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Keymap framework - how to define your keymap

NOTE: This is not final version, may be inconsistent with source code and changed occasionally for a while.

Keymap

Keymap is comprised of multiple layers of key layout, you can define 16 layers at most. Layer is an array of keycodes to define actions on each physical keys. respective layers can be validated simultaneously. Layers are indexed with 0 to 15 and higher layer has precedence.

Keymap with 16 Layers               Layer: array of Keycodes
---------------------               ------------------------
      stack of layers               content of layer
       ____________ precedence               _______________________
      /           / | high                  / ESC / F1  / F2  / F3   ....
  15 /___________// |                      /-----/-----/-----/-----
  14 /___________// |                     / TAB /     /     /      ....
  13 /___________/_ |                    /-----/-----/-----/-----
   :  / : : : : : / |                   /LCtrl/     /     /      ....
   3 /___________// |               :  /  :     :     :     :
   2 /___________// |               2 `--------------------------
   1 /___________// |               1 `--------------------------
   0 /___________/  V low           0 `--------------------------

Keymap status

Keymap has its state in two parameters: default_layer indicates a base keymap layer(0-15) 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.

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. To change default_layer will be useful when you want to switch key layout completely, say you use Colmak instead of Qwerty.

Initial state of Keymap         Change base layout              
-----------------------         ------------------              
                                                                
  15                              15                            
  14                              14                            
  13                              13                            
   :                               :                            
   3                               3   ____________             
   2   ____________                2  /           /             
   1  /           /             ,->1 /___________/              
,->0 /___________/              |  0                            
|                               |                               
`--- default_layer = 0          `--- default_layer = 1          
     keymap_stat   = 0x0001          keymap_stat   = 0x0002

On the other hand, you shall change keymap_state to overlay base layer with some layers for feature such as navigation keys, function key(F1-F12), media keys or special actions.

Overlay feature layer
---------------------      bit|status
       ____________        ---+------
  15  /           /        15 |   0
  14 /___________// -----> 14 |   1
  13 /___________/  -----> 13 |   1
   :                        : |   
   3   ____________         3 |   0
   2  /           /         2 |   0
,->1 /___________/  ----->  1 |   1
|  0                        0 |   0
|                                 |
`--- default_layer = 1            |
     keymap_stat   = 0x6002 <-----'

Layer Precedence and Transparency

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.

You can place KC_TRNS on overlay layer changes just part of layout to fall back on lower or base layer. Key with KC_TRANS doen't has its own keycode and refers to its lower layers for keycode, instead. See layer 1 or 2 below for example.

Keymap Example

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.

This is a keymap example for HHKB keyboard. This example has three layers, 'Qwerty' as base layer, 'Cursor' and 'Mousekey'. In this example,

Fn0 is a momentary layer switching key, you can use keys on Cursor layer while holding the key.

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.

Fn2 is a toggle layer switch key, you can stay switched layer after releasing the key unlike momentary switching.

You can find other keymap definitions in file keymap.c located on project directories.

