tmk_core/doc/keymap.md

   1 Keymap framework - how to define your keymap
   2 ============================================
   3 ***NOTE: This is not final version, may be inconsistent with source code and changed occasionally for a while.***
   4
   5 ## 0. Keymap and layers
   6 **Keymap** is comprised of multiple layers of key layout, you can define **32 layers** at most.
   7 **Layer** is an array of **keycodes** to define **actions** for each physical keys.
   8 respective layers can be validated simultaneously. Layers are indexed with 0 to 31 and higher layer has precedence.
   9
  10     Keymap: 32 Layers                   Layer: Keycode matrix
  11     -----------------                   ---------------------
  12     stack of layers                     array_of_keycode[row][column]
  13            ____________ precedence               _______________________
  14           /           / | high                  / ESC / F1  / F2  / F3   ....
  15       31 /___________// |                      /-----/-----/-----/-----
  16       30 /___________// |                     / TAB /  Q  /  W  /  E   ....
  17       29 /___________/  |                    /-----/-----/-----/-----
  18        :   _:_:_:_:_:__ |               :   /LCtrl/  A  /  S  /  D   ....
  19        :  / : : : : : / |               :  /  :     :     :     :
  20        2 /___________// |               2 `--------------------------
  21        1 /___________// |               1 `--------------------------
  22        0 /___________/  V low           0 `--------------------------
  23
  24
  25
  26 ### 0.1 Keymap status
  27 Keymap has its state in two parameters:
  28 **`default_layer`** indicates a base keymap layer(0-31) which is always valid and to be referred, **`keymap_stat`** is 16bit variable which has current on/off status of layers on its each bit.
  29
  30 Keymap layer '0' is usually `default_layer` and which is the only valid layer and other layers is initially off after boot up firmware, though, you can configured them in `config.h`.
  31 To change `default_layer` will be useful when you switch key layout completely, say you want Colmak instead of Qwerty.
  32
  33     Initial state of Keymap          Change base layout
  34     -----------------------          ------------------
  35
  36       31                               31
  37       30                               30
  38       29                               29
  39        :                                :
  40        :                                :   ____________
  41        2   ____________                 2  /           /
  42        1  /           /              ,->1 /___________/
  43     ,->0 /___________/               |  0
  44     |                                |
  45     `--- default_layer = 0           `--- default_layer = 1
  46          layer_state   = 0x00000001       layer_state   = 0x00000002
  47
  48 On the other hand, you shall change `layer_state` to overlay base layer with some layers for feature such as navigation keys, function key(F1-F12), media keys or special actions.
  49
  50     Overlay feature layer
  51     ---------------------      bit|status
  52            ____________        ---+------
  53       31  /           /        31 |   0
  54       30 /___________// -----> 30 |   1
  55       29 /___________/  -----> 29 |   1
  56        :                        : |   :
  57        :   ____________         : |   :
  58        2  /           /         2 |   0
  59     ,->1 /___________/  ----->  1 |   1
  60     |  0                        0 |   0
  61     |                                 +
  62     `--- default_layer = 1            |
  63          layer_state   = 0x60000002 <-'
  64
  65
  66
  67 ### 0.2 Layer Precedence and Transparency
  68 Note that ***higher layer has higher priority on stack of layers***, namely firmware falls down from top layer to bottom to look up keycode. Once it spots keycode other than **`KC_TRNS`**(transparent) on a layer it stops searching and lower layers aren't referred.
  69
  70 You can place `KC_TRNS` on overlay layer changes just part of layout to fall back on lower or base layer.
  71 Key with `KC_TRANS` doesn't has its own keycode and refers to lower valid layers for keycode, instead.
  72 See example below.
  73
  74
  75 ### 0.3 Keymap Example
  76 Keymap is **`keymaps[]`** C array in fact and you can define layers in it with **`KEYMAP()`** C macro and keycodes. To use complex actions you need to define `Fn` keycode in **`fn_actions[]`** array.
