Unify implementation of LeftPositionOf() and RightPositionOf()

third_party/WebKit/Source/core/editing/SelectionModifierCharacter.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 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
@@ skipping 23 matching lines @@
 #include "core/editing/VisibleUnits.h"
 #include "core/layout/api/LineLayoutAPIShim.h"
 #include "core/layout/api/LineLayoutItem.h"
 #include "core/layout/line/InlineTextBox.h"
 #include "core/layout/line/RootInlineBox.h"
 
 namespace blink {
 
 namespace {
 
+// The traversal strategy for |LeftPositionOf()|.
 template <typename Strategy>
-static PositionTemplate<Strategy> LeftVisuallyDistinctCandidate(
+struct TraversalLeft {
+  STATIC_ONLY(TraversalLeft);
+
+  static InlineBox* BackwardLeafChildOf(const InlineBox& box) {
+    return box.NextLeafChild();
+  }
+
+  static int CaretEndOffsetOf(const InlineBox& box) {
+    return box.CaretRightmostOffset();
+  }
+
+  static int CaretMinOffsetOf(TextDirection direction, const InlineBox& box) {
+    if (direction == TextDirection::kLtr)
+      return box.CaretMinOffset();
+    return box.CaretMaxOffset();
+  }
+
+  static int CaretStartOffsetOf(const InlineBox& box) {
+    return box.CaretLeftmostOffset();
+  }
+
+  static int ForwardGraphemeBoundaryOf(TextDirection direction,
+                                       Node* node,
+                                       int offset) {
+    if (direction == TextDirection::kLtr)
+      return PreviousGraphemeBoundaryOf(node, offset);
+    return NextGraphemeBoundaryOf(node, offset);
+  }
+
+  static InlineBox* ForwardLeafChildOf(const InlineBox& box) {
+    return box.PrevLeafChild();
+  }
+
+  static InlineBox* ForwardLeafChildIgnoringLineBreakOf(const InlineBox& box) {
+    return box.PrevLeafChildIgnoringLineBreak();
+  }
+
+  static PositionTemplate<Strategy> ForwardVisuallyDistinctCandidateOf(
+      TextDirection direction,
+      const PositionTemplate<Strategy>& position) {
+    if (direction == TextDirection::kLtr)
+      return PreviousVisuallyDistinctCandidate(position);
+    return NextVisuallyDistinctCandidate(position);
+  }
+
+  static VisiblePositionTemplate<Strategy> HonorEditingBoundary(
+      TextDirection direction,
+      const VisiblePositionTemplate<Strategy>& visible_position,
+      const PositionTemplate<Strategy>& anchor) {
+    if (direction == TextDirection::kLtr)
+      return HonorEditingBoundaryAtOrBefore(visible_position, anchor);
+    return HonorEditingBoundaryAtOrAfter(visible_position, anchor);
+  }
+
+  static Node* LogicalStartBoxOf(TextDirection direction,
+                                 const InlineBox& box,
+                                 InlineBox*& result_box) {
+    if (direction == TextDirection::kLtr)
+      return box.Root().GetLogicalStartBoxWithNode(result_box);
+    return box.Root().GetLogicalEndBoxWithNode(result_box);
+  }
+
+  static bool IsOvershot(int offset, const InlineBox& box) {
+    if (box.IsLeftToRightDirection())
+      return offset < box.CaretMinOffset();
+    return offset > box.CaretMaxOffset();
+  }
+};
+
+// The traversal strategy for |RightPositionOf()|.
+template <typename Strategy>
+struct TraversalRight {
+  STATIC_ONLY(TraversalRight);
+
+  static InlineBox* BackwardLeafChildOf(const InlineBox& box) {
+    return box.PrevLeafChild();
+  }
+
+  static int CaretEndOffsetOf(const InlineBox& box) {
+    return box.CaretLeftmostOffset();
+  }
+
+  static int CaretMinOffsetOf(TextDirection direction, const InlineBox& box) {
+    if (direction == TextDirection::kLtr)
+      return box.CaretMaxOffset();
+    return box.CaretMinOffset();
+  }
+
+  static int CaretStartOffsetOf(const InlineBox& box) {
+    return box.CaretRightmostOffset();
+  }
+
+  static int ForwardGraphemeBoundaryOf(TextDirection direction,
+                                       Node* node,
+                                       int offset) {
+    if (direction == TextDirection::kLtr)
+      return NextGraphemeBoundaryOf(node, offset);
+    return PreviousGraphemeBoundaryOf(node, offset);
+  }
+
+  static InlineBox* ForwardLeafChildOf(const InlineBox& box) {
+    return box.NextLeafChild();
+  }
+
+  static InlineBox* ForwardLeafChildIgnoringLineBreakOf(const InlineBox& box) {
+    return box.NextLeafChildIgnoringLineBreak();
+  }
+
+  static PositionTemplate<Strategy> ForwardVisuallyDistinctCandidateOf(
+      TextDirection direction,
+      const PositionTemplate<Strategy>& position) {
+    if (direction == TextDirection::kLtr)
+      return NextVisuallyDistinctCandidate(position);
+    return PreviousVisuallyDistinctCandidate(position);
+  }
+
+  static VisiblePositionTemplate<Strategy> HonorEditingBoundary(
+      TextDirection direction,
+      const VisiblePositionTemplate<Strategy>& visible_position,
+      const PositionTemplate<Strategy>& anchor) {
+    if (direction == TextDirection::kLtr)
+      return HonorEditingBoundaryAtOrAfter(visible_position, anchor);
+    return HonorEditingBoundaryAtOrBefore(visible_position, anchor);
+  }
+
+  static Node* LogicalStartBoxOf(TextDirection direction,
+                                 const InlineBox& box,
+                                 InlineBox*& result_box) {
+    if (direction == TextDirection::kLtr)
+      return box.Root().GetLogicalEndBoxWithNode(result_box);
+    return box.Root().GetLogicalStartBoxWithNode(result_box);
+  }
+
+  static bool IsOvershot(int offset, const InlineBox& box) {
+    if (box.IsLeftToRightDirection())
+      return offset > box.CaretMaxOffset();
+    return offset < box.CaretMinOffset();
+  }
+};
+
+// TODO(yosin): We should rename local variables in

