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` doen'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 inidicate 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 contorl 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 aciton
 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` keyocde 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/devclass_docs/Hut1_11.pdf
 202
 203
 204
 205 ## 2. Action
 206 See [`common/action.h`](../common/action.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 jsut 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 #### 2.1.1 Normal key and Modifier
 217 ***This action usually won't be used expressly in keymap*** because you can just use keycodes in `KEYMAP()` instead.
 218
 219 You can define these actions on *'A'* key and *'left shift'* modifier with:
 220
 221     ACTION_KEY(KC_A)
 222     ACTION_KEY(KC_LSFT)
 223
 224 #### 2.1.2 Key with modifiers
 225 This action is comprised of strokes of modifiers and a key. `Macro` action is needed if you want more complex key strokes.
 226
 227 Say you want to assign a key to `Shift + 1` to get charactor *'!'* or `Alt + Tab` to switch application windows.
 228
 229     ACTION_MOD_KEY(KC_LSFT, KC_1)
 230     ACTION_MOD_KEY(KC_LALT, KC_TAB)
 231
 232 Or `Alt,Shift + Tab` can be defined. `ACTION_LMODS_KEY()` requires **4-bit modifier state** and a **keycode** as arguments. See `keycode.h` for `MOD_BIT()` macro.
 233
 234     ACTION_MODS_KEY((MOD_BIT(KC_LALT) | MOD_BIT(KC_LSFT)), KC_TAB)
 235
 236 #### 2.1.3 Multiple Modifiers
 237 Registers multiple modifiers with a key.
 238
 239     ACTION_MODS(MOD_BIT(KC_ALT) | MOD_BIT(KC_LSFT))
 240
 241 #### 2.1.3 Modifier with tap key
 242
 243     ACTION_MODS_TAP_KEY(KC_RSFT, KC_GRV)
 244
 245
 246
 247 ### 2.2 Layer Action
 248 These actions operate layers of keymap.
 249
 250 **Parameters:**
 251
 252 + **layer**: 0-31
 253 + **on**: { press | release | both }
 254
 255
 256 #### 2.2.1 Default Layer
 257 `default_layer` is layer which always is valid and referred to when actions is not defined on other overlay layers.