  77
  78 This is a keymap example for [HHKB](http://en.wikipedia.org/wiki/Happy_Hacking_Keyboard) keyboard.
  79 This example has three layers, 'Qwerty' as base layer, 'Cursor' and  'Mousekey'.
  80 In this example,
  81
  82  `Fn0` is a **momentary layer switching** key, you can use keys on Cursor layer while holding the key.
  83
  84  `Fn1` is a momentary layer switching key with tapping feature, you can get semicolon **';'** with taping the key and switch layers while holding the key. The word **'tap'** or **'tapping'** mean to press and release a key quickly.
  85
  86  `Fn2` is a **toggle layer switch** key, you can stay switched layer after releasing the key unlike momentary switching.
  87
  88 You can find other keymap definitions in file `keymap.c` located on project directories.
  89
  90     static const uint8_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
  91         /* 0: Qwerty
  92          * ,-----------------------------------------------------------.
  93          * |Esc|  1|  2|  3|  4|  5|  6|  7|  8|  9|  0|  -|  =|  \|  `|
  94          * |-----------------------------------------------------------|
  95          * |Tab  |  Q|  W|  E|  R|  T|  Y|  U|  I|  O|  P|  [|  ]|Backs|
  96          * |-----------------------------------------------------------|
  97          * |Contro|  A|  S|  D|  F|  G|  H|  J|  K|  L|Fn1|  '|Enter   |
  98          * |-----------------------------------------------------------|
  99          * |Shift   |  Z|  X|  C|  V|  B|  N|  M|  ,|  .|  /|Shift |Fn0|
 100          * `-----------------------------------------------------------'
 101          *       |Gui|Alt  |Space                  |Alt  |Fn2|
 102          *       `-------------------------------------------'
 103          */
 104         KEYMAP(ESC, 1,   2,   3,   4,   5,   6,   7,   8,   9,   0,   MINS,EQL, BSLS,GRV, \
 105                TAB, Q,   W,   E,   R,   T,   Y,   U,   I,   O,   P,   LBRC,RBRC,BSPC, \
 106                LCTL,A,   S,   D,   F,   G,   H,   J,   K,   L,   FN1, QUOT,ENT, \
 107                LSFT,Z,   X,   C,   V,   B,   N,   M,   COMM,DOT, SLSH,RSFT,FN0, \
 108                     LGUI,LALT,          SPC,                RALT,FN2),
 109         /* 1: Cursor(HHKB mode)
 110          * ,-----------------------------------------------------------.
 111          * |Pwr| F1| F2| F3| F4| F5| F6| F7| F8| F9|F10|F11|F12|Ins|Del|
 112          * |-----------------------------------------------------------|
 113          * |Caps |   |   |   |   |   |   |   |Psc|Slk|Pus|Up |   |Backs|
 114          * |-----------------------------------------------------------|
 115          * |Contro|VoD|VoU|Mut|   |   |  *|  /|Hom|PgU|Lef|Rig|Enter   |
 116          * |-----------------------------------------------------------|
 117          * |Shift   |   |   |   |   |   |  +|  -|End|PgD|Dow|Shift |   |
 118          * `-----------------------------------------------------------'
 119          *      |Gui |Alt  |Space                  |Alt  |Gui|
 120          *      `--------------------------------------------'
 121          */
 122         KEYMAP(PWR, F1,  F2,  F3,  F4,  F5,  F6,  F7,  F8,  F9,  F10, F11, F12, INS, DEL, \
 123                CAPS,TRNS,TRNS,TRNS,TRNS,TRNS,TRNS,TRNS,PSCR,SLCK,PAUS,UP,  TRNS,BSPC, \
 124                LCTL,VOLD,VOLU,MUTE,TRNS,TRNS,PAST,PSLS,HOME,PGUP,LEFT,RGHT,ENT, \
 125                LSFT,TRNS,TRNS,TRNS,TRNS,TRNS,PPLS,PMNS,END, PGDN,DOWN,RSFT,TRNS, \
 126                     LGUI,LALT,          SPC,                RALT,RGUI),
 127         /* 2: Mousekey
 128          * ,-----------------------------------------------------------.
