C++ LayoutMultiColumnFlowThread::enclosingFlowThread方法代码示例

LayoutSize MultiColumnFragmentainerGroup::flowThreadTranslationAtOffset(LayoutUnit offsetInFlowThread) const
{
    LayoutMultiColumnFlowThread* flowThread = m_columnSet.multiColumnFlowThread();
    unsigned columnIndex = columnIndexAtOffset(offsetInFlowThread);
    LayoutRect portionRect(flowThreadPortionRectAt(columnIndex));
    flowThread->flipForWritingMode(portionRect);
    LayoutRect columnRect(columnRectAt(columnIndex));
    m_columnSet.flipForWritingMode(columnRect);
    LayoutSize translationRelativeToGroup = columnRect.location() - portionRect.location();

    LayoutSize enclosingTranslation;
    if (LayoutMultiColumnFlowThread* enclosingFlowThread = flowThread->enclosingFlowThread()) {
        // Translation that would map points in the coordinate space of the outermost flow thread to
        // visual points in the first column in the first fragmentainer group (row) in our multicol
        // container.
        LayoutSize enclosingTranslationOrigin = enclosingFlowThread->flowThreadTranslationAtOffset(flowThread->blockOffsetInEnclosingFragmentationContext());

        // Translation that would map points in the coordinate space of the outermost flow thread to
        // visual points in the first column in this fragmentainer group.
        enclosingTranslation = enclosingFlowThread->flowThreadTranslationAtOffset(blockOffsetInEnclosingFragmentationContext());

        // What we ultimately return from this method is a translation that maps points in the
        // coordinate space of our flow thread to a visual point in a certain column in this
        // fragmentainer group. We had to go all the way up to the outermost flow thread, since this
        // fragmentainer group may be in a different outer column than the first outer column that
        // this multicol container lives in. It's the visual distance between the first
        // fragmentainer group and this fragmentainer group that we need to add to the translation.
        enclosingTranslation -= enclosingTranslationOrigin;
    }

    return enclosingTranslation + translationRelativeToGroup + offsetFromColumnSet() + m_columnSet.topLeftLocationOffset() - flowThread->topLeftLocationOffset();
}

LayoutUnit MultiColumnFragmentainerGroup::calculateMaxColumnHeight() const
{
    LayoutBlockFlow* multicolBlock = m_columnSet.multiColumnBlockFlow();
    const ComputedStyle& multicolStyle = multicolBlock->styleRef();
    LayoutMultiColumnFlowThread* flowThread = m_columnSet.multiColumnFlowThread();
    LayoutUnit availableHeight = flowThread->columnHeightAvailable();
    LayoutUnit maxColumnHeight = availableHeight ? availableHeight : LayoutUnit::max();
    if (!multicolStyle.logicalMaxHeight().isMaxSizeNone()) {
        LayoutUnit logicalMaxHeight = multicolBlock->computeContentLogicalHeight(MaxSize, multicolStyle.logicalMaxHeight(), -1);
        if (logicalMaxHeight != -1 && maxColumnHeight > logicalMaxHeight)
            maxColumnHeight = logicalMaxHeight;
    }
    LayoutUnit maxHeight = heightAdjustedForRowOffset(maxColumnHeight);
    if (LayoutMultiColumnFlowThread* enclosingFlowThread = flowThread->enclosingFlowThread()) {
        if (enclosingFlowThread->isPageLogicalHeightKnown()) {
            // We're nested inside another fragmentation context whose fragmentainer heights are
            // known. This constrains the max height.
            LayoutUnit remainingOuterLogicalHeight = enclosingFlowThread->pageRemainingLogicalHeightForOffset(blockOffsetInEnclosingFlowThread(), LayoutBlock::AssociateWithLatterPage);
            ASSERT(remainingOuterLogicalHeight > 0);
            if (maxHeight > remainingOuterLogicalHeight)
                maxHeight = remainingOuterLogicalHeight;
        }
    }
    return maxHeight;
}

void MultiColumnFragmentainerGroup::resetColumnHeight()
{
    // Nuke previously stored minimum column height. Contents may have changed for all we know.
    m_minimumColumnHeight = 0;

    m_maxColumnHeight = calculateMaxColumnHeight();