[Xiaocheng, 2017/06/12 18:28:15]

nit: And also comments.

[yosin_UTC9, 2017/06/13 06:44:46]

Done.

+// |TraverseInternalAlgorithm()| to generic name based on |Traversal| instead of
+// assuming right-to-left traversal.
+template <typename Strategy, typename Traversal>
+static PositionTemplate<Strategy> TraverseInternalAlgorithm(
     const VisiblePositionTemplate<Strategy>& visible_position) {
   DCHECK(visible_position.IsValid()) << visible_position;
   const PositionTemplate<Strategy> deep_position =
       visible_position.DeepEquivalent();
   PositionTemplate<Strategy> p = deep_position;
 
   if (p.IsNull())
     return PositionTemplate<Strategy>();
 
   const PositionTemplate<Strategy> downstream_start =
       MostForwardCaretPosition(p);
   const TextDirection primary_direction = PrimaryDirectionOf(*p.AnchorNode());
   const TextAffinity affinity = visible_position.Affinity();
 
   while (true) {
     InlineBoxPosition box_position =
         ComputeInlineBoxPosition(p, affinity, primary_direction);
     InlineBox* box = box_position.inline_box;
     int offset = box_position.offset_in_box;
     if (!box) {
-      return primary_direction == TextDirection::kLtr
-                 ? PreviousVisuallyDistinctCandidate(deep_position)
-                 : NextVisuallyDistinctCandidate(deep_position);
+      return Traversal::ForwardVisuallyDistinctCandidateOf(primary_direction,
+                                                           deep_position);
     }
     LineLayoutItem line_layout_item = box->GetLineLayoutItem();
 
