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

Source/core/rendering/RenderBlockFlow.cpp

Index: Source/core/rendering/RenderBlockFlow.cpp
diff --git a/Source/core/rendering/RenderBlockFlow.cpp b/Source/core/rendering/RenderBlockFlow.cpp
index afc0212fa770522ad2b8b05610560df1286d5192..276b8a04976dab08cec661d116cc748680c42e6b 100644
--- a/Source/core/rendering/RenderBlockFlow.cpp
+++ b/Source/core/rendering/RenderBlockFlow.cpp
@@ -546,11 +546,44 @@ void RenderBlockFlow::setLogicalTopForChild(RenderBox* child, LayoutUnit logical
     }
 }
 
+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);
 
@@ -592,7 +625,6 @@ void RenderBlockFlow::layoutBlockChild(RenderBox* child, MarginInfo& marginInfo,
             previousFloatLogicalBottom = std::max(previousFloatLogicalBottom, oldLogicalTop + childRenderBlockFlow->lowestFloatLogicalBottom());
     }
 
-    SubtreeLayoutScope layoutScope(*child);
     if (!child->needsLayout())
         child->markForPaginationRelayoutIfNeeded(layoutScope);