render_flexbox.cpp

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            unsigned int flexGroup = child->style()->boxFlexGroup();
            if (lowestFlexGroup == 0)
                lowestFlexGroup = flexGroup;
            if (flexGroup < lowestFlexGroup)
                lowestFlexGroup = flexGroup;
            if (flexGroup > highestFlexGroup)
                highestFlexGroup = flexGroup;
        }
        child = iterator.next();
    }
    
    // We do 2 passes.  The first pass is simply to lay everyone out at
    // their preferred widths.  The second pass handles flexing the children.
    do {
        // Reset our height.
        m_height = yPos;
        m_overflowHeight = m_height;
        xPos = borderLeft() + paddingLeft();
                
        // Our first pass is done without flexing.  We simply lay the children
        // out within the box.  We have to do a layout first in order to determine
        // our box's intrinsic height.
        int maxAscent = 0, maxDescent = 0;
        child = iterator.first();
        while (child) {
            // make sure we relayout children if we need it.
            if (relayoutChildren || (child->isReplaced() && (child->style()->width().isPercent() || child->style()->height().isPercent())))
                child->setChildNeedsLayout(true, false);
            
            if (child->isPositioned()) {
                child = iterator.next();
                continue;
            }
    
            // Compute the child's vertical margins.
            child->calcVerticalMargins();
    
            // Now do the layout.
            child->layoutIfNeeded();
    
            // Update our height and overflow height.
            if (style()->boxAlign() == BBASELINE) {
                int ascent = child->marginTop() + child->getBaselineOfFirstLineBox();
                if (ascent == -1)
                    ascent = child->marginTop() + child->height() + child->marginBottom();
                int descent = (child->marginTop() + child->height() + child->marginBottom()) - ascent;
                
                // Update our maximum ascent.
                maxAscent = kMax(maxAscent, ascent);
                
                // Update our maximum descent.
                maxDescent = kMax(maxDescent, descent);
                
                // Now update our height.
                m_height = kMax(yPos + maxAscent + maxDescent, m_height);
            }
            else
                m_height = kMax(m_height, yPos + child->marginTop() + child->height() + child->marginBottom());

            child = iterator.next();
        }
        m_height += toAdd;

        // Always make sure our overflowheight is at least our height.
        if (m_overflowHeight < m_height)
            m_overflowHeight = m_height;
        
        oldHeight = m_height;
        calcHeight();

        relayoutChildren = false;
        if (oldHeight != m_height) {
            heightSpecified = true;
    
            // If the block got expanded in size, then increase our overflowheight to match.
            if (m_overflowHeight > m_height)
                m_overflowHeight -= (borderBottom() + paddingBottom());
            if (m_overflowHeight < m_height)
                m_overflowHeight = m_height;
        }
        
        // Now that our height is actually known, we can place our boxes.
        m_stretchingChildren = (style()->boxAlign() == BSTRETCH);
        child = iterator.first();
        while (child) {
            if (child->isPositioned()) {
                child->containingBlock()->insertPositionedObject(child);
                if (child->hasStaticX()) {
                    if (style()->direction() == LTR)
                        child->setStaticX(xPos);
                    else child->setStaticX(width() - xPos);
                }
                if (child->hasStaticY())
                    child->setStaticY(yPos);
                child = iterator.next();
                continue;
            }
    
            // We need to see if this child's height has changed, since we make block elements
            // fill the height of a containing box by default.
            // Now do a layout.
            int oldChildHeight = child->height();
            static_cast<RenderBox*>(child)->calcHeight();
            if (oldChildHeight != child->height())
                child->setChildNeedsLayout(true, false);
            child->layoutIfNeeded();
    
            // We can place the child now, using our value of box-align.
            xPos += child->marginLeft();
            int childY = yPos;
            switch (style()->boxAlign()) {
                case BCENTER:
                    childY += child->marginTop() + (contentHeight() - (child->height() + child->marginTop() + child->marginBottom()))/2;
                    break;
                case BBASELINE: {
                    int ascent = child->marginTop() + child->getBaselineOfFirstLineBox();
                    if (ascent == -1)
                        ascent = child->marginTop() + child->height() + child->marginBottom();
                    childY += child->marginTop() + (maxAscent - ascent);
                    break;
                }
                case BEND:
                    childY += contentHeight() - child->marginBottom() - child->height();
                    break;
                default: // BSTART
                    childY += child->marginTop();
                    break;
            }

            placeChild(child, xPos, childY);
            m_overflowHeight = kMax(m_overflowHeight, childY + child->overflowHeight(false));
            
            xPos += child->width() + child->marginRight();
    
            child = iterator.next();
        }

        remainingSpace = borderLeft() + paddingLeft() + contentWidth() - xPos;
        
        m_stretchingChildren = false;
        if (m_flexingChildren)
            haveFlex = false; // We're done.
        else if (haveFlex) {
            // We have some flexible objects.  See if we need to grow/shrink them at all.
            if (!remainingSpace)
                break;

