Get rid of NGPaintFragmentTraversalContext

Because of |NGPaintFragmentTraversal| and |NGPaintFragmentTraversalContext|
provide same functionalities and we prefer |NGPaintFragmentTraversal|, this
patch removes |NGPaintFragmentTraversalContext| by replacing usage of them by
|NGPaintFragmentTraversal| to simplify code base for improving code health and
ease of introducing |NGFragmentItem|.

Bug: 982194
Change-Id: I6b1f031ef54cd25eb8df56e8a2ed17dd1c5eb288
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1689907
Auto-Submit: Yoshifumi Inoue <yosin@chromium.org>
Reviewed-by: Emil A Eklund <eae@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Commit-Queue: Yoshifumi Inoue <yosin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#691508}

third_party/blink/renderer/core/editing/inline_box_traversal.cc

@@ -35,8 +35,10 @@ class AbstractInlineBox {
 
   explicit AbstractInlineBox(const InlineBox& box)
       : type_(InstanceType::kOldLayout), inline_box_(&box) {}
-  explicit AbstractInlineBox(const NGPaintFragment& fragment)
-      : AbstractInlineBox(NGPaintFragmentTraversalContext::Create(&fragment)) {}
+  explicit AbstractInlineBox(const NGPaintFragment& paint_fragment)
+      : AbstractInlineBox(
+            NGPaintFragmentTraversal(*paint_fragment.ContainerLineBox(),
+                                     paint_fragment)) {}
 
   bool IsNotNull() const { return type_ != InstanceType::kNull; }
   bool IsNull() const { return !IsNotNull(); }
@@ -52,7 +54,7 @@ class AbstractInlineBox {
       case InstanceType::kOldLayout:
         return inline_box_ == other.inline_box_;
       case InstanceType::kNG:
-        return paint_fragment_ == other.paint_fragment_;
+        return paint_fragment_.get() == other.paint_fragment_.get();
     }
     NOTREACHED();
     return false;
@@ -66,8 +68,8 @@ class AbstractInlineBox {
 
   const NGPaintFragment& GetNGPaintFragment() const {
     DCHECK(IsNG());
-    DCHECK(!paint_fragment_.IsNull());
-    return *paint_fragment_.GetFragment();
+    DCHECK(!paint_fragment_.IsAtEnd());
+    return *paint_fragment_;
   }
 
   UBiDiLevel BidiLevel() const {
@@ -89,9 +91,10 @@ class AbstractInlineBox {
       const InlineBox* result = GetInlineBox().PrevLeafChild();
       return result ? AbstractInlineBox(*result) : AbstractInlineBox();
     }
-    const NGPaintFragmentTraversalContext result =
-        NGPaintFragmentTraversal::PreviousInlineLeafOf(paint_fragment_);
-    return result.IsNull() ? AbstractInlineBox() : AbstractInlineBox(result);
+    NGPaintFragmentTraversal result(paint_fragment_);
+    result.MoveToPreviousInlineLeaf();
+    return result.IsAtEnd() ? AbstractInlineBox()
+                            : AbstractInlineBox(std::move(result));
   }
 
   AbstractInlineBox PrevLeafChildIgnoringLineBreak() const {
@@ -100,10 +103,10 @@ class AbstractInlineBox {
       const InlineBox* result = GetInlineBox().PrevLeafChildIgnoringLineBreak();
       return result ? AbstractInlineBox(*result) : AbstractInlineBox();
     }
-    const NGPaintFragmentTraversalContext result =
-        NGPaintFragmentTraversal::PreviousInlineLeafOfIgnoringLineBreak(
-            paint_fragment_);
-    return result.IsNull() ? AbstractInlineBox() : AbstractInlineBox(result);
+    NGPaintFragmentTraversal result(paint_fragment_);
+    result.MoveToPreviousInlineLeafIgnoringLineBreak();
+    return result.IsAtEnd() ? AbstractInlineBox()
+                            : AbstractInlineBox(std::move(result));
   }
 
   AbstractInlineBox NextLeafChild() const {
@@ -112,9 +115,10 @@ class AbstractInlineBox {
       const InlineBox* result = GetInlineBox().NextLeafChild();
       return result ? AbstractInlineBox(*result) : AbstractInlineBox();
     }
-    const NGPaintFragmentTraversalContext result =
-        NGPaintFragmentTraversal::NextInlineLeafOf(paint_fragment_);
-    return result.IsNull() ? AbstractInlineBox() : AbstractInlineBox(result);
+    NGPaintFragmentTraversal result(paint_fragment_);
+    result.MoveToNextInlineLeaf();
+    return result.IsAtEnd() ? AbstractInlineBox()
+                            : AbstractInlineBox(std::move(result));
   }
 
