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 The **keymap** is an array composed of one or more layers.
   7 Each **layer** is an array of **keycodes**, defining **actions** for each physical key.
   8 Layers can be activated and deactivated independently. Multiple layers may be active at once, resulting in the currently-active **layer state**. Each layer has an index between 0-31. As active layers are stacked together, higher layers take precedence over lower layers.
   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 **Note:** The keymap array is limited to **32 layers**.
  25
  26
  27
  28 ### 0.1 Layer state
  29 The current keymap layer state is determined by two parameters: the *default layer*, and the individual *layer states*. Changing the default layer is useful for switching key layouts completely; for example, switching to Dvorak, Colemak or Workman instead of QWERTY. Individual layer states, on the other hand, can be used to overlay the base layer with other functions such as navigation keys, function keys (F1-F12), media keys or other actions.
  30
  31 Because the default layer is really just a special case affecting the overall layer state, it is important to first understand how the layer state is determined.
  32
  33 #### 0.1.1 The layer state
  34 The **layer state** indicates the current on/off status of all layers. It is defined in the firmware by a 32-bit integer, `layer_state`, which stores each layer's on/off status in a single bit: 0 for off, 1 for on. As layers are activated and deactivated, their respective bits are flipped, changing the value of `layer_state`.
  35
  36     Overlay feature layer
  37     ---------------------      bit|status
  38            ____________        ---+------
  39       31  /           /        31 |   0
  40       30 /___________// -----> 30 |   1
  41       29 /___________/  -----> 29 |   1
  42        :                        : |   :
  43        :   ____________         : |   :
  44        2  /           /         2 |   0
  45     ,->1 /___________/  ----->  1 |   1
  46     |  0                        0 |   0
  47     |                                 +
  48     `--- default_layer = 1            |
  49          layer_state   = 0x60000002 <-'
  50
  51 #### 0.1.2 The default layer
  52 The **default layer** is the base keymap layer (0-31) which is always active and considered the "bottom" of the stack. When the firmware boots, the default layer is the only active layer. It is set to layer 0 by default, though this can be changed ~~in *config.h*~~ via Boot Magic settings.
  53
  54     Initial state of Keymap          Change base layout
  55     -----------------------          ------------------
  56
  57       31                               31
  58       30                               30
  59       29                               29
  60        :                                :
  61        :                                :   ____________
  62        2   ____________                 2  /           /
  63        1  /           /              ,->1 /___________/
  64     ,->0 /___________/               |  0
  65     |                                |
  66     `--- default_layer = 0           `--- default_layer = 1
  67          layer_state   = 0x00000001       layer_state   = 0x00000002
  68
  69 Note that the `default_layer_state` variable only determines the lowest value to which `layer_state` may be set, and that `default_layer_state` is used by the core firmware when determining the starting value of `layer_state` before applying changes. In other words, the default layer will *always* be set to *on* in `layer_state`.
  70
  71 The default layer is defined in the firmware by the `default_layer_state` variable, which is identical in format to the `layer_state` variable exlpained above. The value may be changed using the following functions:
  72
  73 - `default_layer_state_set(state)` sets the state to the specified 32-bit integer value.
  74 - AND/OR/XOR functions set the state based on a boolean logic comparison between the current state and the specified 32-bit integer value:
  75     - `default_layer_state_and(state)`
  76     - `default_layer_state_or(state)`
  77     - `default_layer_state_xor(state)`
  78
  79 For example, to set layer 3 as the default layer:
  80
  81 ```C
  82 // convert 3 to a 32-bit unsigned long value, and set the default layer
  83 default_layer_state_set(1UL<<3);
  84 ```
  85
  86
  87
  88 ### 0.2 Layer Precedence and Transparency
  89 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.
