Make {Next,Previous}OnLineInlineNG() for AXLayoutObject to utilize NGInlineCursor

This patch makes {Next,Previous}OnLineInlineNG() for AXLayoutObject to utilize
|NGInlineCursor| for preparation of migrating to |NGFragmentItem|.

This patch also introduces |NGInlineCursor::CurrentMutableLayoutObject()| to
reduce using |const_cast<LayoutObject*>()|.


Bug: 982194
Change-Id: I36d5d76b266968824ecd029851737e45c740f839
Tbr: dmazzoni@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1930243
Commit-Queue: Yoshifumi Inoue <yosin@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Auto-Submit: Yoshifumi Inoue <yosin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#719879}

third_party/blink/renderer/core/layout/ng/inline/ng_fragment_item.h

@@ -95,6 +95,9 @@ class CORE_EXPORT NGFragmentItem : public DisplayItemClient {
     return layout_object_->EffectiveStyle(StyleVariant());
   }
   const LayoutObject* GetLayoutObject() const { return layout_object_; }
+  LayoutObject* GetMutableLayoutObject() const {
+    return const_cast<LayoutObject*>(layout_object_);
+  }
   Node* GetNode() const { return layout_object_->GetNode(); }
   bool HasSameParent(const NGFragmentItem& other) const;
 

third_party/blink/renderer/core/layout/ng/inline/ng_inline_cursor.cc

@@ -447,6 +447,15 @@ const LayoutObject* NGInlineCursor::CurrentLayoutObject() const {
   return nullptr;
 }
 
+LayoutObject* NGInlineCursor::CurrentMutableLayoutObject() const {
+  if (current_paint_fragment_)
+    return current_paint_fragment_->GetMutableLayoutObject();
+  if (current_item_)
+    return current_item_->GetMutableLayoutObject();
+  NOTREACHED();
+  return nullptr;
+}
+
 Node* NGInlineCursor::CurrentNode() const {
   if (const LayoutObject* layout_object = CurrentLayoutObject())
     return layout_object->GetNode();
@@ -752,6 +761,15 @@ void NGInlineCursor::MoveToLastChild() {
     MakeNull();
 }
 
+void NGInlineCursor::MoveToLastForSameLayoutObject() {
+  NGInlineCursor last;
+  while (IsNotNull()) {
+    last = *this;
+    MoveToNextForSameLayoutObject();
+  }
+  *this = last;
+}
+
 void NGInlineCursor::MoveToLastLogicalLeaf() {
   DCHECK(IsLineBox());
   // TODO(yosin): This isn't correct for mixed Bidi. Fix it. Besides, we
@@ -814,6 +832,21 @@ void NGInlineCursor::MoveToNextInlineLeafIgnoringLineBreak() {
   } while (IsNotNull() && IsLineBreak());
 }
 
+void NGInlineCursor::MoveToNextInlineLeafOnLine() {
+  MoveToLastForSameLayoutObject();
+  if (IsNull())
+    return;
+  NGInlineCursor last_item = *this;
+  MoveToContainingLine();
+  NGInlineCursor cursor = CursorForDescendants();
+  cursor.MoveTo(last_item);
+  // Note: AX requires this for AccessibilityLayoutTest.NextOnLine.
+  if (!cursor.IsInlineLeaf())
+    cursor.MoveToNextInlineLeaf();
+  cursor.MoveToNextInlineLeaf();
+  MoveTo(cursor);
+}
+
 void NGInlineCursor::MoveToNextLine() {
   DCHECK(IsLineBox());
   if (current_paint_fragment_) {
@@ -861,6 +894,20 @@ void NGInlineCursor::MoveToPreviousInlineLeafIgnoringLineBreak() {
   } while (IsNotNull() && IsLineBreak());
 }
 