     while (true) {
       if ((line_layout_item.IsAtomicInlineLevel() || line_layout_item.IsBR()) &&
-          offset == box->CaretRightmostOffset()) {
-        return box->IsLeftToRightDirection()
-                   ? PreviousVisuallyDistinctCandidate(deep_position)
-                   : NextVisuallyDistinctCandidate(deep_position);
+          offset == Traversal::CaretEndOffsetOf(*box)) {
+        return Traversal::ForwardVisuallyDistinctCandidateOf(box->Direction(),
+                                                             deep_position);
       }
       if (!line_layout_item.GetNode()) {
-        box = box->PrevLeafChild();
+        box = Traversal::ForwardLeafChildOf(*box);
         if (!box) {
-          return primary_direction == TextDirection::kLtr
-                     ? PreviousVisuallyDistinctCandidate(deep_position)
-                     : NextVisuallyDistinctCandidate(deep_position);
+          return Traversal::ForwardVisuallyDistinctCandidateOf(
+              primary_direction, deep_position);
         }
         line_layout_item = box->GetLineLayoutItem();
-        offset = box->CaretRightmostOffset();
+        offset = Traversal::CaretEndOffsetOf(*box);
         continue;
       }
 
-      offset =
-          box->IsLeftToRightDirection()
-              ? PreviousGraphemeBoundaryOf(line_layout_item.GetNode(), offset)
-              : NextGraphemeBoundaryOf(line_layout_item.GetNode(), offset);
+      offset = Traversal::ForwardGraphemeBoundaryOf(
+          box->Direction(), line_layout_item.GetNode(), offset);
 
       const int caret_min_offset = box->CaretMinOffset();
       const int caret_max_offset = box->CaretMaxOffset();
 
       if (offset > caret_min_offset && offset < caret_max_offset)
         break;
 
-      if (box->IsLeftToRightDirection() ? offset < caret_min_offset
-                                        : offset > caret_max_offset) {
+      if (Traversal::IsOvershot(offset, *box)) {
         // Overshot to the left.

[Xiaocheng, 2017/06/12 18:28:15]

Like this.

[yosin_UTC9, 2017/06/13 06:44:46]

Good catch!

-        InlineBox* const prev_box = box->PrevLeafChildIgnoringLineBreak();
+        InlineBox* const prev_box =
+            Traversal::ForwardLeafChildIgnoringLineBreakOf(*box);
         if (!prev_box) {
-          PositionTemplate<Strategy> position_on_left =
-              primary_direction == TextDirection::kLtr
-                  ? PreviousVisuallyDistinctCandidate(
-                        visible_position.DeepEquivalent())
-                  : NextVisuallyDistinctCandidate(
-                        visible_position.DeepEquivalent());
+          const PositionTemplate<Strategy>& position_on_left =
+              Traversal::ForwardVisuallyDistinctCandidateOf(
+                  primary_direction, visible_position.DeepEquivalent());
           if (position_on_left.IsNull())
             return PositionTemplate<Strategy>();
 
           InlineBox* box_on_left =
               ComputeInlineBoxPosition(position_on_left, affinity,
                                        primary_direction)
                   .inline_box;
           if (box_on_left && box_on_left->Root() == box->Root())
             return PositionTemplate<Strategy>();
           return position_on_left;
         }
 
         // Reposition at the other logical position corresponding to our
         // edge's visual position and go for another round.
         box = prev_box;
         line_layout_item = box->GetLineLayoutItem();
-        offset = prev_box->CaretRightmostOffset();
+        offset = Traversal::CaretEndOffsetOf(*prev_box);
         continue;
       }
 
