1================= 2Keyboard notifier 3================= 4 5One can use register_keyboard_notifier to get called back on keyboard 6events (see kbd_keycode() function for details). The passed structure is 7keyboard_notifier_param: 8 9- 'vc' always provide the VC for which the keyboard event applies; 10- 'down' is 1 for a key press event, 0 for a key release; 11- 'shift' is the current modifier state, mask bit indexes are KG_*; 12- 'value' depends on the type of event. 13 14- KBD_KEYCODE events are always sent before other events, value is the keycode. 15- KBD_UNBOUND_KEYCODE events are sent if the keycode is not bound to a keysym. 16 value is the keycode. 17- KBD_UNICODE events are sent if the keycode -> keysym translation produced a 18 unicode character. value is the unicode value. 19- KBD_KEYSYM events are sent if the keycode -> keysym translation produced a 20 non-unicode character. value is the keysym. 21- KBD_POST_KEYSYM events are sent after the treatment of non-unicode keysyms. 22 That permits one to inspect the resulting LEDs for instance. 23 24For each kind of event but the last, the callback may return NOTIFY_STOP in 25order to "eat" the event: the notify loop is stopped and the keyboard event is 26dropped. 27 28In a rough C snippet, we have:: 29 30 kbd_keycode(keycode) { 31 ... 32 params.value = keycode; 33 if (notifier_call_chain(KBD_KEYCODE,¶ms) == NOTIFY_STOP) 34 || !bound) { 35 notifier_call_chain(KBD_UNBOUND_KEYCODE,¶ms); 36 return; 37 } 38 39 if (unicode) { 40 param.value = unicode; 41 if (notifier_call_chain(KBD_UNICODE,¶ms) == NOTIFY_STOP) 42 return; 43 emit unicode; 44 return; 45 } 46 47 params.value = keysym; 48 if (notifier_call_chain(KBD_KEYSYM,¶ms) == NOTIFY_STOP) 49 return; 50 apply keysym; 51 notifier_call_chain(KBD_POST_KEYSYM,¶ms); 52 } 53 54.. note:: This notifier is usually called from interrupt context. 55