static const uint8_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
    /* 0: Qwerty
     * ,-----------------------------------------------------------.
     * |Esc|  1|  2|  3|  4|  5|  6|  7|  8|  9|  0|  -|  =|  \|  `|
     * |-----------------------------------------------------------|
     * |Tab  |  Q|  W|  E|  R|  T|  Y|  U|  I|  O|  P|  [|  ]|Backs|
     * |-----------------------------------------------------------|
     * |Contro|  A|  S|  D|  F|  G|  H|  J|  K|  L|Fn1|  '|Enter   |
     * |-----------------------------------------------------------|
     * |Shift   |  Z|  X|  C|  V|  B|  N|  M|  ,|  .|  /|Shift |Fn0|
     * `-----------------------------------------------------------'
     *       |Gui|Alt  |Space                  |Alt  |Fn2|
     *       `-------------------------------------------'
     */
    KEYMAP(ESC, 1,   2,   3,   4,   5,   6,   7,   8,   9,   0,   MINS,EQL, BSLS,GRV, \
           TAB, Q,   W,   E,   R,   T,   Y,   U,   I,   O,   P,   LBRC,RBRC,BSPC, \
           LCTL,A,   S,   D,   F,   G,   H,   J,   K,   L,   FN1, QUOT,ENT, \
           LSFT,Z,   X,   C,   V,   B,   N,   M,   COMM,DOT, SLSH,RSFT,FN0, \
                LGUI,LALT,          SPC,                RALT,FN2),
    /* 1: Cursor(HHKB mode)
     * ,-----------------------------------------------------------.
     * |Pwr| F1| F2| F3| F4| F5| F6| F7| F8| F9|F10|F11|F12|Ins|Del|
     * |-----------------------------------------------------------|
     * |Caps |   |   |   |   |   |   |   |Psc|Slk|Pus|Up |   |Backs|
     * |-----------------------------------------------------------|
     * |Contro|VoD|VoU|Mut|   |   |  *|  /|Hom|PgU|Lef|Rig|Enter   |
     * |-----------------------------------------------------------|
     * |Shift   |   |   |   |   |   |  +|  -|End|PgD|Dow|Shift |   |
     * `-----------------------------------------------------------'
     *      |Gui |Alt  |Space                  |Alt  |Gui|
     *      `--------------------------------------------'
     */ 
    KEYMAP(PWR, F1,  F2,  F3,  F4,  F5,  F6,  F7,  F8,  F9,  F10, F11, F12, INS, DEL, \
           CAPS,TRNS,TRNS,TRNS,TRNS,TRNS,TRNS,TRNS,PSCR,SLCK,PAUS,UP,  TRNS,BSPC, \
           LCTL,VOLD,VOLU,MUTE,TRNS,TRNS,PAST,PSLS,HOME,PGUP,LEFT,RGHT,ENT, \
           LSFT,TRNS,TRNS,TRNS,TRNS,TRNS,PPLS,PMNS,END, PGDN,DOWN,RSFT,TRNS, \
                LGUI,LALT,          SPC,                RALT,RGUI),
    /* 2: Mousekey
     * ,-----------------------------------------------------------.
     * |Esc| F1| F2| F3| F4| F5| F6| F7| F8| F9|F10|F11|F12|Ins|Del|
     * |-----------------------------------------------------------|
     * |Tab  |   |   |   |   |   |MwL|MwD|MwU|MwR|   |   |   |Backs|
     * |-----------------------------------------------------------|
     * |Contro|   |   |   |   |   |McL|McD|McU|McR|   |   |Return  |
     * |-----------------------------------------------------------|
     * |Shift   |   |   |   |   |Mb3|Mb2|Mb1|Mb4|Mb5|   |Shift |   |
     * `-----------------------------------------------------------'
     *      |Gui |Alt  |Mb1                    |Alt  |   |
     *      `--------------------------------------------'
     * Mc: Mouse Cursor / Mb: Mouse Button / Mw: Mouse Wheel 
     */
    KEYMAP(ESC, F1,  F2,  F3,  F4,  F5,  F6,  F7,  F8,  F9,  F10, F11, F12, INS, DEL, \
           TAB, TRNS,TRNS,TRNS,TRNS,TRNS,WH_L,WH_D,WH_U,WH_R,TRNS,TRNS,TRNS,BSPC, \
           LCTL,TRNS,ACL0,ACL1,ACL2,TRNS,MS_L,MS_D,MS_U,MS_R,TRNS,QUOT,ENT, \
           LSFT,TRNS,TRNS,TRNS,TRNS,BTN3,BTN2,BTN1,BTN4,BTN5,SLSH,RSFT,TRNS, \
                LGUI,LALT,          BTN1,               RALT,TRNS),
};

static const uint16_t PROGMEM fn_actions[] = {
    ACTION_KEYMAP(1),                            // FN0
    ACTION_KEYMAP_TAP_KEY(2, KC_SCLN),           // FN1
    ACTION_KEYMAP_TOGGLE(2),                     // FN2
};

1. Keycode

See common/keycode.h or keycode table below. 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.

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().

