auri.ee
keyboard stuff
1# Keymap Overview
2
3QMK keymaps are defined inside a C source file. The data structure is an array of arrays. The outer array is a list of layer arrays while the inner layer array is a list of keys. Most keyboards define a `LAYOUT()` macro to help you create this array of arrays.
4
5
6## Keymap and Layers {#keymap-and-layers}
7In QMK, **`const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS]`** holds multiple **layers** of keymap information in **16 bit** data holding the **action code**. You can define **32 layers** at most.
8
9For trivial key definitions, the higher 8 bits of the **action code** are all 0 and the lower 8 bits holds the USB HID usage code generated by the key as **keycode**.
10
11Respective layers can be validated simultaneously. Layers are indexed with 0 to 31 and higher layer has precedence.
12
13```
14Keymap: 32 Layers Layer: action code matrix
15----------------- ---------------------
16stack of layers array_of_action_code[row][column]
17 ____________ precedence _______________________
18 / / | high / ESC / F1 / F2 / F3 ....
19 31 /___________// | /-----/-----/-----/-----
20 30 /___________// | / TAB / Q / W / E ....
21 29 /___________/ | /-----/-----/-----/-----
22 : _:_:_:_:_:__ | : /LCtrl/ A / S / D ....
23 : / : : : : : / | : / : : : :
24 2 /___________// | 2 `--------------------------
25 1 /___________// | 1 `--------------------------
26 0 /___________/ V low 0 `--------------------------
27```
28
29Sometimes, the action code stored in keymap may be referred as keycode in some documents due to the TMK history.
30
31### Keymap Layer Status {#keymap-layer-status}
32
33The state of the Keymap layer is determined by two 32 bit parameters:
34
35* **`default_layer_state`** indicates a base keymap layer (0-31) which is always valid and to be referred (the default layer).
36* **`layer_state`** has current on/off status of each layer in its bits.
37
38Keymap layer '0' is usually the `default_layer`, with other layers initially off after booting up the firmware, although this can configured differently in `config.h`. It is useful to change `default_layer` when you completely switch a key layout, for example, if you want to switch to Colemak instead of Qwerty.
39
40```
41Initial state of Keymap Change base layout
42----------------------- ------------------
43
44 31 31
45 30 30
46 29 29
47 : :
48 : : ____________
49 2 ____________ 2 / /
50 1 / / ,->1 /___________/
51,->0 /___________/ | 0
52| |
53`--- default_layer = 0 `--- default_layer = 1
54 layer_state = 0x00000001 layer_state = 0x00000002
55```
56
57On the other hand, you can change `layer_state` to overlay the base layer with other layers for features such as navigation keys, function keys (F1-F12), media keys, and/or special actions.
58
59```
60Overlay feature layer
61--------------------- bit|status
62 ____________ ---+------
63 31 / / 31 | 0
64 30 /___________// -----> 30 | 1
65 29 /___________/ -----> 29 | 1
66 : : | :
67 : ____________ : | :
68 2 / / 2 | 0
69,->1 /___________/ -----> 1 | 1
70| 0 0 | 0
71| +
72`--- default_layer = 1 |
73 layer_state = 0x60000002 <-'
74```
75
76### Layer Precedence and Transparency
77Note that ***higher layers have higher priority within the stack of layers***. The firmware works its way down from the highest active layers to look up keycodes. Once the firmware locates a keycode other than `KC_TRNS` (transparent) on an active layer, it stops searching, and lower layers aren't referenced.
78
79```
80 ____________
81 / / <--- Higher layer
82 / KC_TRNS //
83/___________// <--- Lower layer (KC_A)
84/___________/
85```
86
87In the above scenario, the non-transparent keys on the higher layer would be usable, but whenever `KC_TRNS` (or equivalent) is defined, the keycode (`KC_A`) on the lower level would be used.
88
89**Note:** Valid ways to denote transparency on a given layer:
90* `KC_TRANSPARENT`
91* `KC_TRNS` (alias)
92* `_______` (alias)
93
94These keycodes allow the processing to fall through to lower layers in search of a non-transparent keycode to process.
95
96## Anatomy of a `keymap.c`
97
98For this example we will walk through an [older version of the default Clueboard 66% keymap](https://github.com/qmk/qmk_firmware/blob/ca01d94005f67ec4fa9528353481faa622d949ae/keyboards/clueboard/keymaps/default/keymap.c). You'll find it helpful to open that file in another browser window so you can look at everything in context.
99
100There are 2 main sections of a `keymap.c` file you'll want to concern yourself with:
101
102* [The Definitions](#definitions)
103* [The Layer/Keymap Datastructure](#layers-and-keymaps)
104
105### Definitions
106
107At the top of the file you'll find this:
108
109```c
110#include QMK_KEYBOARD_H
111
112// Helpful defines
113#define GRAVE_MODS (MOD_BIT(KC_LSFT)|MOD_BIT(KC_RSFT)|MOD_BIT(KC_LGUI)|MOD_BIT(KC_RGUI)|MOD_BIT(KC_LALT)|MOD_BIT(KC_RALT))
114
115/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
116 * You can use _______ in place for KC_TRNS (transparent) *
117 * Or you can use XXXXXXX for KC_NO (NOOP) *
118 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
119
120// Each layer gets a name for readability.