 129          * |Esc| F1| F2| F3| F4| F5| F6| F7| F8| F9|F10|F11|F12|Ins|Del|
 130          * |-----------------------------------------------------------|
 131          * |Tab  |   |   |   |   |   |MwL|MwD|MwU|MwR|   |   |   |Backs|
 132          * |-----------------------------------------------------------|
 133          * |Contro|   |   |   |   |   |McL|McD|McU|McR|   |   |Return  |
 134          * |-----------------------------------------------------------|
 135          * |Shift   |   |   |   |   |Mb3|Mb2|Mb1|Mb4|Mb5|   |Shift |   |
 136          * `-----------------------------------------------------------'
 137          *      |Gui |Alt  |Mb1                    |Alt  |   |
 138          *      `--------------------------------------------'
 139          * Mc: Mouse Cursor / Mb: Mouse Button / Mw: Mouse Wheel
 140          */
 141         KEYMAP(ESC, F1,  F2,  F3,  F4,  F5,  F6,  F7,  F8,  F9,  F10, F11, F12, INS, DEL, \
 142                TAB, TRNS,TRNS,TRNS,TRNS,TRNS,WH_L,WH_D,WH_U,WH_R,TRNS,TRNS,TRNS,BSPC, \
 143                LCTL,TRNS,ACL0,ACL1,ACL2,TRNS,MS_L,MS_D,MS_U,MS_R,TRNS,QUOT,ENT, \
 144                LSFT,TRNS,TRNS,TRNS,TRNS,BTN3,BTN2,BTN1,BTN4,BTN5,SLSH,RSFT,TRNS, \
 145                     LGUI,LALT,          BTN1,               RALT,TRNS),
 146     };
 147
 148     static const uint16_t PROGMEM fn_actions[] = {
 149         ACTION_LAYER_MOMENTARY(1),                  // FN0
 150         ACTION_LAYER_TAP_KEY(2, KC_SCLN),           // FN1
 151         ACTION_LAYER_TOGGLE(2),                     // FN2
 152     };
 153
 154
 155
 156
 157 ## 1. Keycode
 158 See [`common/keycode.h`](../common/keycode.h) or keycode table below for the detail. Keycode is internal **8bit code** to indicate action performed on key in keymap. Keycode has `KC_` prefixed symbol respectively. Most of keycodes like `KC_A` have simple action registers key to host on press and unregister on release, while some of other keycodes has some special actions like `Fn` keys, Media control keys, System control keys and Mousekeys.
 159
 160  ***In `KEYMAP()` macro you should omit prefix part `KC_` of keycode to keep keymap compact.*** For example, just use `A` instead you place `KC_A` in `KEYMAP()`. Some keycodes has 4-letter **short name** in addition to descriptive name, you'll prefer short one in `KEYMAP()`.
 161
 162 ### 1.0 Other key
 163 - `KC_NO` for no action
 164 - `KC_TRNS` for layer transparency (See above)
 165
 166 ### 1.1 Normal key
 167 - `KC_A` to `KC_Z`, `KC_1` to `KC_0` for alpha numeric key
 168 - `KC_MINS`, `KC_EQL`, `KC_GRV`, `KC_RBRC`, `KC_LBRC`, `KC_COMM`, `KC_DOT`, `KC_BSLS`, `KC_SLSH`, `KC_SCLN`, `KC_QUOT`
 169 - `KC_ESC`, `KC_TAB`, `KC_SPC`, `KC_BSPC`, `KC_ENT`, `KC_DEL`, `KC_INS`
 170 - `KC_UP`, `KC_DOWN`, `KC_RGHT`, `KC_LEFT`, `KC_PGUP`, `KC_PGDN`, `KC_HOME`, `KC_END`
 171 - `KC_CAPS`, `KC_NLCK`, `KC_SLCK`, `KC_PSCR`, `KC_PAUS`, `KC_APP`, `KC_F1` to `KC_F24`
 172 - `KC_P1` to `KC_P0`, `KC_PDOT`, `KC_PCMM`, `KC_PSLS`, `KC_PAST`, `KC_PMNS`, `KC_PPLS`, `KC_PEQL`, `KC_PENT` for keypad.