  90
  91 You can place `KC_TRNS` on overlay layer changes just part of layout to fall back on lower or base layer.
  92 Key with `KC_TRANS` doesn't has its own keycode and refers to lower valid layers for keycode, instead.
  93 See example below.
  94
  95
  96 ### 0.3 Keymap Example
  97 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.
  98
  99 This is a keymap example for [HHKB](http://en.wikipedia.org/wiki/Happy_Hacking_Keyboard) keyboard.
 100 This example has three layers, 'Qwerty' as base layer, 'Cursor' and  'Mousekey'.
 101 In this example,
 102
 103  `Fn0` is a **momentary layer switching** key, you can use keys on Cursor layer while holding the key.
 104
 105  `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.
 106
 107  `Fn2` is a **toggle layer switch** key, you can stay switched layer after releasing the key unlike momentary switching.
 108
 109 You can find other keymap definitions in file `keymap.c` located on project directories.
 110
 111     static const uint8_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
 112         /* 0: Qwerty
 113          * ,-----------------------------------------------------------.
 114          * |Esc|  1|  2|  3|  4|  5|  6|  7|  8|  9|  0|  -|  =|  \|  `|
 115          * |-----------------------------------------------------------|
 116          * |Tab  |  Q|  W|  E|  R|  T|  Y|  U|  I|  O|  P|  [|  ]|Backs|
 117          * |-----------------------------------------------------------|
 118          * |Contro|  A|  S|  D|  F|  G|  H|  J|  K|  L|Fn1|  '|Enter   |
 119          * |-----------------------------------------------------------|
 120          * |Shift   |  Z|  X|  C|  V|  B|  N|  M|  ,|  .|  /|Shift |Fn0|
 121          * `-----------------------------------------------------------'
 122          *       |Gui|Alt  |Space                  |Alt  |Fn2|
 123          *       `-------------------------------------------'
 124          */
 125         KEYMAP(ESC, 1,   2,   3,   4,   5,   6,   7,   8,   9,   0,   MINS,EQL, BSLS,GRV, \
 126                TAB, Q,   W,   E,   R,   T,   Y,   U,   I,   O,   P,   LBRC,RBRC,BSPC, \
 127                LCTL,A,   S,   D,   F,   G,   H,   J,   K,   L,   FN1, QUOT,ENT, \
 128                LSFT,Z,   X,   C,   V,   B,   N,   M,   COMM,DOT, SLSH,RSFT,FN0, \
 129                     LGUI,LALT,          SPC,                RALT,FN2),
 130         /* 1: Cursor(HHKB mode)
 131          * ,-----------------------------------------------------------.
 132          * |Pwr| F1| F2| F3| F4| F5| F6| F7| F8| F9|F10|F11|F12|Ins|Del|
 133          * |-----------------------------------------------------------|
 134          * |Caps |   |   |   |   |   |   |   |Psc|Slk|Pus|Up |   |Backs|
 135          * |-----------------------------------------------------------|
 136          * |Contro|VoD|VoU|Mut|   |   |  *|  /|Hom|PgU|Lef|Rig|Enter   |
 137          * |-----------------------------------------------------------|
 138          * |Shift   |   |   |   |   |   |  +|  -|End|PgD|Dow|Shift |   |
 139          * `-----------------------------------------------------------'
 140          *      |Gui |Alt  |Space                  |Alt  |Gui|
 141          *      `--------------------------------------------'
 142          */
 143         KEYMAP(PWR, F1,  F2,  F3,  F4,  F5,  F6,  F7,  F8,  F9,  F10, F11, F12, INS, DEL, \
 144                CAPS,TRNS,TRNS,TRNS,TRNS,TRNS,TRNS,TRNS,PSCR,SLCK,PAUS,UP,  TRNS,BSPC, \
 145                LCTL,VOLD,VOLU,MUTE,TRNS,TRNS,PAST,PSLS,HOME,PGUP,LEFT,RGHT,ENT, \
 146                LSFT,TRNS,TRNS,TRNS,TRNS,TRNS,PPLS,PMNS,END, PGDN,DOWN,RSFT,TRNS, \
 147                     LGUI,LALT,          SPC,                RALT,RGUI),
 148         /* 2: Mousekey
 149          * ,-----------------------------------------------------------.