            // Allocate the remaining space among the flexible objects.  If we are trying to
            // grow, then we go from the lowest flex group to the highest flex group.  For shrinking,
            // we go from the highest flex group to the lowest group.
            bool expanding = remainingSpace > 0;
            unsigned int start = expanding ? lowestFlexGroup : highestFlexGroup;
            unsigned int end = expanding? highestFlexGroup : lowestFlexGroup;
            for (unsigned int i = start; i <= end && remainingSpace; i++) {
                // Always start off by assuming the group can get all the remaining space.
                int groupRemainingSpace = remainingSpace;
                do {
                    // Flexing consists of multiple passes, since we have to change ratios every time an object hits its max/min-width
                    // For a given pass, we always start off by computing the totalFlex of all objects that can grow/shrink at all, and
                    // computing the allowed growth before an object hits its min/max width (and thus
                    // forces a totalFlex recomputation).
                    float totalFlex = 0.0f;
                    child = iterator.first();
                    while (child) {
                        if (allowedChildFlex(child, expanding, i))
                            totalFlex += child->style()->boxFlex();
                        child = iterator.next();
                    }
                    child = iterator.first();
                    int spaceAvailableThisPass = groupRemainingSpace;
                    while (child) {
                        int allowedFlex = allowedChildFlex(child, expanding, i);
                        if (allowedFlex) {
                            int projectedFlex = (allowedFlex == INT_MAX) ? allowedFlex : (int)(allowedFlex * (totalFlex / child->style()->boxFlex()));
                            spaceAvailableThisPass = expanding ? kMin(spaceAvailableThisPass, projectedFlex) : kMax(spaceAvailableThisPass, projectedFlex);
                        }
                        child = iterator.next();
                    }

                    // The flex groups may not have any flexible objects this time around. 
                    if (!spaceAvailableThisPass || totalFlex == 0.0f) {
                        // If we just couldn't grow/shrink any more, then it's time to transition to the next flex group.
                        groupRemainingSpace = 0;
                        continue;
                    }

                    // Now distribute the space to objects.
                    child = iterator.first();
                    while (child && spaceAvailableThisPass && totalFlex) {
                        if (allowedChildFlex(child, expanding, i)) {
                            int spaceAdd = (int)(spaceAvailableThisPass * (child->style()->boxFlex()/totalFlex));
                            if (spaceAdd) {
                                child->setOverrideSize(child->overrideWidth() + spaceAdd);
                                m_flexingChildren = true;
                                relayoutChildren = true;
                            }

                            spaceAvailableThisPass -= spaceAdd;
                            remainingSpace -= spaceAdd;
                            groupRemainingSpace -= spaceAdd;
                            
                            totalFlex -= child->style()->boxFlex();
                        }
                        child = iterator.next();
                    }
                } while (groupRemainingSpace);
            }

            // We didn't find any children that could grow.
            if (haveFlex && !m_flexingChildren)
                haveFlex = false;
        }
    } while (haveFlex);

    m_flexingChildren = false;
    
    if (xPos > m_overflowWidth)
        m_overflowWidth = xPos;

    if (remainingSpace > 0 && ((style()->direction() == LTR && style()->boxPack() != BSTART) ||
                               (style()->direction() == RTL && style()->boxPack() != BEND))) {
        // Children must be repositioned.
        int offset = 0;
        if (style()->boxPack() == BJUSTIFY) {
            // Determine the total number of children.
            int totalChildren = 0;
            child = iterator.first();
            while (child) {
                if (child->isPositioned()) {
                    child = iterator.next();
                    continue;
                }
                totalChildren++;
                child = iterator.next();
            }

