*** DO NOT LAND *** Attempt to understand Regions complexity

Source/core/rendering/RenderObject.cpp

Index: Source/core/rendering/RenderObject.cpp
diff --git a/Source/core/rendering/RenderObject.cpp b/Source/core/rendering/RenderObject.cpp
index 42db6c33d9265f130246fe0a0600e5bc976a9e7e..9b0a8b7bcfaffcaa1e4422d57f7896967474687e 100644
--- a/Source/core/rendering/RenderObject.cpp
+++ b/Source/core/rendering/RenderObject.cpp
@@ -49,7 +49,6 @@
 #include "core/frame/UseCounter.h"
 #include "core/frame/animation/AnimationController.h"
 #include "core/rendering/CompositedLayerMapping.h"
-#include "core/rendering/FlowThreadController.h"
 #include "core/rendering/HitTestResult.h"
 #include "core/rendering/LayoutRectRecorder.h"
 #include "core/rendering/RenderCounter.h"
@@ -64,9 +63,6 @@
 #include "core/rendering/RenderLayerCompositor.h"
 #include "core/rendering/RenderListItem.h"
 #include "core/rendering/RenderMarquee.h"
-#include "core/rendering/RenderMultiColumnBlock.h"
-#include "core/rendering/RenderNamedFlowThread.h"
-#include "core/rendering/RenderRegion.h"
 #include "core/rendering/RenderRuby.h"
 #include "core/rendering/RenderRubyText.h"
 #include "core/rendering/RenderScrollbarPart.h"
@@ -141,8 +137,6 @@ void RenderObject::operator delete(void* ptr)
 
 RenderObject* RenderObject::createObject(Element* element, RenderStyle* style)
 {
-    Document& doc = element->document();
-
     // Minimal support for content properties replacing an entire element.
     // Works only if we have exactly one piece of content and it's a URL.
     // Otherwise acts as if we didn't support this feature.
@@ -182,8 +176,6 @@ RenderObject* RenderObject::createObject(Element* element, RenderStyle* style)
         return new RenderInline(element);
     case BLOCK:
     case INLINE_BLOCK:
-        if ((!style->hasAutoColumnCount() || !style->hasAutoColumnWidth()) && doc.regionBasedColumnsEnabled())
-            return new RenderMultiColumnBlock(element);
         return new RenderBlockFlow(element);
     case LIST_ITEM:
         return new RenderListItem(element);
@@ -282,19 +274,6 @@ bool RenderObject::isLegend() const
     return node() && node()->hasTagName(legendTag);
 }
 
-void RenderObject::setFlowThreadStateIncludingDescendants(FlowThreadState state)
-{
-    setFlowThreadState(state);
-
-    for (RenderObject* child = firstChild(); child; child = child->nextSibling()) {
-        // If the child is a fragmentation context it already updated the descendants flag accordingly.
-        if (child->isRenderFlowThread())
-            continue;
-        ASSERT(state != child->flowThreadState());
-        child->setFlowThreadStateIncludingDescendants(state);
-    }
-}
-
 bool RenderObject::requiresAnonymousTableWrappers(const RenderObject* newChild) const
 {
     // Check should agree with:
@@ -607,34 +586,6 @@ RenderBox* RenderObject::enclosingScrollableBox() const
     return 0;
 }
 