 150          * |Esc| F1| F2| F3| F4| F5| F6| F7| F8| F9|F10|F11|F12|Ins|Del|
 151          * |-----------------------------------------------------------|
 152          * |Tab  |   |   |   |   |   |MwL|MwD|MwU|MwR|   |   |   |Backs|
 153          * |-----------------------------------------------------------|
 154          * |Contro|   |   |   |   |   |McL|McD|McU|McR|   |   |Return  |
 155          * |-----------------------------------------------------------|
 156          * |Shift   |   |   |   |   |Mb3|Mb2|Mb1|Mb4|Mb5|   |Shift |   |
 157          * `-----------------------------------------------------------'
 158          *      |Gui |Alt  |Mb1                    |Alt  |   |
 159          *      `--------------------------------------------'
 160          * Mc: Mouse Cursor / Mb: Mouse Button / Mw: Mouse Wheel
 161          */
 162         KEYMAP(ESC, F1,  F2,  F3,  F4,  F5,  F6,  F7,  F8,  F9,  F10, F11, F12, INS, DEL, \
 163                TAB, TRNS,TRNS,TRNS,TRNS,TRNS,WH_L,WH_D,WH_U,WH_R,TRNS,TRNS,TRNS,BSPC, \
 164                LCTL,TRNS,ACL0,ACL1,ACL2,TRNS,MS_L,MS_D,MS_U,MS_R,TRNS,QUOT,ENT, \
 165                LSFT,TRNS,TRNS,TRNS,TRNS,BTN3,BTN2,BTN1,BTN4,BTN5,SLSH,RSFT,TRNS, \
 166                     LGUI,LALT,          BTN1,               RALT,TRNS),
 167     };
 168
 169     static const uint16_t PROGMEM fn_actions[] = {
 170         ACTION_LAYER_MOMENTARY(1),                  // FN0
 171         ACTION_LAYER_TAP_KEY(2, KC_SCLN),           // FN1
 172         ACTION_LAYER_TOGGLE(2),                     // FN2
 173     };
 174
 175
 176
 177
 178 ## 1. Keycode
 179 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.
 180
 181  ***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()`.
 182
 183 ### 1.0 Other key
 184 - `KC_NO` for no action
 185 - `KC_TRNS` for layer transparency (See above)
 186
 187 ### 1.1 Normal key
 188 - `KC_A` to `KC_Z`, `KC_1` to `KC_0` for alpha numeric key
 189 - `KC_MINS`, `KC_EQL`, `KC_GRV`, `KC_RBRC`, `KC_LBRC`, `KC_COMM`, `KC_DOT`, `KC_BSLS`, `KC_SLSH`, `KC_SCLN`, `KC_QUOT`
 190 - `KC_ESC`, `KC_TAB`, `KC_SPC`, `KC_BSPC`, `KC_ENT`, `KC_DEL`, `KC_INS`
 191 - `KC_UP`, `KC_DOWN`, `KC_RGHT`, `KC_LEFT`, `KC_PGUP`, `KC_PGDN`, `KC_HOME`, `KC_END`
 192 - `KC_CAPS`, `KC_NLCK`, `KC_SLCK`, `KC_PSCR`, `KC_PAUS`, `KC_APP`, `KC_F1` to `KC_F24`
 193 - `KC_P1` to `KC_P0`, `KC_PDOT`, `KC_PCMM`, `KC_PSLS`, `KC_PAST`, `KC_PMNS`, `KC_PPLS`, `KC_PEQL`, `KC_PENT` for keypad.