   AbstractInlineBox NextLeafChildIgnoringLineBreak() const {
@@ -123,10 +127,10 @@ class AbstractInlineBox {
       const InlineBox* result = GetInlineBox().NextLeafChildIgnoringLineBreak();
       return result ? AbstractInlineBox(*result) : AbstractInlineBox();
     }
-    const NGPaintFragmentTraversalContext result =
-        NGPaintFragmentTraversal::NextInlineLeafOfIgnoringLineBreak(
-            paint_fragment_);
-    return result.IsNull() ? AbstractInlineBox() : AbstractInlineBox(result);
+    NGPaintFragmentTraversal result(paint_fragment_);
+    result.MoveToNextInlineLeafIgnoringLineBreak();
+    return result.IsAtEnd() ? AbstractInlineBox()
+                            : AbstractInlineBox(std::move(result));
   }
 
   TextDirection ParagraphDirection() const {
@@ -137,8 +141,8 @@ class AbstractInlineBox {
   }
 
  private:
-  explicit AbstractInlineBox(const NGPaintFragmentTraversalContext& fragment)
-      : type_(InstanceType::kNG), paint_fragment_(fragment) {}
+  explicit AbstractInlineBox(NGPaintFragmentTraversal&& fragment)
+      : type_(InstanceType::kNG), paint_fragment_(std::move(fragment)) {}
 
   enum class InstanceType { kNull, kOldLayout, kNG };
   InstanceType type_;
@@ -146,7 +150,7 @@ class AbstractInlineBox {
   // Only one of |inline_box_| or |paint_fragment_| is used, but we cannot make
   // them union because of non-trivial destructor.
   const InlineBox* inline_box_;
-  NGPaintFragmentTraversalContext paint_fragment_;
+  NGPaintFragmentTraversal paint_fragment_;
 };
 
 // |SideAffinity| represents the left or right side of a leaf inline

third_party/blink/renderer/core/paint/ng/ng_paint_fragment_traversal.h

@@ -13,32 +13,6 @@ namespace blink {
 
 class NGPaintFragment;
 
-// Represents an NGPaintFragment by its parent and its index in the parent's
-// |Children()| vector.
-struct CORE_EXPORT NGPaintFragmentTraversalContext {
-  STACK_ALLOCATED();
-
- public:
-  NGPaintFragmentTraversalContext() = default;
-  explicit NGPaintFragmentTraversalContext(const NGPaintFragment* fragment);
-  NGPaintFragmentTraversalContext(const NGPaintFragment* parent,
-                                  unsigned index);
-  // TODO(kojii): deprecated, prefer constructors to avoid unexpected
-  // instantiation.
-  static NGPaintFragmentTraversalContext Create(const NGPaintFragment*);
-
-  bool IsNull() const { return !parent; }
-  const NGPaintFragment* GetFragment() const;
-
-  bool operator==(const NGPaintFragmentTraversalContext& other) const {
-    return parent == other.parent && index == other.index;
-  }
-
-  const NGPaintFragment* parent = nullptr;
-  unsigned index = 0;
-  Vector<NGPaintFragment*, 16> siblings;
-};
-
 // Utility class for traversing the paint fragment tree.
 //
 // This class has two groups of functions; one is a traversing cursor, by
@@ -48,6 +22,11 @@ class CORE_EXPORT NGPaintFragmentTraversal {
   STACK_ALLOCATED();
 
  public:
+  NGPaintFragmentTraversal(const NGPaintFragmentTraversal& other);
+  NGPaintFragmentTraversal(NGPaintFragmentTraversal&& other);
+  NGPaintFragmentTraversal();
+  NGPaintFragmentTraversal& operator=(const NGPaintFragmentTraversal& other);
+
   // Create an instance to traverse descendants of |root|.
   explicit NGPaintFragmentTraversal(const NGPaintFragment& root);
 
@@ -90,6 +69,15 @@ class CORE_EXPORT NGPaintFragmentTraversal {
   // Note: When |IsAtEnd()| is true, this function does nothing.
   void MoveToPrevious();
 
+  // Returns the previous/next inline leaf fragment (text or atomic inline) of
+  // the passed fragment, which itself must be inline.
+  void MoveToPreviousInlineLeaf();
+  void MoveToNextInlineLeaf();
+
+  // Variants of the above two skipping line break fragments.
+  void MoveToPreviousInlineLeafIgnoringLineBreak();
+  void MoveToNextInlineLeafIgnoringLineBreak();
+
   //
   // Following functions are static, similar to DOM traversal utilities.
   //
@@ -189,27 +177,21 @@ class CORE_EXPORT NGPaintFragmentTraversal {
   // paint fragment of a line box.
   static NGPaintFragment* PreviousLineOf(const NGPaintFragment& line);
 