 258
 259 Sets `default_layer` to given parameter `layer` and turn it on.
 260
 261     ACTION_DEFAULT_LAYER(layer)
 262
 263
 264 #### 2.2.2 Momentary Switch
 265 Turns on `layer` momentarily while holding, in other words turn on when key is pressed and off when released.
 266
 267     ACTION_LAYER_MOMENTARY(layer)
 268
 269
 270 #### 2.2.3 Toggle Switch
 271 Turns on layer on first type and turns off on next.
 272
 273     ACTION_LAYER_TOGGLE(layer)
 274
 275
 276 #### 2.2.4 Momentary Switch with tap key
 277 Turns on layer momentary while holding but registers key on tap.
 278
 279     ACTION_LAYER_TAP_KEY(layer, key)
 280
 281
 282 #### 2.2.5 Momentary Switch with tap toggle
 283 Turns on layer momentary while holding but toggles it with serial taps.
 284
 285     ACTION_LAYER_TAP_TOGGLE(layer)
 286
 287
 288 #### 2.2.6 Invert state of layer
 289 Inverts current layer state. If the layer is on it becomes off with this action.
 290
 291     ACTION_LAYER_INVERT(layer, on)
 292
 293
 294 #### 2.2.7 Turn On layer
 295 Turns on layer state.
 296
 297     ACTION_LAYER_ON(layer, on)
 298
 299 Turns on layer state on press and turns off on release.
 300
 301     ACTION_LAYER_ON_OFF(layer)
 302
 303
 304 #### 2.2.8 Turn Off layer
 305 Turns off layer state.
 306
 307     ACTION_LAYER_OFF(layer, on)
 308
 309 Turns off layer state on press and activates on release.
 310
 311     ACTION_LAYER_OFF_ON(layer)
 312
 313
 314 #### 2.2.9 Set layer
 315 Turn on layer only.
 316 `layer_state = (1<<layer) [layer: 0-31]`
 317
 318     ACTION_LAYER_SET(layer, on)
 319
 320 Turns on layer only and clear all layer on release..
 321
 322     ACTION_LAYER_SET_CLEAR(layer)
 323
 324
 325
 326 ### 2.3 Macro action
 327 ***TBD***
 328
 329 `Macro` action indicates complex key strokes.
 330
 331     MACRO( MD(LSHIFT), D(D), END )
 332     MACRO( U(D), MU(LSHIFT), END )
 333     MACRO( I(255), T(H), T(E), T(L), T(L), W(255), T(O), END )
 334
 335 #### 2.3.1 Normal mode
 336 - **I()**   change interavl of stroke.
 337 - **D()**   press key
 338 - **U()**   release key
 339 - **T()**   type key(press and release)
 340 - **W()**   wait
 341 - **MD()**  modifier down
 342 - **MU()**  modifier up
 343 - **END**   end mark
 344
 345 #### 2.3.2 Extended mode
 346
 347 ***TODO: sample impl***
 348 See `keyboard/hhkb/keymap.c` for sample.
 349
 350
 351
 352 ### 2.4 Function action
 353 ***TBD***
 354
 355 There are two type of action, normal `Function` and tappable `Function`.
 356 These actions call user defined function with `id`, `opt`, and key event information as arguments.
 357
 358 #### 2.4.1 Function
 359 To define normal `Function` action in keymap use this.
 360
 361     ACTION_FUNCTION(id, opt)
 362
 363 #### 2.4.2 Function with tap
 364 To define tappable `Function` action in keymap use this.
 365
 366     ACTION_FUNCTION_TAP(id, opt)
 367
 368 #### 2.4.3 Implement user function
 369 `Function` actions can be defined freely with C by user in callback function:
 370
 371     void keymap_call_function(keyrecord_t *event, uint8_t id, uint8_t opt)
 372
 373 This C function is called every time key is operated, argument `id` selects action to be performed and `opt` can be used for option. Functon `id` can be 0-255 and `opt` can be 0-15.
 374
 375  `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.
 376
 377     typedef struct {
 378         keyevent_t  event;
 379         uint8_t     tap_count;
 380     } keyrecord_t;
 381
 382     typedef struct {
 383         key_t    key;
 384         bool     pressed;
 385         uint16_t time;
 386     } keyevent_t;
 387
 388     typedef struct {
 389         uint8_t col;
 390         uint8_t row;
 391     } key_t;
 392
 393 ***TODO: sample impl***
 394 See `keyboard/hhkb/keymap.c` for sample.
 395
 396
 397
 398
 399
 400 ## 3. Layer switching Example
 401 There are some ways to switch layer with 'Layer' actions.
 402
 403 ### 3.1 Momentary switching
 404 Momentary switching changes layer only while holding Fn key.
 405
 406 This action makes 'Layer 1' active(valid) on key press event and inactive on release event. Namely you can overlay a layer on base layer temporarily with this.
 407
 408     ACTION_LAYER_MOMENTARY(1)
 409
 410
 411 After switch actions of destination layer are perfomed.
 412 ***Thus you shall need to place action to come back on destination layer***, or you will be stuck in destination layer without way to get back. Usually you need to palce same action or 'KC_TRNS` on destination layer to get back.
 413
 414
 415 ### 3.2 Toggle switching
 416 Toggle switching changes layer after press then release. With this you can keep staying on the layer until you press the key again to return.
 417
 418 This is toggle action of 'Layer 2'.
 419
 420     ACTION_LAYER_TOGGLE(2)
 421
 422
 423
 424 ### 3.3 Momentary switching with Tap key
 425 These actions switch layer only while holding `Fn` key and register key on tap. **Tap** means to press and release key quickly.
