qmk_firmware/users/muppetjones/readme/rgblayers.md

Dynamic Underglow Lighting Per-Layer

This bit of code allows you to define layer lighting that respects your current eeprom settings, e.g., brightness. It does this by storing the base state rgb

Setup

1. Enable RGB underglow in your rules.mk

   RGBLIGHT_ENABLE = yes      # Enable keyboard RGB underglow
   

2. (Optional) Add RGB configuration to your config.h

   #ifdef RGBLIGHT_ENABLE
   #    define RGBLIGHT_HUE_STEP 8
   #    define RGBLIGHT_SAT_STEP 16
   #    define RGBLIGHT_VAL_STEP 16
   #    define RGBLIGHT_LIMIT_VAL 150
   #    define RGBLIGHT_SLEEP
   // #    define RGBLIGHT_LAYERS
   #endif
   

3. Add set_layer_hsv function. This is where you define your layer-specific colors by setting the HSV properties on the layer_color pointer. This example uses the QMK RGB configuration parameters to keep the layer colors offset based on the current EEPROM HSV.

   NOTE: The HSV values should be between 0 and 255, but setting the modulus on saturation causes the lights to go white on my board. I think this is due to overflow, but I haven't had the chance to try and resolve it yet.

   #ifdef RGBLIGHT_ENABLE
   void set_layer_hsv(layer_state_t state, HSV* layer_color) {
       int32_t h = layer_color->h, s = layer_color->s, v = layer_color->v;
       switch (get_highest_layer(state)) {
           case _RAISE:
               h += 2 * RGBLIGHT_HUE_STEP;
               break;
           case _LOWER:
               h += -2 * RGBLIGHT_HUE_STEP;
               break;
           case _NAV:
               h += 1 * RGBLIGHT_HUE_STEP;
               break;
           case _MOUSE:
               h += -7 * RGBLIGHT_HUE_STEP;
               break;
           default:
               break;
       }
       layer_color->h = h % 255;
       layer_color->s = s;
       layer_color->v = v % 255;
       return;
   }
   #endif
   

4. (Optional) If you're using post_process_record_user, you'll need to change the name in your keymap to post_process_record_keymap. We use the user function to update the HSV state after one of the RGB keycodes is pressed.