Introduce Find{Left,Right}BoundaryOfBidiRun() and variations

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

+// Copyright 2017 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 InlineBoxTraversal_h
+#define InlineBoxTraversal_h
+
+#include "platform/wtf/Allocator.h"
+
+namespace blink {
+
+class InlineBox;
+
+// This class provides common traveral functions on list of |InlineBox|.
+class InlineBoxTraversal final {
+  STATIC_ONLY(InlineBoxTraversal);
+
+ public:
+  // TODO(yosin): We should take |bidi_level| from |InlineBox::BidiLevel()|,
+  // once all call sites satisfy it.
+  // Find left boundary variations
+  static InlineBox* FindLeftBoundaryOfBidiRunIgnoringLineBreak(
+      const InlineBox&,
+      unsigned bidi_level);
+  static InlineBox* FindLeftBoundaryOfEntireBidiRun(const InlineBox&,
+                                                    unsigned bidi_level);
+  static InlineBox* FindLeftBoundaryOfEntireBidiRunIgnoringLineBreak(
+      const InlineBox&,
+      unsigned bidi_level);
+
+  // Find right boundary variations
+  static InlineBox* FindRightBoundaryOfBidiRunIgnoringLineBreak(
+      const InlineBox&,
+      unsigned bidi_level);
+  static InlineBox* FindRightBoundaryOfEntireBidiRun(const InlineBox&,
+                                                     unsigned bidi_level);
+  static InlineBox* FindRightBoundaryOfEntireBidiRunIgnoringLineBreak(
+      const InlineBox&,
+      unsigned bidi_level);
+};
+
+}  // namespace blink
+
+#endif  // InlineBoxTraversal_h