[Core] Caps Word "Invert on shift" option: pressing Shift inverts the shift state. (#20092)

Co-authored-by: Nick Brassel <nick@tzarc.org>

1 files changed, 20 insertions, 0 deletions

diff --git a/docs/feature_caps_word.md b/docs/feature_caps_word.md
index c58d1a56e2..7f726b059d 100644
--- a/docs/feature_caps_word.md
+++ b/docs/feature_caps_word.md
@@ -90,6 +90,26 @@ by defining `IS_COMMAND()` in config.h:
 
 ## Customizing Caps Word :id=customizing-caps-word
 
+### Invert on shift :id=invert-on-shift
+
+By default, Caps Word turns off when Shift keys are pressed, considering them as
+word-breaking. Alternatively with the `CAPS_WORD_INVERT_ON_SHIFT` option,
+pressing the Shift key continues Caps Word and inverts the shift state. This
+is convenient for uncapitalizing one or a few letters within a word, for
+example with Caps Word on, typing "D, B, Shift+A, Shift+A, S" produces "DBaaS",
+or typing "P, D, F, Shift+S" produces "PDFs".
+
+Enable it by adding in config.h
+
+```c
+#define CAPS_WORD_INVERT_ON_SHIFT
+```
+
+This option works with regular Shift keys `KC_LSFT` and `KC_RSFT`, mod-tap Shift
+keys, and one-shot Shift keys. Note that while Caps Word is on, one-shot Shift
+keys behave like regular Shift keys, and have effect only while they are held.
+
+
 ### Idle timeout :id=idle-timeout
 
 Caps Word turns off automatically if no keys are pressed for