mod_color.c

Color mod_color(Color change, bool add, uint16_t modifier) {
        uint16_t addlim = 359 - modifier;
        uint16_t sublim = modifier;
        uint16_t leftovers; 
        if (add) {
                if (change.h <= addlim) {
                        change.h += modifier;
                } else {
                        leftovers = modifier - (359 - change.h);
                        change.h  = 0 + leftovers;
                }
        } else {
                if (change.h >= sublim) {
                        change.h -= modifier;
                } else {
                        leftovers = modifier - change.h;
                        change.h  = 359 - leftovers;
                }
        }
        return change;
}