 173
 174 ### 1.2 Modifier
 175 There are 8 modifiers which has discrimination between left and right.
 176
 177 - `KC_LCTL` and `KC_RCTL` for Control
 178 - `KC_LSFT` and `KC_RSFT` for Shift
 179 - `KC_LALT` and `KC_RALT` for Alt
 180 - `KC_LGUI` and `KC_RGUI` for Windows key or Command key in Mac
 181
 182 ### 1.3 Mousekey
 183 - `KC_MS_U`, `KC_MS_D`, `KC_MS_L`, `KC_MS_R` for mouse cursor
 184 - `KC_WH_U`, `KC_WH_D`, `KC_WH_L`, `KC_WH_R` for mouse wheel
 185 - `KC_BTN1`, `KC_BTN2`, `KC_BTN3`, `KC_BTN4`, `KC_BTN5` for mouse buttons
 186
 187 ### 1.4 System & Media key
 188 - `KC_PWR`, `KC_SLEP`, `KC_WAKE` for Power, Sleep, Wake
 189 - `KC_MUTE`, `KC_VOLU`, `KC_VOLD` for audio volume control
 190 - `KC_MNXT`, `KC_MPRV`, `KC_MSTP`, `KC_MPLY`, `KC_MSEL` for media control
 191 - `KC_MAIL`, `KC_CALC`, `KC_MYCM` for application launch
 192 - `KC_WSCH`, `KC_WHOM`, `KC_WBAK`, `KC_WFWD`, `KC_WSTP`, `KC_WREF`, `KC_WFAV` for web browser operation
 193
 194 ### 1.5 Fn key
 195 `KC_FNnn` are keycodes for `Fn` key which not given any actions at the beginning unlike most of keycodes has its own inborn action. To use these keycodes in `KEYMAP()` you need to assign action you want at first. Action of `Fn` key is defined in `fn_actions[]` and its index of the array is identical with number part of `KC_FNnn`. Thus `KC_FN0` keycode indicates the action defined in first element of the array. ***32 `Fn` keys can be defined at most.***
 196
 197 ### 1.6 Keycode Table
 198  See keycode table in [`doc/keycode.txt`](./keycode.txt) for description of keycodes.
 199
 200  In regard to implementation side most of keycodes are identical with [HID usage][HID_usage](pdf) sent to host for real and some virtual keycodes are defined to support special actions.
 201 [HID_usage]: http://www.usb.org/developers/hidpage/Hut1_12v2.pdf
 202
 203
 204
 205 ## 2. Action
 206 See [`common/action_code.h`](../common/action_code.h). Action is a **16bit code** and defines function to perform on events of a key like press, release, holding and tapping.
 207
 208 Most of keys just register 8bit scancode to host, but to support other complex features needs 16bit extended action codes internally. However, using 16bit action codes in keymap results in double size in memory compared to using just keycodes. To avoid this waste 8bit keycodes are used in `KEYMAP()` instead of action codes.
 209
 210 ***You can just use keycodes of `Normal key`, `Modifier`, `Mousekey` and `System & Media key` in keymap*** to indicate corresponding actions instead of using action codes. While ***to use other special actions you should use keycode of `Fn` key defined in `fn_actions[]`.***
 211
 212
 213 ### 2.1 Key Action
 214 This is a simple action that registers scancodes(HID usage in fact) to host on press event of key and unregister on release.
