[New Multicolumn] Actual support for layout of column-span:all.

Source/core/rendering/RenderMultiColumnFlowThread.cpp

 /*
  * Copyright (C) 2012 Apple Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 14 matching lines @@
 
 #include "config.h"
 #include "core/rendering/RenderMultiColumnFlowThread.h"
 
 #include "core/rendering/RenderMultiColumnSet.h"
 #include "core/rendering/RenderMultiColumnSpannerSet.h"
 
 namespace blink {
 
 RenderMultiColumnFlowThread::RenderMultiColumnFlowThread()
-    : m_columnCount(1)
+    : m_lastSetWorkedOn(0)
+    , m_columnCount(1)
     , m_columnHeightAvailable(0)
     , m_inBalancingPass(false)
     , m_needsColumnHeightsRecalculation(false)
     , m_progressionIsInline(true)
+    , m_isBeingEvacuated(false)
 {
     setFlowThreadState(InsideInFlowThread);
 }
 
 RenderMultiColumnFlowThread::~RenderMultiColumnFlowThread()
 {
 }
 
 RenderMultiColumnFlowThread* RenderMultiColumnFlowThread::createAnonymous(Document& document, RenderStyle* parentStyle)
 {
@@ skipping 45 matching lines @@
     ASSERT(!nextSibling());
     // Reparent children preceding the flow thread into the flow thread. It's multicol content
     // now. At this point there's obviously nothing after the flow thread, but renderers (column
     // sets and spanners) will be inserted there as we insert elements into the flow thread.
     multicolContainer->moveChildrenTo(this, multicolContainer->firstChild(), this, true);
 }
 
 void RenderMultiColumnFlowThread::evacuateAndDestroy()
 {
     RenderBlockFlow* multicolContainer = multiColumnBlockFlow();
+    m_isBeingEvacuated = true;
 
     // Remove all sets.
     while (RenderMultiColumnSet* columnSet = firstMultiColumnSet())
         columnSet->destroy();
 
     ASSERT(!previousSibling());
     ASSERT(!nextSibling());
 
     // Finally we can promote all flow thread's children. Before we move them to the flow thread's
     // container, we need to unregister the flow thread, so that they aren't just re-added again to
@@ skipping 24 matching lines @@
 }
 
 bool RenderMultiColumnFlowThread::needsNewWidth() const
 {
     LayoutUnit newWidth;
     unsigned dummyColumnCount; // We only care if used column-width changes.
     calculateColumnCountAndWidth(newWidth, dummyColumnCount);
     return newWidth != logicalWidth();
 }
 
+RenderMultiColumnSet* RenderMultiColumnFlowThread::columnSetAtBlockOffset(LayoutUnit offset) const
+{
+    if (m_lastSetWorkedOn) {
+        // Layout in progress. We are calculating the set heights as we speak, so the column set range
+        // information is not up-to-date.
+        return m_lastSetWorkedOn;
+    }
+
+    ASSERT(!m_regionsInvalidated);
+    if (offset <= 0)
+        return m_multiColumnSetList.isEmpty() ? 0 : m_multiColumnSetList.first();
+
+    MultiColumnSetSearchAdapter adapter(offset);
+    m_multiColumnSetIntervalTree.allOverlapsWithAdapter<MultiColumnSetSearchAdapter>(adapter);
+
+    // If no set was found, the offset is in the flow thread overflow.
+    if (!adapter.result() && !m_multiColumnSetList.isEmpty())
+        return m_multiColumnSetList.last();
+    return adapter.result();
+}
+
 void RenderMultiColumnFlowThread::layoutColumns(bool relayoutChildren, SubtreeLayoutScope& layoutScope)
 {
     if (relayoutChildren)
         layoutScope.setChildNeedsLayout(this);
 
     if (!needsLayout()) {
         // Just before the multicol container (our parent RenderBlockFlow) finishes laying out, it
         // will call recalculateColumnHeights() on us unconditionally, but we only want that method
         // to do any work if we actually laid out the flow thread. Otherwise, the balancing
         // machinery would kick in needlessly, and trigger additional layout passes. Furthermore, we
         // actually depend on a proper flowthread layout pass in order to do balancing, since it's
         // flowthread layout that sets up content runs.
         m_needsColumnHeightsRecalculation = false;
         return;
     }
 
