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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,¶ms) == NOTIFY_STOP) |
32 | || !bound) { |
33 | notifier_call_chain(KBD_UNBOUND_KEYCODE,¶ms); |
34 | return; |
35 | } |
36 | |
37 | if (unicode) { |
38 | param.value = unicode; |
39 | if (notifier_call_chain(KBD_UNICODE,¶ms) == NOTIFY_STOP) |
40 | return; |
41 | emit unicode; |
42 | return; |
43 | } |
44 | |
45 | params.value = keysym; |
46 | if (notifier_call_chain(KBD_KEYSYM,¶ms) == NOTIFY_STOP) |
47 | return; |
48 | apply keysym; |
49 | notifier_call_chain(KBD_POST_KEYSYM,¶ms); |
50 | } |
51 | |
52 | NOTE: This notifier is usually called from interrupt context. |
53 |
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