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

/*
 * Copyright (C) 2004, 2006, 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
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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#ifndef Position_h
#define Position_h

#include "core/CoreExport.h"
#include "core/dom/ContainerNode.h"
#include "core/editing/EditingBoundary.h"
#include "core/editing/EditingStrategy.h"
#include "platform/heap/Handle.h"
#include "platform/text/TextDirection.h"
#include "wtf/Assertions.h"
#include "wtf/PassRefPtr.h"
#include "wtf/RefPtr.h"

namespace blink {

class Element;
class Node;
class LayoutObject;
class Text;
enum class TextAffinity;
class TreeScope;

enum class PositionAnchorType : unsigned {
  OffsetInAnchor,
  BeforeAnchor,
  AfterAnchor,
  BeforeChildren,
  AfterChildren,
};

// Instances of |PositionTemplate<Strategy>| are immutable.
template <typename Strategy>
class CORE_TEMPLATE_CLASS_EXPORT PositionTemplate {
  DISALLOW_NEW();

 public:
  PositionTemplate()
      : m_offset(0), m_anchorType(PositionAnchorType::OffsetInAnchor) {}

  static const TreeScope* commonAncestorTreeScope(
      const PositionTemplate<Strategy>&,
      const PositionTemplate<Strategy>& b);
  static PositionTemplate<Strategy> editingPositionOf(Node* anchorNode,
                                                      int offset);

  // For creating before/after positions:
  PositionTemplate(Node* anchorNode, PositionAnchorType);

  // For creating offset positions:
  // FIXME: This constructor should eventually go away. See bug 63040.
  PositionTemplate(Node* anchorNode, int offset);

  PositionTemplate(const PositionTemplate&);

  PositionAnchorType anchorType() const { return m_anchorType; }
  bool isAfterAnchor() const {
    return m_anchorType == PositionAnchorType::AfterAnchor;
  }
  bool isAfterChildren() const {
    return m_anchorType == PositionAnchorType::AfterChildren;
  }
  bool isBeforeAnchor() const {
    return m_anchorType == PositionAnchorType::BeforeAnchor;
  }
  bool isBeforeChildren() const {
    return m_anchorType == PositionAnchorType::BeforeChildren;
  }
  bool isOffsetInAnchor() const {
    return m_anchorType == PositionAnchorType::OffsetInAnchor;
  }

  // These are always DOM compliant values.  Editing positions like [img, 0]
  // (aka [img, before]) will return img->parentNode() and img->nodeIndex() from
  // these functions.

  // null for a before/after position anchored to a node with no parent
  Node* computeContainerNode() const;

  // O(n) for before/after-anchored positions, O(1) for parent-anchored
  // positions
  int computeOffsetInContainerNode() const;

  // Convenience method for DOM positions that also fixes up some positions for
  // editing
  PositionTemplate<Strategy> parentAnchoredEquivalent() const;

  // Returns |PositionIsAnchor| type |Position| which is compatible with
  // |RangeBoundaryPoint| as safe to pass |Range| constructor. Return value
  // of this function is different from |parentAnchoredEquivalent()| which
  // returns editing specific position.
  PositionTemplate<Strategy> toOffsetInAnchor() const;

  // Inline O(1) access for Positions which callers know to be parent-anchored
  int offsetInContainerNode() const {
    DCHECK(isOffsetInAnchor());
    return m_offset;
  }

  // Returns an offset for editing based on anchor type for using with
  // |anchorNode()| function:
  //   - OffsetInAnchor  m_offset
  //   - BeforeChildren  0
  //   - BeforeAnchor    0
  //   - AfterChildren   last editing offset in anchor node
  //   - AfterAnchor     last editing offset in anchor node
  // Editing operations will change in anchor node rather than nodes around
  // anchor node.
  int computeEditingOffset() const;

  // These are convenience methods which are smart about whether the position is
  // neighbor anchored or parent anchored
  Node* computeNodeBeforePosition() const;
  Node* computeNodeAfterPosition() const;

  // Returns node as |Range::firstNode()|. This position must be a
  // |PositionAnchorType::OffsetInAhcor| to behave as |Range| boundary point.
  Node* nodeAsRangeFirstNode() const;

  // Similar to |nodeAsRangeLastNode()|, but returns a node in a range.
  Node* nodeAsRangeLastNode() const;

  // Returns a node as past last as same as |Range::pastLastNode()|. This
  // function is supposed to used in HTML serialization and plain text
  // iterator. This position must be a |PositionAnchorType::OffsetInAhcor| to
  // behave as |Range| boundary point.
  Node* nodeAsRangePastLastNode() const;

  Node* commonAncestorContainer(const PositionTemplate<Strategy>&) const;

  Node* anchorNode() const { return m_anchorNode.get(); }

  Document* document() const {
    return m_anchorNode ? &m_anchorNode->document() : 0;
  }
  bool isConnected() const {
    return m_anchorNode && m_anchorNode->isConnected();
  }

  bool isNull() const { return !m_anchorNode; }
  bool isNotNull() const { return m_anchorNode; }
  bool isOrphan() const { return m_anchorNode && !m_anchorNode->isConnected(); }