 194
 195 ### 1.2 Modifier
 196 There are 8 modifiers which has discrimination between left and right.
 197
 198 - `KC_LCTL` and `KC_RCTL` for Control
 199 - `KC_LSFT` and `KC_RSFT` for Shift
 200 - `KC_LALT` and `KC_RALT` for Alt
 201 - `KC_LGUI` and `KC_RGUI` for Windows key or Command key in Mac
 202
 203 ### 1.3 Mousekey
 204 - `KC_MS_U`, `KC_MS_D`, `KC_MS_L`, `KC_MS_R` for mouse cursor
 205 - `KC_WH_U`, `KC_WH_D`, `KC_WH_L`, `KC_WH_R` for mouse wheel
 206 - `KC_BTN1`, `KC_BTN2`, `KC_BTN3`, `KC_BTN4`, `KC_BTN5` for mouse buttons
 207
 208 ### 1.4 System & Media key
 209 - `KC_PWR`, `KC_SLEP`, `KC_WAKE` for Power, Sleep, Wake
 210 - `KC_MUTE`, `KC_VOLU`, `KC_VOLD` for audio volume control
 211 - `KC_MNXT`, `KC_MPRV`, `KC_MSTP`, `KC_MPLY`, `KC_MSEL` for media control
 212 - `KC_MAIL`, `KC_CALC`, `KC_MYCM` for application launch
 213 - `KC_WSCH`, `KC_WHOM`, `KC_WBAK`, `KC_WFWD`, `KC_WSTP`, `KC_WREF`, `KC_WFAV` for web browser operation
 214
 215 ### 1.5 Fn key
 216 `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.***
 217
 218 ### 1.6 Keycode Table
 219  See keycode table in [`doc/keycode.txt`](./keycode.txt) for description of keycodes.
 220
 221  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.
 222 [HID_usage]: http://www.usb.org/developers/hidpage/Hut1_12v2.pdf
 223
 224
 225
 226 ## 2. Action
 227 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.
 228
 229 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.
 230
 231 ***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[]`.***
 232
 233
 234 ### 2.1 Key Action
 235 This is a simple action that registers scancodes(HID usage in fact) to host on press event of key and unregister on release.
 236
 237 #### Parameters
 238 + **mods**: { ` MOD_LCTL`, ` MOD_LSFT`, ` MOD_LALT`, ` MOD_LGUI`,
 239               ` MOD_RCTL`, ` MOD_RSFT`, ` MOD_RALT`, ` MOD_RGUI` }
 240 + **key**: keycode
 241
 242
 243 #### 2.1.1 Normal key and Modifier
 244 ***This action usually won't be used expressly in keymap*** because you can just use keycodes in `KEYMAP()` instead.
 245
 246 You can define these actions on *'A'* key and *'left shift'* modifier with:
 247
 248     ACTION_KEY(KC_A)
 249     ACTION_KEY(KC_LSFT)
 250
 251 #### 2.1.2 Modified key
 252 This action is comprised of strokes of modifiers and a key. `Macro` action is needed if you want more complex key strokes.
 253
 254 Say you want to assign a key to `Shift + 1` to get character *'!'* or `Alt + Tab` to switch application windows.
 255
 256     ACTION_MODS_KEY(MOD_LSFT, KC_1)
 257     ACTION_MODS_KEY(MOD_LALT, KC_TAB)
 258
 259 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.
 260
 261     ACTION_MODS_KEY(MOD_LALT | MOD_LSFT, KC_TAB)
 262
 263 #### 2.1.3 Multiple Modifiers
 264 Registers multiple modifiers with pressing a key. To specify multiple modifiers use `|`.
 265
 266     ACTION_MODS(MOD_ALT | MOD_LSFT)
 267
 268 #### 2.1.3 Modifier with Tap key([Dual role][dual_role])
 269 Works as a modifier key while holding, but registers a key on tap(press and release quickly).
 270
 271
 272     ACTION_MODS_TAP_KEY(MOD_RCTL, KC_ENT)
 273
 274
 275
 276 ### 2.2 Layer Action
 277 These actions operate layers of keymap.
 278
 279 #### Parameters
 280 You can specify a **target layer** of action and **when the action is executed**. Some actions take a **bit value** for bitwise operation.
