacklist """
    blacklist = ["Virtual core pointer",
                 "Virtual core keyboard",
                 "Virtual core XTEST pointer",
                 "Virtual core XTEST keyboard",
                 "Power Button"]

    def __init__(self, event_handler):
        logger.debug("ScanDevice.__init__()")

        """ Selected device tuple (device id, master id) """
        self._active_device_ids = None

        """ Whether the active device is detached """
        self._floating = False

        """ Event handler for device events """
        self._event_handler = event_handler

        """ The manager for osk XInput devices """
        self._device_manager = XIDeviceManager()  # singleton
        self._device_manager.connect("device-event", self._device_event_handler)

        config.scanner.device_name_notify_add(self._device_name_notify)
        config.scanner.device_detach_notify_add(self._device_detach_notify)

        self._device_name_notify(config.scanner.device_name)

    def __del__(self):
        logger.debug("ScanDevice.__del__()")

    def _device_event_handler(self, event):
        """
        Handler for XI2 events.
        """
        event_type = event.xi_type
        device_id  = event.device_id

        if event_type == XIEventType.DeviceAdded:
            device = self._device_manager.lookup_device_id(device_id)
            show_new_device_dialog(device.name,
                                   device.get_config_string(),
                                   device.is_pointer(),
                                   self._on_new_device_accepted)

        elif event_type == XIEventType.DeviceRemoved:
            # If we are currently using this device,
            # close it and fall back to 'Default'
            if self._active_device_ids and \
               self._active_device_ids[0] == device_id:
                self._active_device_ids = None
                self._floating = False
                config.scanner.device_detach = False
                config.scanner.device_name = self.DEFAULT_NAME

        else:
            # Never handle VCK events.
            if device_id != self.DEFAULT_VCK_ID:
                # Forward VCP events only if 'Default' is selected.
                # Else only handle devices we selected.
                if (device_id == self.DEFAULT_VCP_ID and \
                    config.scanner.device_name == self.DEFAULT_NAME) or \
                   (self._active_device_ids and \
                    device_id == self._active_device_ids[0]):

                    self._event_handler(event)

    def _on_new_device_accepted(self, config_string):
        """
        Callback for the 'New device' dialog.
        Called only if 'Use device' was chosen.
        """
        config.scanner.device_name = config_string
        config.scanner.device_detach = True

    def _device_detach_notify(self, detach):
        """
        Callback for the scanner.device_detach configuration changes.
        """
        if self._active_device_ids is None:
            return

        if detach:
            if not self._floating:
                self.detach(self._active_device_ids[0])
        else:
            if self._floating:
                self.attach(*self._active_device_ids)

    def _device_name_notify(self, name):
        """
        Callback for the scanner.device_name configuration changes.
        """
        self.close()

        if name == self.DEFAULT_NAME:
            return

        for device in self._device_manager.get_devices():
            if self.is_useable(device) and \
               name == device.get_config_string():
                self.open(device)
                break

        if self._active_device_ids is None:
            logger.debug("Unknown device-name in configuration.")
            config.scanner.device_detach = False
            config.scanner.device_name = self.DEFAULT_NAME

    def open(self, device):
        """
        Select for events and optionally detach the device.
        """
        if device.is_pointer():
            event_mask = XIEventMask.ButtonPressMask | \
                         XIEventMask.ButtonReleaseMask
        else:
            event_mask = XIEventMask.KeyPressMask | \
                         XIEventMask.KeyReleaseMask
        try:
            self._device_manager.select_events(None, device, event_mask)
            self._active_device_ids = (device.id, device.attachment)
        except Exception as ex:
            logger.warning("Failed to open device {id}: {ex}"
                           .format(id = device.id, ex = ex))

        if config.scanner.device_detach and not device.is_master():
            self.detach(device.id)

    def close(self):
        """
        Stop using the current device.
        """
        if self._floating:
            self.attach(*self._active_device_ids)

        if self._active_device_ids:
            device = self._device_manager.lookup_device_id( \
                                            self._active_device_ids[0])
            try:
                self._device_manager.unselect_events(None, device)
                self._active_device_ids = None
            except Exception as ex:
                logger.warning("Failed to close device {id}: {ex}"
                               .format(id = self._active_device_ids[0],
                                       ex = ex))

    def attach(self, dev_id, master):
        """
        Attach the device to a master.
        """
        try:
            self._device_manager.attach_device_id(dev_id, master)
            self._floating = False
        except:
            logger.warning("Failed to attach device {id} to {master}"
                           .format(id = dev_id, master = master))

    def detach(self, dev_id):
        """
        Detach the device from its master.
        """
        try:
            self._device_manager.detach_device_id(dev_id)
            self._floating = True
        except:
            logger.warning("Failed to detach device {id}".format(id = dev_id))

    def finalize(self):
        """
        Clean up the ScanDevice instance.
        """
        self._device_manager.disconnect("device-event",
                                        self._device_event_handler)
        config.scanner.device_name_notify_remove(self._device_name_notify)
        config.scanner.device_detach_notify_remove(self._device_detach_notify)
        self.close()
        self._event_handler = None
        self.devices = None

    @staticmethod
    def is_useable(device):
        """
        Check whether this device is useable for scanning.
        """
        return device.name not in ScanDevice.blacklist \
               and device.enabled \
               and not device.is_floating()