7 files changed, 93 insertions, 1 deletions

diff --git a/docs/feature_swap_hands.md b/docs/feature_swap_hands.md
index 09e01d50d..009477d20 100644
--- a/docs/feature_swap_hands.md
+++ b/docs/feature_swap_hands.md
@@ -28,3 +28,4 @@ Note that the array indices are reversed same as the matrix and the values are o
 |`SH_MOFF`  |Momentarily turns off swap.                                              |
 |`SH_TG`    |Toggles swap on and off with every key press.                            |
 |`SH_TT`    |Toggles with a tap; momentary when held.                                 |
+|`SH_OS`    |One shot swap hands: toggles while pressed or until next key press.      |
diff --git a/docs/keycodes.md b/docs/keycodes.md
index 18fd81118..40a46964a 100644
--- a/docs/keycodes.md
+++ b/docs/keycodes.md
@@ -531,6 +531,7 @@ See also: [Swap Hands](feature_swap_hands.md)
 |`SH_MOFF`  |Momentarily turns off swap.                                              |
 |`SH_TG`    |Toggles swap on and off with every key press.                            |
 |`SH_TT`    |Toggles with a tap; momentary when held.                                 |
+|`SH_OS`    |One shot swap hands: toggle while pressed or until next key press.       |
 
 ## Unicode Support :id=unicode-support
 
diff --git a/quantum/quantum_keycodes.h b/quantum/quantum_keycodes.h
index 0958c4f4e..d8f1fa4bb 100644
--- a/quantum/quantum_keycodes.h
+++ b/quantum/quantum_keycodes.h
@@ -794,6 +794,7 @@ enum quantum_keycodes {
 #    define SH_T(kc) (QK_SWAP_HANDS | (kc))
 #    define SH_TG (QK_SWAP_HANDS | OP_SH_TOGGLE)
 #    define SH_TT (QK_SWAP_HANDS | OP_SH_TAP_TOGGLE)
+#    define SH_OS (QK_SWAP_HANDS | OP_SH_ONESHOT)
 #    define SH_MON (QK_SWAP_HANDS | OP_SH_ON_OFF)
 #    define SH_MOFF (QK_SWAP_HANDS | OP_SH_OFF_ON)
 #    define SH_ON (QK_SWAP_HANDS | OP_SH_ON)
diff --git a/tmk_core/common/action.c b/tmk_core/common/action.c
index e5e9e2705..3b1268dc9 100644
--- a/tmk_core/common/action.c
+++ b/tmk_core/common/action.c
@@ -98,6 +98,11 @@ void action_exec(keyevent_t event) {
     if (has_oneshot_mods_timed_out()) {
         clear_oneshot_mods();
     }
+#        ifdef SWAP_HANDS_ENABLE
+    if (has_oneshot_swaphands_timed_out()) {
+        clear_oneshot_swaphands();
+    }
+#        endif
 #    endif
 #endif
 
@@ -165,6 +170,8 @@ void process_record_tap_hint(keyrecord_t *record) {
 #    ifdef SWAP_HANDS_ENABLE
         case ACT_SWAP_HANDS:
             switch (action.swap.code) {
+                case OP_SH_ONESHOT:
+                    break;
                 case OP_SH_TAP_TOGGLE:
                 default:
                     swap_hands = !swap_hands;
@@ -224,7 +231,11 @@ void process_action(keyrecord_t *record, action_t action) {
 #ifndef NO_ACTION_ONESHOT
     bool do_release_oneshot = false;
     // notice we only clear the one shot layer if the pressed key is not a modifier.
-    if (is_oneshot_layer_active() && event.pressed && !IS_MOD(action.key.code)) {
+    if (is_oneshot_layer_active() && event.pressed && !IS_MOD(action.key.code)
+#    ifdef SWAP_HANDS_ENABLE
+        && !(action.kind.id == ACT_SWAP_HANDS && action.swap.code == OP_SH_ONESHOT)
+#    endif
+    ) {
         clear_oneshot_layer_state(ONESHOT_OTHER_KEY_PRESSED);
         do_release_oneshot = !is_oneshot_layer_active();
     }
@@ -593,6 +604,14 @@ void process_action(keyrecord_t *record, action_t action) {
                         swap_hands = false;
                     }
                     break;
+                case OP_SH_ONESHOT:
+                    if (event.pressed) {
+                        set_oneshot_swaphands();
+                    } else {
+                        release_oneshot_swaphands();
+                    }
+                    break;
+
 #    ifndef NO_ACTION_TAPPING
                 case OP_SH_TAP_TOGGLE:
                     /* tap toggle */
@@ -681,6 +700,12 @@ void process_action(keyrecord_t *record, action_t action) {
 #    endif
 #endif
 
+#ifdef SWAP_HANDS_ENABLE
+    if (event.pressed && !(action.kind.id == ACT_SWAP_HANDS && action.swap.code == OP_SH_ONESHOT)) {
+        use_oneshot_swaphands();
+    }
+#endif
+
 #ifndef NO_ACTION_ONESHOT
     /* Because we switch layers after a oneshot event, we need to release the
      * key before we leave the layer or no key up event will be generated.
diff --git a/tmk_core/common/action_code.h b/tmk_core/common/action_code.h
index f80b7a782..eea554ff2 100644
--- a/tmk_core/common/action_code.h
+++ b/tmk_core/common/action_code.h
@@ -294,11 +294,13 @@ enum swap_hands_param_tap_op {
     OP_SH_OFF_ON,
     OP_SH_OFF,
     OP_SH_ON,
+    OP_SH_ONESHOT,
 };
 