 215
 216 #### Parameters
 217 + **mods**: { ` MOD_LCTL`, ` MOD_LSFT`, ` MOD_LALT`, ` MOD_LGUI`,
 218               ` MOD_RCTL`, ` MOD_RSFT`, ` MOD_RALT`, ` MOD_RGUI` }
 219 + **key**: keycode
 220
 221
 222 #### 2.1.1 Normal key and Modifier
 223 ***This action usually won't be used expressly in keymap*** because you can just use keycodes in `KEYMAP()` instead.
 224
 225 You can define these actions on *'A'* key and *'left shift'* modifier with:
 226
 227     ACTION_KEY(KC_A)
 228     ACTION_KEY(KC_LSFT)
 229
 230 #### 2.1.2 Modified key
 231 This action is comprised of strokes of modifiers and a key. `Macro` action is needed if you want more complex key strokes.
 232
 233 Say you want to assign a key to `Shift + 1` to get character *'!'* or `Alt + Tab` to switch application windows.
 234
 235     ACTION_MODS_KEY(MOD_LSFT, KC_1)
 236     ACTION_MODS_KEY(MOD_LALT, KC_TAB)
 237
 238 Or `Alt,Shift + Tab` can be defined. `ACTION_MODS_KEY(mods, key)` requires **4-bit modifier state** and a **keycode** as arguments. See `keycode.h` for `MOD_BIT()` macro.
 239
 240     ACTION_MODS_KEY(MOD_LALT | MOD_LSFT, KC_TAB)
 241
 242 #### 2.1.3 Multiple Modifiers
 243 Registers multiple modifiers with pressing a key. To specify multiple modifiers use `|`.
 244
 245     ACTION_MODS(MOD_ALT | MOD_LSFT)
 246
 247 #### 2.1.3 Modifier with Tap key([Dual role][dual_role])
 248 Works as a modifier key while holding, but registers a key on tap(press and release quickly).
 249
 250
 251     ACTION_MODS_TAP_KEY(MOD_RCTL, KC_ENT)
 252
 253
 254
 255 ### 2.2 Layer Action
 256 These actions operate layers of keymap.
 257
 258 #### Parameters
 259 You can specify a **target layer** of action and **when the action is executed**. Some actions take a **bit value** for bitwise operation.
 260
 261
 262 + **layer**: `0`-`31`
 263 + **on**: { `ON_PRESS` | `ON_RELEASE` | `ON_BOTH` }
 264 + **bits**: 4-bit value and 1-bit mask bit
 265
 266
 267 #### 2.2.1 Default Layer
 268 Default Layer is a layer which always is valid and referred to when actions is not defined on other overlay layers.
 269
 270 This sets Default Layer to given parameter `layer` and activate it.
 271
 272     ACTION_DEFAULT_LAYER_SET(layer)
 273
 274
 275 #### 2.2.2 Momentary
 276 Turns on `layer` momentarily while holding, in other words it activates when key is pressed and deactivate when released.