-      DCHECK_EQ(offset, box->CaretLeftmostOffset());
+      DCHECK_EQ(offset, Traversal::CaretStartOffsetOf(*box));
 
       unsigned char level = box->BidiLevel();
-      InlineBox* prev_box = box->PrevLeafChild();
+      InlineBox* prev_box = Traversal::ForwardLeafChildOf(*box);
 
       if (box->Direction() == primary_direction) {
         if (!prev_box) {
           InlineBox* logical_start = nullptr;
-          if (primary_direction == TextDirection::kLtr
-                  ? box->Root().GetLogicalStartBoxWithNode(logical_start)
-                  : box->Root().GetLogicalEndBoxWithNode(logical_start)) {
+          if (Traversal::LogicalStartBoxOf(primary_direction, *box,
+                                           logical_start)) {
             box = logical_start;
             line_layout_item = box->GetLineLayoutItem();
-            offset = primary_direction == TextDirection::kLtr
-                         ? box->CaretMinOffset()
-                         : box->CaretMaxOffset();
+            offset = Traversal::CaretMinOffsetOf(primary_direction, *box);
           }
           break;
         }
         if (prev_box->BidiLevel() >= level)
           break;
 
         level = prev_box->BidiLevel();
 
         InlineBox* next_box = box;
         do {
-          next_box = next_box->NextLeafChild();
+          next_box = Traversal::BackwardLeafChildOf(*next_box);
         } while (next_box && next_box->BidiLevel() > level);
 
         if (next_box && next_box->BidiLevel() == level)
           break;
 
         box = prev_box;
         line_layout_item = box->GetLineLayoutItem();
-        offset = box->CaretRightmostOffset();
+        offset = Traversal::CaretEndOffsetOf(*box);
         if (box->Direction() == primary_direction)
           break;
         continue;
       }
 
       while (prev_box && !prev_box->GetLineLayoutItem().GetNode())
-        prev_box = prev_box->PrevLeafChild();
+        prev_box = Traversal::ForwardLeafChildOf(*prev_box);
 
       if (prev_box) {
         box = prev_box;
         line_layout_item = box->GetLineLayoutItem();
-        offset = box->CaretRightmostOffset();
+        offset = Traversal::CaretEndOffsetOf(*box);
         if (box->BidiLevel() > level) {
           do {
-            prev_box = prev_box->PrevLeafChild();
+            prev_box = Traversal::ForwardLeafChildOf(*prev_box);
           } while (prev_box && prev_box->BidiLevel() > level);
 
           if (!prev_box || prev_box->BidiLevel() < level)
             continue;
         }
       } else {
         // Trailing edge of a secondary run. Set to the leading edge of
         // the entire run.
         while (true) {
-          while (InlineBox* next_box = box->NextLeafChild()) {
+          while (InlineBox* next_box = Traversal::BackwardLeafChildOf(*box)) {
             if (next_box->BidiLevel() < level)
               break;
             box = next_box;
           }
           if (box->BidiLevel() == level)
             break;
           level = box->BidiLevel();
-          while (InlineBox* prev_box = box->PrevLeafChild()) {
+          while (InlineBox* prev_box = Traversal::ForwardLeafChildOf(*box)) {
             if (prev_box->BidiLevel() < level)
               break;
             box = prev_box;
           }
           if (box->BidiLevel() == level)
             break;
           level = box->BidiLevel();
         }
         line_layout_item = box->GetLineLayoutItem();
-        offset = primary_direction == TextDirection::kLtr
-                     ? box->CaretMinOffset()
-                     : box->CaretMaxOffset();
+        offset = Traversal::CaretMinOffsetOf(primary_direction, *box);
       }
       break;
     }
 
     p = PositionTemplate<Strategy>::EditingPositionOf(
         line_layout_item.GetNode(), offset);
 
     if ((IsVisuallyEquivalentCandidate(p) &&
          MostForwardCaretPosition(p) != downstream_start) ||
         p.AtStartOfTree() || p.AtEndOfTree())
       return p;
 