 281
 282
 283 + **layer**: `0`-`31`
 284 + **on**: { `ON_PRESS` | `ON_RELEASE` | `ON_BOTH` }
 285 + **bits**: 4-bit value and 1-bit mask bit
 286
 287
 288 #### 2.2.1 Default Layer
 289 Default Layer is a layer which always is valid and referred to when actions is not defined on other overlay layers.
 290
 291 This sets Default Layer to given parameter `layer` and activate it.
 292
 293     ACTION_DEFAULT_LAYER_SET(layer)
 294
 295
 296 #### 2.2.2 Momentary
 297 Turns on `layer` momentarily while holding, in other words it activates when key is pressed and deactivate when released.
 298
 299     ACTION_LAYER_MOMENTARY(layer)
 300
 301
 302 #### 2.2.3 Toggle Switch
 303 Turns on `layer` with first type(press and release) and turns off with next.
 304
 305     ACTION_LAYER_TOGGLE(layer)
 306
 307
 308 #### 2.2.4 Momentary Switch with tap key
 309 Turns on `layer` momentary while holding, but registers key on tap(press and release quickly).
 310
 311     ACTION_LAYER_TAP_KEY(layer, key)
 312
 313
 314 #### 2.2.5 Momentary Switch with tap toggle
 315 Turns on `layer` momentary while holding and toggles it with serial taps.
 316
 317     ACTION_LAYER_TAP_TOGGLE(layer)
 318
 319
 320 #### 2.2.6 Invert state of layer
 321 Inverts current state of `layer`. If the layer is on it becomes off with this action.
 322
 323     ACTION_LAYER_INVERT(layer, on)
 324
 325
 326 #### 2.2.7 Turn On layer
 327 Turns on layer state.
 328
 329     ACTION_LAYER_ON(layer, on)
 330
 331 Turns on layer state on press and turns off on release.
 332
 333     ACTION_LAYER_ON_OFF(layer)
 334
 335
 336 #### 2.2.8 Turn Off layer
 337 Turns off layer state.
 338
 339     ACTION_LAYER_OFF(layer, on)
 340
 341 Turns off layer state on press and activates on release.
 342
 343     ACTION_LAYER_OFF_ON(layer)
 344
 345
 346 #### 2.2.9 Set layer
 347 Turn on layer only.
 348 `layer_state = (1<<layer) [layer: 0-31]`
 349
 350     ACTION_LAYER_SET(layer, on)
 351
 352 Turns on layer only and clear all layer on release..
 353
 354     ACTION_LAYER_SET_CLEAR(layer)
 355
 356
 357 #### 2.2.10 Bitwise operation
 358
 359 **part** indicates which part of 32bit layer state(0-7). **bits** is 5-bit value. **on** indicates when the action is executed.
 360
 361     ACTION_LAYER_BIT_AND(part, bits, on)
 362     ACTION_LAYER_BIT_OR(part, bits, on)
 363     ACTION_LAYER_BIT_XOR(part, bits, on)
 364     ACTION_LAYER_BIT_SET(part, bits, on)
 365
 366 These actions works with parameters as following code.
 367
 368     uint8_t shift = part*4;
 369     uint32_t mask = (bits&0x10) ? ~(0xf<<shift) : 0;
 370     uint32_t layer_state = layer_state <bitop> ((bits<<shift)|mask);
 371
 372
 373 Default Layer also has bitwise operations, they are executed when key is released.
 374
 375     ACTION_DEFAULT_LAYER_BIT_AND(part, bits)
 376     ACTION_DEFAULT_LAYER_BIT_OR(part, bits)
 377     ACTION_DEFAULT_LAYER_BIT_XOR(part, bits)
 378     ACTION_DEFAULT_LAYER_BIT_SET(part, bits)
 379
 380
 381
 382 ### 2.3 Macro action
 383 ***TBD***
 384
 385 `Macro` action indicates complex key strokes.
