Introduce VisiblePosition::isValid

third_party/WebKit/Source/core/editing/VisiblePosition.h

 /*
  * Copyright (C) 2004, 2008 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 64 matching lines @@
     // |createVisiblePositionDeprecated()|, we should not use |create()|.
     static VisiblePositionTemplate create(const PositionWithAffinityTemplate<Strategy>&);
 
     // Intentionally delete |operator==()| and |operator!=()| for reducing
     // compilation error message.
     // TODO(yosin) We'll have |equals()| when we have use cases of checking
     // equality of both position and affinity.
     bool operator==(const VisiblePositionTemplate&) const = delete;
     bool operator!=(const VisiblePositionTemplate&) const = delete;
 
+    bool isValid() const;
+
+    // TODO(xiaochengh): We should have |DCHECK(isValid())| in the following
+    // functions. However, there are some clients storing a VisiblePosition and
+    // inspecting its properties after mutation. This should be fixed.
     bool isNull() const { return m_positionWithAffinity.isNull(); }
     bool isNotNull() const { return m_positionWithAffinity.isNotNull(); }
     bool isOrphan() const { return deepEquivalent().isOrphan(); }
 
     PositionTemplate<Strategy> deepEquivalent() const { return m_positionWithAffinity.position(); }
     PositionTemplate<Strategy> toParentAnchoredPosition() const { return deepEquivalent().parentAnchoredEquivalent(); }
     PositionWithAffinityTemplate<Strategy> toPositionWithAffinity() const { return m_positionWithAffinity; }
     TextAffinity affinity() const { return m_positionWithAffinity.affinity(); }
 
     static VisiblePositionTemplate<Strategy> afterNode(Node*);
     static VisiblePositionTemplate<Strategy> beforeNode(Node*);
     static VisiblePositionTemplate<Strategy> firstPositionInNode(Node*);
     static VisiblePositionTemplate<Strategy> inParentAfterNode(const Node&);
     static VisiblePositionTemplate<Strategy> inParentBeforeNode(const Node&);
     static VisiblePositionTemplate<Strategy> lastPositionInNode(Node*);
 
     DEFINE_INLINE_TRACE()
     {
         visitor->trace(m_positionWithAffinity);
     }
 
 #ifndef NDEBUG
     void showTreeForThis() const;
 #endif
 
 private:
     explicit VisiblePositionTemplate(const PositionWithAffinityTemplate<Strategy>&);
 
     PositionWithAffinityTemplate<Strategy> m_positionWithAffinity;
+
+#if DCHECK_IS_ON()
+    uint64_t m_domTreeVersion;
+    uint64_t m_styleVersion;
+#endif
 };
 
 extern template class CORE_EXTERN_TEMPLATE_EXPORT VisiblePositionTemplate<EditingStrategy>;
 extern template class CORE_EXTERN_TEMPLATE_EXPORT VisiblePositionTemplate<EditingInFlatTreeStrategy>;
 
 using VisiblePosition = VisiblePositionTemplate<EditingStrategy>;
 using VisiblePositionInFlatTree = VisiblePositionTemplate<EditingInFlatTreeStrategy>;
 
 // |createVisiblePositionDeprecated| updates layout before creating the
 // VisiblePosition, which messes up the rendering pipeline. The callers should
@@ skipping 13 matching lines @@
 
 } // namespace blink
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 void showTree(const blink::VisiblePosition*);
 void showTree(const blink::VisiblePosition&);
 #endif
 
 #endif // VisiblePosition_h