[css-flexbox] Implement new abspos handling

third_party/WebKit/Source/core/layout/LayoutBlock.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2010. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 1206 matching lines @@
         if (!positionedObject->needsLayout())
             positionedObject->markForPaginationRelayoutIfNeeded(layoutScope);
 
         // FIXME: We should be able to do a r->setNeedsPositionedMovementLayout() here instead of a full layout. Need
         // to investigate why it does not trigger the correct invalidations in that case. crbug.com/350756
         if (info == ForcedLayoutAfterContainingBlockMoved)
             positionedObject->setNeedsLayout(LayoutInvalidationReason::AncestorMoved, MarkOnlyThis);
 
         positionedObject->layoutIfNeeded();
 
+        LayoutObject* parent = positionedObject->parent();
+        bool relaidOut = false;

[eae, 2016/04/25 02:37:28]

How about needsLayout or layoutChanged instead?

[cbiesinger, 2016/04/26 18:21:56]

Done, though I'm not certain I like this one either :-)

+        if (parent->isFlexibleBox() && toLayoutFlexibleBox(parent)->setStaticPositionForPositionedLayout(*positionedObject)) {
+            // The static position of an abspos child of a flexbox depends on its size (for example,
+            // they can be centered). So we may have to reposition the item after layout.
+            // TODO(cbiesinger): We could probably avoid a layout here and just reposition?
+            positionedObject->forceChildLayout();
+            relaidOut = true;
+        }
+
         // Lay out again if our estimate was wrong.
-        if (needsBlockDirectionLocationSetBeforeLayout && logicalTopEstimate != logicalTopForChild(*positionedObject))
+        if (!relaidOut && needsBlockDirectionLocationSetBeforeLayout && logicalTopEstimate != logicalTopForChild(*positionedObject))
             positionedObject->forceChildLayout();
     }
 }
 
 void LayoutBlock::markPositionedObjectsForLayout()
 {
     if (TrackedLayoutBoxListHashSet* positionedDescendants = positionedObjects()) {
         for (auto* descendant : *positionedDescendants)
             descendant->setChildNeedsLayout();
     }
@@ skipping 1593 matching lines @@
 void LayoutBlock::showLineTreeAndMark(const InlineBox* markedBox1, const char* markedLabel1, const InlineBox* markedBox2, const char* markedLabel2, const LayoutObject* obj) const
 {
     showLayoutObject();
     for (const RootInlineBox* root = firstRootBox(); root; root = root->nextRootBox())
         root->showLineTreeAndMark(markedBox1, markedLabel1, markedBox2, markedLabel2, obj, 1);
 }
 
 #endif
 
 } // namespace blink