     DCHECK_NE(p, deep_position);
   }
 }
 
-template <typename Strategy>
-VisiblePositionTemplate<Strategy> LeftPositionOfAlgorithm(
+template <typename Strategy, typename Traversal>
+VisiblePositionTemplate<Strategy> TraverseAlgorithm(
     const VisiblePositionTemplate<Strategy>& visible_position) {
   DCHECK(visible_position.IsValid()) << visible_position;
   const PositionTemplate<Strategy> pos =
-      LeftVisuallyDistinctCandidate(visible_position);
+      TraverseInternalAlgorithm<Strategy, Traversal>(visible_position);
   // TODO(yosin) Why can't we move left from the last position in a tree?
   if (pos.AtStartOfTree() || pos.AtEndOfTree())
     return VisiblePositionTemplate<Strategy>();
 
-  const VisiblePositionTemplate<Strategy> left = CreateVisiblePosition(pos);
-  DCHECK_NE(left.DeepEquivalent(), visible_position.DeepEquivalent());
+  const VisiblePositionTemplate<Strategy> result = CreateVisiblePosition(pos);
+  DCHECK_NE(result.DeepEquivalent(), visible_position.DeepEquivalent());
 
-  return DirectionOfEnclosingBlockOf(left.DeepEquivalent()) ==
-                 TextDirection::kLtr
-             ? HonorEditingBoundaryAtOrBefore(left,
-                                              visible_position.DeepEquivalent())
-             : HonorEditingBoundaryAtOrAfter(left,
-                                             visible_position.DeepEquivalent());
-}
-
-template <typename Strategy>
-PositionTemplate<Strategy> RightVisuallyDistinctCandidate(
-    const VisiblePositionTemplate<Strategy>& visible_position) {
-  DCHECK(visible_position.IsValid()) << visible_position;
-  const PositionTemplate<Strategy> deep_position =
-      visible_position.DeepEquivalent();
-  PositionTemplate<Strategy> p = deep_position;
-  if (p.IsNull())
-    return PositionTemplate<Strategy>();
-
-  const PositionTemplate<Strategy> downstream_start =
-      MostForwardCaretPosition(p);
-  const TextDirection primary_direction = PrimaryDirectionOf(*p.AnchorNode());
-  const TextAffinity affinity = visible_position.Affinity();
-
-  while (true) {
-    InlineBoxPosition box_position =
-        ComputeInlineBoxPosition(p, affinity, primary_direction);
-    InlineBox* box = box_position.inline_box;
-    int offset = box_position.offset_in_box;
-    if (!box) {
-      return primary_direction == TextDirection::kLtr
-                 ? NextVisuallyDistinctCandidate(deep_position)
-                 : PreviousVisuallyDistinctCandidate(deep_position);
-    }
-    LayoutObject* layout_object =
-        LineLayoutAPIShim::LayoutObjectFrom(box->GetLineLayoutItem());
-
-    while (true) {
-      if ((layout_object->IsAtomicInlineLevel() || layout_object->IsBR()) &&
-          offset == box->CaretLeftmostOffset()) {
-        return box->IsLeftToRightDirection()
-                   ? NextVisuallyDistinctCandidate(deep_position)
-                   : PreviousVisuallyDistinctCandidate(deep_position);
-      }
-      if (!layout_object->GetNode()) {
-        box = box->NextLeafChild();
-        if (!box) {
-          return primary_direction == TextDirection::kLtr
-                     ? NextVisuallyDistinctCandidate(deep_position)
-                     : PreviousVisuallyDistinctCandidate(deep_position);
-        }
-        layout_object =
-            LineLayoutAPIShim::LayoutObjectFrom(box->GetLineLayoutItem());
-        offset = box->CaretLeftmostOffset();
-        continue;
-      }
-
-      offset =
-          box->IsLeftToRightDirection()
-              ? NextGraphemeBoundaryOf(layout_object->GetNode(), offset)
-              : PreviousGraphemeBoundaryOf(layout_object->GetNode(), offset);
-
-      const int caret_min_offset = box->CaretMinOffset();
-      const int caret_max_offset = box->CaretMaxOffset();
-
-      if (offset > caret_min_offset && offset < caret_max_offset)
-        break;
-
-      if (box->IsLeftToRightDirection() ? offset > caret_max_offset
-                                        : offset < caret_min_offset) {
-        // Overshot to the right.
-        InlineBox* const next_box = box->NextLeafChildIgnoringLineBreak();
-        if (!next_box) {
-          PositionTemplate<Strategy> position_on_right =
-              primary_direction == TextDirection::kLtr
-                  ? NextVisuallyDistinctCandidate(deep_position)
-                  : PreviousVisuallyDistinctCandidate(deep_position);
-          if (position_on_right.IsNull())
-            return PositionTemplate<Strategy>();
-
-          InlineBox* box_on_right =
-              ComputeInlineBoxPosition(position_on_right, affinity,
-                                       primary_direction)
-                  .inline_box;
-          if (box_on_right && box_on_right->Root() == box->Root())
-            return PositionTemplate<Strategy>();
-          return position_on_right;
-        }
-
-        // Reposition at the other logical position corresponding to our