1.0 Other key

KC_NO for no aciton
KC_TRNS for layer transparency (See above)

1.1 Normal key

KC_A to KC_Z, KC_1 to KC_0 for alpha numeric key
KC_MINS, KC_EQL, KC_GRV, KC_RBRC, KC_LBRC, KC_COMM, KC_DOT, KC_BSLS, KC_SLSH, KC_SCLN, KC_QUOT
KC_ESC, KC_TAB, KC_SPC, KC_BSPC, KC_ENT, KC_DEL, KC_INS
KC_UP, KC_DOWN, KC_RGHT, KC_LEFT, KC_PGUP, KC_PGDN, KC_HOME, KC_END
KC_CAPS, KC_NLCK, KC_SLCK, KC_PSCR, KC_PAUS, KC_APP, KC_F1 to KC_F24
KC_P1 to KC_P0, KC_PDOT, KC_PCMM, KC_PSLS, KC_PAST, KC_PMNS, KC_PPLS, KC_PEQL, KC_PENT for keypad.

1.2 Modifier

There are 8 modifiers which has discrimination between left and right.

KC_LCTL and KC_RCTL for Control
KC_LSFT and KC_RSFT for Shift
KC_LALT and KC_RALT for Alt
KC_LGUI and KC_RGUI for Windows key or Command key in Mac

1.3 Mousekey

KC_MS_U, KC_MS_D, KC_MS_L, KC_MS_R for mouse cursor
KC_WH_U, KC_WH_D, KC_WH_L, KC_WH_R for mouse wheel
KC_BTN1, KC_BTN2, KC_BTN3, KC_BTN4, KC_BTN5 for mouse buttons

1.4 System & Media key

KC_PWR, KC_SLEP, KC_WAKE for Power, Sleep, Wake
KC_MUTE, KC_VOLU, KC_VOLD for audio volume control
KC_MNXT, KC_MPRV, KC_MSTP, KC_MPLY, KC_MSEL for media control
KC_MAIL, KC_CALC, KC_MYCM for application launch
KC_WSCH, KC_WHOM, KC_WBAK, KC_WFWD, KC_WSTP, KC_WREF, KC_WFAV for web browser operation

1.5 Fn key

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.

1.6 Keycode Table

See keycode table in doc/keycode.txt for description of keycodes.

In regard to implementation side most of keycodes are identical with [HID usage]HID_usage sent to host for real and some virtual keycodes are defined to support special actions. [HID_usage]: http://www.usb.org/developers/devclass_docs/Hut1_11.pdf

2. Action

See common/action.h. Action is a 16bit code and defines function to perform on events of a key like press, release, holding and tapping.

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 against using jsut keycodes. To avoid this waste 8bit keycodes are used in KEYMAP instead of action codes.

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[].

Usually action codes are needed only when you want to use layer switching, or

2.1 Key action

This is a simple action that registers scancodes(HID usage in fact) to host on press event of key and unregister on release.

2.1.1 Normal key and Modifier

This action usually won't be used expressly because you can use keycodes in KEYMAP() instead. You can define Key action on 'A' key and 'left shift' modifier with:

ACTION_KEY(KC_A)
ACTION_KEY(KC_LSHIFT)

2.1.2 Key with modifiers

This action is comprised of strokes of modifiers and a key. Macro action is needed if you want more complex key strokes. Say you want to assign a key to Shift + 1 to get charactor '!' or Alt + Tab to switch application windows.

ACTION_LMOD_KEY(KC_LSHIFT, KC_1)
ACTION_LMOD_KEY(KC_LALT, KC_TAB)

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.

ACTION_LMODS_KEY((MOD_BIT(KC_LALT) | MOD_BIT(KC_LSHIFT)), KC_TAB)

2.2 Layer Actions

2.2.0 Default Layer

default_layer is layer which always is on and refered to when actions is not defined on other layers.

Return to Default Layer

Turns on default layer only with clearing other all layers.

ACTION_DEFAULT_LAYER

Set Default Layer

Sets 'default layer' to layer and turn it on without clear any other layers.

ACTION_DEFAULT_LAYER_SET(layer)

This does it on { press | release | both }.

ACTION_DEFAULT_LAYER_SET(layer, on)

2.2.1 Keymap

These actions operate given layer argument which ranges from 0 to 15.

Switch to layer

Turns on layer momentary while holding, in other words turn on when key is pressed and off when released.

