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

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 c90e924371983ad626d39bdc3eca9ec124489dbd..340583e4d815c6e6f1cc4290cc021f102b2621ae 100644
--- a/Source/core/rendering/RenderBlockFlow.cpp
+++ b/Source/core/rendering/RenderBlockFlow.cpp
@@ -38,8 +38,6 @@
 #include "core/rendering/LayoutRectRecorder.h"
 #include "core/rendering/LayoutRepainter.h"
 #include "core/rendering/RenderLayer.h"
-#include "core/rendering/RenderNamedFlowFragment.h"
-#include "core/rendering/RenderNamedFlowThread.h"
 #include "core/rendering/RenderText.h"
 #include "core/rendering/RenderView.h"
 #include "core/rendering/line/LineWidth.h"
@@ -145,7 +143,7 @@ static bool inNormalFlow(RenderBox* child)
     RenderBlock* curr = child->containingBlock();
     RenderView* renderView = child->view();
     while (curr && curr != renderView) {
-        if (curr->hasColumns() || curr->isRenderFlowThread())
+        if (curr->hasColumns())
             return true;
         if (curr->isFloatingOrOutOfFlowPositioned())
             return false;
@@ -181,9 +179,6 @@ void RenderBlockFlow::willBeDestroyed()
     if (lineGridBox())
         lineGridBox()->destroy();
 
-    if (renderNamedFlowFragment())
-        setRenderNamedFlowFragment(0);
-
     RenderBlock::willBeDestroyed();
 }
 
@@ -278,15 +273,6 @@ inline void RenderBlockFlow::layoutBlockFlow(bool relayoutChildren, LayoutUnit p
     RenderView* renderView = view();
     LayoutStateMaintainer statePusher(renderView, this, locationOffset(), hasColumns() || hasTransform() || hasReflection() || style()->isFlippedBlocksWritingMode(), pageLogicalHeight, pageLogicalHeightChanged, columnInfo());
 
-    // Regions changing widths can force us to relayout our children.
-    RenderFlowThread* flowThread = flowThreadContainingBlock();
-    if (logicalWidthChangedInRegions(flowThread))
-        relayoutChildren = true;
-    if (updateRegionsAndShapesLogicalSize(flowThread))
-        relayoutChildren = true;
-    if (!relayoutChildren && isRenderNamedFlowFragmentContainer())
-        relayoutChildren = true;
-
     // We use four values, maxTopPos, maxTopNeg, maxBottomPos, and maxBottomNeg, to track
     // our current maximal positive and negative margins. These values are used when we
     // are collapsed with adjacent blocks, so for example, if you have block A and B
@@ -347,11 +333,6 @@ inline void RenderBlockFlow::layoutBlockFlow(bool relayoutChildren, LayoutUnit p
     LayoutUnit oldHeight = logicalHeight();
     LayoutUnit oldClientAfterEdge = clientLogicalBottom();
 
-    // Before updating the final size of the flow thread make sure a forced break is applied after the content.
-    // This ensures the size information is correctly computed for the last auto-height region receiving content.
-    if (isRenderFlowThread())
-        toRenderFlowThread(this)->applyBreakAfterContent(oldClientAfterEdge);
-
     updateLogicalHeight();
     LayoutUnit newHeight = logicalHeight();
     if (oldHeight != newHeight) {
@@ -373,8 +354,6 @@ inline void RenderBlockFlow::layoutBlockFlow(bool relayoutChildren, LayoutUnit p
 
     layoutPositionedObjects(relayoutChildren || isRoot());
 
-    updateRegionsAndShapesAfterChildLayout(flowThread, heightChanged);
-
     // Add overflow from children (unless we're multi-column, since in that case all our child overflow is clipped anyway).
     computeOverflow(oldClientAfterEdge);
 
@@ -864,7 +843,7 @@ MarginInfo::MarginInfo(RenderBlockFlow* blockFlow, LayoutUnit beforeBorderPaddin
     ASSERT(blockFlow->isRenderView() || blockFlow->parent());
     m_canCollapseWithChildren = !blockFlow->isRenderView() && !blockFlow->isRoot() && !blockFlow->isOutOfFlowPositioned()
         && !blockFlow->isFloating() && !blockFlow->isTableCell() && !blockFlow->hasOverflowClip() && !blockFlow->isInlineBlockOrInlineTable()
-        && !blockFlow->isRenderFlowThread() && !blockFlow->isWritingModeRoot() && !blockFlow->parent()->isFlexibleBox()
+        && !blockFlow->isWritingModeRoot() && !blockFlow->parent()->isFlexibleBox()
         && blockStyle->hasAutoColumnCount() && blockStyle->hasAutoColumnWidth() && !blockStyle->columnSpan();
 
     m_canCollapseMarginBeforeWithChildren = m_canCollapseWithChildren && !beforeBorderPadding && blockStyle->marginBeforeCollapse() != MSEPARATE;
@@ -1134,19 +1113,16 @@ void RenderBlockFlow::adjustPositionedBlock(RenderBox* child, const MarginInfo&
     }
 }
 
