aboutsummaryrefslogtreecommitdiff
path: root/libX11/specs/XKB/ch04.xml
blob: dee00b32f57616026a03e760520616a815485b94 (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
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN"
	  "http://www.oasis-open.org/docbook/xml/4.3/docbookx.dtd">
<chapter id='Xkb_Events'>
<title>Xkb Events</title>
<indexterm zone="Xkb_Events"><primary>events</primary></indexterm>

<para>
The primary way the X server communicates with clients is by sending X events
to them. Some events are sent to all clients, while others are sent only to
clients that have requested them. Some of the events that can be requested are
associated with a particular window and are only sent to those clients who have
both requested the event and specified the window in which the event occurred.
</para>


<para>
The Xkb extension uses events to communicate the keyboard status to interested
clients. These events are not associated with a particular window. Instead, all
Xkb keyboard status events are reported to all interested clients, regardless
of which window currently has the keyboard focus and regardless of the grab
state of the keyboard.<footnote><para>The one exception to this rule is the
XkbExtensionDeviceNotify event report that is sent when a client attempts to
use an unsupported feature of an X Input Extension device (see <link linkend="Setting_Xkb_Features_for_Non_KeyClass_Input_Extension_Devices">section 21.4</link>).
</para></footnote>
</para>


<para>
The X server reports the events defined by the Xkb extension to your client
application only if you have requested them. You may request Xkb events by
calling either
<function>XkbSelectEvents</function>
or
<function>XkbSelectEventDetails</function>.
<function>XkbSelectEvents</function>
requests Xkb events by their event type and causes them to be reported to your
client application under all circumstances. You can specify a finer granularity
for event reporting by using
<function>XkbSelectEventDetails</function>;
in this case events are reported only when the specific detail conditions you
specify have been met.
</para>

<sect1 id='Xkb_Event_Types'>
<title>Xkb Event Types</title>

<para>
The Xkb Extension adds new event types to the X protocol definition. An Xkb
event type is defined by two fields in the X event data structure. One is the
<structfield>type</structfield>
field, containing the
<emphasis>base event code</emphasis>.
This base event code is a value the X server assigns to each X extension at
runtime and that identifies the extension that generated the event; thus, the
event code in the
<structfield>type</structfield>
field identifies the event as an Xkb extension event, rather than an event
from another extension or a core X protocol event. You can obtain the base
event code via a call to
<function>XkbQueryExtension</function>
or
<function>XkbOpenDisplay</function>.
The second field is the Xkb event type, which contains a value uniquely
identifying each different Xkb event type. Possible values are defined by
constants declared in the header file
<filename class="headerfile">&lt;X11/extensions/Xkb.h&gt;</filename>.
</para>


<para>
<link linkend="table4.1">Table 4.1</link>
lists the categories of events defined by Xkb and their associated
event types, as defined in
<filename class="headerfile">Xkb.h</filename>.
Each event is described in more detail in the section referenced for that
event.
</para>

