renderblock.cpp

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    //
    // Note also that the previous flow may collapse its margin into the top of
    // our block.  If this is the case, then we do not add the margin in to our
    // height when computing the position of the float.   This condition can be tested
    // for by simply calling canCollapseWithTop.  See
    // http://www.hixie.ch/tests/adhoc/css/box/block/margin-collapse/046.html for
    // an example of this scenario.
    int marginOffset = marginInfo.canCollapseWithTop() ? 0 : marginInfo.margin();
    setHeight(height() + marginOffset);
    positionNewFloats();
    setHeight(height() - marginOffset);
}

RenderBox* RenderBlock::handleSpecialChild(RenderBox* child, const MarginInfo& marginInfo, bool& handled)
{
    // Handle positioned children first.
    RenderBox* next = handlePositionedChild(child, marginInfo, handled);
    if (handled) return next;
    
    // Handle floating children next.
    next = handleFloatingChild(child, marginInfo, handled);
    if (handled) return next;

    // Finally, see if we have a run-in element.
    return handleRunInChild(child, handled);
}


RenderBox* RenderBlock::handlePositionedChild(RenderBox* child, const MarginInfo& marginInfo, bool& handled)
{
    if (child->isPositioned()) {
        handled = true;
        child->containingBlock()->insertPositionedObject(child);
        adjustPositionedBlock(child, marginInfo);
        return child->nextSiblingBox();
    }

    return 0;
}

RenderBox* RenderBlock::handleFloatingChild(RenderBox* child, const MarginInfo& marginInfo, bool& handled)
{
    if (child->isFloating()) {
        handled = true;
        insertFloatingObject(child);
        adjustFloatingBlock(marginInfo);
        return child->nextSiblingBox();
    }
    
    return 0;
}

RenderBox* RenderBlock::handleRunInChild(RenderBox* child, bool& handled)
{
    // See if we have a run-in element with inline children.  If the
    // children aren't inline, then just treat the run-in as a normal
    // block.
    if (child->isRunIn() && (child->childrenInline() || child->isReplaced())) {
        RenderBlock* blockRunIn = toRenderBlock(child);
        // Get the next non-positioned/non-floating RenderBlock.
        RenderObject* curr = blockRunIn->nextSibling();
        while (curr && curr->isFloatingOrPositioned())
            curr = curr->nextSibling();
        if (curr && (curr->isRenderBlock() && curr->childrenInline() && !curr->isRunIn())) {
            RenderBlock* currBlock = toRenderBlock(curr);
        
            // The block acts like an inline, so just null out its
            // position.
            handled = true;
            
            // Remove the old child.
            RenderBox* next = blockRunIn->nextSiblingBox();
            children()->removeChildNode(this, blockRunIn);

            // Create an inline.
            RenderInline* inlineRunIn = new (renderArena()) RenderInline(blockRunIn->node());
            inlineRunIn->setStyle(blockRunIn->style());

            // Move the nodes from the old child to the new child, but skip any :before/:after content.  It has already
            // been regenerated by the new inline.
            for (RenderObject* runInChild = blockRunIn->firstChild(); runInChild; runInChild = runInChild->nextSibling()) {
                if (runInChild->style()->styleType() != BEFORE && runInChild->style()->styleType() != AFTER) {
                    blockRunIn->children()->removeChildNode(blockRunIn, runInChild, false);
                    inlineRunIn->addChild(runInChild); // Use addChild instead of appendChildNode since it handles correct placement of the children relative to :after-generated content.
                }
            }

            // Now insert the new child under |currBlock|.
            currBlock->children()->insertChildNode(currBlock, inlineRunIn, currBlock->firstChild());
            
            // If the run-in had an element, we need to set the new renderer.
            if (blockRunIn->node())
                blockRunIn->node()->setRenderer(inlineRunIn);
            
            // Destroy the block run-in.
            blockRunIn->destroy();

            return next;
        }
    }
    return 0;
}

int RenderBlock::collapseMargins(RenderBox* child, MarginInfo& marginInfo)
{
    // Get our max pos and neg top margins.
    int posTop = child->maxTopMargin(true);
    int negTop = child->maxTopMargin(false);

    // For self-collapsing blocks, collapse our bottom margins into our
    // top to get new posTop and negTop values.
    if (child->isSelfCollapsingBlock()) {
        posTop = max(posTop, child->maxBottomMargin(true));
        negTop = max(negTop, child->maxBottomMargin(false));
    }
    