 426
 427     ACTION_LAYER_TAP_KEY(2, KC_SCLN)
 428
 429 With this you can place layer switching function on normal key like ';' without losing its original key register function.
 430
 431
 432
 433 ### 3.4 Momentary switching with Tap Toggle
 434 This switches layer only while holding `Fn` key and toggle layer after several taps. **Tap** means to press and release key quickly.
 435
 436     ACTION_LAYER_TAP_TOGGLE(1)
 437
 438 Number of taps can be defined with `TAPPING_TOGGLE` in `config.h`, `5` by default.
 439
 440
 441
 442 ## 4. Tapping
 443 Tapping is to press and release key quickly. Tapping speed is determined with setting of `TAPPING_TERM`, which can be defined in `config.h`, 200ms by default.
 444
 445 ### 4.1 Tap Key
 446 This is feature to assign normal key action and modifier including `Fn` to just one physical key. This is a kind of [Dual role modifier][dual_role]. It works as modifier or `Fn` when holding a key but registers normal key when tapping.
 447
 448 Action for modifier with tap key.
 449
 450     ACTION_LMODS_TAP_KEY(mods, key)
 451
 452 Action for `Fn` with tap key.
 453
 454     ACTION_LAYER_TAP_KEY(layer, key)
 455
 456 [dual_role]: http://en.wikipedia.org/wiki/Modifier_key#Dual-role_modifier_keys
 457
 458
 459 ### 4.2 Tap Toggle
 460 This is feature to assign both toggle layer and momentary switch layer action to just one physical key. It works as mementary switch when holding a key but toggle switch when tapping.
 461
 462     ACTION_LAYER_TAP_TOGGLE(layer)
 463
 464
 465 ### 4.3 One Shot Modifier
 466 This adds oneshot feature to modifier key. 'One Shot Modifier' is one time modifier which has effect only on following one alpha key.
 467 It works as normal modifier key when holding but oneshot modifier when tapping.
 468
 469     ACTION_LMODS_ONESHOT(mods)
 470
 471 Say you want to type 'The', you have to push and hold Shift before type 't' then release Shift before type 'h' and 'e' or you'll get 'THe'. With One Shot Modifier you can tap Shift then type 't', 'h' and 'e' normally, you don't need to holding Shift key properly  here.
 472
 473
 474
 475
 476 ## 5. Legacy Keymap
 477 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.***
 478
 479 To enable Legacy Keymap support define this macro in `config.h`.
 480
 481     #define USE_LEGACY_KEYMAP
 482
 483 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.
 484
 485 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.
 486
 487     static const uint8_t PROGMEM fn_layer[] = {
 488         1,              // Fn0
 489         2,              // Fn1
 490         2,              // Fn2
 491     };
 492
 493     static const uint8_t PROGMEM fn_keycode[] = {
 494         KC_NO,          // Fn0
 495         KC_NO,          // Fn1
 496         KC_SPC,         // Fn2
 497     };
 498
 499
 500 ## 6. Terminology
 501 ***TBD***
 502 ### keymap
 503 is comprised of multiple layers.
 504 ### layer
 505 is matrix of keycodes.
 506 ### key
 507 is physical button on keyboard or logical switch on software.
 508 ### keycode
 509 is codes used on firmware.
 510 ### action
 511 is a function assigned on a key.
 512 ### layer transparency
 513 Using transparent keycode one layer can refer key definition on other lower layer.
 514 ### layer precedence
 515 Top layer has higher precedence than lower layers.
 516 ### tapping
 517 is to press and release a key quickly.
 518 ### Fn key
 519 is key which executes a special action like layer switching, mouse key, macro or etc.
 520 ### dual role modifier
 521 <http://en.wikipedia.org/wiki/Modifier_key#Dual-role_modifier_keys>