+    bool hasSpannerOrAutoHeightColumnSet = false;
     for (RenderMultiColumnSet* columnSet = firstMultiColumnSet(); columnSet; columnSet = columnSet->nextSiblingMultiColumnSet()) {
         if (!m_inBalancingPass) {
             // This is the initial layout pass. We need to reset the column height, because contents
             // typically have changed.
             columnSet->resetColumnHeight();
         }
+        if (!hasSpannerOrAutoHeightColumnSet)
+            hasSpannerOrAutoHeightColumnSet = columnSet->isRenderMultiColumnSpannerSet() || columnSet->heightIsAuto();

[Julien - ping for review, 2014/11/26 21:09:01]

We usually avoid a branch but using some boolean magic:

hasSpannerOrAutoHeightColumnSet |= columnSet->isRenderMultiColumnSpannerSet() ||
columnSet->heightIsAuto();

[mstensho (USE GERRIT), 2014/11/27 21:20:29]

|= is a bit-wise operator (there's no logical ||= operator), so then you would
have to evaluate "columnSet->isRenderMultiColumnSpannerSet() ||
columnSet->heightIsAuto()" even when hasSpannerOrAutoHeightColumnSet is set.

     }
 
     invalidateRegions();
-    m_needsColumnHeightsRecalculation = heightIsAuto();
+    m_needsColumnHeightsRecalculation = hasSpannerOrAutoHeightColumnSet;

[Julien - ping for review, 2014/11/26 21:09:00]

Note that you don't really need hasSpannerOrAutoHeightColumnSet if you just
reset the member boolean before the for-loop above :)

[mstensho (USE GERRIT), 2014/11/27 21:20:29]

Doh! :) Done.

     layout();
 }
 
 bool RenderMultiColumnFlowThread::recalculateColumnHeights()
 {
     // All column sets that needed layout have now been laid out, so we can finally validate them.
     validateRegions();
 
     if (!m_needsColumnHeightsRecalculation)
         return false;
@@ skipping 124 matching lines @@
     m_spannerMap.clear();
     // Detach all column sets from the flow thread. Cannot destroy them at this point, since they
     // are siblings of this object, and there may be pointers to this object's sibling somewhere
     // further up on the call stack.
     for (RenderMultiColumnSet* columnSet = firstMultiColumnSet(); columnSet; columnSet = columnSet->nextSiblingMultiColumnSet())
         columnSet->detachRegion();
     multiColumnBlockFlow()->resetMultiColumnFlowThread();
     RenderFlowThread::willBeRemovedFromTree();
 }
 
+bool RenderMultiColumnFlowThread::isColumnSpanner(const RenderObject* descendant) const
+{
+    ASSERT(descendant->isDescendantOf(this));
+    return m_spannerMap.get(descendant);
+}
+
+bool RenderMultiColumnFlowThread::isInsideColumnSpanner(const RenderObject* descendant) const
+{
+    ASSERT(descendant->isDescendantOf(this));
+    return containingColumnSpannerSet(descendant);
+}
+
+LayoutUnit RenderMultiColumnFlowThread::enterColumnSpannerBeforeLayout(RenderBox* renderer, LayoutUnit logicalTop, SubtreeLayoutScope& layoutScope)
+{
+    ASSERT(isColumnSpanner(renderer));
+    RenderMultiColumnSpannerSet* spannerSet = m_spannerMap.get(renderer);
+
+    // FIXME: it's really only necessary to mark the spanner set for layout when the height of
+    // |renderer| changes.
+    spannerSet->setChildNeedsLayout(MarkOnlyThis, &layoutScope);
+
+    RenderMultiColumnSet* previousSet = spannerSet->previousSiblingMultiColumnSet();
+    if (!previousSet) {
+        // The first set is entered at the beginning of flow thread layout. If the first set happens
+        // to be a spanner, we have nothing more to do here.
+        return LayoutUnit();
+    }
+
+    LayoutUnit logicalTopInFlowThread = renderer->parentBlock()->offsetFromLogicalTopOfFirstPage() + logicalTop;
+    LayoutUnit adjustment;
+    if (!previousSet->isRenderMultiColumnSpannerSet() && previousSet->pageLogicalHeight()) {
+        // Pad flow thread offset to a column boundary, so that contents that's supposed to come
+        // after the spanner (or the spanner itself) don't bleed into the column preceding the

[Julien - ping for review, 2014/11/26 21:09:01]

It seems like it's missing an 'any' before contents (or just use content
singular but we need to update the verb). I am not a native speakers so I could
be completely wrong.