 277
 278     ACTION_LAYER_MOMENTARY(layer)
 279
 280
 281 #### 2.2.3 Toggle Switch
 282 Turns on `layer` with first type(press and release) and turns off with next.
 283
 284     ACTION_LAYER_TOGGLE(layer)
 285
 286
 287 #### 2.2.4 Momentary Switch with tap key
 288 Turns on `layer` momentary while holding, but registers key on tap(press and release quickly).
 289
 290     ACTION_LAYER_TAP_KEY(layer, key)
 291
 292
 293 #### 2.2.5 Momentary Switch with tap toggle
 294 Turns on `layer` momentary while holding and toggles it with serial taps.
 295
 296     ACTION_LAYER_TAP_TOGGLE(layer)
 297
 298
 299 #### 2.2.6 Invert state of layer
 300 Inverts current state of `layer`. If the layer is on it becomes off with this action.
 301
 302     ACTION_LAYER_INVERT(layer, on)
 303
 304
 305 #### 2.2.7 Turn On layer
 306 Turns on layer state.
 307
 308     ACTION_LAYER_ON(layer, on)
 309
 310 Turns on layer state on press and turns off on release.
 311
 312     ACTION_LAYER_ON_OFF(layer)
 313
 314
 315 #### 2.2.8 Turn Off layer
 316 Turns off layer state.
 317
 318     ACTION_LAYER_OFF(layer, on)
 319
 320 Turns off layer state on press and activates on release.
 321
 322     ACTION_LAYER_OFF_ON(layer)
 323
 324
 325 #### 2.2.9 Set layer
 326 Turn on layer only.
 327 `layer_state = (1<<layer) [layer: 0-31]`
 328
 329     ACTION_LAYER_SET(layer, on)
 330
 331 Turns on layer only and clear all layer on release..
 332
 333     ACTION_LAYER_SET_CLEAR(layer)
 334
 335
 336 #### 2.2.10 Bitwise operation
 337
 338 **part** indicates which part of 32bit layer state(0-7). **bits** is 5-bit value. **on** indicates when the action is executed.
 339
 340     ACTION_LAYER_BIT_AND(part, bits, on)
 341     ACTION_LAYER_BIT_OR(part, bits, on)
 342     ACTION_LAYER_BIT_XOR(part, bits, on)
 343     ACTION_LAYER_BIT_SET(part, bits, on)
 344
 345 These actions works with parameters as following code.
 346
 347     uint8_t shift = part*4;
 348     uint32_t mask = (bits&0x10) ? ~(0xf<<shift) : 0;
 349     uint32_t layer_state = layer_state <bitop> ((bits<<shift)|mask);
 350
 351
 352 Default Layer also has bitwise operations, they are executed when key is released.
 353
 354     ACTION_DEFAULT_LAYER_BIT_AND(part, bits)
 355     ACTION_DEFAULT_LAYER_BIT_OR(part, bits)
 356     ACTION_DEFAULT_LAYER_BIT_XOR(part, bits)
 357     ACTION_DEFAULT_LAYER_BIT_SET(part, bits)
 358
 359
 360
 361 ### 2.3 Macro action
 362 ***TBD***
 363
 364 `Macro` action indicates complex key strokes.
 365
 366     MACRO( D(LSHIFT), D(D), END )
 367     MACRO( U(D), U(LSHIFT), END )
 368     MACRO( I(255), T(H), T(E), T(L), T(L), W(255), T(O), END )
 369
 370 #### 2.3.1 Macro Commands
 371 - **I()**   change interval of stroke.
 372 - **D()**   press key
 373 - **U()**   release key
 374 - **T()**   type key(press and release)
 375 - **W()**   wait
 376 - **END**   end mark
 377
 378 #### 2.3.2 Examples
 379
 380 ***TODO: sample implementation***
 381 See `keyboard/hhkb/keymap.c` for sample.
 382
 383
 384
 385 ### 2.4 Function action
 386 ***TBD***
 387
 388 There are two type of action, normal `Function` and tappable `Function`.
 389 These actions call user defined function with `id`, `opt`, and key event information as arguments.
 390
 391 #### 2.4.1 Function
 392 To define normal `Function` action in keymap use this.
 393
 394     ACTION_FUNCTION(id, opt)
 395
 396 #### 2.4.2 Function with tap
 397 To define tappable `Function` action in keymap use this.
 398
 399     ACTION_FUNCTION_TAP(id, opt)
 400
 401 #### 2.4.3 Implement user function
 402 `Function` actions can be defined freely with C by user in callback function:
 403
 404     void keymap_call_function(keyrecord_t *event, uint8_t id, uint8_t opt)
 405
 406 This C function is called every time key is operated, argument `id` selects action to be performed and `opt` can be used for option. Function `id` can be 0-255 and `opt` can be 0-15.
 407
 408  `keyrecord_t` is comprised of key event and tap count. `keyevent_t` indicates which and when key is pressed or released. From `tap_count` you can know tap state, 0 means no tap. These information will be used in user function to decide how action of key is performed.
