private boolean previousIsSpace(int currentIndex) {
   return sequence.size() > 0
       && currentIndex > 0
       && (sequence.getElements().get(currentIndex - 1) instanceof SpaceElement);
 }
  private BalancingResult _go() {
    if (b.drawBorders) {
      b.getCanvasBuilder().drawGrayRectangle(origRectangle.get(), BaseColor.LIGHT_GRAY);
    }

    currentLeftResult.totalElementCount =
        currentRightResult.totalElementCount = bestResult.totalElementCount = sequence.size();

    // try adding into a single infinite column to calc height
    final float hCenter = horCenter();

    referenceHeight = calcReferenceHeight(hCenter);

    currentLeftResult.referenceHeight =
        currentRightResult.referenceHeight = bestResult.referenceHeight = referenceHeight;

    leftCTB =
        setColumn(
            (float) referenceHeight,
            hCenter,
            true,
            true,
            singleColumnRect,
            b.newColumnTextBuilder());
    rightCTB =
        setColumn(
            (float) referenceHeight,
            hCenter,
            false,
            true,
            singleColumnRect,
            b.newColumnTextBuilder());

    minimalLeftColumnHeight = MINIMAL_HEIGHT_COEFFICIENT * referenceHeight / 2;

    int i;

    List<Element> elements = sequence.getElements();

    final DirectContentAdder.Result quickResult =
        new DirectContentAdder(leftCTB)
            .setStartWith(initialLeftCTB)
            .setStartAtIndex(startAtElement)
            .setQuickHeight(minimalLeftColumnHeight)
            .setSimulate(true)
            .go();

    i = quickResult.index;

    bestResult.assignIfWorseThan(
        currentLeftResult
            .setElementsAddedCount(i)
            .setLeftElementSplitHeight(0, 0)
            .setLeftColumnHeight(leftCTB.getCurrentHeight())
            .setPageSplit(i, quickResult.hasContentLeft(elements.size())));

    boolean pageOverFlow = false;

    // the only situation possible is the content left from initialContent
    if (quickResult.contentLeft != null) {
      leftCTB.copyContentFrom(quickResult.contentLeft);
      pageOverFlow =
          iterateOnLeft(
              leftCTB.newAtomicIteratorFor(),
              i - 1,
              currentLeftResult,
              leftCTB.getTop(),
              sequence.initialContentHeight);
    }

    if (i == elements.size()) {
      bestResult.assignIfWorseThan(
          currentLeftResult
              .setLeftElementSplitHeight(0, 0)
              .setLeftColumnHeight(leftCTB.getCurrentHeight())
              .setElementsAddedCount(i)
              .setPageSplit(i, leftCTB.hasMoreText()));
    }

    if (pageOverFlow) {
      return applyBestResult();
    }

    elementsCycle:
    for (; i < elements.size(); i++) {
      Element el = elements.get(i);
      final SplitResult currentResult = currentLeftResult;

      currentResult
          .setLeftElementSplitHeight(0, 0)
          .setElementsAddedCount(i)
          .setLeftColumnHeight(leftCTB.getCurrentHeight());

      considerAddingOnRightAtWholeElement(i);

      if (el instanceof SpaceElement) {
        SpaceElement space = (SpaceElement) el;

        currentResult.setElementsAddedCount(i);

        considerAddingToRight(i + 1, false);

        if (space.fits(leftCTB, origRectangle.getBottom())) {
          space.add(leftCTB, true);
        } else {
          if (leftCTB.getSimpleColumnRectangle().getBottom() - space.getHeight()
              < b.getDocument().bottom()) {
            break;
          }

          leftCTB.growBottom(space.getHeight()).setYLine(leftCTB.getYLine() - space.getHeight());
        }
      } else {
        float elementTop = leftCTB.getYLine();

        final Iterator<AtomicIncreaseResult> iterator = leftCTB.newAtomicIteratorFor(el);

        if (iterateOnLeft(iterator, i, currentResult, elementTop, sequence.getHeight(i))) {
          break elementsCycle;
        }

        //                leftCTB.restoreState();
      }

      currentResult.setLeftColumnHeight(leftCTB.getCurrentHeight()).setElementsAddedCount(i + 1);
    }

    considerAddingOnRightAtWholeElement(i);

    // here we have bestResult, so let's add our content with no simulation!

    //        setColumn(bestResult, b.newColumnTextBuilder())
    return applyBestResult();
  }