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

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

+// 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.
+
+#include "core/editing/InlineBoxTraversal.h"
+
+#include "core/layout/line/InlineBox.h"
+
+namespace blink {
+
+namespace {
+
+// "Left" Traversal strategy
+struct TraverseLeft {
+  STATIC_ONLY(TraverseLeft);
+
+  static InlineBox* Forward(const InlineBox& inline_box) {
+    return inline_box.PrevLeafChild();
+  }
+};
+
+// "Left" Traversal strategy ignoring line break
+struct TraverseLeftIgnoringLineBreak {
+  STATIC_ONLY(TraverseLeftIgnoringLineBreak);
+
+  static InlineBox* Forward(const InlineBox& inline_box) {
+    return inline_box.PrevLeafChildIgnoringLineBreak();
+  }
+};
+
+// "Right" Traversal strategy
+struct TraverseRight {
+  STATIC_ONLY(TraverseRight);
+
+  static InlineBox* Forward(const InlineBox& inline_box) {
+    return inline_box.NextLeafChild();
+  }
+};
+
+// "Right" Traversal strategy ignoring line break
+struct TraverseRightIgnoringLineBreak {
+  STATIC_ONLY(TraverseRightIgnoringLineBreak);
+
+  static InlineBox* Forward(const InlineBox& inline_box) {
+    return inline_box.NextLeafChildIgnoringLineBreak();
+  }
+};
+
+template <typename TraversalStrategy>
+InlineBox* FindBoudnaryOfBidiRun(const InlineBox& start) {
+  const unsigned bidi_level = start.BidiLevel();
+  InlineBox* result = const_cast<InlineBox*>(&start);
+  for (InlineBox* runner = TraversalStrategy::Forward(start); runner;
+       runner = TraversalStrategy::Forward(*runner)) {
+    if (runner->BidiLevel() <= bidi_level)
+      return result;
+    result = runner;
+  }
+  return result;
+}
+
+template <typename TraversalStrategy>
+InlineBox* FindBoudnaryOfEntireBidiRun(const InlineBox& start) {
+  const unsigned bidi_level = start.BidiLevel();
+  InlineBox* result = const_cast<InlineBox*>(&start);
+  for (InlineBox* runner = TraversalStrategy::Forward(start); runner;
+       runner = TraversalStrategy::Forward(*runner)) {
+    if (runner->BidiLevel() < bidi_level)
+      return result;
+    result = runner;
+  }
+  return result;
+}
+
+}  // namespace
+
+InlineBox* InlineBoxTraversal::FindLeftBoundaryOfBidiRunIgnoringLineBreak(
+    const InlineBox& inline_box) {
+  return FindBoudnaryOfBidiRun<TraverseLeftIgnoringLineBreak>(inline_box);
+}
+
+InlineBox* InlineBoxTraversal::FindLeftBoundaryOfEntireBidiRun(
+    const InlineBox& inline_box) {
+  return FindBoudnaryOfEntireBidiRun<TraverseLeft>(inline_box);
+}
+
+InlineBox* InlineBoxTraversal::FindLeftBoundaryOfEntireBidiRunIgnoringLineBreak(
+    const InlineBox& inline_box) {
+  return FindBoudnaryOfEntireBidiRun<TraverseLeftIgnoringLineBreak>(inline_box);
+}
+
+InlineBox* InlineBoxTraversal::FindRightBoundaryOfBidiRunIgnoringLineBreak(
+    const InlineBox& inline_box) {
+  return FindBoudnaryOfBidiRun<TraverseRightIgnoringLineBreak>(inline_box);
+}
+
+InlineBox* InlineBoxTraversal::FindRightBoundaryOfEntireBidiRun(
+    const InlineBox& inline_box) {
+  return FindBoudnaryOfEntireBidiRun<TraverseRight>(inline_box);
+}
+
+InlineBox*
+InlineBoxTraversal::FindRightBoundaryOfEntireBidiRunIgnoringLineBreak(
+    const InlineBox& inline_box) {
+  return FindBoudnaryOfEntireBidiRun<TraverseRightIgnoringLineBreak>(
+      inline_box);
+}
+
+}  // namespace blink