  // Note: Comparison of positions require both parameters are non-null. You
  // should check null-position before comparing them.
  // TODO(yosin): We should use |Position::operator<()| instead of
  // |Position::comapreTo()| to utilize |DHCECK_XX()|.
  int compareTo(const PositionTemplate<Strategy>&) const;
  bool operator<(const PositionTemplate<Strategy>&) const;
  bool operator<=(const PositionTemplate<Strategy>&) const;
  bool operator>(const PositionTemplate<Strategy>&) const;
  bool operator>=(const PositionTemplate<Strategy>&) const;

  // These can be either inside or just before/after the node, depending on
  // if the node is ignored by editing or not.
  // FIXME: These should go away. They only make sense for legacy positions.
  bool atFirstEditingPositionForNode() const;
  bool atLastEditingPositionForNode() const;

  bool atStartOfTree() const;
  bool atEndOfTree() const;

  static PositionTemplate<Strategy> beforeNode(Node* anchorNode);
  static PositionTemplate<Strategy> afterNode(Node* anchorNode);
  static PositionTemplate<Strategy> inParentBeforeNode(const Node& anchorNode);
  static PositionTemplate<Strategy> inParentAfterNode(const Node& anchorNode);
  static int lastOffsetInNode(Node* anchorNode);
  static PositionTemplate<Strategy> firstPositionInNode(Node* anchorNode);
  static PositionTemplate<Strategy> lastPositionInNode(Node* anchorNode);
  static int minOffsetForNode(Node* anchorNode, int offset);
  static PositionTemplate<Strategy> firstPositionInOrBeforeNode(
      Node* anchorNode);
  static PositionTemplate<Strategy> lastPositionInOrAfterNode(Node* anchorNode);

  String toAnchorTypeAndOffsetString() const;
#ifndef NDEBUG
  void showTreeForThis() const;
  void showTreeForThisInFlatTree() const;
#endif

  DEFINE_INLINE_TRACE() { visitor->trace(m_anchorNode); }

 private:
  bool isAfterAnchorOrAfterChildren() const {
    return isAfterAnchor() || isAfterChildren();
  }

  Member<Node> m_anchorNode;
  // m_offset can be the offset inside m_anchorNode, or if
  // editingIgnoresContent(m_anchorNode) returns true, then other places in
  // editing will treat m_offset == 0 as "before the anchor" and m_offset > 0 as
  // "after the anchor node".  See parentAnchoredEquivalent for more info.
  int m_offset;
  PositionAnchorType m_anchorType;
};

extern template class CORE_EXTERN_TEMPLATE_EXPORT
    PositionTemplate<EditingStrategy>;
extern template class CORE_EXTERN_TEMPLATE_EXPORT
    PositionTemplate<EditingInFlatTreeStrategy>;

using Position = PositionTemplate<EditingStrategy>;
using PositionInFlatTree = PositionTemplate<EditingInFlatTreeStrategy>;

template <typename Strategy>
bool operator==(const PositionTemplate<Strategy>& a,
                const PositionTemplate<Strategy>& b) {
  if (a.isNull())
    return b.isNull();

  if (a.anchorNode() != b.anchorNode() || a.anchorType() != b.anchorType())
    return false;

  if (!a.isOffsetInAnchor()) {
    // Note: |m_offset| only has meaning when
    // |PositionAnchorType::OffsetInAnchor|.
    return true;
  }

  // FIXME: In <div><img></div> [div, 0] != [img, 0] even though most of the
  // editing code will treat them as identical.
  return a.offsetInContainerNode() == b.offsetInContainerNode();
}

template <typename Strategy>
bool operator!=(const PositionTemplate<Strategy>& a,
                const PositionTemplate<Strategy>& b) {
  return !(a == b);
}

CORE_EXPORT PositionInFlatTree toPositionInFlatTree(const Position&);
CORE_EXPORT Position toPositionInDOMTree(const Position&);
CORE_EXPORT Position toPositionInDOMTree(const PositionInFlatTree&);

template <typename Strategy>
PositionTemplate<Strategy> fromPositionInDOMTree(const Position&);

template <>
inline Position fromPositionInDOMTree<EditingStrategy>(
    const Position& position) {
  return position;
}

template <>
inline PositionInFlatTree fromPositionInDOMTree<EditingInFlatTreeStrategy>(
    const Position& position) {
  return toPositionInFlatTree(position);
}

CORE_EXPORT std::ostream& operator<<(std::ostream&, PositionAnchorType);
CORE_EXPORT std::ostream& operator<<(std::ostream&, const Position&);
CORE_EXPORT std::ostream& operator<<(std::ostream&, const PositionInFlatTree&);

}  // namespace blink

#ifndef NDEBUG
// Outside the WebCore namespace for ease of invocation from gdb.
void showTree(const blink::Position&);
void showTree(const blink::Position*);
#endif

#endif  // Position_h