<table id='table4.1' frame='topbot'>
<title>Xkb Event Types</title>
<?dbfo keep-together="always" ?>
<tgroup cols='3' align='left' colsep='0' rowsep='0'>
<colspec colname='c1' colwidth='3.0*'/>
<colspec colname='c2' colwidth='4.0*'/>
<colspec colname='c3' colwidth='1.0*'/>
<thead>
<row rowsep='1'>
  <entry>Event Type</entry>
  <entry>Conditions Generating Event</entry>
  <entry>Section</entry>
</row>
</thead>
<tbody>
<row>
  <entry><symbol>XkbNewKeyboardNotify</symbol></entry>
  <entry>Keyboard geometry; keycode range change</entry>
  <entry><link linkend="Replacing_a_Keyboard_On_the_Fly">19</link></entry>
</row>
<row>
  <entry><symbol>XkbMapNotify</symbol></entry>
  <entry>Keyboard mapping change</entry>
  <entry><link linkend="Tracking_Changes_to_Map_Components">14.4</link></entry>
</row>
<row>
  <entry><symbol>XkbStateNotify</symbol></entry>
  <entry>Keyboard state change</entry>
  <entry><link linkend="Tracking_Keyboard_State">5.4</link></entry>
</row>
<row>
  <entry><symbol>XkbControlsNotify</symbol></entry>
  <entry>Keyboard controls state change</entry>
  <entry><link linkend="Tracking_Changes_to_Keyboard_Controls">10.11</link></entry>
</row>
<row>
  <entry><symbol>XkbIndicatorStateNotify</symbol></entry>
  <entry>Keyboard indicators state change</entry>
  <entry><link linkend="Tracking_Changes_to_Indicator_State_or_Map">8.5</link></entry>
</row>
<row>
  <entry><symbol>XkbIndicatorMapNotify</symbol></entry>
  <entry>Keyboard indicators map change</entry>
  <entry><link linkend="Tracking_Changes_to_Indicator_State_or_Map">8.5</link></entry>
</row>
<row>
  <entry><symbol>XkbNamesNotify</symbol></entry>
  <entry>Keyboard name change</entry>
  <entry><link linkend="Tracking_Name_Changes">18.5</link></entry>
</row>
<row>
  <entry><symbol>XkbCompatMapNotify</symbol></entry>
  <entry>Keyboard compatibility map change</entry>
  <entry><link linkend="Tracking_Changes_to_the_Compatibility_Map">17.5</link></entry>
</row>
<row>
  <entry><symbol>XkbBellNotify</symbol></entry>
  <entry>Keyboard bell generated</entry>
  <entry><link linkend="Detecting_Bells">9.4</link></entry>
</row>
<row>
  <entry><symbol>XkbActionMessage</symbol></entry>
  <entry>Keyboard action message</entry>
  <entry><link linkend="Actions_for_Generating_Messages">16.1.11</link></entry>
</row>
<row>
  <entry><symbol>XkbAccessXNotify</symbol></entry>
  <entry>AccessX state change</entry>
  <entry><link linkend="AccessXNotify_Events">10.6.4</link></entry>
</row>
<row>
  <entry><symbol>XkbExtensionDeviceNotify</symbol></entry>
  <entry>Extension device change</entry>
  <entry><link linkend="Tracking_Changes_to_Extension_Devices">21.6</link></entry>
</row>
</tbody>
</tgroup>
</table>

</sect1>
<sect1 id='Xkb_Event_Data_Structures'>
<title>Xkb Event Data Structures</title>

<para id='XkbAnyEvent'>
<indexterm significance="preferred" zone="Xkb_Event_Data_Structures">
<primary>events</primary><secondary><structname>XkbAnyEvent</structname></secondary></indexterm>
<indexterm significance="preferred" zone="Xkb_Event_Data_Structures">
<primary><structname>XkbAnyEvent</structname></primary></indexterm>
Xkb reports each event it generates in a unique structure holding the data
values needed to describe the conditions the event is reporting. However, all
Xkb events have certain things in common. These common features are contained
in the same fields at the beginning of all Xkb event structures and are
described in the
<structname>XkbAnyEvent</structname>
structure:

<programlisting>
typedef struct {
    int             type;        /* Xkb extension base event code */
    unsigned long   serial;      /* X server serial number for event */
    Bool            send_event;  /* <symbol>True</symbol> &rArr; synthetically generated */
    Display *       display;     /* server connection where event generated */
    Time            time;        /* server time when event generated */
    int             xkb_type;    /* Xkb minor event code */
    unsigned int    device;      /* Xkb device ID, will not be <symbol>XkbUseCoreKbd</symbol> */
} <structname>XkbAnyEvent</structname>;
</programlisting></para>

