Add documentation for Combo feature

1 files changed, 88 insertions, 0 deletions

diff --git a/docs/feature_combo.md b/docs/feature_combo.md
new file mode 100644
index 000000000..f509e9f33
--- /dev/null
+++ b/docs/feature_combo.md
@@ -0,0 +1,88 @@
+# Combos
+
+The Combo feature is a chording type solution for adding custom actions.  It lets you hit multiple keys at once and produce a different effect.  For instance, hitting `A` and `S` within the tapping term would hit `ESC` instead, or have it perform even more complex tasks.
+
+To enable this feature, yu need to add `COMBO_ENABLE = yes` to your `rules.mk`.
+
+Additionally, in your `config.h`, you'll need to specify the number of combos that you'll be using, by adding `#define COMBO_COUNT 1` (replacing 1 with the number that you're using).
+<!-- At this time, this is necessary -->
+
+Also, by default, the tapping term for the Combos is set to the same value as `TAPPING_TERM` (200 by default on most boards). But you can specify a different value by defining it in your `config.h`.  For instance: `#define COMBO_TERM 300` would set the time out period for combos to 300ms.
+
+Then, your `keymap.c` file, you'll need to define a sequence of keys, terminated with `COMBO_END`, and a structure to list the combination of keys, and it's resulting action.
+
+```c
+const uint16_t PROGMEM test_combo[] = {KC_A, KC_B, COMBO_END};
+combo_t key_combos[COMBO_COUNT] = {COMBO(test_combo, KC_ESC)};
+```
+
+This will send "Escape" if you hit the A and B keys.
+
+!> This method only supports [basic keycodes](keycodes_basic.md). See the examples for more control.
+
+## Examples
+
+If you want to add a list, then you'd use something like this:
+
+```c
+enum combos {
+  AB_ESC,
+  JK_TAB
+}
+const uint16_t PROGMEM ab_combo[] = {KC_A, KC_B, COMBO_END};
+const uint16_t PROGMEM jk_combo[] = {KC_J, KC_K, COMBO_END};
+
+combo_t key_combos[COMBO_COUNT] = {
+  [AB_ESC] = COMBO(ab_combo, KC_ESC),
+  [JK_TAB] = COMBO(jk_combo, KC_TAB)
+};
+```
+
+For a more complicated implementation, you can use the `process_combo_event` function to add custom handling.
+
+```c
+enum combo_events {
+  ZC_COPY,
+  ZV_PASTE
+  };
+
+const uint16_t PROGMEM copy_combo[] = {KC_Z, KC_C, COMBO_END};
+const uint16_t PROGMEM paste_combo[] = {KC_Z, KC_V, COMBO_END};
+
+combo_t key_combos[COMBO_COUNT] = {
+  [ZC_COPY] = COMBO_ACTION(copy_combo),
+  [ZV_PASTE] = COMBO_ACTION(paste_combo),
+};
+
+void process_combo_event(uint8_t combo_index, bool pressed) {
+  switch(combo_index) {
+    case ZC_COPY:
+      if (pressed) {
+        register_code(KC_LCTL);
+        register_code(KC_C);
+        unregister_code(KC_C);
+        unregister_code(KC_LCTL);
+      }
+      break;
+
+    case ZV_PASTE:
+      if (pressed) {
+        register_code(KC_LCTL);
+        register_code(KC_V);
+        unregister_code(KC_V);
+        unregister_code(KC_LCTL);
+      }
+      break;
+  }
+}
+```
+
+This will send Ctrl+C if you hit Z and C, and Ctrl+V if you hit Z and V.  But you could change this to do stuff like change layers, play sounds, or change settings.
+
+## Additional Configuration
+
+If you're using long combos, or even longer combos, you may run into issues with this, as the structure may not be large enough to accommodate what you're doing.
+
+In this case, you can add either `#define EXTRA_LONG_COMBOS` or `#define EXTRA_EXTRA_LONG_COMBOS` in your `config.h` file.
+
+You may also be able to enable action keys by defining `COMBO_ALLOW_ACTION_KEYS`.