-LayoutUnit RenderBlockFlow::computeStartPositionDeltaForChildAvoidingFloats(const RenderBox* child, LayoutUnit childMarginStart, RenderRegion* region)
+LayoutUnit RenderBlockFlow::computeStartPositionDeltaForChildAvoidingFloats(const RenderBox* child, LayoutUnit childMarginStart)
 {
-    LayoutUnit startPosition = startOffsetForContent(region);
+    LayoutUnit startPosition = startOffsetForContent();
 
     // Add in our start margin.
     LayoutUnit oldPosition = startPosition + childMarginStart;
     LayoutUnit newPosition = oldPosition;
 
     LayoutUnit blockOffset = logicalTopForChild(child);
-    if (region)
-        blockOffset = max(blockOffset, blockOffset + (region->logicalTopForFlowThreadContent() - offsetFromLogicalTopOfFirstPage()));
-
-    LayoutUnit startOff = startOffsetForLineInRegion(blockOffset, false, region, logicalHeightForChild(child));
+    LayoutUnit startOff = startOffsetForLine(blockOffset, false, logicalHeightForChild(child));
 
     if (style()->textAlign() != WEBKIT_CENTER && !child->style()->marginStartUsing(style()).isAuto()) {
         if (childMarginStart < 0)
@@ -1529,18 +1505,10 @@ LayoutUnit RenderBlockFlow::applyBeforeBreak(RenderBox* child, LayoutUnit logica
     // FIXME: Add page break checking here when we support printing.
     bool checkColumnBreaks = 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)
-        || (checkRegionBreaks && child->style()->regionBreakBefore() == PBALWAYS);
+    bool checkBeforeAlways = (checkColumnBreaks && child->style()->columnBreakBefore() == PBALWAYS) || (checkPageBreaks && child->style()->pageBreakBefore() == PBALWAYS);
     if (checkBeforeAlways && inNormalFlow(child) && hasNextPage(logicalOffset, IncludePageBoundary)) {
         if (checkColumnBreaks)
             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;
@@ -1551,23 +1519,13 @@ LayoutUnit RenderBlockFlow::applyAfterBreak(RenderBox* child, LayoutUnit logical
     // FIXME: Add page break checking here when we support printing.
     bool checkColumnBreaks = 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)
-        || (checkRegionBreaks && child->style()->regionBreakAfter() == PBALWAYS);
+    bool checkAfterAlways = (checkColumnBreaks && child->style()->columnBreakAfter() == PBALWAYS) || (checkPageBreaks && child->style()->pageBreakAfter() == 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 (checkRegionBreaks) {
-            LayoutUnit offsetBreakAdjustment = 0;
-            if (flowThread->addForcedRegionBreak(offsetFromLogicalTopOfFirstPage() + logicalOffset + marginOffset, child, false, &offsetBreakAdjustment))
-                return logicalOffset + marginOffset + offsetBreakAdjustment;
-        }
         return nextPageLogicalTop(logicalOffset, IncludePageBoundary);
     }
     return logicalOffset;
@@ -1695,11 +1653,10 @@ LayoutUnit RenderBlockFlow::getClearDelta(RenderBox* child, LayoutUnit logicalTo
         LayoutUnit newLogicalTop = logicalTop;
         while (true) {
             LayoutUnit availableLogicalWidthAtNewLogicalTopOffset = availableLogicalWidthForLine(newLogicalTop, false, logicalHeightForChild(child));
-            if (availableLogicalWidthAtNewLogicalTopOffset == availableLogicalWidthForContent(newLogicalTop))
+            if (availableLogicalWidthAtNewLogicalTopOffset == availableLogicalWidthForContent())
                 return newLogicalTop - logicalTop;
 