<para>
For any Xkb event, the
<structfield>type</structfield>
field is set to the base event code for the Xkb extension, assigned by the
server to all Xkb extension events. The
<structfield>serial</structfield>,
<structfield>send_event</structfield>,
and
<structfield>display</structfield>
fields are as described for all X11 events. The
<structfield>time</structfield>
field is set to the time when the event was generated and is expressed in
milliseconds. The
<structfield>xkb_type</structfield>
field contains the minor extension event code, which is the extension event
type, and is one of the values listed in
<link linkend="table4.1">Table 4.1</link>. The
<structfield>device</structfield>
field contains the keyboard device identifier associated with the event. This
is never
<symbol>XkbUseCoreKbd</symbol>,
even if the request that generated the event specified a device of
<symbol>XkbUseCoreKbd</symbol>.
If the request that generated the event specified
<symbol>XkbUseCoreKbd</symbol>,
<structfield>device</structfield>
contains a value assigned by the server to specify the core keyboard. If the
request that generated the event specified an X input extension device,
<structfield>device</structfield>
contains that same identifier.
</para>


<para>
Other data fields specific to individual Xkb events are described in subsequent
chapters where the events are described.
</para>


</sect1>
<sect1 id='Selecting_Xkb_Events'>
<title>Selecting Xkb Events</title>
<indexterm significance="preferred" zone="Selecting_Xkb_Events">
<primary>events</primary><secondary>mask</secondary></indexterm>
<indexterm significance="preferred" zone="Selecting_Xkb_Events">
<primary>mask</primary><secondary>event</secondary></indexterm>

<para>
Xkb events are selected using an event mask, much the same as normal core X
events are selected. However, unlike selecting core X events, where you must
specify the selection status (on or off) for all possible event types whenever
you wish to change the selection criteria for any one event, Xkb allows you to
restrict the specification to only the event types you wish to change. This
means that you do not need to remember the event selection values for all
possible types each time you want to change one of them.
</para>


<para>
Many Xkb event types are generated under several different circumstances. When
selecting to receive an Xkb event, you may specify either that you want it
delivered under all circumstances, or that you want it delivered only for a
subset of the possible circumstances.
</para>

<para>
You can also deselect an event type that was previously selected for, using the
same granularity.
</para>

<para>
Xkb provides two functions to select and deselect delivery of Xkb events.
<function>XkbSelectEvents</function>
allows you to select or deselect delivery of more than one Xkb event type at
once. Events selected using
<function>XkbSelectEvents</function>
are delivered to your program under all circumstances that generate the
events. To restrict delivery of an event to a subset of the conditions under
which it occurs, use
<function>XkbSelectEventDetails</function>.
<function>XkbSelectEventDetails</function>
only allows you to change the selection conditions for a single event at a
time, but it provides a means of fine-tuning the conditions under which the
event is delivered.
</para>


<para>
To select and / or deselect for delivery of one or more Xkb events and have
them delivered under all conditions, use
<function>XkbSelectEvents</function>.
</para>

<indexterm significance="preferred" zone="XkbSelectEvents"><primary><function>XkbSelectEvents</function></primary></indexterm>
<funcsynopsis id="XkbSelectEvents">
  <funcprototype>
    <funcdef>Bool <function>XkbSelectEvents</function></funcdef>
<!-- (
<parameter>display, device_spec, bits_to_change, values_for_bits</parameter>
) -->

    <paramdef>Display *<parameter>display</parameter></paramdef>
    <paramdef>unsigned int <parameter>device_spec</parameter></paramdef>
    <paramdef>unsigned long int <parameter>bits_to_change</parameter></paramdef>
    <paramdef>unsigned long int <parameter>values_for_bits</parameter></paramdef>
  </funcprototype>
</funcsynopsis>
<variablelist>
  <varlistentry>
    <term>
      <parameter>display</parameter>
    </term>
    <listitem>
      <para>
        connection to the X server
      </para>
    </listitem>
  </varlistentry>
  <varlistentry>
    <term>
      <parameter>device_spec</parameter>
    </term>
    <listitem>
      <para>
        device ID, or <symbol>XkbUseCoreKbd</symbol>
      </para>
    </listitem>
  </varlistentry>
  <varlistentry>
    <term>
      <parameter>bits_to_change</parameter>
    </term>
    <listitem>
      <para>
        determines events to be selected / deselected
      </para>
    </listitem>
  </varlistentry>
  <varlistentry>
    <term>
      <parameter>values_for_bits</parameter>
    </term>
    <listitem>
      <para>
        1&rArr;select, 0&rarr;deselect; for events in <parameter>bits_to_change</parameter>
      </para>
    </listitem>
  </varlistentry>
</variablelist>