 #define ACTION_SWAP_HANDS() ACTION_SWAP_HANDS_ON_OFF()
 #define ACTION_SWAP_HANDS_TOGGLE() ACTION(ACT_SWAP_HANDS, OP_SH_TOGGLE)
 #define ACTION_SWAP_HANDS_TAP_TOGGLE() ACTION(ACT_SWAP_HANDS, OP_SH_TAP_TOGGLE)
+#define ACTION_SWAP_HANDS_ONESHOT() ACTION(ACT_SWAP_HANDS, OP_SH_ONESHOT)
 #define ACTION_SWAP_HANDS_TAP_KEY(key) ACTION(ACT_SWAP_HANDS, key)
 #define ACTION_SWAP_HANDS_ON_OFF() ACTION(ACT_SWAP_HANDS, OP_SH_ON_OFF)
 #define ACTION_SWAP_HANDS_OFF_ON() ACTION(ACT_SWAP_HANDS, OP_SH_OFF_ON)
diff --git a/tmk_core/common/action_util.c b/tmk_core/common/action_util.c
index 335aa36e6..371acfa61 100644
--- a/tmk_core/common/action_util.c
+++ b/tmk_core/common/action_util.c
@@ -83,9 +83,63 @@ static int8_t oneshot_layer_data = 0;
 inline uint8_t get_oneshot_layer(void) { return oneshot_layer_data >> 3; }
 inline uint8_t get_oneshot_layer_state(void) { return oneshot_layer_data & 0b111; }
 
+#    ifdef SWAP_HANDS_ENABLE
+enum {
+    SHO_OFF,
+    SHO_ACTIVE,   // Swap hands button was pressed, and we didn't send any swapped keys yet
+    SHO_PRESSED,  // Swap hands button is currently pressed
+    SHO_USED,     // Swap hands button is still pressed, and we already sent swapped keys
+} swap_hands_oneshot = SHO_OFF;
+#    endif
+
 #    if (defined(ONESHOT_TIMEOUT) && (ONESHOT_TIMEOUT > 0))
 static uint16_t oneshot_layer_time = 0;
 inline bool     has_oneshot_layer_timed_out() { return TIMER_DIFF_16(timer_read(), oneshot_layer_time) >= ONESHOT_TIMEOUT && !(get_oneshot_layer_state() & ONESHOT_TOGGLED); }
+#        ifdef SWAP_HANDS_ENABLE
+static uint16_t oneshot_swaphands_time = 0;
+inline bool     has_oneshot_swaphands_timed_out() { return TIMER_DIFF_16(timer_read(), oneshot_swaphands_time) >= ONESHOT_TIMEOUT && !(swap_hands_oneshot >= SHO_PRESSED); }
+#        endif
+#    endif
+
+#    ifdef SWAP_HANDS_ENABLE
+
+void set_oneshot_swaphands(void) {
+    swap_hands_oneshot = SHO_PRESSED;
+    swap_hands         = true;
+#        if (defined(ONESHOT_TIMEOUT) && (ONESHOT_TIMEOUT > 0))
+    oneshot_swaphands_time = timer_read();
+    if (oneshot_layer_time != 0) {
+        oneshot_layer_time = oneshot_swaphands_time;
+    }
+#        endif
+}
+
+void release_oneshot_swaphands(void) {
+    if (swap_hands_oneshot == SHO_PRESSED) {
+        swap_hands_oneshot = SHO_ACTIVE;
+    }
+    if (swap_hands_oneshot == SHO_USED) {
+        clear_oneshot_swaphands();
+    }
+}
+
+void use_oneshot_swaphands(void) {
+    if (swap_hands_oneshot == SHO_PRESSED) {
+        swap_hands_oneshot = SHO_USED;
+    }
+    if (swap_hands_oneshot == SHO_ACTIVE) {
+        clear_oneshot_swaphands();
+    }
+}
+
+void clear_oneshot_swaphands(void) {
+    swap_hands_oneshot = SHO_OFF;
+    swap_hands         = false;
+#        if (defined(ONESHOT_TIMEOUT) && (ONESHOT_TIMEOUT > 0))
+    oneshot_swaphands_time = 0;
+#        endif
+}
+
 #    endif
 
 /** \brief Set oneshot layer
diff --git a/tmk_core/common/action_util.h b/tmk_core/common/action_util.h
index 1ce03ed0e..5dd8393da 100644
--- a/tmk_core/common/action_util.h
+++ b/tmk_core/common/action_util.h
@@ -77,6 +77,7 @@ void    reset_oneshot_layer(void);
 bool    is_oneshot_layer_active(void);
 uint8_t get_oneshot_layer_state(void);
 bool    has_oneshot_layer_timed_out(void);
+bool    has_oneshot_swaphands_timed_out(void);
 
 void oneshot_locked_mods_changed_user(uint8_t mods);
 void oneshot_locked_mods_changed_kb(uint8_t mods);
@@ -88,6 +89,13 @@ void oneshot_layer_changed_kb(uint8_t layer);
 /* inspect */
 uint8_t has_anymod(void);
 
+#ifdef SWAP_HANDS_ENABLE
+void set_oneshot_swaphands(void);
+void release_oneshot_swaphands(void);
+void use_oneshot_swaphands(void);
+void clear_oneshot_swaphands(void);
+#endif
+
 #ifdef __cplusplus
 }
 #endif