[mstensho (USE GERRIT), 2014/11/27 21:20:29]

Your country of residence trumps mine, I guess. Besides, I agree. :)

My verb usage seems inconsistent as well. I hate that "contents" word.

Done.

+        // spanner.
+        LayoutUnit columnLogicalTopInFlowThread = previousSet->pageLogicalTopForOffset(logicalTopInFlowThread);
+        if (columnLogicalTopInFlowThread != logicalTopInFlowThread) {
+            adjustment = columnLogicalTopInFlowThread + previousSet->pageLogicalHeight() - logicalTopInFlowThread;
+            logicalTopInFlowThread += adjustment;
+        }
+    }
+
+    if (!previousSet->isRenderMultiColumnSpannerSet())
+        previousSet->endFlow(logicalTopInFlowThread);
+    spannerSet->beginFlow(logicalTopInFlowThread);
+
+    m_lastSetWorkedOn = spannerSet;
+    return adjustment;
+}
+
+void RenderMultiColumnFlowThread::exitColumnSpannerAfterLayout(RenderBox* renderer, LayoutUnit logicalBottom)
+{
+    ASSERT(m_lastSetWorkedOn == m_spannerMap.get(renderer));
+
+    LayoutUnit logicalBottomInFlowThread = renderer->parentBlock()->offsetFromLogicalTopOfFirstPage() + logicalBottom;
+    m_lastSetWorkedOn->endFlow(logicalBottomInFlowThread);
+    if (RenderMultiColumnSet* nextSet = m_lastSetWorkedOn->nextSiblingMultiColumnSet()) {
+        m_lastSetWorkedOn = nextSet;
+        if (!m_lastSetWorkedOn->isRenderMultiColumnSpannerSet())
+            m_lastSetWorkedOn->beginFlow(logicalBottomInFlowThread);
+    }
+}
+
 void RenderMultiColumnFlowThread::flowThreadDescendantWasInserted(RenderObject* descendant)
 {
+    ASSERT(!m_isBeingEvacuated);
     // Go through the subtree that was just inserted and create column sets (needed by regular
     // column content) and spanner sets (one needed by each spanner).
     for (RenderObject* renderer = descendant; renderer; renderer = renderer->nextInPreOrder(descendant)) {
         if (containingColumnSpannerSet(renderer))
             continue; // Inside a column spanner set. Nothing to do, then.
         if (descendantIsValidColumnSpanner(renderer)) {
             // This renderer is a spanner, so it needs to establish a spanner set.
             createAndInsertSpannerSet(toRenderBox(renderer));
             continue;
         }
         // This renderer is regular column content (i.e. not a spanner). Create a set if necessary.
         RenderMultiColumnSet* lastSet = lastMultiColumnSet();
         if (!lastSet || lastSet->isRenderMultiColumnSpannerSet())
             createAndInsertMultiColumnSet();
     }
 }
 
+void RenderMultiColumnFlowThread::flowThreadDescendantWillBeRemoved(RenderObject* descendant)
+{
+    if (m_isBeingEvacuated)
+        return;
+    RenderObject* next;
+    // Remove spanner sets that are no longer needed, and merge column sets around them.
+    for (RenderObject* renderer = descendant; renderer; renderer = next) {
+        RenderMultiColumnSpannerSet* spanner = m_spannerMap.get(renderer);
+        if (!spanner) {
+            next = renderer->nextInPreOrder(descendant);
+            continue;
+        }
+        next = renderer->nextInPreOrderAfterChildren(descendant); // It's a spanner. Its children are of no interest to us.
+        if (RenderMultiColumnSet* nextSet = spanner->nextSiblingMultiColumnSet()) {
+            RenderMultiColumnSet* previousSet = spanner->previousSiblingMultiColumnSet();
+            if (nextSet && !nextSet->isRenderMultiColumnSpannerSet()
+                && previousSet && !previousSet->isRenderMultiColumnSpannerSet()) {
+                // Need to merge two column sets.
+                nextSet->destroy();

[Julien - ping for review, 2014/11/26 21:09:01]

It would be worth checking that nextSet is not in m_spannerMap. The best way
should be a RELEASE_ASSERT(isValidColumnSpanAll()) check to
RenderObject::willBeDestroyed (with a comment that we should have removed it
from the flow-thread map before destroying it).

