C++ RenderMultiColumnSet类代码示例

void RenderFlowThread::validateRegions()
{
    if (m_regionsInvalidated) {
        m_regionsInvalidated = false;
        m_regionsHaveUniformLogicalHeight = true;

        if (hasRegions()) {
            LayoutUnit previousRegionLogicalHeight = 0;
            bool firstRegionVisited = false;

            for (RenderMultiColumnSetList::iterator iter = m_multiColumnSetList.begin(); iter != m_multiColumnSetList.end(); ++iter) {
                RenderMultiColumnSet* columnSet = *iter;
                LayoutUnit regionLogicalHeight = columnSet->pageLogicalHeight();

                if (!firstRegionVisited) {
                    firstRegionVisited = true;
                } else {
                    if (m_regionsHaveUniformLogicalHeight && previousRegionLogicalHeight != regionLogicalHeight)
                        m_regionsHaveUniformLogicalHeight = false;
                }

                previousRegionLogicalHeight = regionLogicalHeight;
            }
        }
    }

    updateLogicalWidth(); // Called to get the maximum logical width for the columnSet.
    updateRegionsFlowThreadPortionRect();
}

RenderMultiColumnSet* RenderMultiColumnSet::createAnonymous(RenderFlowThread* flowThread)
{
    Document& document = flowThread->document();
    RenderMultiColumnSet* renderer = new RenderMultiColumnSet(flowThread);
    renderer->setDocumentForAnonymous(&document);
    return renderer;
}

void RenderMultiColumnBlock::ensureColumnSets()
{
    // This function ensures we have the correct column set information before we get into layout.
    // For a simple multi-column layout in continuous media, only one column set child is required.
    // Once a column is nested inside an enclosing pagination context, the number of column sets
    // required becomes 2n-1, where n is the total number of nested pagination contexts. For example:
    //
    // Column layout with no enclosing pagination model = 2 * 1 - 1 = 1 column set.
    // Columns inside pages = 2 * 2 - 1 = 3 column sets (bottom of first page, all the subsequent pages, then the last page).
    // Columns inside columns inside pages = 2 * 3 - 1 = 5 column sets.
    //
    // In addition, column spans will force a column set to "split" into before/after sets around the spanning region.
    //
    // Finally, we will need to deal with columns inside regions. If regions have variable widths, then there will need
    // to be unique column sets created inside any region whose width is different from its surrounding regions. This is
    // actually pretty similar to the spanning case, in that we break up the column sets whenever the width varies.
    //
    // FIXME: For now just make one column set. This matches the old multi-column code.
    // Right now our goal is just feature parity with the old multi-column code so that we can switch over to the
    // new code as soon as possible.
    if (flowThread() && !firstChild()->isRenderMultiColumnSet()) {
        RenderMultiColumnSet* columnSet = new (renderArena()) RenderMultiColumnSet(document(), flowThread());
        columnSet->setStyle(RenderStyle::createAnonymousStyleWithDisplay(style(), BLOCK));
        RenderBlock::addChild(columnSet, firstChild());
        flowThread()->addRegionToThread(columnSet);
    }
}

LayoutUnit RenderFlowThread::pageLogicalHeightForOffset(LayoutUnit offset)
{
    RenderMultiColumnSet* columnSet = columnSetAtBlockOffset(offset);
    if (!columnSet)
        return 0;

    return columnSet->pageLogicalHeight();
}

RenderMultiColumnSet* RenderMultiColumnSet::createAnonymous(RenderFlowThread* flowThread, RenderStyle* parentStyle)
{
    Document& document = flowThread->document();
    RenderMultiColumnSet* renderer = new RenderMultiColumnSet(flowThread);
    renderer->setDocumentForAnonymous(&document);
    renderer->setStyle(RenderStyle::createAnonymousStyleWithDisplay(parentStyle, BLOCK));
    return renderer;
}

