Function is_outside

plugins/burrow.cpp:509–524

if the outside tile flag is set or it's light and it's a tree or there are just outside or light tree tiles above it

// or it's light and it's a tree
// or there are just outside or light tree tiles above it
static bool is_outside(const df::coord & pos, const df::tile_designation *des) {
    if (!des)
        return false;
    if (des->bits.outside)
        return true;
    if (!des->bits.light)
        return false;

    df::coord pos_above = pos + df::coord(0, 0, 1);
    df::tile_designation *des_above = Maps::getTileDesignation(pos_above);
    df::tiletype *tt_above = Maps::getTileType(pos_above);
    if (!des_above || !tt_above || (!is_tree(tt_above) && !LowPassable(*tt_above)))
        return false;

    return is_outside(pos_above, des_above);
}

static void flood_fill(lua_State *L, bool enable) {
    df::coord start_pos;