121// The underscores don't mean anything - you can
122// have a layer called STUFF or any other name.
123// Layer names don't all need to be of the same
124// length, and you can also skip them entirely
125// and just use numbers.
126enum layer_names {
127 _BL,
128 _FL,
129 _CL,
130};
131```
132
133These are some handy definitions we can use when building our keymap and our custom function. The `GRAVE_MODS` definition will be used later in our custom function, and the following `_BL`, `_FL`, and `_CL` defines make it easier to refer to each of our layers.
134
135Note: You may also find some older keymap files may also have a define(s) for `_______` and/or `XXXXXXX`. These can be used in place for `KC_TRNS` and `KC_NO` respectively, making it easier to see what keys a layer is overriding. These definitions are now unnecessary, as they are included by default.
136
137### Layers and Keymaps
138
139The main part of this file is the `keymaps[]` definition. This is where you list your layers and the contents of those layers. This part of the file begins with this definition:
140
141```c
142const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
143```
144
145After this you'll find the layer definitions. Typically you'll have one or more "base layers" (such as QWERTY, Dvorak, or Colemak) and then you'll layer on top of that one or more "function" layers. Due to the way layers are processed you can't overlay a "lower" layer on top of a "higher" layer.
146
147`keymaps[][MATRIX_ROWS][MATRIX_COLS]` in QMK holds the 16 bit action code (sometimes referred as the quantum keycode) in it. For the keycode representing typical keys, its high byte is 0 and its low byte is the USB HID usage ID for keyboard.
148
149::: info
150TMK from which QMK was forked uses `const uint8_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS]` instead and holds the 8 bit keycode.
151:::
152
153#### Base Layer
154
155Here is an example of the Clueboard's base layer:
156
157```c
158[_BL] = LAYOUT(
159 F(0), KC_1, KC_2, KC_3, KC_4, KC_5, KC_6, KC_7, KC_8, KC_9, KC_0, KC_MINS, KC_EQL, KC_GRV, KC_BSPC, KC_PGUP,
160 KC_TAB, KC_Q, KC_W, KC_E, KC_R, KC_T, KC_Y, KC_U, KC_I, KC_O, KC_P, KC_LBRC, KC_RBRC, KC_BSLS, KC_PGDN,
161 KC_CAPS, KC_A, KC_S, KC_D, KC_F, KC_G, KC_H, KC_J, KC_K, KC_L, KC_SCLN, KC_QUOT, KC_NUHS, KC_ENT,
162 KC_LSFT, KC_NUBS, KC_Z, KC_X, KC_C, KC_V, KC_B, KC_N, KC_M, KC_COMM, KC_DOT, KC_SLSH, KC_INT1, KC_RSFT, KC_UP,
163 KC_LCTL, KC_LGUI, KC_LALT, KC_INT5, KC_SPC,KC_SPC, KC_INT4, KC_RALT, KC_RCTL, MO(_FL), KC_LEFT, KC_DOWN, KC_RGHT
164),
165```
166
167Some interesting things to note about this:
168
169* The layer is defined using the LAYOUT macro, traditionally defined in the keyboard's `.h` file.
170* The LAYOUT macro takes a single list of keycodes, but we have written it in the C source using embedded whitespace and newlines to visualize where each key is on the physical device.
171* The LAYOUT macro hides and handles the mapping to the hardware's key scan matrix.
172* Plain keyboard scancodes are prefixed with KC_, while "special" keys are not.
173* The upper left key activates custom function 0 (`F(0)`)
174* The "Fn" key is defined with `MO(_FL)`, which moves to the `_FL` layer while that key is being held down.
175
176#### Function Overlay Layer
177
178Our function layer is, from a code point of view, no different from the base layer. Conceptually, however, you will build that layer as an overlay, not a replacement. For many people this distinction does not matter, but as you build more complicated layering setups it matters more and more.
179
180```c
181[_FL] = LAYOUT(
182 KC_GRV, KC_F1, KC_F2, KC_F3, KC_F4, KC_F5, KC_F6, KC_F7, KC_F8, KC_F9, KC_F10, KC_F11, KC_F12, _______, KC_DEL, BL_STEP,
183 _______, _______, _______,_______,_______,_______,_______,_______,KC_PSCR,KC_SCRL, KC_PAUS, _______, _______, _______, _______,
184 _______, _______, MO(_CL),_______,_______,_______,_______,_______,_______,_______, _______, _______, _______, _______,
185 _______, _______, _______,_______,_______,_______,_______,_______,_______,_______, _______, _______, _______, _______, KC_PGUP,
186 _______, _______, _______, _______, _______,_______, _______, _______, _______, MO(_FL), KC_HOME, KC_PGDN, KC_END
187),
188```
189
190Some interesting things to note:
191
192* We have used our `_______` definition to turn `KC_TRNS` into `_______`. This makes it easier to spot the keys that have changed on this layer.
193* While in this layer if you press one of the `_______` keys it will activate the key in the next lowest active layer.
194
195# Nitty Gritty Details
196
197This should have given you a basic overview for creating your own keymap. For more details see the following resources:
198
199* [Keycodes](keycodes)
200* [Keymap FAQ](faq_keymap)
201
202We are actively working to improve these docs. If you have suggestions for how they could be made better please [file an issue](https://github.com/qmk/qmk_firmware/issues/new)!