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1 Keyboard notifier
2
3 One can use register_keyboard_notifier to get called back on keyboard
4 events (see kbd_keycode() function for details). The passed structure is
5 keyboard_notifier_param:
6
7 - 'vc' always provide the VC for which the keyboard event applies;
8 - 'down' is 1 for a key press event, 0 for a key release;
9 - 'shift' is the current modifier state, mask bit indexes are KG_*;
10 - 'value' depends on the type of event.
11
12 - KBD_KEYCODE events are always sent before other events, value is the keycode.
13 - KBD_UNBOUND_KEYCODE events are sent if the keycode is not bound to a keysym.
14 value is the keycode.
15 - KBD_UNICODE events are sent if the keycode -> keysym translation produced a
16 unicode character. value is the unicode value.
17 - KBD_KEYSYM events are sent if the keycode -> keysym translation produced a
18 non-unicode character. value is the keysym.
19 - KBD_POST_KEYSYM events are sent after the treatment of non-unicode keysyms.
20 That permits one to inspect the resulting LEDs for instance.
21
22 For each kind of event but the last, the callback may return NOTIFY_STOP in
23 order to "eat" the event: the notify loop is stopped and the keyboard event is
24 dropped.
25
26 In a rough C snippet, we have:
27
28 kbd_keycode(keycode) {
29 ...
30 params.value = keycode;
31 if (notifier_call_chain(KBD_KEYCODE,&params) == NOTIFY_STOP)
32 || !bound) {
33 notifier_call_chain(KBD_UNBOUND_KEYCODE,&params);
34 return;
35 }
36
37 if (unicode) {
38 param.value = unicode;
39 if (notifier_call_chain(KBD_UNICODE,&params) == NOTIFY_STOP)
40 return;
41 emit unicode;
42 return;
43 }
44
45 params.value = keysym;
46 if (notifier_call_chain(KBD_KEYSYM,&params) == NOTIFY_STOP)
47 return;
48 apply keysym;
49 notifier_call_chain(KBD_POST_KEYSYM,&params);
50 }
51
52 NOTE: This notifier is usually called from interrupt context.