<para>
This request changes the Xkb event selection mask for the keyboard specified by
<parameter>device_spec</parameter>.
</para>


<para>
Each Xkb event that can be selected is represented by a bit in the
<parameter>bits_to_change</parameter>
and
<parameter>values_for_bits</parameter>
masks. Only the event selection bits specified by the
<parameter>bits_to_change</parameter>
parameter are affected; any unspecified bits are left unchanged. To turn on
event selection for an event, set the bit for the event in the
<parameter>bits_to_change</parameter>
parameter and set the corresponding bit in the
<parameter>values_for_bits</parameter>
parameter. To turn off event selection for an event, set the bit for the event
in the
<parameter>bits_to_change</parameter>
parameter and do not set the corresponding bit in the
<parameter>values_for_bits</parameter>
parameter. The valid values for both of these parameters are an inclusive
bitwise OR of the masks shown in <link linkend="table4.2">Table 4.2</link>.
There is no interface to return
your client’s current event selection mask. Clients cannot set other
clients’ event selection masks.
</para>


<para>
If a bit is not set in the
<parameter>bits_to_change</parameter>
parameter, but the corresponding bit is set in the
<parameter>values_for_bits</parameter>
parameter, a
<errorname>BadMatch</errorname>
protocol error results. If an undefined bit is set in either the
<parameter>bits_to_change</parameter>
or the
<parameter>values_for_bits</parameter>
parameter, a
<errorname>BadValue</errorname>
protocol error results.
</para>


<para>
All event selection bits are initially zero for clients using the Xkb
extension. Once you set some bits, they remain set for your client until you
clear them via another call to
<function>XkbSelectEvents</function>.
</para>


<para>
<function>XkbSelectEvents</function>
returns
<symbol>False</symbol>
if the Xkb extension has not been initialized and
<symbol>True</symbol>
otherwise.
</para>


<para>
To select or deselect for a specific Xkb event and optionally place conditions
on when events of that type are reported to your client, use
<function>XkbSelectEventDetails</function>.
This allows you to exercise a finer granularity of control over delivery of
Xkb events with
<function>XkbSelectEvents</function>.
</para>


<indexterm significance="preferred" zone="XkbSelectEventDetails"><primary><function>XkbSelectEventDetails</function></primary></indexterm>
<funcsynopsis id="XkbSelectEventDetails">
  <funcprototype>
    <funcdef>Bool <function>XkbSelectEventDetails</function></funcdef>
<!-- (
<parameter>display, device_spec, event_type, bits_to_change</parameter>,
<parameter>values_for_bits</parameter>
) -->

    <paramdef>Display *<parameter>display</parameter></paramdef>
    <paramdef>unsigned int <parameter>device_spec</parameter></paramdef>
    <paramdef>unsigned int <parameter>event_type</parameter></paramdef>
    <paramdef>unsigned long int <parameter>bits_to_change</parameter></paramdef>
    <paramdef>unsigned long int <parameter>values_for_bits</parameter></paramdef>
  </funcprototype>
</funcsynopsis>
<variablelist>
  <varlistentry>
    <term>
      <parameter>display</parameter>
    </term>
    <listitem>
      <para>
        connection to the X server
      </para>
    </listitem>
  </varlistentry>
  <varlistentry>
    <term>
      <parameter>device_spec</parameter>
    </term>
    <listitem>
      <para>
        device ID, or <symbol>XkbUseCoreKbd</symbol>
      </para>
    </listitem>
  </varlistentry>
  <varlistentry>
    <term>
      <parameter>event_type</parameter>
    </term>
    <listitem>
      <para>
        Xkb event type of interest
      </para>
    </listitem>
  </varlistentry>
  <varlistentry>
    <term>
      <parameter>bits_to_change</parameter>
    </term>
    <listitem>
      <para>
        event selection details
      </para>
    </listitem>
  </varlistentry>
  <varlistentry>
    <term>
      <parameter>values_for_bits</parameter>
    </term>
    <listitem>
      <para>
        values for bits selected by <parameter>bits_to_change</parameter>
      </para>
    </listitem>
  </varlistentry>
</variablelist>

