Prepare height calculation methods in LayoutFlowThread for nested multicol.

Source/core/layout/LayoutMultiColumnSet.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 50 matching lines @@
     // FIXME: implement this, once we have support for multiple rows.
     return m_fragmentainerGroups.first();
 }
 
 const MultiColumnFragmentainerGroup& LayoutMultiColumnSet::fragmentainerGroupAtVisualPoint(const LayoutPoint&) const
 {
     // FIXME: implement this, once we have support for multiple rows.
     return m_fragmentainerGroups.first();
 }
 
-LayoutUnit LayoutMultiColumnSet::pageLogicalHeight() const
+LayoutUnit LayoutMultiColumnSet::pageLogicalHeightForOffset(LayoutUnit offsetInFlowThread) const
 {
-    // FIXME: pageLogicalHeight() needs to take a flow thread offset parameter, so that we can
-    // locate the right row.
+    return fragmentainerGroupAtFlowThreadOffset(offsetInFlowThread).logicalHeight();
+}
+
+LayoutUnit LayoutMultiColumnSet::pageRemainingLogicalHeightForOffset(LayoutUnit offsetInFlowThread, PageBoundaryRule pageBoundaryRule) const
+{
+    const MultiColumnFragmentainerGroup& row = fragmentainerGroupAtFlowThreadOffset(offsetInFlowThread);
+    LayoutUnit pageLogicalHeight = row.logicalHeight();
+    ASSERT(pageLogicalHeight); // It's not allowed to call this method if the height is unknown.
+    LayoutUnit pageLogicalBottom = row.columnLogicalTopForOffset(offsetInFlowThread) + pageLogicalHeight;
+    LayoutUnit remainingLogicalHeight = pageLogicalBottom - offsetInFlowThread;
+
+    if (pageBoundaryRule == IncludePageBoundary) {
+        // If IncludePageBoundary is set, the line exactly on the top edge of a
+        // column will act as being part of the previous column.
+        remainingLogicalHeight = intMod(remainingLogicalHeight, pageLogicalHeight);
+    }
+    return remainingLogicalHeight;
+}
+
+bool LayoutMultiColumnSet::isPageLogicalHeightKnown() const
+{
     return firstFragmentainerGroup().logicalHeight();
 }
 
 LayoutMultiColumnSet* LayoutMultiColumnSet::nextSiblingMultiColumnSet() const
 {
     for (LayoutObject* sibling = nextSibling(); sibling; sibling = sibling->nextSibling()) {
         if (sibling->isLayoutMultiColumnSet())
             return toLayoutMultiColumnSet(sibling);
     }
     return nullptr;
@@ skipping 232 matching lines @@
 
 LayoutRect LayoutMultiColumnSet::flowThreadPortionRect() const
 {
     LayoutRect portionRect(LayoutUnit(), logicalTopInFlowThread(), pageLogicalWidth(), logicalHeightInFlowThread());
     if (!isHorizontalWritingMode())
         return portionRect.transposedRect();
     return portionRect;
 }
 
 }