Merge branch 'adb_iso_fix'

[max/tmk_keyboard.git] / tmk_core / doc / keymap.md

diff --git a/tmk_core/doc/keymap.md b/tmk_core/doc/keymap.md
index 572cf2f892929e24e816b280670832ffdf7673a1..3a196a2dd5bb17e3ff8c0af8b29c156024fe548e 100644 (file)
--- a/tmk_core/doc/keymap.md
+++ b/tmk_core/doc/keymap.md
@@ -51,8 +51,8 @@ The **layer state** indicates the current on/off status of all layers. It is def
 #### 0.1.2 The default layer
 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.
 
-    Initial state of Keymap          Change base layout              
-    -----------------------          ------------------              
+    Initial state of Keymap          Change base layout
+    -----------------------          ------------------
 
       31                               31
       30                               30
@@ -86,25 +86,26 @@ default_layer_state_set(1UL<<3);
 
 
 ### 0.2 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.
+Note that ***higher layers have priority in the layer stack***. The firmware starts at the topmost active layer, and works down to the bottom to find the an active keycode. Once the search encounters any keycode other than **`KC_TRNS`** (transparent) on an active layer, the search is halted and the remaining lower layers aren't examined, even if they are active.
+
+**Note:** a layer must be activated before it may be included in the stack search.
+
+`KC_TRNS` is a special placeholder which can be used on overlay layers. This allows for the creation of "partial" layers which fall back on the lower layers, eliminating a good deal of repetition in keymap files.
 
-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` doesn't has its own keycode and refers to lower valid layers for keycode, instead.
-See example below.
 
 
 ### 0.3 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.
+The keymap is defined in the **`keymaps[]`** array, a 2-dimensional array of rows and columns corresponding to positions in the keyboard matrix. But most often the layers are defined using C macros to allow for easier reading and editing of the keymap files. To use complex actions you need to define `Fn` keycodes in the **`fn_actions[]`** array.
 
-This is a keymap example for [HHKB](http://en.wikipedia.org/wiki/Happy_Hacking_Keyboard) keyboard.
-This example has three layers, 'Qwerty' as base layer, 'Cursor' and  'Mousekey'.
+This is a keymap example for the [HHKB](http://en.wikipedia.org/wiki/Happy_Hacking_Keyboard) keyboard.
+This example has three layers: the QWERTY base layer, and two overlay layers for cursor and mousekey control, respectively.
 In this example,
 
- `Fn0` is a **momentary layer switching** key, you can use keys on Cursor layer while holding the key.
+ `Fn0` is a **momentary layer switching** key--you can use keys on the 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.
+ `Fn1` is a momentary layer switching key with tapping function--tapping the key as one would normally use it, sends the semicolon **';'** keycode, while holding the key down switches layers.
 
- `Fn2` is a **toggle layer switch** key, you can stay switched layer after releasing the key unlike momentary switching.
+ `Fn2` is a **toggle layer switch** key--pressing the key toggles the layer on until you press it again.
 
 You can find other keymap definitions in file `keymap.c` located on project directories.