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()
{
m_maxColumnHeight = calculateMaxColumnHeight();
LayoutMultiColumnFlowThread* flowThread = m_columnSet.multiColumnFlowThread();
if (m_columnSet.heightIsAuto()) {
FragmentationContext* enclosingFragmentationContext = flowThread->enclosingFragmentationContext();
if (enclosingFragmentationContext && enclosingFragmentationContext->isFragmentainerLogicalHeightKnown()) {
// Even if height is auto, we set an initial height, in order to tell how much content
// this MultiColumnFragmentainerGroup can hold, and when we need to append a new one.
m_columnHeight = m_maxColumnHeight;
} else {
m_columnHeight = LayoutUnit();
}
} else {
setAndConstrainColumnHeight(heightAdjustedForRowOffset(flowThread->columnHeightAvailable()));
}
}
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()));
}
}
bool LayoutMultiColumnSet::heightIsAuto() const
{
LayoutMultiColumnFlowThread* flowThread = multiColumnFlowThread();
if (!flowThread->isLayoutPagedFlowThread()) {
// If support for the column-fill property isn't enabled, we want to behave as if
// column-fill were auto, so that multicol containers with specified height don't get their
// columns balanced (auto-height multicol containers will still get their columns balanced,
// even if column-fill isn't 'balance' - in accordance with the spec). Pretending that
// column-fill is auto also matches the old multicol implementation, which has no support
// for this property.
if (multiColumnBlockFlow()->style()->getColumnFill() == ColumnFillBalance)
return true;
if (LayoutBox* next = nextSiblingBox()) {
if (next->isLayoutMultiColumnSpannerPlaceholder()) {
// If we're followed by a spanner, we need to balance.
return true;
}
}
}
return !flowThread->columnHeightAvailable();
}