Add one-hand support.

This adds an action, `ACTION_SWAP_HANDS`, that swaps the the keys on the keyboard across a keymap-defined hemisphere in order to support one-hand typing without requiring a separate one-handed layer. See updated `doc/keymap.md` for more information.

1 files changed, 18 insertions, 0 deletions

diff --git a/doc/keymap.md b/doc/keymap.md
index d1985e567c..1285ad6cd1 100644
--- a/doc/keymap.md
+++ b/doc/keymap.md
@@ -455,6 +455,24 @@ Turn the backlight on and off without changing level.
 
 
 
+### 2.6 Swap-Hands Action
+The swap-hands action allows support for one-handed keyboards without requiring a separate layer. Set `ONEHAND_ENABLE` in the Makefile and define a `hand_swap_config` entry in your keymap. Now whenever the `ACTION_SWAP_HANDS` command is executed the keyboard is mirrored. For instance, to type "Hello, World" on QWERTY you would type `^Ge^s^s^w^c W^wr^sd`
+
+The configuration table is a simple 2-dimensional array to map from column/row to new column/row. Example `hand_swap_config` for Planck:
+
+```
+const keypos_t hand_swap_config[MATRIX_ROWS][MATRIX_COLS] = {
+  {{11, 0}, {10, 0}, {9, 0}, {8, 0}, {7, 0}, {6, 0}, {5, 0}, {4, 0}, {3, 0}, {2, 0}, {1, 0}, {0, 0}},
+  {{11, 1}, {10, 1}, {9, 1}, {8, 1}, {7, 1}, {6, 1}, {5, 1}, {4, 1}, {3, 1}, {2, 1}, {1, 1}, {0, 1}},
+  {{11, 2}, {10, 2}, {9, 2}, {8, 2}, {7, 2}, {6, 2}, {5, 2}, {4, 2}, {3, 2}, {2, 2}, {1, 2}, {0, 2}},
+  {{11, 3}, {10, 3}, {9, 3}, {8, 3}, {7, 3}, {6, 3}, {5, 3}, {4, 3}, {3, 3}, {2, 3}, {1, 3}, {0, 3}},
+};
+```
+
+Note that the array indices are reversed same as the matrix and the values are of type `keypos_t` which is `{col, row}` and all values are zero-based. In the example above, `hand_swap_config[2][4]` (third row, fifth column) would return {7, 2} (third row, eighth column).
+
+
+
 ## 3. Layer switching Example
 There are some ways to switch layer with 'Layer' actions.