assert (t->w == NULL && t->h == NULL);
t->w = pool_nalloc (t->container, t->nc, sizeof *t->w);
t->h = pool_nalloc (t->container, t->nr, sizeof *t->h);
assert (t->w == NULL && t->h == NULL);
t->w = pool_nalloc (t->container, t->nc, sizeof *t->w);
t->h = pool_nalloc (t->container, t->nr, sizeof *t->h);