RenderMultiColumnSet* RenderMultiColumnFlowThread::findSetRendering(RenderObject* renderer) const
{
    for (RenderMultiColumnSet* multicolSet = firstMultiColumnSet(); multicolSet; multicolSet = multicolSet->nextSiblingMultiColumnSet()) {
        if (multicolSet->containsRendererInFlowThread(renderer))
            return multicolSet;
    }
    return nullptr;
}

void RenderFlowThread::collectLayerFragments(LayerFragments& layerFragments, const LayoutRect& layerBoundingBox, const LayoutRect& dirtyRect)
{
    ASSERT(!m_regionsInvalidated);

    for (RenderMultiColumnSetList::const_iterator iter = m_multiColumnSetList.begin(); iter != m_multiColumnSetList.end(); ++iter) {
        RenderMultiColumnSet* columnSet = *iter;
        columnSet->collectLayerFragments(layerFragments, layerBoundingBox, dirtyRect);
    }
}

void RenderMultiColumnFlowThread::willBeRemovedFromTree()
{
    // Detach all column sets from the flow thread. Cannot destroy them at this point, since they
    // are siblings of this object, and there may be pointers to this object's sibling somewhere
    // further up on the call stack.
    for (RenderMultiColumnSet* columnSet = firstMultiColumnSet(); columnSet; columnSet = columnSet->nextSiblingMultiColumnSet())
        columnSet->detachRegion();
    multiColumnBlockFlow()->setMultiColumnFlowThread(nullptr);
    RenderFlowThread::willBeRemovedFromTree();
}

void RenderFlowThread::computeLogicalHeight(LayoutUnit, LayoutUnit logicalTop, LogicalExtentComputedValues& computedValues) const
{
    computedValues.m_position = logicalTop;
    computedValues.m_extent = 0;

    for (RenderMultiColumnSetList::const_iterator iter = m_multiColumnSetList.begin(); iter != m_multiColumnSetList.end(); ++iter) {
        RenderMultiColumnSet* columnSet = *iter;
        computedValues.m_extent += columnSet->logicalHeightOfAllFlowThreadContent();
    }
}

void RenderMultiColumnFlowThread::addRegionToThread(RenderRegion* renderRegion)
{
    RenderMultiColumnSet* columnSet = toRenderMultiColumnSet(renderRegion);
    if (RenderMultiColumnSet* nextSet = columnSet->nextSiblingMultiColumnSet()) {
        RenderRegionList::iterator it = m_regionList.find(nextSet);
        ASSERT(it != m_regionList.end());
        m_regionList.insertBefore(it, columnSet);
    } else
        m_regionList.add(columnSet);
    renderRegion->setIsValid(true);
}

RenderRegion* RenderMultiColumnFlowThread::regionAtBlockOffset(const RenderBox* box, LayoutUnit offset, bool extendLastRegion, RegionAutoGenerationPolicy autoGenerationPolicy)
{
    if (!m_inLayout)
        return RenderFlowThread::regionAtBlockOffset(box, offset, extendLastRegion, autoGenerationPolicy);

    // Layout in progress. We are calculating the set heights as we speak, so the region range
    // information is not up-to-date.

    RenderMultiColumnSet* columnSet = m_lastSetWorkedOn ? m_lastSetWorkedOn : firstMultiColumnSet();
    if (!columnSet) {
        // If there's no set, bail. This multicol is empty or only consists of spanners. There
        // are no regions.
        return nullptr;
    }
    // The last set worked on is a good guess. But if we're not within the bounds, search for the
    // right one.
    if (offset < columnSet->logicalTopInFlowThread()) {
        do {
            if (RenderMultiColumnSet* prev = columnSet->previousSiblingMultiColumnSet())
                columnSet = prev;
            else
                break;
        } while (offset < columnSet->logicalTopInFlowThread());
    } else {
        while (offset >= columnSet->logicalBottomInFlowThread()) {
            RenderMultiColumnSet* next = columnSet->nextSiblingMultiColumnSet();
            if (!next || !next->hasBeenFlowed())
                break;
            columnSet = next;
        }
    }
    return columnSet;
}

void RenderFlowThread::repaintRectangleInRegions(const LayoutRect& repaintRect) const
{
    if (!shouldRepaint(repaintRect) || !hasValidRegionInfo())
        return;

    ForceHorriblySlowRectMapping slowRectMapping(*this); // We can't use layout state to repaint, since the regions are somewhere else.

