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

Source/core/rendering/RenderBlockFlow.cpp

 /*
  * Copyright (C) 2013 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 528 matching lines @@
 
 void RenderBlockFlow::setLogicalTopForChild(RenderBox* child, LayoutUnit logicalTop)
 {
     if (isHorizontalWritingMode()) {
         child->setY(logicalTop);
     } else {
         child->setX(logicalTop);
     }
 }
 
+class ColumnSpannerLayoutScope {
+public:
+    ColumnSpannerLayoutScope()
+        : m_spanner(0) { }

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

Nit: I prefer to stick with a statement per line, which moves the curly braces
to their own lines.

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

Done.

+
+    ~ColumnSpannerLayoutScope()
+    {
+        if (!m_spanner)
+            return;
+        m_spanner->flowThreadContainingBlock()->exitColumnSpannerAfterLayout(m_spanner, m_spanner->parentBlock()->logicalHeight());
+    }
+
+    LayoutUnit enterSpanner(RenderBox* spanner, SubtreeLayoutScope& layoutScope)
+    {
+        ASSERT(!m_spanner);
+        m_spanner = spanner;
+        return m_spanner->flowThreadContainingBlock()->enterColumnSpannerBeforeLayout(m_spanner, m_spanner->parentBlock()->logicalHeight(), layoutScope);
+    }
+
+private:
+    RenderBox* m_spanner;
+};
+
 void RenderBlockFlow::layoutBlockChild(RenderBox* child, MarginInfo& marginInfo, LayoutUnit& previousFloatLogicalBottom)
 {
     LayoutUnit oldPosMarginBefore = maxPositiveMarginBefore();
     LayoutUnit oldNegMarginBefore = maxNegativeMarginBefore();
 
+    SubtreeLayoutScope layoutScope(*child);
+
+    ColumnSpannerLayoutScope columnSpannerLayoutScope;
+    if (child->isColumnSpanAll()) {
+        LayoutUnit adjustment = columnSpannerLayoutScope.enterSpanner(child, layoutScope);
+        // A spanner needs to start at an exact column boundary inside the flow thread, so that it
+        // doesn't bleed into a preceding column. That's what the adjustment is about.
+        setLogicalHeight(logicalHeight() + adjustment);
+    }
+
     // The child is a normal flow object. Compute the margins we will use for collapsing now.
     child->computeAndSetBlockDirectionMargins(this);
 
     // Try to guess our correct logical top position. In most cases this guess will
     // be correct. Only if we're wrong (when we compute the real logical top position)
     // will we have to potentially relayout.
     LayoutUnit estimateWithoutPagination;
     LayoutUnit logicalTopEstimate = estimateLogicalTopPosition(child, marginInfo, estimateWithoutPagination);
 
     // Cache our old rect so that we can dirty the proper paint invalidation rects if the child moves.
@@ skipping 21 matching lines @@
             markDescendantsWithFloats = true;
     }
 
     if (childRenderBlockFlow) {
         if (markDescendantsWithFloats)
             childRenderBlockFlow->markAllDescendantsWithFloatsForLayout();
         if (!child->isWritingModeRoot())
             previousFloatLogicalBottom = std::max(previousFloatLogicalBottom, oldLogicalTop + childRenderBlockFlow->lowestFloatLogicalBottom());
     }
 
-    SubtreeLayoutScope layoutScope(*child);
     if (!child->needsLayout())
         child->markForPaginationRelayoutIfNeeded(layoutScope);
 
     bool childNeededLayout = child->needsLayout();
     if (childNeededLayout)
         child->layout();
 
     // Cache if we are at the top of the block right now.
     bool atBeforeSideOfBlock = marginInfo.atBeforeSideOfBlock();
     bool childIsSelfCollapsing = child->isSelfCollapsingBlock();
@@ skipping 2472 matching lines @@
     FrameView* frameView = document().view();
     LayoutUnit top = (style()->position() == FixedPosition) ? 0 : frameView->scrollOffset().height();
     int visibleHeight = frameView->visibleContentRect(IncludeScrollbars).height();
     if (height() < visibleHeight)
         top += (visibleHeight - height()) / 2;
     setY(top);
     dialog->setCentered(top);
 }
 
 } // namespace blink