-        // edge's visual position and go for another round.
-        box = next_box;
-        layout_object =
-            LineLayoutAPIShim::LayoutObjectFrom(box->GetLineLayoutItem());
-        offset = next_box->CaretLeftmostOffset();
-        continue;
-      }
-
-      DCHECK_EQ(offset, box->CaretRightmostOffset());
-
-      unsigned char level = box->BidiLevel();
-      InlineBox* next_box = box->NextLeafChild();
-
-      if (box->Direction() == primary_direction) {
-        if (!next_box) {
-          InlineBox* logical_end = nullptr;
-          if (primary_direction == TextDirection::kLtr
-                  ? box->Root().GetLogicalEndBoxWithNode(logical_end)
-                  : box->Root().GetLogicalStartBoxWithNode(logical_end)) {
-            box = logical_end;
-            layout_object =
-                LineLayoutAPIShim::LayoutObjectFrom(box->GetLineLayoutItem());
-            offset = primary_direction == TextDirection::kLtr
-                         ? box->CaretMaxOffset()
-                         : box->CaretMinOffset();
-          }
-          break;
-        }
-
-        if (next_box->BidiLevel() >= level)
-          break;
-
-        level = next_box->BidiLevel();
-
-        InlineBox* prev_box = box;
-        do {
-          prev_box = prev_box->PrevLeafChild();
-        } while (prev_box && prev_box->BidiLevel() > level);
-
-        // For example, abc FED 123 ^ CBA
-        if (prev_box && prev_box->BidiLevel() == level)
-          break;
-
-        // For example, abc 123 ^ CBA or 123 ^ CBA abc
-        box = next_box;
-        layout_object =
-            LineLayoutAPIShim::LayoutObjectFrom(box->GetLineLayoutItem());
-        offset = box->CaretLeftmostOffset();
-        if (box->Direction() == primary_direction)
-          break;
-        continue;
-      }
-
-      while (next_box && !next_box->GetLineLayoutItem().GetNode())
-        next_box = next_box->NextLeafChild();
-
-      if (next_box) {
-        box = next_box;
-        layout_object =
-            LineLayoutAPIShim::LayoutObjectFrom(box->GetLineLayoutItem());
-        offset = box->CaretLeftmostOffset();
-
-        if (box->BidiLevel() > level) {
-          do {
-            next_box = next_box->NextLeafChild();
-          } while (next_box && next_box->BidiLevel() > level);
-
-          if (!next_box || next_box->BidiLevel() < level)
-            continue;
-        }
-      } else {
-        // Trailing edge of a secondary run. Set to the leading edge of the
-        // entire run.
-        while (true) {
-          while (InlineBox* prev_box = box->PrevLeafChild()) {
-            if (prev_box->BidiLevel() < level)
-              break;
-            box = prev_box;
-          }
-          if (box->BidiLevel() == level)
-            break;
-          level = box->BidiLevel();
-          while (InlineBox* next_box = box->NextLeafChild()) {
-            if (next_box->BidiLevel() < level)
-              break;
-            box = next_box;
-          }
-          if (box->BidiLevel() == level)
-            break;
-          level = box->BidiLevel();
-        }
-        layout_object =
-            LineLayoutAPIShim::LayoutObjectFrom(box->GetLineLayoutItem());
-        offset = primary_direction == TextDirection::kLtr
-                     ? box->CaretMaxOffset()
-                     : box->CaretMinOffset();
-      }
-      break;
-    }
-
-    p = PositionTemplate<Strategy>::EditingPositionOf(layout_object->GetNode(),
-                                                      offset);
-
-    if ((IsVisuallyEquivalentCandidate(p) &&
-         MostForwardCaretPosition(p) != downstream_start) ||
-        p.AtStartOfTree() || p.AtEndOfTree())
-      return p;
-
-    DCHECK_NE(p, deep_position);
-  }
-}
-
-template <typename Strategy>
-VisiblePositionTemplate<Strategy> RightPositionOfAlgorithm(
-    const VisiblePositionTemplate<Strategy>& visible_position) {
-  DCHECK(visible_position.IsValid()) << visible_position;
-  const PositionTemplate<Strategy> pos =
-      RightVisuallyDistinctCandidate(visible_position);
-  // TODO(editing-dev): Why can't we move left from the last position in a tree?
-  if (pos.AtStartOfTree() || pos.AtEndOfTree())
-    return VisiblePositionTemplate<Strategy>();
-
-  const VisiblePositionTemplate<Strategy> right = CreateVisiblePosition(pos);
-  DCHECK_NE(right.DeepEquivalent(), visible_position.DeepEquivalent());
-
-  return DirectionOfEnclosingBlockOf(right.DeepEquivalent()) ==
-                 TextDirection::kLtr
-             ? HonorEditingBoundaryAtOrAfter(right,
-                                             visible_position.DeepEquivalent())
-             : HonorEditingBoundaryAtOrBefore(
-                   right, visible_position.DeepEquivalent());
+  return Traversal::HonorEditingBoundary(
+      DirectionOfEnclosingBlockOf(result.DeepEquivalent()), result,
+      visible_position.DeepEquivalent());
 }
 
