LayoutUnit LayoutMultiColumnSet::nextLogicalTopForUnbreakableContent(LayoutUnit flowThreadOffset, LayoutUnit contentLogicalHeight) const
{
ASSERT(flowThreadOffset.mightBeSaturated() || pageLogicalTopForOffset(flowThreadOffset) == flowThreadOffset);
FragmentationContext* enclosingFragmentationContext = multiColumnFlowThread()->enclosingFragmentationContext();
if (!enclosingFragmentationContext) {
// If there's no enclosing fragmentation context, there'll ever be only one row, and all
// columns there will have the same height.
return flowThreadOffset;
}
// Assert the problematic situation. If we have no problem with the column height, why are we
// even here?
ASSERT(pageLogicalHeightForOffset(flowThreadOffset) < contentLogicalHeight);
// There's a likelihood for subsequent rows to be taller than the first one.
// TODO(mstensho): if we're doubly nested (e.g. multicol in multicol in multicol), we need to
// look beyond the first row here.
const MultiColumnFragmentainerGroup& firstRow = firstFragmentainerGroup();
LayoutUnit firstRowLogicalBottomInFlowThread = firstRow.logicalTopInFlowThread() + fragmentainerGroupCapacity(firstRow);
if (flowThreadOffset >= firstRowLogicalBottomInFlowThread)
return flowThreadOffset; // We're not in the first row. Give up.
LayoutUnit newLogicalHeight = enclosingFragmentationContext->fragmentainerLogicalHeightAt(firstRow.blockOffsetInEnclosingFragmentationContext() + firstRow.logicalHeight());
if (contentLogicalHeight > newLogicalHeight) {
// The next outer column or page doesn't have enough space either. Give up and stay where
// we are.
return flowThreadOffset;
}
return firstRowLogicalBottomInFlowThread;
}
void LayoutMultiColumnFlowThread::appendNewFragmentainerGroupIfNeeded(LayoutUnit bottomOffsetInFlowThread)
{
if (!isPageLogicalHeightKnown()) {
// If we have no clue about the height of the multicol container, bail. This situation
// occurs initially when an auto-height multicol container is nested inside another
// auto-height multicol container. We need at least an estimated height of the outer
// multicol container before we can check what an inner fragmentainer group has room for.
// Its height is indefinite for now.
return;
}
// TODO(mstensho): bottomOffsetInFlowThread is an endpoint-exclusive offset, i.e. the offset
// just after the bottom of some object. So, ideally, columnSetAtBlockOffset() should be
// informed about this (i.e. take a PageBoundaryRule argument). This is not the only place with
// this issue; see also pageRemainingLogicalHeightForOffset().
LayoutMultiColumnSet* columnSet = columnSetAtBlockOffset(bottomOffsetInFlowThread);
if (columnSet->isInitialHeightCalculated()) {
// We only insert additional fragmentainer groups in the initial layout pass. We only want
// to balance columns in the last fragmentainer group (if we need to balance at all), so we
// want that last fragmentainer group to be the same one in all layout passes that follow.
return;
}
if (!columnSet->hasFragmentainerGroupForColumnAt(bottomOffsetInFlowThread)) {
FragmentationContext* enclosingFragmentationContext = this->enclosingFragmentationContext();
if (!enclosingFragmentationContext)
return; // Not nested. We'll never need more rows than the one we already have then.
ASSERT(!isLayoutPagedFlowThread());
// We have run out of columns here, so we add another row to hold more columns. When we add
// a new row, it implicitly means that we're inserting another column in our enclosing
// multicol container. That in turn may mean that we've run out of columns there too.
const MultiColumnFragmentainerGroup& newRow = columnSet->appendNewFragmentainerGroup();
if (LayoutMultiColumnFlowThread* enclosingFlowThread = enclosingFragmentationContext->associatedFlowThread())
enclosingFlowThread->appendNewFragmentainerGroupIfNeeded(newRow.blockOffsetInEnclosingFragmentationContext() + newRow.logicalHeight());
}
}
void LayoutMultiColumnFlowThread::appendNewFragmentainerGroupIfNeeded(LayoutUnit offsetInFlowThread)
{
if (!isPageLogicalHeightKnown()) {
// If we have no clue about the height of the multicol container, bail. This situation
// occurs initially when an auto-height multicol container is nested inside another
// auto-height multicol container. We need at least an estimated height of the outer
// multicol container before we can check what an inner fragmentainer group has room for.
// Its height is indefinite for now.
return;
}
LayoutMultiColumnSet* columnSet = columnSetAtBlockOffset(offsetInFlowThread);
if (columnSet->isInitialHeightCalculated()) {
// We only insert additional fragmentainer groups in the initial layout pass. We only want
// to balance columns in the last fragmentainer group (if we need to balance at all), so we
// want that last fragmentainer group to be the same one in all layout passes that follow.
return;
}
if (!columnSet->hasFragmentainerGroupForColumnAt(offsetInFlowThread)) {
FragmentationContext* enclosingFragmentationContext = this->enclosingFragmentationContext();
if (!enclosingFragmentationContext)
return; // Not nested. We'll never need more rows than the one we already have then.
ASSERT(!isLayoutPagedFlowThread());
// We have run out of columns here, so we add another row to hold more columns. When we add
// a new row, it implicitly means that we're inserting another column in our enclosing
// multicol container. That in turn may mean that we've run out of columns there too.
const MultiColumnFragmentainerGroup& newRow = columnSet->appendNewFragmentainerGroup();
if (LayoutMultiColumnFlowThread* enclosingFlowThread = enclosingFragmentationContext->associatedFlowThread())
enclosingFlowThread->appendNewFragmentainerGroupIfNeeded(newRow.blockOffsetInEnclosingFragmentationContext());
}
}
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()));
}
}