Added a new keycode for cycling through RBG modes which reverses directions when shift is hold.

This commit adds a new keycode `RGB_SMOD` which is the same as `RGB_MOD` (cycle through all modes),
but when it is used in combination with shift it will reverse the direction.

docs/feature_rgblight.md

@@ -88,6 +88,7 @@ These control the RGB Lighting functionality.
 |-----------|------------|-------------|
 ||`RGB_TOG`|toggle on/off|
 ||`RGB_MOD`|cycle through modes|
+||`RGB_SMOD`|cycle through modes, use reverse direction when shift is hold|
 ||`RGB_HUI`|hue increase|
 ||`RGB_HUD`|hue decrease|
 ||`RGB_SAI`|saturation increase|

quantum/quantum.c

@@ -290,6 +290,18 @@ bool process_record_quantum(keyrecord_t *record) {
       rgblight_step();
     }
     return false;
+  case RGB_SMOD:
+    // same as RBG_MOD, but if shift is pressed, it will use the reverese direction instead.
+    if (record->event.pressed) {
+      uint8_t shifted = get_mods() & (MOD_BIT(KC_LSHIFT)|MOD_BIT(KC_RSHIFT));
+      if(shifted) {
+        rgblight_step_reverse();
+      }
+      else {
+        rgblight_step();
+      }
+    }
+    return false;
   case RGB_HUI:
     if (record->event.pressed) {
       rgblight_increase_hue();

quantum/quantum_keycodes.h

@@ -400,6 +400,7 @@ enum quantum_keycodes {
     // RGB functionality
     RGB_TOG,
     RGB_MOD,
+    RGB_SMOD,
     RGB_HUI,
     RGB_HUD,
     RGB_SAI,