ACTION_KEYMAP_MOMENTARY(layer)

Toggle layer

Turns on layer on first type and turns off on next.

ACTION_KEYMAP_TOGGLE(layer)

Switch to layer with tap key

Turns on layer momentary while holding but registers key on tap.

ACTION_KEYMAP_TAP_KEY(layer, key)

Switch to layer with tap toggle

Turns on layer momentary while holding but toggles it with serial taps.

ACTION_KEYMAP_TAP_TOGGLE(layer)

Invert layer

Inverts current layer state. If the layer is on it becomes off with this action.

ACTION_KEYMAP_INV(layer, on)

Turn On layer

Turns on layer state.

ACTION_KEYMAP_ON(layer, on)

Turns on layer state on press and turn off on release. This is identical to 'Switch to layer' action.

ACTION_KEYMAP_ON_OFF(layer)

Turn Off layer

Turns off layer state.

ACTION_KEYMAP_OFF(layer, on)

Set layer

Turn on layer only. keymap_stat = (1<<layer) [layer: 0-15]

ACTION_KEYMAP_SET(layer, on)

Turns on layer only and clear all layer on release..

ACTION_KEYMAP_SET_CLEAR(layer)

2.2.2 Overlay

TBD

In addition to actions of Keymap above these actions are also available.

Invert 4bit layer states

Invert 4bits out of 16bits of overlay status on both press and release. overlay_stat = (overlay_stat ^ bits<<(shift*4)) [bits: 0-15, shift: 0-3]

ACTION_OVERLAY_INV4(bits, shift)

2.3 Macro action

TBD

Macro action indicates complex key strokes.

MACRO( MD(LSHIFT), D(D), END )
MACRO( U(D), MU(LSHIFT), END )
MACRO( I(255), T(H), T(E), T(L), T(L), W(255), T(O), END )

2.3.1 Normal mode

I() change interavl of stroke.
D() press key
U() release key
T() type key(press and release)
W() wait
MD() modifier down
MU() modifier up
END end mark

2.3.2 Extended mode

TODO: sample impl See keyboard/hhkb/keymap.c for sample.

2.4 Function action

TBD

There are two type of action, normal Function and tappable Function. These actions call user defined function with id, opt, and key event information as arguments.

2.4.1 Function

To define normal Function action in keymap use this.

ACTION_FUNCTION(id, opt)

2.4.2 Function with tap

To define tappable Function action in keymap use this.

ACTION_FUNCTION_TAP(id, opt)

2.4.3 Implement user function

Function actions can be defined freely with C by user in callback function:

void keymap_call_function(keyrecord_t *event, uint8_t id, uint8_t opt)

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.

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.

typedef struct {
    keyevent_t  event;
    uint8_t     tap_count;
} keyrecord_t;

typedef struct {
    key_t    key;
    bool     pressed;
    uint16_t time;
} keyevent_t;

typedef struct {
    uint8_t col;
    uint8_t row;
} key_t;

TODO: sample impl See keyboard/hhkb/keymap.c for sample.

3. Layer

Layer is key-action map to assign action to every physical key. You can define multiple layers in keymap and make layers active out of keymap during operation at will.

First layer is indexed by 0 which usually become default layer and active in initial state.

You can define 16 layers at most in each keymaps and overlays.

        ____________
       /           /
      /           //
  15 /___________///
  14 /___________//_
  13 /___________/ /
      /: : : : :  //
   3 /___________///
   2 /___________///
   1 /___________//
.->0 /___________/ 
`--- default_layer = 0

you can define a layer with placing keycode symbols separated with comma in KEYMAP, which is formed with resemblance to physical keyboard layout so as you can easily put keycode on place you want to map. You can define most of keys with just using keycodes except for Fn key serving special actions.

3.0 Transparency

With KC_TRNS you can define transparent key which itself doesn't have action but refer to lower valid layer. Transparent key is useful when you want to change part of layout not over all.

4. Layer switching

You can have some ways to switch layer with these actions. There are two kind of layer switch action Layer Set and Layer Bit and two type of switching behaviour Momentary and Toggle.

4.1 Momentary switching

Momentary switching changes layer only while holding Fn key.

4.1.1 Momentary Set

This action makes Layer 1 active on key press event and inactive on release event..

