1 files changed, 34 insertions, 11 deletions

diff --git a/Source/WebCore/rendering/RenderRegion.cpp b/Source/WebCore/rendering/RenderRegion.cpp
index 5362836a4..aa4e05077 100644
--- a/Source/WebCore/rendering/RenderRegion.cpp
+++ b/Source/WebCore/rendering/RenderRegion.cpp
@@ -49,7 +49,6 @@ RenderRegion::RenderRegion(Node* node, RenderFlowThread* flowThread)
     , m_isValid(false)
     , m_hasCustomRegionStyle(false)
     , m_regionState(RegionUndefined)
-    , m_dispatchRegionLayoutUpdateEvent(false)
 {
 }
 
@@ -63,13 +62,14 @@ LayoutUnit RenderRegion::logicalHeightForFlowThreadContent() const
     return m_flowThread->isHorizontalWritingMode() ? contentHeight() : contentWidth();
 }
 
-LayoutRect RenderRegion::regionOverflowRect() const
+LayoutRect RenderRegion::regionOversetRect() const
 {
     // FIXME: Would like to just use hasOverflowClip() but we aren't a block yet. When RenderRegion is eliminated and
     // folded into RenderBlock, switch to hasOverflowClip().
     bool clipX = style()->overflowX() != OVISIBLE;
     bool clipY = style()->overflowY() != OVISIBLE;
-    if ((clipX && clipY) || !isValid() || !m_flowThread)
+    bool isLastRegionWithRegionOverflowBreak = (isLastRegion() && (style()->regionOverflow() == BreakRegionOverflow));
+    if ((clipX && clipY) || !isValid() || !m_flowThread || isLastRegionWithRegionOverflowBreak)
         return regionRect();
 
     LayoutRect flowThreadOverflow = m_flowThread->visualOverflowRect();
@@ -141,6 +141,18 @@ bool RenderRegion::nodeAtPoint(const HitTestRequest& request, HitTestResult& res
     return false;
 }
 
+void RenderRegion::checkRegionStyle()
+{
+    ASSERT(m_flowThread);
+    bool customRegionStyle = false;
+    if (node()) {
+        Element* regionElement = static_cast<Element*>(node());
+        customRegionStyle = view()->document()->styleResolver()->checkRegionStyle(regionElement);
+    }
+    setHasCustomRegionStyle(customRegionStyle);
+    m_flowThread->checkRegionsWithStyling();
+}
+
 void RenderRegion::styleDidChange(StyleDifference diff, const RenderStyle* oldStyle)
 {
     RenderReplaced::styleDidChange(diff, oldStyle);
@@ -153,13 +165,7 @@ void RenderRegion::styleDidChange(StyleDifference diff, const RenderStyle* oldSt
         return;
     }
 
-    bool customRegionStyle = false;
-    if (node()) {
-        Element* regionElement = static_cast<Element*>(node());
-        customRegionStyle = view()->document()->styleResolver()->checkRegionStyle(regionElement);
-    }
-    setHasCustomRegionStyle(customRegionStyle);
-    m_flowThread->checkRegionsWithStyling();
+    checkRegionStyle();
 }
 
 void RenderRegion::layout()
@@ -187,9 +193,19 @@ void RenderRegion::layout()
 
 void RenderRegion::attachRegion()
 {
-    if (!m_flowThread)
+    if (documentBeingDestroyed())
         return;
 
+    ASSERT(!m_flowThread);
+    // Initialize the flow thread reference and create the flow thread object if needed.
+    // The flow thread lifetime is influenced by the number of regions attached to it,
+    // and we are attaching the region to the flow thread.
+    m_flowThread = view()->flowThreadController()->ensureRenderFlowThreadWithName(style()->regionThread());
+
+    // A region is valid if it is not part of a circular reference, which is checked below
+    // and in RenderNamedFlowThread::addRegionToThread.
+    setIsValid(false);
+
     // By now the flow thread should already be added to the rendering tree,
     // so we go up the rendering parents and check that this region is not part of the same
     // flow that it actually needs to display. It would create a circular reference.
@@ -202,6 +218,8 @@ void RenderRegion::attachRegion()
             // cannot change, so it is not worth adding it to the list.
             if (m_flowThread == m_parentNamedFlowThread) {
                 m_flowThread = 0;
+                // This region is not valid for this flow thread (as being part of a circular dependency).
+                setIsValid(false);
                 return;
             }
             break;
@@ -209,12 +227,17 @@ void RenderRegion::attachRegion()
     }
 
     m_flowThread->addRegionToThread(this);
+
+    // The region just got attached to the flow thread, lets check whether
+    // it has region styling rules associated.
+    checkRegionStyle();
 }
 
 void RenderRegion::detachRegion()
 {
     if (m_flowThread)
         m_flowThread->removeRegionFromThread(this);
+    m_flowThread = 0;
 }
 
 RenderBoxRegionInfo* RenderRegion::renderBoxRegionInfo(const RenderBox* box) const