<para>
While
<function>XkbSelectEvents</function>
allows multiple events to be selected,
<function>XkbSelectEventDetails</function>
changes the selection criteria for a single type of Xkb event. The
interpretation of the
<parameter>bits_to_change</parameter>
and
<parameter>values_for_bits</parameter>
masks depends on the event type in question.
</para>


<para>
<function>XkbSelectEventDetails</function>
changes the Xkb event selection mask for the keyboard specified by
<parameter>device_spec</parameter>
and the Xkb event specified by
<parameter>event_type</parameter>.
To turn on event selection for an event detail, set the bit for the detail in
the
<parameter>bits_to_change</parameter>
parameter and set the corresponding bit in the
<parameter>values_for_bits</parameter>
parameter. To turn off event detail selection for a detail, set the bit for
the detail in the
<parameter>bits_to_change</parameter>
parameter and do not set the corresponding bit in the
<parameter>values_for_bits</parameter>
parameter.
</para>


<para>
If an invalid event type is specified, a
<errorname>BadValue</errorname>
protocol error results. If a bit is not set in the
<parameter>bits_to_change</parameter>
parameter, but the corresponding bit is set in the
<parameter>values_for_bits</parameter>
parameter, a
<errorname>BadMatch</errorname>
protocol error results. If an undefined bit is set in either the
<parameter>bits_to_change</parameter>
or the
<parameter>values_for_bits</parameter>
parameter, a
<errorname>BadValue</errorname>
protocol error results.
</para>


<para>
For each type of Xkb event, the legal event details that you can specify in the
<function>XkbSelectEventDetails</function>
request are listed in the chapters that describe each event in detail.
</para>


<sect2 id='Event_Masks'>
<title>Event Masks</title>

<para>
The X server reports the events defined by Xkb to your client application only
if you have requested them via a call to
<function>XkbSelectEvents</function>
or
<function>XkbSelectEventDetails</function>.
Specify the event types in which you are interested in a mask, as described
in <link linkend="Selecting_Xkb_Events">section 4.3</link>.
</para>


<para>
<link linkend="table4.2">Table 4.2</link>
lists the event mask constants that can be specified with the
<function>XkbSelectEvents</function>
request and the circumstances in which the mask should be specified.
</para>

