return (grd(pos) == DNGN_FLOOR);

    return (grd(pos) == DNGN_FLOOR && !dungeon_events.has_listeners_at(pos));

        dungeon_events.move_listeners(pos, dest);

    void clear_listeners_at(const coord_def &pos);
    bool has_listeners_at(const coord_def &pos) const;
    void move_listeners(const coord_def &from, const coord_def &to);

void dgn_event_dispatcher::clear_listeners_at(const coord_def &pos)
{
    grid_triggers[pos.x][pos.y].reset(NULL);
}
void dgn_event_dispatcher::move_listeners(
    const coord_def &from, const coord_def &to)
{
    // Any existing listeners at to will be discarded. YHBW.
    grid_triggers[to.x][to.y] = grid_triggers[from.x][from.y];
}
bool dgn_event_dispatcher::has_listeners_at(const coord_def &pos) const
{
    return (grid_triggers[pos.x][pos.y].get());
}