-            RenderRegion* region = regionAtBlockOffset(logicalTopForChild(child));
-            LayoutRect borderBox = child->borderBoxRectInRegion(region, DoNotCacheRenderBoxRegionInfo);
+            LayoutRect borderBox = child->borderBoxRect();
             LayoutUnit childLogicalWidthAtOldLogicalTopOffset = isHorizontalWritingMode() ? borderBox.width() : borderBox.height();
 
             // FIXME: None of this is right for perpendicular writing-mode children.
@@ -1710,8 +1667,7 @@ LayoutUnit RenderBlockFlow::getClearDelta(RenderBox* child, LayoutUnit logicalTo
 
             child->setLogicalTop(newLogicalTop);
             child->updateLogicalWidth();
-            region = regionAtBlockOffset(logicalTopForChild(child));
-            borderBox = child->borderBoxRectInRegion(region, DoNotCacheRenderBoxRegionInfo);
+            borderBox = child->borderBoxRect();
             LayoutUnit childLogicalWidthAtNewLogicalTopOffset = isHorizontalWritingMode() ? borderBox.width() : borderBox.height();
 
             child->setLogicalTop(childOldLogicalTop);
@@ -1787,9 +1743,6 @@ void RenderBlockFlow::styleDidChange(StyleDifference diff, const RenderStyle* ol
         parentBlockFlow->markAllDescendantsWithFloatsForLayout();
         parentBlockFlow->markSiblingsWithFloatsForLayout();
     }
-
-    if (renderNamedFlowFragment())
-        renderNamedFlowFragment()->setStyleForNamedFlowFragment(style());
 }
 
 void RenderBlockFlow::updateStaticInlinePositionForChild(RenderBox* child, LayoutUnit logicalTop)
@@ -1797,15 +1750,11 @@ void RenderBlockFlow::updateStaticInlinePositionForChild(RenderBox* child, Layou
     if (child->style()->isOriginalDisplayInlineType())
         setStaticInlinePositionForChild(child, logicalTop, startAlignedOffsetForLine(logicalTop, false));
     else
-        setStaticInlinePositionForChild(child, logicalTop, startOffsetForContent(logicalTop));
+        setStaticInlinePositionForChild(child, logicalTop, startOffsetForContent());
 }
 
 void RenderBlockFlow::setStaticInlinePositionForChild(RenderBox* child, LayoutUnit blockOffset, LayoutUnit inlinePosition)
 {
-    if (flowThreadContainingBlock()) {
-        // Shift the inline position to exclude the region offset.
-        inlinePosition += startOffsetForContent() - startOffsetForContent(blockOffset);
-    }
     child->layer()->setStaticInlinePosition(inlinePosition);
 }
 
@@ -2117,7 +2066,7 @@ LayoutUnit RenderBlockFlow::adjustLogicalRightOffsetForLine(LayoutUnit offsetFro
 LayoutPoint RenderBlockFlow::computeLogicalLocationForFloat(const FloatingObject* floatingObject, LayoutUnit logicalTopOffset) const
 {
     RenderBox* childBox = floatingObject->renderer();
-    LayoutUnit logicalLeftOffset = logicalLeftOffsetForContent(logicalTopOffset); // Constant part of left offset.
+    LayoutUnit logicalLeftOffset = logicalLeftOffsetForContent(); // Constant part of left offset.
     LayoutUnit logicalRightOffset; // Constant part of right offset.
     // FIXME Bug 102948: This only works for shape outside directly set on this block.
     ShapeInsideInfo* shapeInsideInfo = this->layoutShapeInsideInfo();
@@ -2140,15 +2089,13 @@ LayoutPoint RenderBlockFlow::computeLogicalLocationForFloat(const FloatingObject
             logicalLeftOffset += segments[0].logicalLeft;
         }
     } else {
-        logicalRightOffset = logicalRightOffsetForContent(logicalTopOffset);
+        logicalRightOffset = logicalRightOffsetForContent();
     }
 
     LayoutUnit floatLogicalWidth = min(logicalWidthForFloat(floatingObject), logicalRightOffset - logicalLeftOffset); // The width we look for.
 
