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;
}
LayoutUnit LayoutMultiColumnSet::pageRemainingLogicalHeightForOffset(LayoutUnit offsetInFlowThread, PageBoundaryRule pageBoundaryRule) const
{
const MultiColumnFragmentainerGroup& row = fragmentainerGroupAtFlowThreadOffset(offsetInFlowThread);
LayoutUnit pageLogicalHeight = row.logicalHeight();
ASSERT(pageLogicalHeight); // It's not allowed to call this method if the height is unknown.
LayoutUnit pageLogicalBottom = row.columnLogicalTopForOffset(offsetInFlowThread) + pageLogicalHeight;
LayoutUnit remainingLogicalHeight = pageLogicalBottom - offsetInFlowThread;
if (pageBoundaryRule == AssociateWithFormerPage) {
// An offset exactly at a column boundary will act as being part of the former column in
// question (i.e. no remaining space), rather than being part of the latter (i.e. one whole
// column length of remaining space).
remainingLogicalHeight = intMod(remainingLogicalHeight, pageLogicalHeight);
} else if (!remainingLogicalHeight) {
// When pageBoundaryRule is AssociateWithLatterPage, we should never return 0, because if
// there's no space left, it means that we should be at a column boundary, in which case we
// should return the amount of space remaining in the *next* column. But this is not true if
// the offset is "infinite" (saturated), so allow this to happen in that case.
ASSERT(offsetInFlowThread.mightBeSaturated());
remainingLogicalHeight = pageLogicalHeight;
}
return remainingLogicalHeight;
}
