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| -rw-r--r-- | Keymap.md | 76 |
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@@ -2,6 +2,81 @@ QMK 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 `KEYMAP()` macro to help you create this array of arrays. + +## Keymap and layers +In 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. + +For 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**. + +Respective layers can be validated simultaneously. Layers are indexed with 0 to 31 and higher layer has precedence. + + Keymap: 32 Layers Layer: action code matrix + ----------------- --------------------- + stack of layers array_of_action_code[row][column] + ____________ precedence _______________________ + / / | high / ESC / F1 / F2 / F3 .... + 31 /___________// | /-----/-----/-----/----- + 30 /___________// | / TAB / Q / W / E .... + 29 /___________/ | /-----/-----/-----/----- + : _:_:_:_:_:__ | : /LCtrl/ A / S / D .... + : / : : : : : / | : / : : : : + 2 /___________// | 2 `-------------------------- + 1 /___________// | 1 `-------------------------- + 0 /___________/ V low 0 `-------------------------- + + +Sometimes, the action code stored in keymap may be referred as keycode in some documents due to the TMK history. + +### Keymap layer status +Keymap layer has its state in two 32 bit parameters: + +* **`default_layer_state`** indicates a base keymap layer(0-31) which is always valid and to be referred. +* **`layer_state`** () has current on/off status of the layer on its each bit. + +Keymap has its state in two parameter **`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. +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 switch key layout completely, say you want Colmak instead of Qwerty. + + Initial state of Keymap Change base layout + ----------------------- ------------------ + + 31 31 + 30 30 + 29 29 + : : + : : ____________ + 2 ____________ 2 / / + 1 / / ,->1 /___________/ + ,->0 /___________/ | 0 + | | + `--- default_layer = 0 `--- default_layer = 1 + layer_state = 0x00000001 layer_state = 0x00000002 + +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. + + Overlay feature layer + --------------------- bit|status + ____________ ---+------ + 31 / / 31 | 0 + 30 /___________// -----> 30 | 1 + 29 /___________/ -----> 29 | 1 + : : | : + : ____________ : | : + 2 / / 2 | 0 + ,->1 /___________/ -----> 1 | 1 + | 0 0 | 0 + | + + `--- default_layer = 1 | + layer_state = 0x60000002 <-' + + + +### 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_TRANS` on overlay layer changes just part of layout to fall back on lower or base layer. +Key with `KC_TRANS` (`KC_TRNS` and `_______` are the alias) doesn't has its own keycode and refers to lower valid layers for keycode, instead. + ## Anatomy Of A `keymap.c` For this example we will walk through the [default Clueboard keymap](https://github.com/qmk/qmk_firmware/blob/master/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. @@ -140,7 +215,6 @@ To actually handle the keypress event we define an `action_function()`. This fun This should have given you a basic overview for creating your own keymap. For more details see the following resources: -* https://github.com/qmk/qmk_firmware/blob/master/doc/keymap.md (If you see `static const uint8_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS]`, it is still the TMK code example code.) * https://github.com/qmk/qmk_firmware/wiki/Keycodes * https://github.com/qmk/qmk_firmware/wiki/FAQ-Keymap * https://github.com/qmk/qmk_firmware/wiki/Keymap-examples |