 409
 410     typedef struct {
 411         keyevent_t  event;
 412         uint8_t     tap_count;
 413     } keyrecord_t;
 414
 415     typedef struct {
 416         key_t    key;
 417         bool     pressed;
 418         uint16_t time;
 419     } keyevent_t;
 420
 421     typedef struct {
 422         uint8_t col;
 423         uint8_t row;
 424     } key_t;
 425
 426 ***TODO: sample implementation***
 427 See `keyboard/hhkb/keymap.c` for sample.
 428
 429
 430
 431 ### 2.5 Backlight Action
 432 These actions control the backlight.
 433
 434 #### 2.5.1 Change backlight level
 435 Increase backlight level.
 436
 437     ACTION_BACKLIGHT_INCREASE()
 438
 439 Decrease backlight level.
 440
 441     ACTION_BACKLIGHT_DECREASE()
 442
 443 Step through backlight levels.
 444
 445     ACTION_BACKLIGHT_STEP()
 446
 447 Turn a specific backlight level on or off.
 448
 449     ACTION_BACKLIGHT_LEVEL(1)
 450
 451 #### 2.5.2 Turn on / off backlight
 452 Turn the backlight on and off without changing level.
 453
 454     ACTION_BACKLIGHT_TOGGLE()
 455
 456
 457
 458 ## 3. Layer switching Example
 459 There are some ways to switch layer with 'Layer' actions.
 460
 461 ### 3.1 Momentary switching
 462 Momentary switching changes layer only while holding Fn key.
 463
 464 This action makes 'Layer 1' active(valid) on key press event and inactive on release event. Namely you can overlay a layer on lower layers or default layer temporarily with this action.
 465
 466     ACTION_LAYER_MOMENTARY(1)
 467
 468
 469 Note that after switching on press the actions on destination layer(Layer 1) are performed.
 470 ***Thus you shall need to place an action to go back on destination layer***, or you will be stuck in destination layer without way to get back. Usually you need to place same action or 'KC_TRNS` on destination layer to get back.
 471
 472
 473 ### 3.2 Toggle switching
 474 Toggle switching performed after releasing a key. With this action you can keep staying on the destination layer until you type the key again to return.
 475
 476 This performs toggle switching action of 'Layer 2'.
 477
 478     ACTION_LAYER_TOGGLE(2)
 479
 480
 481
 482 ### 3.3 Momentary switching with Tap key
 483 These actions switch a layer only while holding a key but register the key on tap. **Tap** means to press and release a key quickly.
 484
 485     ACTION_LAYER_TAP_KEY(2, KC_SCLN)
 486
 487 With this you can place a layer switching action on normal key like ';' without losing its original key register function. This action allows you to have layer switching action without necessity of a dedicated key. It means you can have it even on home row of keyboard.
 488
 489
 490
 491 ### 3.4 Momentary switching with Tap Toggle
 492 This switches layer only while holding a key but toggle layer with several taps. **Tap** means to press and release key quickly.
 493
 494     ACTION_LAYER_TAP_TOGGLE(1)
 495
 496 Number of taps can be configured with `TAPPING_TOGGLE` in `config.h`, `5` by default.
 497
 498
 499
 500 ### 3.5 Momentary switching with Modifiers
 501 This registers modifier key(s) simultaneously with layer switching.
 502
 503     ACTION_LAYER_MODS(2, MOD_LSFT | MOD_LALT)
 504
 505
 506
 507 ## 4. Tapping
 508 Tapping is to press and release a key quickly. Tapping speed is determined with setting of `TAPPING_TERM`, which can be defined in `config.h`, 200ms by default.
 509
 510 ### 4.1 Tap Key
 511 This is a feature to assign normal key action and modifier including layer switching to just same one physical key. This is a kind of [Dual role key][dual_role]. It works as modifier when holding the key but registers normal key when tapping.
