Invalidate objects when containing block changed

third_party/WebKit/Source/core/layout/LayoutObject.h

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2004 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Google Inc. 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
@@ skipping 752 matching lines @@
     // This function should be used for any invalidation as it would correctly
     // walk the containing block chain. See e.g. markContainerChainForLayout.
     // It is also used for correctly sizing absolutely positioned elements
     // (point 3 above).
     //
     // If |paintInvalidationContainer| and |paintInvalidationContainerSkipped|
     // are not null, on return *paintInvalidationContainerSkipped is true if
     // the layoutObject returned is an ancestor of |paintInvalidationContainer|.
     LayoutObject* container(const LayoutBoxModelObject* paintInvalidationContainer = nullptr, bool* paintInvalidationContainerSkipped = nullptr) const;
     LayoutObject* containerCrossingFrameBoundaries() const;
+    // Finds the container as if this object is a fixed position element.

[chrishtr, 2015/10/30 18:28:18]

Is it ever called for an object which is not fixed position?

[Xianzhu, 2015/10/30 19:15:28]

Now LayoutBlock::styleWillChange() calls this to find the current containing
block of its fixed-position descendants. The block may become a containing
block, so it needs to find the original containing block of the descendants and
change their containing block relationships.

Now the method works in the similar way as containingBlockForAbsolutePosition()
which also doesn't require the caller is absolute-position.

     LayoutBlock* containerForFixedPosition(const LayoutBoxModelObject* paintInvalidationContainer = nullptr, bool* paintInvalidationContainerSkipped = nullptr) const;
     LayoutBlock* containingBlockForAbsolutePosition() const;
 
     virtual LayoutObject* hoverAncestor() const { return parent(); }
 
     Element* offsetParent() const;
 
     void markContainerChainForLayout(bool scheduleRelayout = true, SubtreeLayoutScope* = nullptr);
     void setNeedsLayout(LayoutInvalidationReasonForTracing, MarkingBehavior = MarkContainerChain, SubtreeLayoutScope* = nullptr);
     void setNeedsLayoutAndFullPaintInvalidation(LayoutInvalidationReasonForTracing, MarkingBehavior = MarkContainerChain, SubtreeLayoutScope* = nullptr);
@@ skipping 714 matching lines @@
     // FIXME: This should be 'markContaingBoxChainForOverflowRecalc when we make LayoutBox
     // recomputeOverflow-capable. crbug.com/437012 and crbug.com/434700.
     inline void markContainingBlocksForOverflowRecalc();
 
     inline void markContainerChainForPaintInvalidation();
 
     inline void invalidateSelectionIfNeeded(const LayoutBoxModelObject&, PaintInvalidationReason);
 
     inline void invalidateContainerPreferredLogicalWidths();
 
-    void invalidatePaintOfPreviousPaintInvalidationRect(const LayoutBoxModelObject& paintInvalidationContainer, PaintInvalidationReason) const;
+    void invalidatePaintOfPreviousPaintInvalidationRect(const LayoutBoxModelObject& paintInvalidationContainer, PaintInvalidationReason);
 
     LayoutRect previousSelectionRectForPaintInvalidation() const;
     void setPreviousSelectionRectForPaintInvalidation(const LayoutRect&);
 
     LayoutObject* containerForAbsolutePosition(const LayoutBoxModelObject* paintInvalidationContainer = nullptr, bool* paintInvalidationContainerSkipped = nullptr) const;
 
     const LayoutBoxModelObject* enclosingCompositedContainer() const;
 
     LayoutFlowThread* locateFlowThreadContainingBlock() const;
     void removeFromLayoutFlowThreadRecursive(LayoutFlowThread*);
@@ skipping 522 matching lines @@
 void showTree(const blink::LayoutObject*);
 void showLineTree(const blink::LayoutObject*);
 void showLayoutTree(const blink::LayoutObject* object1);
 // We don't make object2 an optional parameter so that showLayoutTree
 // can be called from gdb easily.
 void showLayoutTree(const blink::LayoutObject* object1, const blink::LayoutObject* object2);
 
 #endif
 
 #endif // LayoutObject_h