 386
 387     MACRO( D(LSHIFT), D(D), END )
 388     MACRO( U(D), U(LSHIFT), END )
 389     MACRO( I(255), T(H), T(E), T(L), T(L), W(255), T(O), END )
 390
 391 #### 2.3.1 Macro Commands
 392 - **MACRO()**
 393 - **MACRO_NONE**
 394
 395 - **I()**   change interval of stroke.
 396 - **D()**   press key
 397 - **U()**   release key
 398 - **T()**   type key(press and release)
 399 - **W()**   wait
 400 - **SM()**  store modifier state
 401 - **RM()**  restore modifier state
 402 - **CM()**  clear modifier state
 403 - **END**   end mark
 404
 405 #### 2.3.2 Examples
 406 ***TBD***
 407
 408     const macro_t *action_get_macro(keyrecord_t *record, uint8_t id, uint8_t opt)
 409     {
 410         switch (id) {
 411             case HELLO:
 412                 return (record->event.pressed ?
 413                         MACRO( I(0), T(H), T(E), T(L), T(L), W(255), T(O), END ) :
 414                         MACRO_NONE );
 415             case ALT_TAB:
 416                 return (record->event.pressed ?
 417                         MACRO( D(LALT), D(TAB), END ) :
 418                         MACRO( U(TAB), END ));
 419         }
 420         return MACRO_NONE;
 421     }
 422
 423
 424
 425
 426 ### 2.4 Function action
 427 ***TBD***
 428
 429 There are two type of action, normal `Function` and tappable `Function`.
 430 These actions call user defined function with `id`, `opt`, and key event information as arguments.
 431
 432 #### 2.4.1 Function
 433 To define normal `Function` action in keymap use this.
 434
 435     ACTION_FUNCTION(id, opt)
 436
 437 #### 2.4.2 Function with tap
 438 To define tappable `Function` action in keymap use this.
 439
 440     ACTION_FUNCTION_TAP(id, opt)
 441
 442 #### 2.4.3 Implement user function
 443 `Function` actions can be defined freely with C by user in callback function:
 444
 445     void keymap_call_function(keyrecord_t *event, uint8_t id, uint8_t opt)
 446
 447 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.
 448
 449  `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.
 450
 451     typedef struct {
 452         keyevent_t  event;
 453         uint8_t     tap_count;
 454     } keyrecord_t;
 455
 456     typedef struct {
 457         key_t    key;
 458         bool     pressed;
 459         uint16_t time;
 460     } keyevent_t;
 461
 462     typedef struct {
 463         uint8_t col;
 464         uint8_t row;
 465     } key_t;
 466
 467 ***TODO: sample implementation***
 468 See `keyboard/hhkb/keymap.c` for sample.
 469
 470
 471
 472 ### 2.5 Backlight Action
 473 These actions control the backlight.
 474
 475 #### 2.5.1 Change backlight level
 476 Increase backlight level.
 477
 478     ACTION_BACKLIGHT_INCREASE()
 479
 480 Decrease backlight level.
 481
 482     ACTION_BACKLIGHT_DECREASE()
 483
 484 Step through backlight levels.
 485
 486     ACTION_BACKLIGHT_STEP()
 487
 488 Turn a specific backlight level on or off.
 489
 490     ACTION_BACKLIGHT_LEVEL(1)
 491
 492 #### 2.5.2 Turn on / off backlight
 493 Turn the backlight on and off without changing level.
 494
 495     ACTION_BACKLIGHT_TOGGLE()
 496
 497
 498
 499 ## 3. Layer switching Example
 500 There are some ways to switch layer with 'Layer' actions.
 501
 502 ### 3.1 Momentary switching
 503 Momentary switching changes layer only while holding Fn key.
 504
 505 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.