    // See if the top margin is quirky. We only care if this child has
    // margins that will collapse with us.
    bool topQuirk = child->isTopMarginQuirk() || style()->marginTopCollapse() == MDISCARD;

    if (marginInfo.canCollapseWithTop()) {
        // This child is collapsing with the top of the
        // block.  If it has larger margin values, then we need to update
        // our own maximal values.
        if (!style()->htmlHacks() || !marginInfo.quirkContainer() || !topQuirk)
            setMaxTopMargins(max(posTop, maxTopPosMargin()), max(negTop, maxTopNegMargin()));

        // The minute any of the margins involved isn't a quirk, don't
        // collapse it away, even if the margin is smaller (www.webreference.com
        // has an example of this, a <dt> with 0.8em author-specified inside
        // a <dl> inside a <td>.
        if (!marginInfo.determinedTopQuirk() && !topQuirk && (posTop-negTop)) {
            setTopMarginQuirk(false);
            marginInfo.setDeterminedTopQuirk(true);
        }

        if (!marginInfo.determinedTopQuirk() && topQuirk && marginTop() == 0)
            // We have no top margin and our top child has a quirky margin.
            // We will pick up this quirky margin and pass it through.
            // This deals with the <td><div><p> case.
            // Don't do this for a block that split two inlines though.  You do
            // still apply margins in this case.
            setTopMarginQuirk(true);
    }

    if (marginInfo.quirkContainer() && marginInfo.atTopOfBlock() && (posTop - negTop))
        marginInfo.setTopQuirk(topQuirk);

    int ypos = height();
    if (child->isSelfCollapsingBlock()) {
        // This child has no height.  We need to compute our
        // position before we collapse the child's margins together,
        // so that we can get an accurate position for the zero-height block.
        int collapsedTopPos = max(marginInfo.posMargin(), child->maxTopMargin(true));
        int collapsedTopNeg = max(marginInfo.negMargin(), child->maxTopMargin(false));
        marginInfo.setMargin(collapsedTopPos, collapsedTopNeg);
        
        // Now collapse the child's margins together, which means examining our
        // bottom margin values as well. 
        marginInfo.setPosMarginIfLarger(child->maxBottomMargin(true));
        marginInfo.setNegMarginIfLarger(child->maxBottomMargin(false));

        if (!marginInfo.canCollapseWithTop())
            // We need to make sure that the position of the self-collapsing block
            // is correct, since it could have overflowing content
            // that needs to be positioned correctly (e.g., a block that
            // had a specified height of 0 but that actually had subcontent).
            ypos = height() + collapsedTopPos - collapsedTopNeg;
    }
    else {
        if (child->style()->marginTopCollapse() == MSEPARATE) {
            setHeight(height() + marginInfo.margin() + child->marginTop());
            ypos = height();
        }
        else if (!marginInfo.atTopOfBlock() ||
            (!marginInfo.canCollapseTopWithChildren()
             && (!style()->htmlHacks() || !marginInfo.quirkContainer() || !marginInfo.topQuirk()))) {
            // We're collapsing with a previous sibling's margins and not
            // with the top of the block.
            setHeight(height() + max(marginInfo.posMargin(), posTop) - max(marginInfo.negMargin(), negTop));
            ypos = height();
        }

        marginInfo.setPosMargin(child->maxBottomMargin(true));
        marginInfo.setNegMargin(child->maxBottomMargin(false));

        if (marginInfo.margin())
            marginInfo.setBottomQuirk(child->isBottomMarginQuirk() || style()->marginBottomCollapse() == MDISCARD);

        marginInfo.setSelfCollapsingBlockClearedFloat(false);
    }
    
    return ypos;
}

int RenderBlock::clearFloatsIfNeeded(RenderBox* child, MarginInfo& marginInfo, int oldTopPosMargin, int oldTopNegMargin, int yPos)
{
    int heightIncrease = getClearDelta(child, yPos);
    if (!heightIncrease)
        return yPos;

    if (child->isSelfCollapsingBlock()) {
        // For self-collapsing blocks that clear, they can still collapse their
        // margins with following siblings.  Reset the current margins to represent
        // the self-collapsing block's margins only.
        marginInfo.setPosMargin(max(child->maxTopMargin(true), child->maxBottomMargin(true)));
        marginInfo.setNegMargin(max(child->maxTopMargin(false), child->maxBottomMargin(false)));
        
        // Adjust our height such that we are ready to be collapsed with subsequent siblings.
        setHeight(child->y() - max(0, marginInfo.margin()));
        