    LayoutMultiColumnFlowThread* flowThread = m_columnSet.multiColumnFlowThread();
    LayoutMultiColumnFlowThread* enclosingFlowThread = flowThread->enclosingFlowThread();
    if (enclosingFlowThread && enclosingFlowThread->isPageLogicalHeightKnown()) {
        // TODO(mstensho): Do this better. If height is auto here, we shouldn't set a
        // height, or forced breaks and pagination struts might mess up column balancing.
        LayoutUnit columnHeight = heightIsAuto() ? m_maxColumnHeight : heightAdjustedForRowOffset(flowThread->columnHeightAvailable());
        setAndConstrainColumnHeight(columnHeight);
    } else if (heightIsAuto()) {
        m_columnHeight = LayoutUnit();
    } else {
        setAndConstrainColumnHeight(heightAdjustedForRowOffset(flowThread->columnHeightAvailable()));
    }
}

LayoutSize MultiColumnFragmentainerGroup::flowThreadTranslationAtOffset(
    LayoutUnit offsetInFlowThread,
    LayoutBox::PageBoundaryRule rule,
    CoordinateSpaceConversion mode) const {
  LayoutMultiColumnFlowThread* flowThread = m_columnSet.multiColumnFlowThread();

  // A column out of range doesn't have a flow thread portion, so we need to
  // clamp to make sure that we stay within the actual columns. This means that
  // content in the overflow area will be mapped to the last actual column,
  // instead of being mapped to an imaginary column further ahead.
  unsigned columnIndex = offsetInFlowThread >= logicalBottomInFlowThread()
                             ? actualColumnCount() - 1
                             : columnIndexAtOffset(offsetInFlowThread, rule);

  LayoutRect portionRect(flowThreadPortionRectAt(columnIndex));
  flowThread->flipForWritingMode(portionRect);
  portionRect.moveBy(flowThread->topLeftLocation());

  LayoutRect columnRect(columnRectAt(columnIndex));
  columnRect.move(offsetFromColumnSet());
  m_columnSet.flipForWritingMode(columnRect);
  columnRect.moveBy(m_columnSet.topLeftLocation());

  LayoutSize translationRelativeToFlowThread =
      columnRect.location() - portionRect.location();
  if (mode == CoordinateSpaceConversion::Containing)
    return translationRelativeToFlowThread;

  LayoutSize enclosingTranslation;
  if (LayoutMultiColumnFlowThread* enclosingFlowThread =
          flowThread->enclosingFlowThread()) {
    const MultiColumnFragmentainerGroup& firstRow =
        flowThread->firstMultiColumnSet()->firstFragmentainerGroup();
    // Translation that would map points in the coordinate space of the
    // outermost flow thread to visual points in the first column in the first
    // fragmentainer group (row) in our multicol container.
    LayoutSize enclosingTranslationOrigin =
        enclosingFlowThread->flowThreadTranslationAtOffset(
            firstRow.blockOffsetInEnclosingFragmentationContext(),
            LayoutBox::AssociateWithLatterPage, mode);

    // Translation that would map points in the coordinate space of the
    // outermost flow thread to visual points in the first column in this
    // fragmentainer group.
    enclosingTranslation = enclosingFlowThread->flowThreadTranslationAtOffset(
        blockOffsetInEnclosingFragmentationContext(),
        LayoutBox::AssociateWithLatterPage, mode);

    // What we ultimately return from this method is a translation that maps
    // points in the coordinate space of our flow thread to a visual point in a
    // certain column in this fragmentainer group. We had to go all the way up
    // to the outermost flow thread, since this fragmentainer group may be in a
    // different outer column than the first outer column that this multicol
    // container lives in. It's the visual distance between the first
    // fragmentainer group and this fragmentainer group that we need to add to
    // the translation.
    enclosingTranslation -= enclosingTranslationOrigin;
  }

  return enclosingTranslation + translationRelativeToFlowThread;
}