fix(underglow): Handle cycling effects on splits.

* Convert relative effect cycling to absolute effect selection.

app/include/dt-bindings/zmk/rgb.h

@@ -17,7 +17,8 @@
 #define RGB_SPD_CMD 10
 #define RGB_EFF_CMD 11
 #define RGB_EFR_CMD 12
-#define RGB_COLOR_HSB_CMD 13
+#define RGB_EFS_CMD 13
+#define RGB_COLOR_HSB_CMD 14
 
 #define RGB_TOG RGB_TOG_CMD 0
 #define RGB_ON RGB_ON_CMD 0

app/include/zmk/rgb_underglow.h

@@ -17,6 +17,8 @@ int zmk_rgb_underglow_get_state(bool *state);
 int zmk_rgb_underglow_on();
 int zmk_rgb_underglow_off();
 int zmk_rgb_underglow_cycle_effect(int direction);
+int zmk_rgb_underglow_calc_effect(int direction);
+int zmk_rgb_underglow_select_effect(int effect);
 struct zmk_led_hsb zmk_rgb_underglow_calc_hue(int direction);
 struct zmk_led_hsb zmk_rgb_underglow_calc_sat(int direction);
 struct zmk_led_hsb zmk_rgb_underglow_calc_brt(int direction);

app/src/behaviors/behavior_rgb_underglow.c

@@ -77,6 +77,16 @@ on_keymap_binding_convert_central_state_dependent_params(struct zmk_behavior_bin
         binding->param2 = RGB_COLOR_HSB_VAL(color.h, color.s, color.b);
         break;
     }
+    case RGB_EFR_CMD: {
+        binding->param1 = RGB_EFS_CMD;
+        binding->param2 = zmk_rgb_underglow_calc_effect(-1);
+        break;
+    }
+    case RGB_EFF_CMD: {
+        binding->param1 = RGB_EFS_CMD;
+        binding->param2 = zmk_rgb_underglow_calc_effect(1);
+        break;
+    }
     default:
         return 0;
     }
@@ -111,6 +121,8 @@ static int on_keymap_binding_pressed(struct zmk_behavior_binding *binding,
         return zmk_rgb_underglow_change_spd(1);
     case RGB_SPD_CMD:
         return zmk_rgb_underglow_change_spd(-1);
+    case RGB_EFS_CMD:
+        return zmk_rgb_underglow_select_effect(binding->param2);
     case RGB_EFF_CMD:
         return zmk_rgb_underglow_cycle_effect(1);
     case RGB_EFR_CMD:

app/src/rgb_underglow.c

@@ -332,18 +332,28 @@ int zmk_rgb_underglow_off() {
     return zmk_rgb_underglow_save_state();
 }
 
-int zmk_rgb_underglow_cycle_effect(int direction) {
+int zmk_rgb_underglow_calc_effect(int direction) {
+    return (state.current_effect + UNDERGLOW_EFFECT_NUMBER + direction) % UNDERGLOW_EFFECT_NUMBER;
+}
+
+int zmk_rgb_underglow_select_effect(int effect) {
     if (!led_strip)
         return -ENODEV;
 
-    state.current_effect += UNDERGLOW_EFFECT_NUMBER + direction;
-    state.current_effect %= UNDERGLOW_EFFECT_NUMBER;
+    if (effect < 0 || effect >= UNDERGLOW_EFFECT_NUMBER) {
+        return -EINVAL;
+    }
 
+    state.current_effect = effect;
     state.animation_step = 0;
 
     return zmk_rgb_underglow_save_state();
 }
 
+int zmk_rgb_underglow_cycle_effect(int direction) {
+    return zmk_rgb_underglow_select_effect(zmk_rgb_underglow_calc_effect(direction));
+}
+
 int zmk_rgb_underglow_toggle() {
     return state.on ? zmk_rgb_underglow_off() : zmk_rgb_underglow_on();
 }