Support for multiple block fragments in getClientRects().

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

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef FragmentainerIterator_h
 #define FragmentainerIterator_h
 
 #include "core/layout/LayoutFlowThread.h"
 
 namespace blink {
 
 class MultiColumnFragmentainerGroup;
 
 // Used to find the fragmentainers that intersect with a given portion of the flow thread. The
 // portion typically corresponds to the bounds of some descendant layout object. The iterator walks
 // in block direction order.
 class FragmentainerIterator {
 public:
-    FragmentainerIterator(const LayoutFlowThread&, const LayoutRect& physicalBoundingBoxInFlowThread, const LayoutRect& clipRectInMulticolContainer);
+    // Initialize the iterator, and move to the first fragmentainer of interest.
+    // The clip rectangle is optional. If it's empty, it means that no clipping will be performed,
+    // and that the only thing that can limit the set of fragmentainers to visit is
+    // |physicalBoundingBox|.
+    FragmentainerIterator(const LayoutFlowThread&, const LayoutRect& physicalBoundingBoxInFlowThread, const LayoutRect& clipRectInMulticolContainer = LayoutRect());
 
     // Advance to the next fragmentainer. Not allowed to call this if atEnd() is true.
     void advance();
 
     // Return true if we have walked through all relevant fragmentainers.
     bool atEnd() const { return !m_currentColumnSet; }
 
     // The physical translation to apply to shift the box when converting from flowthread to visual
     // coordinates.
-    LayoutSize paginationOffset() const { DCHECK(!atEnd()); return m_paginationOffset; }
+    LayoutSize paginationOffset() const;
+
+    // Return the physical content box of the current fragmentainer, relative to the flow thread.
+    LayoutRect fragmentainerInFlowThread() const;
 
     // Return the physical clip rectangle of the current fragmentainer, relative to the flow thread.
-    LayoutRect clipRectInFlowThread() const { DCHECK(!atEnd()); return m_clipRectInFlowThread; }
+    LayoutRect clipRectInFlowThread() const;
 
 private:
     const LayoutFlowThread& m_flowThread;
     const LayoutRect m_clipRectInMulticolContainer;
 
     const LayoutMultiColumnSet* m_currentColumnSet;
     unsigned m_currentFragmentainerGroupIndex;
     unsigned m_currentFragmentainerIndex;
     unsigned m_endFragmentainerIndex;
 
     LayoutUnit m_logicalTopInFlowThread;
     LayoutUnit m_logicalBottomInFlowThread;
 
-    LayoutSize m_paginationOffset;
-    LayoutRect m_clipRectInFlowThread;
-
     const MultiColumnFragmentainerGroup& currentGroup() const;
     void moveToNextFragmentainerGroup();
     bool setFragmentainersOfInterest();
-    void updateOutput();
     void setAtEnd() { m_currentColumnSet = nullptr; }
+    bool hasClipRect() const { return !m_clipRectInMulticolContainer.isEmpty(); }
 };
 
 } // namespace blink
 
 #endif // FragmentainerIterator_h