docs: private boolean checkCandidateUpdate(double[] point) {
      final double x = point[0], y = point[1];
      if(points.isEmpty()) {
        leftx = rightx = x;
        topy = bottomy = y;
        topleft = topright = bottomleft = bottomright = point;
        return true;
      }
      // A non-regular diamond spanned by left, top, right, and bottom.
      if(x <= leftx || x >= rightx || y <= bottomy || y >= topy) {
        double xpy = x + y, xmy = x - y;
        // Update bounds:
        boolean changed = false;
        if(xpy < bottomleft[0] + bottomleft[1]) {
          bottomleft = point;
          changed = true;
        }
        else if(xpy > topright[0] + topright[1]) {
          topright = point;
          changed = true;
        }
        if(xmy < topleft[0] - topleft[1]) {
          topleft = point;
          changed = true;
        }
        else if(xmy > bottomright[0] - bottomright[1]) {
          bottomright = point;
          changed = true;
        }
        if(changed) {
          leftx = Math.max(bottomleft[0], topleft[0]);
          rightx = Math.min(bottomright[0], topright[0]);
          topy = Math.min(topleft[1], topright[1]);
          bottomy = Math.max(bottomleft[1], bottomright[1]);
        }
        return true;
      }
      return false;
    }