<table id='table4.2' frame='topbot'>
<title>XkbSelectEvents Mask Constants</title>
<?dbfo keep-together="always" ?>
<tgroup cols='3' align='left' colsep='0' rowsep='0'>
<colspec colname='c1' colwidth='2.0*'/>
<colspec colname='c2' colwidth='1.0*'/>
<colspec colname='c3' colwidth='2.0*'/>
<thead>
<row rowsep='1'>
  <entry>Event Mask</entry>
  <entry>Value</entry>
  <entry>Notification Wanted</entry>
</row>
</thead>
<tbody>
  <row>
    <entry>
<symbol>XkbNewKeyboardNotifyMask</symbol>
    </entry>
    <entry>(1L&lt;&lt;0)</entry>
    <entry>Keyboard geometry change</entry>
  </row>
  <row>
    <entry>
      <symbol>XkbMapNotifyMask</symbol>
    </entry>
    <entry>(1L&lt;&lt;1)</entry>
    <entry>Keyboard mapping change</entry>
  </row>
  <row>
    <entry>
<para><symbol>XkbStateNotifyMask</symbol></para>
    </entry>
    <entry>(1L&lt;&lt;2)</entry>
    <entry><para>Keyboard state change</para></entry>
  </row>
  <row>
    <entry>
<para><symbol>XkbControlsNotifyMask</symbol></para>
    </entry>
    <entry>(1L&lt;&lt;3)</entry>
    <entry>Keyboard control change</entry>
  </row>
  <row>
    <entry>
<symbol>XkbIndicatorStateNotifyMask</symbol>
    </entry>
    <entry>(1L&lt;&lt;4)</entry>
    <entry>Keyboard indicator state change</entry>
  </row>
  <row>
    <entry>
<symbol>XkbIndicatorMapNotifyMask</symbol>
    </entry>
    <entry>(1L&lt;&lt;5)</entry>
    <entry>Keyboard indicator map change</entry>
  </row>
  <row>
    <entry>
<symbol>XkbNamesNotifyMask</symbol>
    </entry>
    <entry>(1L&lt;&lt;6)</entry>
    <entry>Keyboard name change</entry>
  </row>
  <row>
    <entry>
<symbol>XkbCompatMapNotifyMask</symbol>
    </entry>
    <entry>(1L&lt;&lt;7)</entry>
    <entry>Keyboard compat map change</entry>
  </row>
  <row>
    <entry>
<symbol>XkbBellNotifyMask</symbol>
    </entry>
    <entry>(1L&lt;&lt;8)</entry>
    <entry>Bell</entry>
  </row>
  <row>
    <entry>
<symbol>XkbActionMessageMask</symbol>
    </entry>
    <entry>(1L&lt;&lt;9)</entry>
    <entry>Action message</entry>
  </row>
  <row>
    <entry>
<symbol>XkbAccessXNotifyMask</symbol>
    </entry>
    <entry>(1L&lt;&lt;10)</entry>
    <entry>AccessX features</entry>
  </row>
  <row>
    <entry>
<symbol>XkbExtensionDeviceNotifyMask</symbol>
    </entry>
    <entry>(1L&lt;&lt;11)</entry>
    <entry>Extension device</entry>
  </row>
  <row>
    <entry>
<symbol>XkbAllEventsMask</symbol>
    </entry>
    <entry>(0xFFF)</entry>
    <entry>All Xkb events</entry>
  </row>
</tbody>
</tgroup>
</table>

</sect2>
</sect1>
<sect1 id='Unified_Xkb_Event_Type'>
<title>Unified Xkb Event Type</title>
<indexterm significance="preferred" zone="Unified_Xkb_Event_Type">
<primary>events</primary><secondary><structname>XkbEvent</structname></secondary></indexterm>
<indexterm significance="preferred" zone="Unified_Xkb_Event_Type">
<primary><structname>XkbEvent</structname></primary></indexterm>

<para>
The
<structname>XkbEvent</structname>
structure is a union of the individual structures declared for each Xkb event
type and for the core protocol
<structname>XEvent</structname>
type. Given an
<structname>XkbEvent</structname>
structure, you may use the
<structfield>type</structfield>
field to determine if the event is an Xkb event
(<structfield>type</structfield>
equals the Xkb base event code; see <link linkend="Initializing_the_Keyboard_Extension">section 2.4</link>). If the event is an Xkb
event, you may then use the
<structfield>any.xkb_type</structfield>
field to determine the type of Xkb event and thereafter access the
event-dependent components using the union member corresponding to the
particular Xkb event type.
</para>

<para><programlisting>
typedef union _XkbEvent {
      int                            type;
      XkbAnyEvent                    any;
      XkbStateNotifyEvent            state;
      XkbMapNotifyEvent              map;
      XkbControlsNotifyEvent         ctrls;
      XkbIndicatorNotifyEvent        indicators;
      XkbBellNotifyEvent             bell;
      XkbAccessXNotifyEvent          accessx;
      XkbNamesNotifyEvent            names;
      XkbCompatMapNotifyEvent        compat;
      XkbActionMessageEvent          message;
      XkbExtensionDeviceNotifyEvent  device;
      XkbNewKeyboardNotifyEvent      new_kbd;
      XEvent                         core;
} <structname>XkbEvent</structname>;
</programlisting></para>

<para>
This unified Xkb event type includes a normal
<structname>XEvent</structname>
as used by the core protocol, so it is straightforward for applications that
use Xkb events to call the X library event functions without having to cast
every reference. For example, to get the next event, you can simply declare a
variable of type
<structname>XkbEvent</structname>
and call:

<programlisting>XNextEvent(dpy,&amp;xkbev.core);</programlisting>
</para>
</sect1>
</chapter>