            // Iterate over the children and space them out according to the
            // justification level.
            if (totalChildren > 1) {
                totalChildren--;
                bool firstChild = true;
                child = iterator.first();
                while (child) {
                    if (child->isPositioned()) {
                        child = iterator.next();
                        continue;
                    }

                    if (firstChild) {
                        firstChild = false;
                        child = iterator.next();
                        continue;
                    }

                    offset += remainingSpace/totalChildren;
                    remainingSpace -= (remainingSpace/totalChildren);
                    totalChildren--;

                    placeChild(child, child->xPos()+offset, child->yPos());
                    child = iterator.next();
                }
            }
        }
        else {
            if (style()->boxPack() == BCENTER)
                offset += remainingSpace/2;
            else // END for LTR, START for RTL
                offset += remainingSpace;
            child = iterator.first();
            while (child) {
                if (child->isPositioned()) {
                    child = iterator.next();
                    continue;
                }
                placeChild(child, child->xPos()+offset, child->yPos());
                child = iterator.next();
            }
        }
    }
    
    // So that the calcHeight in layoutBlock() knows to relayout positioned objects because of
    // a height change, we revert our height back to the intrinsic height before returning.
    if (heightSpecified)
        m_height = oldHeight;
}

void RenderFlexibleBox::layoutVerticalBox(bool relayoutChildren)
{
    int xPos = borderLeft() + paddingLeft();
    int yPos = borderTop() + paddingTop();
    if( style()->direction() == RTL )
        xPos = m_width - paddingRight() - borderRight();
    int toAdd = borderBottom() + paddingBottom();
    bool heightSpecified = false;
    int oldHeight = 0;
    
    unsigned int highestFlexGroup = 0;
    unsigned int lowestFlexGroup = 0;
    bool haveFlex = false;
    int remainingSpace = 0;
    
    // The first walk over our kids is to find out if we have any flexible children.
    FlexBoxIterator iterator(this);
    RenderObject *child = iterator.next();
    while (child) {
        // Check to see if this child flexes.
        if (!child->isPositioned() && child->style()->boxFlex() > 0.0f) {
            // We always have to lay out flexible objects again, since the flex distribution
            // may have changed, and we need to reallocate space.
            child->setOverrideSize(-1);
            if (!relayoutChildren)
                child->setChildNeedsLayout(true);
            haveFlex = true;
            unsigned int flexGroup = child->style()->boxFlexGroup();
            if (lowestFlexGroup == 0)
                lowestFlexGroup = flexGroup;
            if (flexGroup < lowestFlexGroup)
                lowestFlexGroup = flexGroup;
            if (flexGroup > highestFlexGroup)
                highestFlexGroup = flexGroup;
        }
        child = iterator.next();
    }

#if APPLE_CHANGES
    // We confine the line clamp ugliness to vertical flexible boxes (thus keeping it out of
    // mainstream block layout) and put it all inside APPLE_CHANGES to denote that this is not
    // really part of the XUL box model.
    bool haveLineClamp = style()->lineClamp() >= 0 && style()->lineClamp() <= 100;
    if (haveLineClamp) {
        int maxLineCount = 0;
        child = iterator.first();
        while (child) {
            if (!child->isPositioned()) {
                if (relayoutChildren || (child->isReplaced() && (child->style()->width().isPercent() || child->style()->height().isPercent())) ||
                    (child->style()->height().isVariable() && child->isBlockFlow() && !child->needsLayout())) {
                    child->setChildNeedsLayout(true);
                    
                    // Dirty all the positioned objects.
                    static_cast<RenderBlock*>(child)->markPositionedObjectsForLayout();
                    static_cast<RenderBlock*>(child)->clearTruncation();
                }
                child->layoutIfNeeded();
                if (child->style()->height().isVariable() && child->isBlockFlow())
                    maxLineCount = kMax(maxLineCount, static_cast<RenderBlock*>(child)->lineCount());
            }
            child = iterator.next();
        }
        
        // Get the # of lines and then alter all block flow children with auto height to use the
        // specified height.
        int numVisibleLines = int((maxLineCount+1)*style()->lineClamp()/100.0);
        if (numVisibleLines < maxLineCount) {
            for (child = iterator.first(); child; child = iterator.next()) {
                if (child->isPositioned() || !child->style()->height().isVariable() || !child->isBlockFlow())
                    continue;
                
                RenderBlock* blockChild = static_cast<RenderBlock*>(child);
                int lineCount = blockChild->lineCount();
                if (lineCount <= numVisibleLines) continue;
                
                int newHeight = blockChild->heightForLineCount(numVisibleLines);
                if (newHeight == child->height()) continue;
                
                child->setChildNeedsLayout(true);
                child->setOverrideSize(newHeight);
                m_flexingChildren = true;
                child->layoutIfNeeded();
                m_flexingChildren = false;