+ * Utilities for actions.
+ */
+void register_code(uint8_t code);
+void unregister_code(uint8_t code);
+void add_mods(uint8_t mods);
+void del_mods(uint8_t mods);
+void set_mods(uint8_t mods);
+void clear_keyboard(void);
+void clear_keyboard_but_mods(void);
+bool sending_anykey(void);
+void layer_switch(uint8_t new_layer);
+bool is_tap_key(key_t key);
+bool waiting_buffer_has_anykey_pressed(void);
+
+
+
+/*
+ * Action codes
+ * ============
+ * 16bit code: action_kind(4bit) + action_parameter(12bit)
+ *
+ * Keyboard Keys(00XX)
+ * -------------------
+ * ACT_LMODS(0000):
+ * 0000|0000|000000|00 No action
+ * 0000|0000|000000|01 Transparent
+ * 0000|0000| keycode Key
+ * 0000|mods|000000|00 Left mods
+ * 0000|mods| keycode Key & Left mods
+ *
+ * ACT_RMODS(0001):
+ * 0001|0000|000000|00 No action(not used)
+ * 0001|0000|000000|01 Transparent(not used)
+ * 0001|0000| keycode Key(no used)
+ * 0001|mods|000000|00 Right mods
+ * 0001|mods| keycode Key & Right mods
+ *
+ * ACT_LMODS_TAP(0010):
+ * 0010|mods|000000|00 Left mods OneShot
+ * 0010|mods|000000|01 (reserved)
+ * 0010|mods|000000|10 (reserved)
+ * 0010|mods|000000|11 (reserved)
+ * 0010|mods| keycode Left mods + tap Key
+ *
+ * ACT_RMODS_TAP(0011):
+ * 0011|mods|000000|00 Right mods OneShot
+ * 0011|mods|000000|01 (reserved)
+ * 0011|mods|000000|10 (reserved)
+ * 0011|mods|000000|11 (reserved)
+ * 0011|mods| keycode Right mods + tap Key
+ *
+ *
+ * Other keys(01XX)
+ * --------------------
+ * This action handles other usages than keyboard.
+ * ACT_USAGE(0100):
+ * 0100|00| usage(10) System control(0x80) - General Desktop page(0x01)
+ * 0100|01| usage(10) Consumer control(0x01) - Consumer page(0x0C)
+ * 0100|10| usage(10) (reserved)
+ * 0100|11| usage(10) (reserved)
+ *
+ * ACT_MOUSEKEY(0110):
+ * 0101|XXXX| keycode Mouse key
+ *
+ *
+ * Layer Actions(10XX)
+ * -------------------
+ * ACT_KEYMAP:
+ * 1000|--xx|0000 0000 Clear keyamp and overlay
+ * 1000|LLLL|0000 00xx Reset default layer and clear keymap and overlay
+ * 1000|LLLL| keycode Invert with tap key
+ * 1000|LLLL|1111 0000 Invert with tap toggle
+ * 1000|LLLL|1111 00xx Invert[^= 1<<L]
+ * 1000|LLLL|1111 0100 On/Off
+ * 1000|LLLL|1111 01xx On[|= 1<<L]
+ * 1000|LLLL|1111 1000 Off/On
+ * 1000|LLLL|1111 10xx Off[&= ~(1<<L)]
+ * 1000|LLLL|1111 1100 Set/Clear
+ * 1000|LLLL|1111 11xx Set[= 1<<L]
+ * default layer: 0-15(4bit)
+ * xx: On {00:for special use, 01:press, 10:release, 11:both}
+ *
+ * ACT_OVERLAY:
+ * 1011|0000|0000 0000 Clear overlay
+ * 1011|LLLL|0000 00ss Invert 4-bit chunk [^= L<<(4*ss)]
+ * 1011|LLLL| keycode Invert with tap key
+ * 1011|LLLL|1111 0000 Invert with tap toggle
+ * 1011|LLLL|1111 00xx Invert[^= 1<<L]
+ * 1011|LLLL|1111 0100 On/Off(momentary)
+ * 1011|LLLL|1111 01xx On[|= 1<<L]
+ * 1011|LLLL|1111 1000 Off/On
+ * 1011|LLLL|1111 10xx Off[&= ~(1<<L)]
+ * 1011|LLLL|1111 1100 Set/Clear
+ * 1011|LLLL|1111 11xx Set[= 1<<L]
+ * overlays: 16-layer on/off status(16bit)
+ * xx: On {00:for special use, 01:press, 10:release, 11:both}
+ *
+ *
+ * Extensions(11XX)
+ * ----------------
+ * ACT_MACRO(1100):
+ * 1100|opt | id(8) Macro play?
+ * 1100|1111| id(8) Macro record?
+ *
+ * ACT_COMMAND(1110):
+ * 1110|opt | id(8) Built-in Command exec
+ *
+ * ACT_FUNCTION(1111):
+ * 1111| address(12) Function?
+ * 1111|opt | id(8) Function?
+ *
+ */
+enum action_kind_id {
+ ACT_LMODS = 0b0000,
+ ACT_RMODS = 0b0001,
+ ACT_LMODS_TAP = 0b0010,
+ ACT_RMODS_TAP = 0b0011,
+
+ ACT_USAGE = 0b0100,
+ ACT_MOUSEKEY = 0b0101,
+
+ ACT_KEYMAP = 0b1000,
+ ACT_OVERLAY = 0b1001,
+
+ ACT_MACRO = 0b1100,
+ ACT_COMMAND = 0b1110,
+ ACT_FUNCTION = 0b1111
+};