code: function beforechange(start1, stop1) {
      if (!isFinite(start)) start = start1;
      values.splice(0, Math.max(0, Math.min(size, Math.round((start1 - start) / step))));
      start = start1;
      stop = stop1;
    }
docs: When the context changes, switch to the new data, ready-or-not!