 506
 507     ACTION_LAYER_MOMENTARY(1)
 508
 509
 510 Note that after switching on press the actions on destination layer(Layer 1) are performed.
 511 ***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.
 512
 513
 514 ### 3.2 Toggle switching
 515 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.
 516
 517 This performs toggle switching action of 'Layer 2'.
 518
 519     ACTION_LAYER_TOGGLE(2)
 520
 521
 522
 523 ### 3.3 Momentary switching with Tap key
 524 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.
 525
 526     ACTION_LAYER_TAP_KEY(2, KC_SCLN)
 527
 528 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.
 529
 530
 531
 532 ### 3.4 Momentary switching with Tap Toggle
 533 This switches layer only while holding a key but toggle layer with several taps. **Tap** means to press and release key quickly.
 534
 535     ACTION_LAYER_TAP_TOGGLE(1)
 536
 537 Number of taps can be configured with `TAPPING_TOGGLE` in `config.h`, `5` by default.
 538
 539
 540
 541 ### 3.5 Momentary switching with Modifiers
 542 This registers modifier key(s) simultaneously with layer switching.
 543
 544     ACTION_LAYER_MODS(2, MOD_LSFT | MOD_LALT)
 545
 546
 547
 548 ## 4. Tapping
 549 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.
 550
 551 ### 4.1 Tap Key
 552 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.
 553
 554 Modifier with tap key:
 555
 556     ACTION_MODS_TAP_KEY(MOD_RSFT, KC_GRV)
 557
 558 Layer switching with tap key:
 559
 560     ACTION_LAYER_TAP_KEY(2, KC_SCLN)
 561
 562 [dual_role]: http://en.wikipedia.org/wiki/Modifier_key#Dual-role_keys
 563
 564
 565 ### 4.2 Tap Toggle
 566 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.
 567
 568     ACTION_LAYER_TAP_TOGGLE(1)
 569
 570
 571 ### 4.3 Oneshot Modifier
 572 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.
 573
 574     ACTION_MODS_ONESHOT(MOD_LSFT)
 575
 576 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.
 577
 578 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.
 579
 580
 581 ### 4.4 Tap Toggle Mods
 582 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.
 583
 584     ACTION_MODS_TAP_TOGGLE(MOD_LSFT)
 585
 586
 587
 588
 589 ## 5. Legacy Keymap
 590 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.***
 591
 592 To enable Legacy Keymap support define this macro in `config.h`.
 593
 594     #define USE_LEGACY_KEYMAP
 595
 596 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.
 597
 598 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.
 599
 600     static const uint8_t PROGMEM fn_layer[] = {
 601         1,              // Fn0
 602         2,              // Fn1
 603         2,              // Fn2
 604     };
 605
 606     static const uint8_t PROGMEM fn_keycode[] = {
 607         KC_NO,          // Fn0
 608         KC_NO,          // Fn1
 609         KC_SPC,         // Fn2
 610     };
 611
 612
 613 ## 6. Terminology
 614 ***TBD***
 615 ### keymap
 616 is comprised of multiple layers.
 617 ### layer
 618 is matrix of keycodes.
 619 ### key
 620 is physical button on keyboard or logical switch on software.
 621 ### keycode
 622 is codes used on firmware.
 623 ### action
 624 is a function assigned on a key.
 625 ### layer transparency
 626 Using transparent keycode one layer can refer key definition on other lower layer.
 627 ### layer precedence
 628 Top layer has higher precedence than lower layers.
 629 ### tapping
 630 is to press and release a key quickly.
 631 ### Fn key
 632 is key which executes a special action like layer switching, mouse key, macro or etc.
 633 ### dual role key
 634 <http://en.wikipedia.org/wiki/Modifier_key#Dual-role_keys>