     LayoutUnit floatLogicalLeft;
 
-    bool insideFlowThread = flowThreadContainingBlock();
-
     if (childBox->style()->floating() == LeftFloat) {
         LayoutUnit heightRemainingLeft = 1;
         LayoutUnit heightRemainingRight = 1;
@@ -2156,12 +2103,6 @@ LayoutPoint RenderBlockFlow::computeLogicalLocationForFloat(const FloatingObject
         while (logicalRightOffsetForPositioningFloat(logicalTopOffset, logicalRightOffset, false, &heightRemainingRight) - floatLogicalLeft < floatLogicalWidth) {
             logicalTopOffset += min(heightRemainingLeft, heightRemainingRight);
             floatLogicalLeft = logicalLeftOffsetForPositioningFloat(logicalTopOffset, logicalLeftOffset, false, &heightRemainingLeft);
-            if (insideFlowThread) {
-                // Have to re-evaluate all of our offsets, since they may have changed.
-                logicalRightOffset = logicalRightOffsetForContent(logicalTopOffset); // Constant part of right offset.
-                logicalLeftOffset = logicalLeftOffsetForContent(logicalTopOffset); // Constant part of left offset.
-                floatLogicalWidth = min(logicalWidthForFloat(floatingObject), logicalRightOffset - logicalLeftOffset);
-            }
         }
         floatLogicalLeft = max(logicalLeftOffset - borderAndPaddingLogicalLeft(), floatLogicalLeft);
     } else {
@@ -2171,12 +2112,6 @@ LayoutPoint RenderBlockFlow::computeLogicalLocationForFloat(const FloatingObject
         while (floatLogicalLeft - logicalLeftOffsetForPositioningFloat(logicalTopOffset, logicalLeftOffset, false, &heightRemainingLeft) < floatLogicalWidth) {
             logicalTopOffset += min(heightRemainingLeft, heightRemainingRight);
             floatLogicalLeft = logicalRightOffsetForPositioningFloat(logicalTopOffset, logicalRightOffset, false, &heightRemainingRight);
-            if (insideFlowThread) {
-                // Have to re-evaluate all of our offsets, since they may have changed.
-                logicalRightOffset = logicalRightOffsetForContent(logicalTopOffset); // Constant part of right offset.
-                logicalLeftOffset = logicalLeftOffsetForContent(logicalTopOffset); // Constant part of left offset.
-                floatLogicalWidth = min(logicalWidthForFloat(floatingObject), logicalRightOffset - logicalLeftOffset);
-            }
         }
         // Use the original width of the float here, since the local variable
         // |floatLogicalWidth| was capped to the available line width. See
@@ -2770,53 +2705,9 @@ RootInlineBox* RenderBlockFlow::createRootInlineBox()
     return new RootInlineBox(this);
 }
 
-void RenderBlockFlow::createRenderNamedFlowFragmentIfNeeded()
-{
-    if (!RuntimeEnabledFeatures::cssRegionsEnabled()
-        || renderNamedFlowFragment()
-        || isRenderNamedFlowFragment())
-        return;
-
-    RenderStyle* styleToUse = style();
-    if (styleToUse->isDisplayRegionType() && styleToUse->hasFlowFrom() && document().renderView()) {
-        RenderNamedFlowFragment* flowFragment = RenderNamedFlowFragment::createAnonymous(&document());
-        flowFragment->setStyleForNamedFlowFragment(styleToUse);
-        setRenderNamedFlowFragment(flowFragment);
-        addChild(flowFragment);
-    }
-}
-
-void RenderBlockFlow::insertedIntoTree()
-{
-    RenderBlock::insertedIntoTree();
-
-    createRenderNamedFlowFragmentIfNeeded();
-}
-
-bool RenderBlockFlow::canHaveChildren() const
-{
-    return !renderNamedFlowFragment() ? RenderBlock::canHaveChildren() : renderNamedFlowFragment()->canHaveChildren();
-}
-
-bool RenderBlockFlow::canHaveGeneratedChildren() const
-{
-    return !renderNamedFlowFragment() ? RenderBlock::canHaveGeneratedChildren() : renderNamedFlowFragment()->canHaveGeneratedChildren();
-}
-
 void RenderBlockFlow::updateLogicalHeight()
 {
     RenderBlock::updateLogicalHeight();
-
-    if (renderNamedFlowFragment())
-        renderNamedFlowFragment()->setLogicalHeight(max<LayoutUnit>(0, logicalHeight() - borderAndPaddingLogicalHeight()));
-}
-
-void RenderBlockFlow::setRenderNamedFlowFragment(RenderNamedFlowFragment* flowFragment)
-{
-    RenderBlockFlow::RenderBlockFlowRareData& rareData = ensureRareData();
-    if (rareData.m_renderNamedFlowFragment)
-        rareData.m_renderNamedFlowFragment->destroy();
-    rareData.m_renderNamedFlowFragment = flowFragment;
 }
 
 RenderBlockFlow::RenderBlockFlowRareData& RenderBlockFlow::ensureRareData()