#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.