void RenderMathMLRoot::layout()
    // Our computePreferredLogicalWidths() may change our logical width and then layout our children, which
    // RenderBlock::layout()'s relayoutChildren logic isn't expecting.
    if (preferredLogicalWidthsDirty())
    RenderBoxModelObject* index = this->index();
    // If |index|, it should be a RenderBlock here, unless the user has overriden its { position: absolute }.
    if (index && index->isBox())
LayoutPoint RenderFlowThread::adjustedPositionRelativeToOffsetParent(const RenderBoxModelObject& boxModelObject, const LayoutPoint& startPoint)
    LayoutPoint referencePoint = startPoint;

    // FIXME: This needs to be adapted for different writing modes inside the flow thread.
    RenderMultiColumnSet* startColumnSet = columnSetAtBlockOffset(referencePoint.y());
    if (startColumnSet) {
        // Take into account the offset coordinates of the columnSet.
        RenderObject* currObject = startColumnSet;
        RenderObject* currOffsetParentRenderer;
        Element* currOffsetParentElement;
        while ((currOffsetParentElement = currObject->offsetParent()) && (currOffsetParentRenderer = currOffsetParentElement->renderer())) {
            if (currObject->isBoxModelObject())
                referencePoint.move(toRenderBoxModelObject(currObject)->offsetLeft(), toRenderBoxModelObject(currObject)->offsetTop());

            // Since we're looking for the offset relative to the body, we must also
            // take into consideration the borders of the columnSet's offsetParent.
            if (currOffsetParentRenderer->isBox() && !currOffsetParentRenderer->isBody())
                referencePoint.move(toRenderBox(currOffsetParentRenderer)->borderLeft(), toRenderBox(currOffsetParentRenderer)->borderTop());

            currObject = currOffsetParentRenderer;

        // We need to check if any of this box's containing blocks start in a different columnSet
        // and if so, drop the object's top position (which was computed relative to its containing block
        // and is no longer valid) and recompute it using the columnSet in which it flows as reference.
        bool wasComputedRelativeToOtherRegion = false;
        const RenderBlock* objContainingBlock = boxModelObject.containingBlock();
        while (objContainingBlock) {
            // Check if this object is in a different columnSet.
            RenderMultiColumnSet* parentStartRegion = 0;
            RenderMultiColumnSet* parentEndRegion = 0;
            getRegionRangeForBox(objContainingBlock, parentStartRegion, parentEndRegion);
            if (parentStartRegion && parentStartRegion != startColumnSet) {
                wasComputedRelativeToOtherRegion = true;
            objContainingBlock = objContainingBlock->containingBlock();

        if (wasComputedRelativeToOtherRegion) {
            // Get the logical top coordinate of the current object.
            LayoutUnit top = 0;
            if (boxModelObject.isRenderBlock()) {
                top = toRenderBlock(&boxModelObject)->offsetFromLogicalTopOfFirstPage();
            } else {
                if (boxModelObject.containingBlock())
                    top = boxModelObject.containingBlock()->offsetFromLogicalTopOfFirstPage();

                if (boxModelObject.isBox())
                    top += toRenderBox(&boxModelObject)->topLeftLocation().y();
                else if (boxModelObject.isRenderInline())
                    top -= toRenderInline(&boxModelObject)->borderTop();

            // Get the logical top of the columnSet this object starts in
            // and compute the object's top, relative to the columnSet's top.
            LayoutUnit regionLogicalTop = startColumnSet->pageLogicalTopForOffset(top);
            LayoutUnit topRelativeToRegion = top - regionLogicalTop;
            referencePoint.setY(startColumnSet->offsetTop() + topRelativeToRegion);

            // Since the top has been overriden, check if the
            // relative positioning must be reconsidered.
            if (boxModelObject.isRelPositioned())
                referencePoint.move(0, boxModelObject.relativePositionOffset().height());

        // Since we're looking for the offset relative to the body, we must also
        // take into consideration the borders of the columnSet.
        referencePoint.move(startColumnSet->borderLeft(), startColumnSet->borderTop());

    return referencePoint;