typedef opacity_type (*opacity_func)(const coord_def&);
typedef bool (*bounds_func)(const coord_def&);

opacity_type opc_default(const coord_def&);
bool bounds_los_radius(const coord_def& p);

opacity_type opc_default(const coord_def& p)
{
    int m;
    dungeon_feature_type f = env.grid(p);
    if (grid_is_opaque(f))
        return OPC_OPAQUE;
    else if (is_opaque_cloud(env.cgrid(p)))
        return OPC_HALF;
    else if (f == DNGN_TREES)
        return OPC_HALF;
    else if ((m = mgrd(p)) != NON_MONSTER && menv[m].type == MONS_BUSH)
        return OPC_HALF;
    else
        return OPC_CLEAR;
}

bool bounds_los_radius(const coord_def& p)
{
    return (p.abs() <= get_los_radius_squared());
}

void losight(env_show_grid& sh, const los_param& dat);

void losight(env_show_grid& sh, const coord_def& center,
             opacity_func opc = &opc_default,
             bounds_func bounds = &bounds_los_radius);
void losight(env_show_grid& sh, const los_param& param);

}
struct los_param_funcs : public los_param
{
    coord_def center;
    opacity_func opc;
    bounds_func bounds;
    los_param_funcs(const coord_def& c,
                    opacity_func o, bounds_func b)
        : center(c), opc(o), bounds(b)
    {
    }
    bool los_bounds(const coord_def& p) const
    {
        return (map_bounds(p + center) && bounds(p));
    }
    unsigned appearance(const coord_def& p) const
    {
        return (grid_appearance(p + center));
    }
    opacity_type opacity(const coord_def& p) const
    {
        return (opc(p + center));
    }
};
void losight(env_show_grid& sh, const coord_def& center,
             opacity_func opc, bounds_func bounds)
{
    losight(sh, los_param_funcs(center, opc, bounds));

        losight(env.show, los_param_base(you.pos()));

        losight(env.show, you.pos());