qmk-firmware/users/drashna/rgb_stuff.h

#include "quantum.h"

typedef struct {
    bool enabled;
    uint8_t hue;
    uint16_t timer;
    uint8_t life;
} rgblight_fadeout;

bool process_record_user_rgb(uint16_t keycode, keyrecord_t *record);
void scan_rgblight_fadeout(void);
void matrix_init_rgb(void);
void matrix_scan_rgb(void);
uint32_t layer_state_set_rgb(uint32_t state);
uint32_t default_layer_state_set_rgb(uint32_t state);