-RenderFlowThread* RenderObject::locateFlowThreadContainingBlock() const
-{
-    ASSERT(flowThreadState() != NotInsideFlowThread);
-
-    // See if we have the thread cached because we're in the middle of layout.
-    RenderFlowThread* flowThread = view()->flowThreadController()->currentRenderFlowThread();
-    if (flowThread)
-        return flowThread;
-
-    // Not in the middle of layout so have to find the thread the slow way.
-    RenderObject* curr = const_cast<RenderObject*>(this);
-    while (curr) {
-        if (curr->isRenderFlowThread())
-            return toRenderFlowThread(curr);
-        curr = curr->containingBlock();
-    }
-    return 0;
-}
-
-RenderNamedFlowThread* RenderObject::renderNamedFlowThreadWrapper() const
-{
-    RenderObject* object = const_cast<RenderObject*>(this);
-    while (object && object->isAnonymousBlock() && !object->isRenderNamedFlowThread())
-        object = object->parent();
-
-    return object && object->isRenderNamedFlowThread() ? toRenderNamedFlowThread(object) : 0;
-}
-
 RenderBlock* RenderObject::firstLineBlock() const
 {
     return 0;
@@ -1362,22 +1313,6 @@ RenderLayerModelObject* RenderObject::containerForRepaint() const
                 return enclosingFilterLayer->renderer();
         }
     }
-
-    // If we have a flow thread, then we need to do individual repaints within the RenderRegions instead.
-    // Return the flow thread as a repaint container in order to create a chokepoint that allows us to change
-    // repainting to do individual region repaints.
-    RenderFlowThread* parentRenderFlowThread = flowThreadContainingBlock();
-    if (parentRenderFlowThread) {
-        // The ancestor document will do the reparenting when the repaint propagates further up.
-        // We're just a seamless child document, and we don't need to do the hacking.
-        if (parentRenderFlowThread->document() != document())
-            return repaintContainer;
-        // If we have already found a repaint container then we will repaint into that container only if it is part of the same
-        // flow thread. Otherwise we will need to catch the repaint call and send it to the flow thread.
-        RenderFlowThread* repaintContainerFlowThread = repaintContainer ? repaintContainer->flowThreadContainingBlock() : 0;
-        if (!repaintContainerFlowThread || repaintContainerFlowThread != parentRenderFlowThread)
-            repaintContainer = parentRenderFlowThread;
-    }
     return repaintContainer;
 }
 
@@ -1416,11 +1351,6 @@ void RenderObject::repaintUsingContainer(const RenderLayerModelObject* repaintCo
         return;
     }
 
-    if (repaintContainer->isRenderFlowThread()) {
-        toRenderFlowThread(repaintContainer)->repaintRectangleInRegions(r);
-        return;
-    }
-
     if (repaintContainer->hasFilter() && repaintContainer->layer()->requiresFullLayerImageForFilters()) {
         repaintContainer->layer()->repainter().setFilterBackendNeedsRepaintingInRect(r);
         return;
@@ -2323,7 +2253,7 @@ LayoutSize RenderObject::offsetFromContainer(RenderObject* o, const LayoutPoint&
         offset -= toRenderBox(o)->scrolledContentOffset();
 
     if (offsetDependsOnPoint)
-        *offsetDependsOnPoint = hasColumns() || o->isRenderFlowThread();
+        *offsetDependsOnPoint = hasColumns();
 
     return offset;
 }
@@ -2578,18 +2508,6 @@ void RenderObject::willBeDestroyed()
     if (AXObjectCache* cache = document().existingAXObjectCache())
         cache->remove(this);
 
-#ifndef NDEBUG
-    if (!documentBeingDestroyed() && view() && view()->hasRenderNamedFlowThreads()) {
-        // After remove, the object and the associated information should not be in any flow thread.
-        const RenderNamedFlowThreadList* flowThreadList = view()->flowThreadController()->renderNamedFlowThreadList();
-        for (RenderNamedFlowThreadList::const_iterator iter = flowThreadList->begin(); iter != flowThreadList->end(); ++iter) {
-            const RenderNamedFlowThread* renderFlowThread = *iter;
-            ASSERT(!renderFlowThread->hasChild(this));
-            ASSERT(!renderFlowThread->hasChildInfo(this));
-        }
-    }
-#endif
-
     // If this renderer had a parent, remove should have destroyed any counters
     // attached to this renderer and marked the affected other counters for
     // reevaluation. This apparently redundant check is here for the case when
@@ -2626,9 +2544,6 @@ void RenderObject::insertedIntoTree()
 
     if (!isFloating() && parent()->childrenInline())
         parent()->dirtyLinesFromChangedChild(this);
-
-    if (RenderNamedFlowThread* containerFlowThread = parent()->renderNamedFlowThreadWrapper())
-        containerFlowThread->addFlowChild(this);
 }
 
 void RenderObject::willBeRemovedFromTree()
@@ -2652,43 +2567,11 @@ void RenderObject::willBeRemovedFromTree()
     if (isOutOfFlowPositioned() && parent()->childrenInline())
         parent()->dirtyLinesFromChangedChild(this);
 
-    removeFromRenderFlowThread();
-
-    if (RenderNamedFlowThread* containerFlowThread = parent()->renderNamedFlowThreadWrapper())
-        containerFlowThread->removeFlowChild(this);
-
     // Update cached boundaries in SVG renderers if a child is removed.
     if (parent()->isSVG())
         parent()->setNeedsBoundariesUpdate();
 }
 
