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

Source/core/rendering/RenderFlexibleBox.cpp

 /*
  * Copyright (C) 2011 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 226 matching lines @@
     LayoutRectRecorder recorder(*this);
 
     if (updateLogicalWidthAndColumnWidth())
         relayoutChildren = true;
 
     LayoutUnit previousHeight = logicalHeight();
     setLogicalHeight(borderAndPaddingLogicalHeight() + scrollbarLogicalHeight());
 
     LayoutStateMaintainer statePusher(view(), this, locationOffset(), hasTransform() || hasReflection() || style()->isFlippedBlocksWritingMode());
 
-    // Regions changing widths can force us to relayout our children.
-    RenderFlowThread* flowThread = flowThreadContainingBlock();
-    if (logicalWidthChangedInRegions(flowThread))
-        relayoutChildren = true;
-    if (updateRegionsAndShapesLogicalSize(flowThread))
-        relayoutChildren = true;
-
     m_numberOfInFlowChildrenOnFirstLine = -1;
 
     RenderBlock::startDelayUpdateScrollInfo();
 
     prepareOrderIteratorAndMargins();
 
     ChildFrameRects oldChildRects;
     appendChildFrameRects(oldChildRects);
 
     Vector<LineContext> lineContexts;
     layoutFlexItems(relayoutChildren, lineContexts);
 
     updateLogicalHeight();
     repositionLogicalHeightDependentFlexItems(lineContexts);
 
     RenderBlock::finishDelayUpdateScrollInfo();
 
     if (logicalHeight() != previousHeight)
         relayoutChildren = true;
 
     layoutPositionedObjects(relayoutChildren || isRoot());
 
-    computeRegionRangeForBlock(flowThread);
-
     repaintChildrenDuringLayoutIfMoved(oldChildRects);
     // FIXME: css3/flexbox/repaint-rtl-column.html seems to repaint more overflow than it needs to.
     computeOverflow(clientLogicalBottomAfterRepositioning());
     statePusher.pop();
 
     updateLayerTransform();
 
     // Update our scroll information if we're overflow:auto/scroll/hidden now that we know if
     // we overflow or not.
     updateScrollInfoAfterLayout();
@@ skipping 153 matching lines @@
 LayoutUnit RenderFlexibleBox::computeMainAxisExtentForChild(RenderBox* child, SizeType sizeType, const Length& size)
 {
     // FIXME: This is wrong for orthogonal flows. It should use the flexbox's writing-mode, not the child's in order
     // to figure out the logical height/width.
     if (isColumnFlow()) {
         // We don't have to check for "auto" here - computeContentLogicalHeight will just return -1 for that case anyway.
         if (size.isIntrinsic())
             child->layoutIfNeeded();
         return child->computeContentLogicalHeight(size, child->logicalHeight() - child->borderAndPaddingLogicalHeight());
     }
-    // FIXME: Figure out how this should work for regions and pass in the appropriate values.
-    RenderRegion* region = 0;
-    return child->computeLogicalWidthInRegionUsing(sizeType, size, contentLogicalWidth(), this, region) - child->borderAndPaddingLogicalWidth();
+    return child->computeLogicalWidthUsing(sizeType, size, contentLogicalWidth(), this) - child->borderAndPaddingLogicalWidth();
 }
 
 WritingMode RenderFlexibleBox::transformedWritingMode() const
 {
     WritingMode mode = style()->writingMode();
     if (!isColumnFlow())
         return mode;
 
     switch (mode) {
     case TopToBottomWritingMode:
@@ skipping 547 matching lines @@
 }
 
 void RenderFlexibleBox::prepareChildForPositionedLayout(RenderBox* child, LayoutUnit mainAxisOffset, LayoutUnit crossAxisOffset, PositionedLayoutMode layoutMode)
 {
     ASSERT(child->isOutOfFlowPositioned());
     child->containingBlock()->insertPositionedObject(child);
     RenderLayer* childLayer = child->layer();
     LayoutUnit inlinePosition = isColumnFlow() ? crossAxisOffset : mainAxisOffset;
     if (layoutMode == FlipForRowReverse && style()->flexDirection() == FlowRowReverse)
         inlinePosition = mainAxisExtent() - mainAxisOffset;
-    childLayer->setStaticInlinePosition(inlinePosition); // FIXME: Not right for regions.
+    childLayer->setStaticInlinePosition(inlinePosition);
 
     LayoutUnit staticBlockPosition = isColumnFlow() ? mainAxisOffset : crossAxisOffset;
     if (childLayer->staticBlockPosition() != staticBlockPosition) {
         childLayer->setStaticBlockPosition(staticBlockPosition);
         if (child->style()->hasStaticBlockPosition(style()->isHorizontalWritingMode()))
             child->setChildNeedsLayout(MarkOnlyThis);
     }
 }
 
 ItemPosition RenderFlexibleBox::alignmentForChild(RenderBox* child) const
@@ skipping 319 matching lines @@
             if (desiredLogicalHeight != child->logicalHeight()) {
                 child->setOverrideLogicalContentHeight(desiredLogicalHeight - child->borderAndPaddingLogicalHeight());
                 child->setLogicalHeight(0);
                 child->forceChildLayout();
             }
         }
     } else if (isColumnFlow() && child->style()->logicalWidth().isAuto()) {
         // FIXME: If the child doesn't have orthogonal flow, then it already has an override width set, so use it.
         if (hasOrthogonalFlow(child)) {
             LayoutUnit childWidth = std::max<LayoutUnit>(0, lineCrossAxisExtent - crossAxisMarginExtentForChild(child));
-            childWidth = child->constrainLogicalWidthInRegionByMinMax(childWidth, childWidth, this);
+            childWidth = child->constrainLogicalWidthByMinMax(childWidth, childWidth, this);
 
             if (childWidth != child->logicalWidth()) {
                 child->setOverrideLogicalContentWidth(childWidth - child->borderAndPaddingLogicalWidth());
                 child->forceChildLayout();
             }
         }
     }
 }
 
 void RenderFlexibleBox::flipForRightToLeftColumn()
@@ skipping 22 matching lines @@
             ASSERT(child);
             LayoutUnit lineCrossAxisExtent = lineContexts[lineNumber].crossAxisExtent;
             LayoutUnit originalOffset = lineContexts[lineNumber].crossAxisOffset - crossAxisStartEdge;
             LayoutUnit newOffset = contentExtent - originalOffset - lineCrossAxisExtent;
             adjustAlignmentForChild(child, newOffset - originalOffset);
         }
     }
 }
 
 }