code: function(a, b)
  {
      return (a.bb_l <= b.bb_r && b.bb_l <= a.bb_r && a.bb_b <= b.bb_t && b.bb_b <= a.bb_t);
  }
docs: **** Marking Functions /*
  typedef struct MarkContext {
  bbTree *tree;
  Node *staticRoot;
  cpSpatialIndexQueryFunc func;
  } MarkContext;