-void RenderObject::removeFromRenderFlowThread()
-{
-    if (flowThreadState() == NotInsideFlowThread)
-        return;
-
-    // Sometimes we remove the element from the flow, but it's not destroyed at that time.
-    // It's only until later when we actually destroy it and remove all the children from it.
-    // Currently, that happens for firstLetter elements and list markers.
-    // Pass in the flow thread so that we don't have to look it up for all the children.
-    removeFromRenderFlowThreadRecursive(flowThreadContainingBlock());
-}
-
-void RenderObject::removeFromRenderFlowThreadRecursive(RenderFlowThread* renderFlowThread)
-{
-    if (const RenderObjectChildList* children = virtualChildren()) {
-        for (RenderObject* child = children->firstChild(); child; child = child->nextSibling())
-            child->removeFromRenderFlowThreadRecursive(renderFlowThread);
-    }
-
-    RenderFlowThread* localFlowThread = renderFlowThread;
-    if (flowThreadState() == InsideInFlowThread)
-        localFlowThread = flowThreadContainingBlock(); // We have to ask. We can't just assume we are in the same flow thread.
-    if (localFlowThread)
-        localFlowThread->removeFlowChildInfo(this);
-    setFlowThreadState(NotInsideFlowThread);
-}
-
 void RenderObject::destroyAndCleanupAnonymousWrappers()
 {
     // If the tree is destroyed, there is no need for a clean-up phase.
@@ -2702,9 +2585,8 @@ void RenderObject::destroyAndCleanupAnonymousWrappers()
         // Anonymous block continuations are tracked and destroyed elsewhere (see the bottom of RenderBlock::removeChild)
         if (destroyRootParent->isRenderBlock() && toRenderBlock(destroyRootParent)->isAnonymousBlockContinuation())
             break;
-        // Render flow threads are tracked by the FlowThreadController, so we can't destroy them here.
         // Column spans are tracked elsewhere.
-        if (destroyRootParent->isRenderFlowThread() || destroyRootParent->isAnonymousColumnSpanBlock())
+        if (destroyRootParent->isAnonymousColumnSpanBlock())
             break;
 
         if (destroyRootParent->firstChild() != this || destroyRootParent->lastChild() != this)
@@ -3162,29 +3044,8 @@ void RenderObject::imageChanged(ImageResource* image, const IntRect* rect)
 
 RenderObject* RenderObject::hoverAncestor() const
 {
-    // When searching for the hover ancestor and encountering a named flow thread,
-    // the search will continue with the DOM ancestor of the top-most element
-    // in the named flow thread.
-    // See https://code.google.com/p/chromium/issues/detail?id=243278
-    RenderObject* hoverAncestor = parent();
-
-    // Skip anonymous blocks directly flowed into flow threads as it would
-    // prevent us from continuing the search on the DOM tree when reaching the named flow thread.
-    if (hoverAncestor && hoverAncestor->isAnonymousBlock() && hoverAncestor->parent() && hoverAncestor->parent()->isRenderNamedFlowThread())
-        hoverAncestor = hoverAncestor->parent();
-
-    if (hoverAncestor && hoverAncestor->isRenderNamedFlowThread()) {
-        hoverAncestor = 0;
-
-        Node* node = this->node();
-        if (node) {
-            Node* domAncestorNode = node->parentNode();
-            if (domAncestorNode)
-                hoverAncestor = domAncestorNode->renderer();
-        }
-    }
-
-    return hoverAncestor;
+    // FIXME: Remove.
+    return parent();
 }
 
 Element* RenderObject::offsetParent() const
@@ -3204,10 +3065,6 @@ Element* RenderObject::offsetParent() const
     for (RenderObject* ancestor = parent(); ancestor; ancestor = ancestor->parent()) {
         // Spec: http://www.w3.org/TR/cssom-view/#offset-attributes
 
-        // CSS regions specification says that region flows should return the body element as their offsetParent.
-        if (ancestor->isRenderNamedFlowThread())
-            return document().body();
-
         node = ancestor->node();
 
         if (!node)
@@ -3365,11 +3222,6 @@ bool RenderObject::isRelayoutBoundaryForInspector() const
     return objectIsRelayoutBoundary(this);
 }
 
-bool RenderObject::isRenderNamedFlowFragmentContainer() const
-{
-    return isRenderBlockFlow() && toRenderBlockFlow(this)->renderNamedFlowFragment();
-}
-
 } // namespace WebCore
 
 #ifndef NDEBUG