+ Interval hp = head_positions (me);
+ if (dir == UP)
+ iv = Interval (0, len);
+ else
+ iv = Interval (-len, 0);
+
+ if (!hp.is_empty ())
+ iv.translate (hp[dir] * ss / 2);
+
+ /* extend the stem (away from the head) to cover the staff */
+ if (dir == UP)
+ iv[UP] = max (iv[UP], rad * ss);
+ else
+ iv[DOWN] = min (iv[DOWN], -rad * ss);
+ }
+ else
+ iv = Interval (-rad * ss, rad * ss);