 }  // namespace
 
 VisiblePosition LeftPositionOf(const VisiblePosition& visible_position) {
-  return LeftPositionOfAlgorithm<EditingStrategy>(visible_position);
+  return TraverseAlgorithm<EditingStrategy, TraversalLeft<EditingStrategy>>(
+      visible_position);
 }
 
 VisiblePositionInFlatTree LeftPositionOf(
     const VisiblePositionInFlatTree& visible_position) {
-  return LeftPositionOfAlgorithm<EditingInFlatTreeStrategy>(visible_position);
+  return TraverseAlgorithm<EditingInFlatTreeStrategy,
+                           TraversalLeft<EditingInFlatTreeStrategy>>(
+      visible_position);
 }
 
 VisiblePosition RightPositionOf(const VisiblePosition& visible_position) {
-  return RightPositionOfAlgorithm<EditingStrategy>(visible_position);
+  return TraverseAlgorithm<EditingStrategy, TraversalRight<EditingStrategy>>(
+      visible_position);
 }
 
 VisiblePositionInFlatTree RightPositionOf(
     const VisiblePositionInFlatTree& visible_position) {
-  return RightPositionOfAlgorithm<EditingInFlatTreeStrategy>(visible_position);
+  return TraverseAlgorithm<EditingInFlatTreeStrategy,
+                           TraversalRight<EditingInFlatTreeStrategy>>(
+      visible_position);
 }
 
 }  // namespace blink