 512
 513 Modifier with tap key:
 514
 515     ACTION_MODS_TAP_KEY(MOD_RSFT, KC_GRV)
 516
 517 Layer switching with tap key:
 518
 519     ACTION_LAYER_TAP_KEY(2, KC_SCLN)
 520
 521 [dual_role]: http://en.wikipedia.org/wiki/Modifier_key#Dual-role_keys
 522
 523
 524 ### 4.2 Tap Toggle
 525 This is a feature to assign both toggle layer and momentary switch layer action to just same one physical key. It works as momentary layer switch when holding a key but toggle switch with several taps.
 526
 527     ACTION_LAYER_TAP_TOGGLE(1)
 528
 529
 530 ### 4.3 Oneshot Modifier
 531 This runs onetime effects which modify only on just one following key. It works as normal modifier key when holding down while oneshot modifier when tapping.
 532
 533     ACTION_MODS_ONESHOT(MOD_LSFT)
 534
 535 Say you want to type 'The', you have to push and hold Shift key before type 't' then release it before type 'h' and 'e', otherwise you'll get 'THe' or 'the' unintentionally. With Oneshot Modifier you can tap Shift then type 't', 'h' and 'e' normally, you don't need to holding Shift key properly here. This mean you can release Shift before 't' is pressed down.
 536
 537 Oneshot effect is cancel unless following key is pressed down within `ONESHOT_TIMEOUT` of `config.h`. No timeout when it is `0` or not defined.
 538
 539
 540 ### 4.4 Tap Toggle Mods
 541 Similar to layer tap toggle, this works as a momentary modifier when holding, but toggles on with several taps. A single tap will 'unstick' the modifier again.
 542
 543     ACTION_MODS_TAP_TOGGLE(MOD_LSFT)
 544
 545
 546
 547
 548 ## 5. Legacy Keymap
 549 This was used in prior version and still works due to legacy support code in `common/keymap.c`. Legacy keymap doesn't support many of features that new keymap offers. ***It is not recommended to use Legacy Keymap for new project.***
 550
 551 To enable Legacy Keymap support define this macro in `config.h`.
 552
 553     #define USE_LEGACY_KEYMAP
 554
 555 Legacy Keymap uses two arrays `fn_layer[]` and `fn_keycode[]` to define Fn key. The index of arrays corresponds with postfix number of `Fn` key. Array `fn_layer[]` indicates destination layer to switch and `fn_keycode[]` has keycodes to send when tapping `Fn` key.
 556
 557 In following setting example, `Fn0`, `Fn1` and `Fn2` switch layer to 1, 2 and 2 respectively. `Fn2` registers `Space` key when tapping while `Fn0` and `Fn1` doesn't send any key.
 558
 559     static const uint8_t PROGMEM fn_layer[] = {
 560         1,              // Fn0
 561         2,              // Fn1
 562         2,              // Fn2
 563     };
 564
 565     static const uint8_t PROGMEM fn_keycode[] = {
 566         KC_NO,          // Fn0
 567         KC_NO,          // Fn1
 568         KC_SPC,         // Fn2
 569     };
 570
 571
 572 ## 6. Terminology
 573 ***TBD***
 574 ### keymap
 575 is comprised of multiple layers.
 576 ### layer
 577 is matrix of keycodes.
 578 ### key
 579 is physical button on keyboard or logical switch on software.
 580 ### keycode
 581 is codes used on firmware.
 582 ### action
 583 is a function assigned on a key.
 584 ### layer transparency
 585 Using transparent keycode one layer can refer key definition on other lower layer.
 586 ### layer precedence
 587 Top layer has higher precedence than lower layers.
 588 ### tapping
 589 is to press and release a key quickly.
 590 ### Fn key
 591 is key which executes a special action like layer switching, mouse key, macro or etc.
 592 ### dual role key
 593 <http://en.wikipedia.org/wiki/Modifier_key#Dual-role_keys>