LayoutUnit MultiColumnFragmentainerGroup::rebalanceColumnHeightIfNeeded() const
{
if (actualColumnCount() <= m_columnSet.usedColumnCount()) {
// With the current column height, the content fits without creating overflowing columns. We're done.
return m_columnHeight;
}
if (m_columnHeight >= m_maxColumnHeight) {
// We cannot stretch any further. We'll just have to live with the overflowing columns. This
// typically happens if the max column height is less than the height of the tallest piece
// of unbreakable content (e.g. lines).
return m_columnHeight;
}
MinimumSpaceShortageFinder shortageFinder(*this);
if (shortageFinder.forcedBreaksCount() + 1 >= m_columnSet.usedColumnCount()) {
// Too many forced breaks to allow any implicit breaks. Initial balancing should already
// have set a good height. There's nothing more we should do.
return m_columnHeight;
}
// If the initial guessed column height wasn't enough, stretch it now. Stretch by the lowest
// amount of space.
LayoutUnit minSpaceShortage = shortageFinder.minimumSpaceShortage();
ASSERT(minSpaceShortage > 0); // We should never _shrink_ the height!
ASSERT(minSpaceShortage != LayoutUnit::max()); // If this happens, we probably have a bug.
if (minSpaceShortage == LayoutUnit::max())
return m_columnHeight; // So bail out rather than looping infinitely.
return m_columnHeight + minSpaceShortage;
}
LayoutUnit MultiColumnFragmentainerGroup::calculateColumnHeight(BalancedColumnHeightCalculation calculationMode) const
{
if (calculationMode == GuessFromFlowThreadPortion) {
// Initial balancing. Start with the lowest imaginable column height. We use the tallest
// content run (after having "inserted" implicit breaks), and find its start offset (by
// looking at the previous run's end offset, or, if there's no previous run, the set's start
// offset in the flow thread).
return std::max(InitialColumnHeightFinder::initialMinimalBalancedHeight(*this), m_minimumColumnHeight);
}
if (actualColumnCount() <= m_columnSet.usedColumnCount()) {
// With the current column height, the content fits without creating overflowing columns. We're done.
return m_columnHeight;
}
if (m_columnHeight >= m_maxColumnHeight) {
// We cannot stretch any further. We'll just have to live with the overflowing columns. This
// typically happens if the max column height is less than the height of the tallest piece
// of unbreakable content (e.g. lines).
return m_columnHeight;
}
MinimumSpaceShortageFinder shortageFinder(*this);
if (shortageFinder.forcedBreaksCount() + 1 >= m_columnSet.usedColumnCount()) {
// Too many forced breaks to allow any implicit breaks. Initial balancing should already
// have set a good height. There's nothing more we should do.
return m_columnHeight;
}
// If the initial guessed column height wasn't enough, stretch it now. Stretch by the lowest
// amount of space.
LayoutUnit minSpaceShortage = shortageFinder.minimumSpaceShortage();
ASSERT(minSpaceShortage > 0); // We should never _shrink_ the height!
ASSERT(minSpaceShortage != LayoutUnit::max()); // If this happens, we probably have a bug.
if (minSpaceShortage == LayoutUnit::max())
return m_columnHeight; // So bail out rather than looping infinitely.
return m_columnHeight + minSpaceShortage;
}