[mstensho (USE GERRIT), 2014/11/27 21:20:29]

Done.

Better do it in willBeRemovedFromTree(), though. In willBeDestroyed(), there's
no way to locate the flow thread, since you've been taken out from the tree.
Also, the correct expression is !isColumnSpanAll().

+                previousSet->setNeedsLayout();

[Julien - ping for review, 2014/11/26 21:09:01]

What ensures that the exiting content under |nextSet| gets moved into the
previousSet?

[mstensho (USE GERRIT), 2014/11/27 21:20:29]

A column set doesn't own / contain / reference any of the renderers inside the
flow thread. It just has a flow thread portion rectangle, which gets updated to
enclose everything it should during layout.

+                invalidateRegions();
+            }
+        }
+        m_spannerMap.remove(renderer);
+        spanner->destroy();
+    }
+}
+
 void RenderMultiColumnFlowThread::computeLogicalHeight(LayoutUnit logicalHeight, LayoutUnit logicalTop, LogicalExtentComputedValues& computedValues) const
 {
     // We simply remain at our intrinsic height.
     computedValues.m_extent = logicalHeight;
     computedValues.m_position = logicalTop;
 }
 
 void RenderMultiColumnFlowThread::updateLogicalWidth()
 {
     LayoutUnit columnWidth;
     calculateColumnCountAndWidth(columnWidth, m_columnCount);
     setLogicalWidth(columnWidth);
 }
 
 void RenderMultiColumnFlowThread::layout()
 {
+    ASSERT(!m_lastSetWorkedOn);
+    m_lastSetWorkedOn = firstMultiColumnSet();
+    if (m_lastSetWorkedOn)
+        m_lastSetWorkedOn->beginFlow(LayoutUnit());
     RenderFlowThread::layout();
-    if (RenderMultiColumnSet* lastSet = lastMultiColumnSet())
+    if (RenderMultiColumnSet* lastSet = lastMultiColumnSet()) {
+        ASSERT(lastSet == m_lastSetWorkedOn);
+        lastSet->endFlow(logicalHeight());
         lastSet->expandToEncompassFlowThreadContentsIfNeeded();
+    }
+    m_lastSetWorkedOn = 0;
 }
 
 void RenderMultiColumnFlowThread::setPageBreak(LayoutUnit offset, LayoutUnit spaceShortage)
 {
     // Only positive values are interesting (and allowed) here. Zero space shortage may be reported
     // when we're at the top of a column and the element has zero height. Ignore this, and also
     // ignore any negative values, which may occur when we set an early break in order to honor
     // widows in the next column.
     if (spaceShortage <= 0)
         return;
 
     if (RenderMultiColumnSet* multicolSet = columnSetAtBlockOffset(offset))
         multicolSet->recordSpaceShortage(spaceShortage);
 }
 
 void RenderMultiColumnFlowThread::updateMinimumPageHeight(LayoutUnit offset, LayoutUnit minHeight)
 {
     if (RenderMultiColumnSet* multicolSet = columnSetAtBlockOffset(offset))
         multicolSet->updateMinimumColumnHeight(minHeight);
 }
 
-RenderMultiColumnSet* RenderMultiColumnFlowThread::columnSetAtBlockOffset(LayoutUnit /*offset*/) const
-{
-    // For now there's only one column set, so this is easy:
-    return firstMultiColumnSet();
-}
-
 bool RenderMultiColumnFlowThread::addForcedRegionBreak(LayoutUnit offset, RenderObject* /*breakChild*/, bool /*isBefore*/, LayoutUnit* offsetBreakAdjustment)
 {
     if (RenderMultiColumnSet* multicolSet = columnSetAtBlockOffset(offset)) {
         multicolSet->addContentRun(offset);
         if (offsetBreakAdjustment)
             *offsetBreakAdjustment = pageLogicalHeightForOffset(offset) ? pageRemainingLogicalHeightForOffset(offset, IncludePageBoundary) : LayoutUnit();
         return true;
     }
     return false;
 }
 
 bool RenderMultiColumnFlowThread::isPageLogicalHeightKnown() const
 {
     if (RenderMultiColumnSet* columnSet = lastMultiColumnSet())
         return columnSet->pageLogicalHeight();
     return false;
 }
 
 }