-  // Returns the previous/next inline leaf fragment (text or atomic inline)of
-  // the passed fragment, which itself must be inline.
-  static NGPaintFragmentTraversalContext PreviousInlineLeafOf(
-      const NGPaintFragmentTraversalContext&);
-  static NGPaintFragmentTraversalContext NextInlineLeafOf(
-      const NGPaintFragmentTraversalContext&);
-
-  // Variants of the above two skipping line break fragments.
-  static NGPaintFragmentTraversalContext PreviousInlineLeafOfIgnoringLineBreak(
-      const NGPaintFragmentTraversalContext&);
-  static NGPaintFragmentTraversalContext NextInlineLeafOfIgnoringLineBreak(
-      const NGPaintFragmentTraversalContext&);
-
  private:
+  void EnsureIndex();
+  bool IsInlineLeaf() const;
+  bool IsLineBreak() const;
+  void MoveToFirstChild();
+  void MoveToLastChild();
+  void Reset();
+
   // |current_| holds a |NGPaintFragment| specified by |index|th child of
   // |parent| of the last element of |stack_|.
   const NGPaintFragment* current_ = nullptr;
 
   // The root of subtree where traversing is taken place. |root_| is excluded
   // from traversal. |current_| can't |root_|.
-  const NGPaintFragment& root_;
+  const NGPaintFragment* root_ = nullptr;
 
   // Keep a list of siblings for MoveToPrevious().
   // TODO(kojii): We could keep a stack of this to avoid repetitive
@@ -217,8 +199,6 @@ class CORE_EXPORT NGPaintFragmentTraversal {
   // sharing with NGPaintFragmentTraversalContext.
   unsigned current_index_ = 0;
   Vector<NGPaintFragment*, 16> siblings_;
-
-  DISALLOW_COPY_AND_ASSIGN(NGPaintFragmentTraversal);
 };
 
 }  // namespace blink

third_party/blink/renderer/modules/accessibility/ax_layout_object.cc

@@ -1261,13 +1261,11 @@ static AXObject* NextOnLineInternalNG(const AXObject& ax_object) {
   const auto fragments = NGPaintFragment::InlineFragmentsFor(&layout_object);
   if (fragments.IsEmpty() || !fragments.IsInLayoutNGInlineFormattingContext())
     return nullptr;
-  for (NGPaintFragmentTraversalContext runner =
-           NGPaintFragmentTraversal::NextInlineLeafOf(
-               NGPaintFragmentTraversalContext::Create(&fragments.back()));
-       !runner.IsNull();
-       runner = NGPaintFragmentTraversal::NextInlineLeafOf(runner)) {
-    LayoutObject* runner_layout_object =
-        runner.GetFragment()->GetMutableLayoutObject();
+  NGPaintFragmentTraversal runner(*fragments.back().ContainerLineBox(),
+                                  fragments.back());
+  for (runner.MoveToNextInlineLeaf(); !runner.IsAtEnd();
+       runner.MoveToNextInlineLeaf()) {
+    LayoutObject* runner_layout_object = runner->GetMutableLayoutObject();
     if (AXObject* result =
             ax_object.AXObjectCache().GetOrCreate(runner_layout_object))
       return result;
@@ -1341,13 +1339,11 @@ static AXObject* PreviousOnLineInlineNG(const AXObject& ax_object) {
   const auto fragments = NGPaintFragment::InlineFragmentsFor(&layout_object);
   if (fragments.IsEmpty() || !fragments.IsInLayoutNGInlineFormattingContext())
     return nullptr;
-  for (NGPaintFragmentTraversalContext runner =
-           NGPaintFragmentTraversal::PreviousInlineLeafOf(
-               NGPaintFragmentTraversalContext::Create(&fragments.front()));
-       !runner.IsNull();
-       runner = NGPaintFragmentTraversal::PreviousInlineLeafOf(runner)) {
-    LayoutObject* earlier_layout_object =
-        runner.GetFragment()->GetMutableLayoutObject();
+  NGPaintFragmentTraversal runner(*fragments.front().ContainerLineBox(),
+                                  fragments.front());
+  for (runner.MoveToPreviousInlineLeaf(); !runner.IsAtEnd();
+       runner.MoveToPreviousInlineLeaf()) {
+    LayoutObject* earlier_layout_object = runner->GetMutableLayoutObject();
     if (AXObject* result =
             ax_object.AXObjectCache().GetOrCreate(earlier_layout_object))
       return result;