        // Set a flag that we cleared a float so that we know both to increase the height of the block
        // to compensate for the clear and to avoid collapsing our margins with the parent block's
        // bottom margin.
        marginInfo.setSelfCollapsingBlockClearedFloat(true);
    } else
        // Increase our height by the amount we had to clear.
        setHeight(height() + heightIncrease);
    
    if (marginInfo.canCollapseWithTop()) {
        // We can no longer collapse with the top of the block since a clear
        // occurred.  The empty blocks collapse into the cleared block.
        // FIXME: This isn't quite correct.  Need clarification for what to do
        // if the height the cleared block is offset by is smaller than the
        // margins involved.
        setMaxTopMargins(oldTopPosMargin, oldTopNegMargin);
        marginInfo.setAtTopOfBlock(false);
    }
    
    return yPos + heightIncrease;
}

int RenderBlock::estimateVerticalPosition(RenderBox* child, const MarginInfo& marginInfo)
{
    // FIXME: We need to eliminate the estimation of vertical position, because when it's wrong we sometimes trigger a pathological
    // relayout if there are intruding floats.
    int yPosEstimate = height();
    if (!marginInfo.canCollapseWithTop()) {
        int childMarginTop = child->selfNeedsLayout() ? child->marginTop() : child->collapsedMarginTop();
        yPosEstimate += max(marginInfo.margin(), childMarginTop);
    }
    yPosEstimate += getClearDelta(child, yPosEstimate);
    return yPosEstimate;
}

void RenderBlock::determineHorizontalPosition(RenderBox* child)
{
    if (style()->direction() == LTR) {
        int xPos = borderLeft() + paddingLeft();
        
        // Add in our left margin.
        int chPos = xPos + child->marginLeft();
        
        // Some objects (e.g., tables, horizontal rules, overflow:auto blocks) avoid floats.  They need
        // to shift over as necessary to dodge any floats that might get in the way.
        if (child->avoidsFloats()) {
            int leftOff = leftOffset(height(), false);
            if (style()->textAlign() != WEBKIT_CENTER && child->style()->marginLeft().type() != Auto) {
                if (child->marginLeft() < 0)
                    leftOff += child->marginLeft();
                chPos = max(chPos, leftOff); // Let the float sit in the child's margin if it can fit.
            }
            else if (leftOff != xPos) {
                // The object is shifting right. The object might be centered, so we need to
                // recalculate our horizontal margins. Note that the containing block content
                // width computation will take into account the delta between |leftOff| and |xPos|
                // so that we can just pass the content width in directly to the |calcHorizontalMargins|
                // function.
                child->calcHorizontalMargins(child->style()->marginLeft(), child->style()->marginRight(), lineWidth(child->y(), false));
                chPos = leftOff + child->marginLeft();
            }
        }
        view()->addLayoutDelta(IntSize(child->x() - chPos, 0));
        child->setLocation(chPos, child->y());
    } else {
        int xPos = width() - borderRight() - paddingRight() - verticalScrollbarWidth();
        int chPos = xPos - (child->width() + child->marginRight());
        if (child->avoidsFloats()) {
            int rightOff = rightOffset(height(), false);
            if (style()->textAlign() != WEBKIT_CENTER && child->style()->marginRight().type() != Auto) {
                if (child->marginRight() < 0)
                    rightOff -= child->marginRight();
                chPos = min(chPos, rightOff - child->width()); // Let the float sit in the child's margin if it can fit.
            } else if (rightOff != xPos) {
                // The object is shifting left. The object might be centered, so we need to
                // recalculate our horizontal margins. Note that the containing block content
                // width computation will take into account the delta between |rightOff| and |xPos|
                // so that we can just pass the content width in directly to the |calcHorizontalMargins|
                // function.
                child->calcHorizontalMargins(child->style()->marginLeft(), child->style()->marginRight(), lineWidth(child->y(), false));
                chPos = rightOff - child->marginRight() - child->width();
            }
        }
        view()->addLayoutDelta(IntSize(child->x() - chPos, 0));
        child->setLocation(chPos, child->y());
    }
}

void RenderBlock::setCollapsedBottomMargin(const MarginInfo& marginInfo)
{
    if (marginInfo.canCollapseWithBottom() && !marginInfo.canCollapseWithTop()) {
        // Update our max pos/neg bottom margins, since we collapsed our bottom margins
        // with our children.
        setMaxBottomMargins(max(maxBottomPosMargin(), marginInfo.posMargin()), max(maxBottomNegMargin(), marginInfo.negMargin()));

        if (!marginInfo.bottomQuirk())
            setBottomMarginQuirk(false);