void RenderMultiColumnSet::distributeImplicitBreaks()
{
unsigned breakCount = forcedBreaksCount();
#ifndef NDEBUG
// There should be no implicit breaks assumed at this point.
for (unsigned i = 0; i < breakCount; i++)
ASSERT(!m_contentRuns[i].assumedImplicitBreaks());
#endif // NDEBUG
// There will always be at least one break, since the flow thread reports a "forced break" at
// end of content.
ASSERT(breakCount >= 1);
// If there is room for more breaks (to reach the used value of column-count), imagine that we
// insert implicit breaks at suitable locations. At any given time, the content run with the
// currently tallest columns will get another implicit break "inserted", which will increase its
// column count by one and shrink its columns' height. Repeat until we have the desired total
// number of breaks. The largest column height among the runs will then be the initial column
// height for the balancer to use.
while (breakCount < m_computedColumnCount) {
unsigned index = findRunWithTallestColumns();
m_contentRuns[index].assumeAnotherImplicitBreak();
breakCount++;
}
}
void MultiColumnFragmentainerGroup::distributeImplicitBreaks()
{
#if ENABLE(ASSERT)
// There should be no implicit breaks assumed at this point.
for (unsigned i = 0; i < m_contentRuns.size(); i++)
ASSERT(!m_contentRuns[i].assumedImplicitBreaks());
#endif // ENABLE(ASSERT)
// Insert a final content run to encompass all content. This will include overflow if this is
// the last set.
addContentRun(m_logicalBottomInFlowThread);
unsigned columnCount = m_contentRuns.size();
// If there is room for more breaks (to reach the used value of column-count), imagine that we
// insert implicit breaks at suitable locations. At any given time, the content run with the
// currently tallest columns will get another implicit break "inserted", which will increase its
// column count by one and shrink its columns' height. Repeat until we have the desired total
// number of breaks. The largest column height among the runs will then be the initial column
// height for the balancer to use.
while (columnCount < m_columnSet.usedColumnCount()) {
unsigned index = findRunWithTallestColumns();
m_contentRuns[index].assumeAnotherImplicitBreak();
columnCount++;
}
}
LayoutUnit RenderMultiColumnSet::calculateBalancedHeight(bool initial) const
{
if (initial) {
// Start with the lowest imaginable column height.
unsigned index = findRunWithTallestColumns();
LayoutUnit startOffset = index > 0 ? m_contentRuns[index - 1].breakOffset() : LayoutUnit();
return std::max<LayoutUnit>(m_contentRuns[index].columnLogicalHeight(startOffset), m_minimumColumnHeight);
}
if (columnCount() <= computedColumnCount()) {
// With the current column height, the content fits without creating overflowing columns. We're done.
return m_computedColumnHeight;
}
if (forcedBreaksCount() > 1 && forcedBreaksCount() >= computedColumnCount()) {
// 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_computedColumnHeight;
}
// If the initial guessed column height wasn't enough, stretch it now. Stretch by the lowest
// amount of space shortage found during layout.
ASSERT(m_minSpaceShortage > 0); // We should never _shrink_ the height!
ASSERT(m_minSpaceShortage != RenderFlowThread::maxLogicalHeight()); // If this happens, we probably have a bug.
if (m_minSpaceShortage == RenderFlowThread::maxLogicalHeight())
return m_computedColumnHeight; // So bail out rather than looping infinitely.
return m_computedColumnHeight + m_minSpaceShortage;
}
LayoutUnit RenderMultiColumnSet::calculateColumnHeight(BalancedHeightCalculation 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).
unsigned index = findRunWithTallestColumns();
LayoutUnit startOffset = index > 0 ? m_contentRuns[index - 1].breakOffset() : logicalTopInFlowThread();
return std::max<LayoutUnit>(m_contentRuns[index].columnLogicalHeight(startOffset), m_minimumColumnHeight);
}
if (actualColumnCount() <= usedColumnCount()) {
// With the current column height, the content fits without creating overflowing columns. We're done.
return m_columnHeight;
}
if (m_contentRuns.size() >= 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 shortage found during layout.
ASSERT(m_minSpaceShortage > 0); // We should never _shrink_ the height!
ASSERT(m_minSpaceShortage != RenderFlowThread::maxLogicalHeight()); // If this happens, we probably have a bug.
if (m_minSpaceShortage == RenderFlowThread::maxLogicalHeight())
return m_columnHeight; // So bail out rather than looping infinitely.
return m_columnHeight + m_minSpaceShortage;
}