    // We can't use currentFlowThread as it is possible to have interleaved flow threads and the wrong one could be used.
    // Let each columnSet figure out the proper enclosing flow thread.
    CurrentRenderFlowThreadDisabler disabler(view());

    for (RenderMultiColumnSetList::const_iterator iter = m_multiColumnSetList.begin(); iter != m_multiColumnSetList.end(); ++iter) {
        RenderMultiColumnSet* columnSet = *iter;

        columnSet->repaintFlowThreadContent(repaintRect);
    }
}

void RenderMultiColumnFlowThread::setRegionRangeForBox(const RenderBox* box, RenderRegion* startRegion, RenderRegion* endRegion)
{
    // Some column sets may have zero height, which means that two or more sets may start at the
    // exact same flow thread position, which means that some parts of the code may believe that a
    // given box lives in sets that it doesn't really live in. Make some adjustments here and
    // include such sets if they are adjacent to the start and/or end regions.
    for (RenderMultiColumnSet* columnSet = toRenderMultiColumnSet(startRegion)->previousSiblingMultiColumnSet(); columnSet; columnSet = columnSet->previousSiblingMultiColumnSet()) {
        if (columnSet->logicalHeightInFlowThread())
            break;
        startRegion = columnSet;
    }
    for (RenderMultiColumnSet* columnSet = toRenderMultiColumnSet(startRegion)->nextSiblingMultiColumnSet(); columnSet; columnSet = columnSet->nextSiblingMultiColumnSet()) {
        if (columnSet->logicalHeightInFlowThread())
            break;
        endRegion = columnSet;
    }

    RenderFlowThread::setRegionRangeForBox(box, startRegion, endRegion);
}

void RenderFlowThread::updateRegionsFlowThreadPortionRect()
{
    LayoutUnit logicalHeight = 0;
    // FIXME: Optimize not to clear the interval all the time. This implies manually managing the tree nodes lifecycle.
    m_multiColumnSetIntervalTree.clear();
    m_multiColumnSetIntervalTree.initIfNeeded();
    for (RenderMultiColumnSetList::iterator iter = m_multiColumnSetList.begin(); iter != m_multiColumnSetList.end(); ++iter) {
        RenderMultiColumnSet* columnSet = *iter;

        LayoutUnit columnSetLogicalWidth = columnSet->pageLogicalWidth();
        LayoutUnit columnSetLogicalHeight = std::min<LayoutUnit>(RenderFlowThread::maxLogicalHeight() - logicalHeight, columnSet->logicalHeightOfAllFlowThreadContent());

        LayoutRect columnSetRect(style()->direction() == LTR ? LayoutUnit() : logicalWidth() - columnSetLogicalWidth, logicalHeight, columnSetLogicalWidth, columnSetLogicalHeight);

        columnSet->setFlowThreadPortionRect(isHorizontalWritingMode() ? columnSetRect : columnSetRect.transposedRect());

        m_multiColumnSetIntervalTree.add(MultiColumnSetIntervalTree::createInterval(logicalHeight, logicalHeight + columnSetLogicalHeight, columnSet));

        logicalHeight += columnSetLogicalHeight;
    }
}

bool RenderMultiColumnBlock::relayoutForPagination(bool, LayoutUnit, LayoutStateMaintainer& statePusher)
{
    if (m_inBalancingPass || !requiresBalancing())
        return false;
    m_inBalancingPass = true; // Prevent re-entering this method (and recursion into layout).

    bool needsRelayout;
    bool neededRelayout = false;
    bool firstPass = true;
    do {
        // Column heights may change here because of balancing. We may have to do multiple layout
        // passes, depending on how the contents is fitted to the changed column heights. In most
        // cases, laying out again twice or even just once will suffice. Sometimes we need more
        // passes than that, though, but the number of retries should not exceed the number of
        // columns, unless we have a bug.
        needsRelayout = false;
        for (RenderBox* childBox = firstChildBox(); childBox; childBox = childBox->nextSiblingBox())
            if (childBox != m_flowThread && childBox->isRenderMultiColumnSet()) {
                RenderMultiColumnSet* multicolSet = toRenderMultiColumnSet(childBox);
                if (multicolSet->calculateBalancedHeight(firstPass)) {
                    multicolSet->setChildNeedsLayout(MarkOnlyThis);
                    needsRelayout = true;
                }
            }

        if (needsRelayout) {
            // Layout again. Column balancing resulted in a new height.
            neededRelayout = true;
            m_flowThread->setChildNeedsLayout(MarkOnlyThis);
            setChildNeedsLayout(MarkOnlyThis);
            if (firstPass)
                statePusher.pop();
            layoutBlock(false);
        }
        firstPass = false;
    } while (needsRelayout);
    m_inBalancingPass = false;
    return neededRelayout;
}