Region based multicol: support explicit column breaks

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 1509 matching lines @@
     if (child->isHorizontalWritingMode() == isHorizontalWritingMode())
         return childStyle->marginBeforeCollapse() == MSEPARATE;
 
     // FIXME: See |mustDiscardMarginBeforeForChild| above.
     return false;
 }
 
 LayoutUnit RenderBlockFlow::applyBeforeBreak(RenderBox* child, LayoutUnit logicalOffset)
 {
     // FIXME: Add page break checking here when we support printing.
-    bool checkColumnBreaks = view()->layoutState()->isPaginatingColumns();
+    RenderFlowThread* flowThread = flowThreadContainingBlock();
+    bool isInsideMulticolFlowThread = flowThread && !flowThread->isRenderNamedFlowThread();
+    bool checkColumnBreaks = isInsideMulticolFlowThread || view()->layoutState()->isPaginatingColumns();
     bool checkPageBreaks = !checkColumnBreaks && view()->layoutState()->m_pageLogicalHeight; // FIXME: Once columns can print we have to check this.
-    RenderFlowThread* flowThread = flowThreadContainingBlock();
     bool checkRegionBreaks = flowThread && flowThread->isRenderNamedFlowThread();
-    bool checkBeforeAlways = (checkColumnBreaks && child->style()->columnBreakBefore() == PBALWAYS) || (checkPageBreaks && child->style()->pageBreakBefore() == PBALWAYS)
+    bool checkBeforeAlways = (checkColumnBreaks && child->style()->columnBreakBefore() == PBALWAYS)
+        || (checkPageBreaks && child->style()->pageBreakBefore() == PBALWAYS)
         || (checkRegionBreaks && child->style()->regionBreakBefore() == PBALWAYS);
     if (checkBeforeAlways && inNormalFlow(child) && hasNextPage(logicalOffset, IncludePageBoundary)) {
-        if (checkColumnBreaks)
-            view()->layoutState()->addForcedColumnBreak(child, logicalOffset);
+        if (checkColumnBreaks) {
+            if (isInsideMulticolFlowThread)
+                checkRegionBreaks = true;
+            else
+                view()->layoutState()->addForcedColumnBreak(child, logicalOffset);
+        }
         if (checkRegionBreaks) {
             LayoutUnit offsetBreakAdjustment = 0;
             if (flowThread->addForcedRegionBreak(offsetFromLogicalTopOfFirstPage() + logicalOffset, child, true, &offsetBreakAdjustment))
                 return logicalOffset + offsetBreakAdjustment;
         }
         return nextPageLogicalTop(logicalOffset, IncludePageBoundary);
     }
     return logicalOffset;
 }
 
 LayoutUnit RenderBlockFlow::applyAfterBreak(RenderBox* child, LayoutUnit logicalOffset, MarginInfo& marginInfo)
 {
     // FIXME: Add page break checking here when we support printing.
-    bool checkColumnBreaks = view()->layoutState()->isPaginatingColumns();
+    RenderFlowThread* flowThread = flowThreadContainingBlock();
+    bool isInsideMulticolFlowThread = flowThread && !flowThread->isRenderNamedFlowThread();
+    bool checkColumnBreaks = isInsideMulticolFlowThread || view()->layoutState()->isPaginatingColumns();
     bool checkPageBreaks = !checkColumnBreaks && view()->layoutState()->m_pageLogicalHeight; // FIXME: Once columns can print we have to check this.
-    RenderFlowThread* flowThread = flowThreadContainingBlock();
     bool checkRegionBreaks = flowThread && flowThread->isRenderNamedFlowThread();
-    bool checkAfterAlways = (checkColumnBreaks && child->style()->columnBreakAfter() == PBALWAYS) || (checkPageBreaks && child->style()->pageBreakAfter() == PBALWAYS)
+    bool checkAfterAlways = (checkColumnBreaks && child->style()->columnBreakAfter() == PBALWAYS)
+        || (checkPageBreaks && child->style()->pageBreakAfter() == PBALWAYS)
         || (checkRegionBreaks && child->style()->regionBreakAfter() == PBALWAYS);
     if (checkAfterAlways && inNormalFlow(child) && hasNextPage(logicalOffset, IncludePageBoundary)) {
         LayoutUnit marginOffset = marginInfo.canCollapseWithMarginBefore() ? LayoutUnit() : marginInfo.margin();
 
         // So our margin doesn't participate in the next collapsing steps.
         marginInfo.clearMargin();
 
-        if (checkColumnBreaks)
-            view()->layoutState()->addForcedColumnBreak(child, logicalOffset);
+        if (checkColumnBreaks) {
+            if (isInsideMulticolFlowThread)
+                checkRegionBreaks = true;
+            else
+                view()->layoutState()->addForcedColumnBreak(child, logicalOffset);
+        }
         if (checkRegionBreaks) {
             LayoutUnit offsetBreakAdjustment = 0;
             if (flowThread->addForcedRegionBreak(offsetFromLogicalTopOfFirstPage() + logicalOffset + marginOffset, child, false, &offsetBreakAdjustment))
                 return logicalOffset + marginOffset + offsetBreakAdjustment;
         }
         return nextPageLogicalTop(logicalOffset, IncludePageBoundary);
     }
     return logicalOffset;
 }
 
@@ skipping 1246 matching lines @@
 RenderBlockFlow::RenderBlockFlowRareData& RenderBlockFlow::ensureRareData()
 {
     if (m_rareData)
         return *m_rareData;
 
     m_rareData = adoptPtr(new RenderBlockFlowRareData(this));
     return *m_rareData;
 }
 
 } // namespace WebCore