ACTION_KEYMAP_MOMENTARY(1)

It switches to destination layer immediately when key is pressed, after that actions on keymap of destination layer is perfomed. 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. To get back to default layer you can use this action.

ACTION_LAYER_DEFAULT

4.1.2 Momentary Bit

This Layer Bit action performs XOR 1 with current layer on both press and release event. If you are on Layer 0 now next layer to switch will be Layer 1. To come back to previous layer you need to place same action on destination layer.

ACTION_LAYER_BIT(1)

4.2 Toggle switching

Toggle switching changes layer after press then release. You keep being on the layer until you press key to return.

4.2.1 Toggle Set

This Layer Set Toggle action is to set Layer 1 to current layer on release and do none on press.

ACTION_LAYER_SET_TOGGLE(1)

To get back to default layer you can use this action.

ACTION_LAYER_DEFAULT

4.2.2 Toggle Bit

This Layer Bit Toggle action is to XOR 1 with current layer on release and do none on press. If you are on Layer 2 you'll switch to Layer 3 on press. To come back to previous layer you need to place same action on destination layer.

ACTION_LAYER_BIT_TOGGLE(1)

4.3 Momentary switching with Tap key

These actions switch to layer only while holding Fn key and register key on tap. Tap means to press and release key quickly.

ACTION_LAYER_SET_TAP_KEY(2, KC_SCLN)
ACTION_LAYER_SET_BIT_KEY(2, KC_SCLN)

With these you can place layer switching function on normal alphabet key like ; without losing its original register function.

4.4 Momentary switching with Tap Toggle

This changes layer only while holding Fn key and toggle layer after several taps. Tap means to press and release key quickly.

ACTION_LAYER_SET_TAP_TOGGLE(layer)
ACTION_LAYER_BIT_TAP_TOGGLE(layer)

Number of taps can be defined with TAPPING_TOGGLE in config.h, 5 by default.

Tapping

Tap Key

One Shot Modifier

Legacy Keymap

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.

In comparison with new keymap how to define Fn key is different. It uses two arrays fn_layer[] and fn_keycode[]. 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.

In following setting example, Fn0, Fn1 and Fn2 switch layer to 1, 2 and 2 respectively. Fn2 registers Space key when tap while Fn0 and Fn1 doesn't send any key.

static const uint8_t PROGMEM fn_layer[] = {
    1,              // Fn0
    2,              // Fn1
    2,              // Fn2
};

static const uint8_t PROGMEM fn_keycode[] = {
    KC_NO,          // Fn0
    KC_NO,          // Fn1
    KC_SPC,         // Fn2
};

Terminology

keymap
layer
layout
key
keycode
scancode
action
layer transparency
layer precedence
register
tap
Fn key

23 KiB Raw Blame History

Keymap framework - how to define your keymap

Keymap

Keymap status

Layer Precedence and Transparency

Keymap Example

1. Keycode

1.0 Other key

1.1 Normal key

1.2 Modifier

1.3 Mousekey

1.4 System & Media key

1.5 Fn key

1.6 Keycode Table

2. Action

2.1 Key action

2.1.1 Normal key and Modifier

2.1.2 Key with modifiers

2.2 Layer Actions

2.2.0 Default Layer

Return to Default Layer

Set Default Layer

2.2.1 Keymap

Switch to layer

Toggle layer

Switch to layer with tap key

Switch to layer with tap toggle

Invert layer

Turn On layer

Turn Off layer

Set layer

2.2.2 Overlay

Invert 4bit layer states

2.3 Macro action

2.3.1 Normal mode

2.3.2 Extended mode

2.4 Function action

2.4.1 Function

2.4.2 Function with tap

2.4.3 Implement user function

3. Layer

3.0 Transparency

4. Layer switching

4.1 Momentary switching

4.1.1 Momentary Set

4.1.2 Momentary Bit

4.2 Toggle switching

4.2.1 Toggle Set

4.2.2 Toggle Bit

4.3 Momentary switching with Tap key

4.4 Momentary switching with Tap Toggle

Tapping

Tap Key

One Shot Modifier

Legacy Keymap

Terminology

23 KiB

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