Add documentation for TAPPING_FORCE_HOLD (#2957) (#3320)

Also improve documentation for related settings.

1 files changed, 28 insertions, 0 deletions

diff --git a/docs/feature_advanced_keycodes.md b/docs/feature_advanced_keycodes.md
index aeb7ce1bf4..a4b681ec14 100644
--- a/docs/feature_advanced_keycodes.md
+++ b/docs/feature_advanced_keycodes.md
@@ -175,3 +175,31 @@ Example: (Tapping Term = 200ms)
 - SHFT_T(KC_A) Up
 
 With defaults, if above is typed within tapping term, this will emit `ax`. With permissive hold, if above is typed within tapping term, this will emit `X` (so, Shift+X).
+
+# Mod tap interrupt
+
+When a dual role key used for a modifier is quickly followed by another keys, it is interpreted as held even before the tapping term elapsed.  This is a problem if a key is used for example inside a rolling combo because the second key will be pressed before the first key is released.
+
+For example, when trying to type the rolling combo "zx" and z being configured to send Ctrl when hold, z rapidly followed by x actually sends Ctrl-x. That's bad.
+
+You can disable this behavior by defining `IGNORE_MOD_TAP_INTERRUPT` in `config.h`.
+
+Note that this only concerns modifiers and not layer switching keys.
+
+# Hold after tap
+
+When the user holds a key after tap, this repeats the tapped key rather to hold a modifier key.  This allows to use auto repeat for the tapped key.  If you prefer to hold a modifier instead, define `TAPPING_FORCE_HOLD` in `config.h`.
+
+Example:
+
+- SHFT_T(KC_A) Down
+- SHFT_T(KC_A) Up
+- SHFT_T(KC_A) Down
+- wait more than tapping term...
+- SHFT_T(KC_A) Up
+
+With default settings, `a` will be sent on the first release, then `a` will be sent on the second press allowing the computer to trigger its auto repeat function.
+
+With `TAPPING_FORCE_HOLD`, the second press will be interpreted as a Shift, allowing to use it as a modifier shortly after having used it as a tap.
+
+!> `TAPPING_FORCE_HOLD` will break anything that uses tapping toggles (Such as the `TT` layer keycode, and the One Shot Tapping Toggle).