+void NGInlineCursor::MoveToPreviousInlineLeafOnLine() {
+  if (IsNull())
+    return;
+  NGInlineCursor first_item = *this;
+  MoveToContainingLine();
+  NGInlineCursor cursor = CursorForDescendants();
+  cursor.MoveTo(first_item);
+  // Note: AX requires this for AccessibilityLayoutTest.NextOnLine.
+  if (!cursor.IsInlineLeaf())
+    cursor.MoveToPreviousInlineLeaf();
+  cursor.MoveToPreviousInlineLeaf();
+  MoveTo(cursor);
+}
+
 void NGInlineCursor::MoveToPreviousLine() {
   // Note: List marker is sibling of line box.
   DCHECK(IsLineBox());

third_party/blink/renderer/core/layout/ng/inline/ng_inline_cursor.h

@@ -165,6 +165,7 @@ class CORE_EXPORT NGInlineCursor {
   const NGPhysicalBoxFragment* CurrentBoxFragment() const;
   const DisplayItemClient* CurrentDisplayItemClient() const;
   const LayoutObject* CurrentLayoutObject() const;
+  LayoutObject* CurrentMutableLayoutObject() const;
   Node* CurrentNode() const;
 
   // Returns bidi level of current position. It is error to call other than
@@ -279,6 +280,14 @@ class CORE_EXPORT NGInlineCursor {
   void MoveToPreviousInlineLeaf();
   void MoveToPreviousInlineLeafIgnoringLineBreak();
 
+  // Move the current position to next/previous inline leaf item on line.
+  // Note: If the current position isn't leaf item, this function moves the
+  // current position to leaf item then moves to next/previous leaf item. This
+  // behavior doesn't match |MoveTo{Next,Previous}InlineLeaf()|, but AX requires
+  // this. See AccessibilityLayoutTest.NextOnLine
+  void MoveToNextInlineLeafOnLine();
+  void MoveToPreviousInlineLeafOnLine();
+
   // Move the cursor position to previous fragment in pre-order DFS.
   void MoveToPrevious();
 
@@ -317,6 +326,9 @@ class CORE_EXPORT NGInlineCursor {
   // Move the cursor position to the first fragment in tree.
   void MoveToFirst();
 
+  // Move the current position to the last fragment on same layout object.
+  void MoveToLastForSameLayoutObject();
+
   // Same as |MoveTo()| but not support culled inline.
   void InternalMoveTo(const LayoutObject& layout_object);
 

third_party/blink/renderer/core/layout/ng/inline/ng_inline_cursor_test.cc

@@ -454,6 +454,43 @@ TEST_P(NGInlineCursorTest, NextInlineLeaf) {
   EXPECT_THAT(list, ElementsAre("#linebox", "abc", "DEF", "", "xyz"));
 }
 
+// Note: This is for AccessibilityLayoutTest.NextOnLine.
+TEST_P(NGInlineCursorTest, NextInlineLeafOnLineFromLayoutInline) {
+  // TDOO(yosin): Remove <style> once NGFragmentItem don't do culled inline.
+  InsertStyleElement("b { background: gray; }");
+  NGInlineCursor cursor = SetupCursor(
+      "<div id=root>"
+      "<b id=start>abc</b> def<br>"
+      "<b>ABC</b> DEF<br>"
+      "</div>");
+  cursor.MoveTo(*GetElementById("start")->GetLayoutObject());
+  Vector<String> list;
+  while (cursor) {
+    list.push_back(ToDebugString(cursor));
+    cursor.MoveToNextInlineLeafOnLine();
+  }
+  EXPECT_THAT(list, ElementsAre("#start", "def", ""))
+      << "we don't have 'abc' and items in second line.";
+}
+
+TEST_P(NGInlineCursorTest, NextInlineLeafOnLineFromLayoutText) {
+  // TDOO(yosin): Remove <style> once NGFragmentItem don't do culled inline.
+  InsertStyleElement("b { background: gray; }");
+  NGInlineCursor cursor = SetupCursor(
+      "<div id=root>"
+      "<b id=start>abc</b> def<br>"
+      "<b>ABC</b> DEF<br>"
+      "</div>");
+  cursor.MoveTo(*GetElementById("start")->firstChild()->GetLayoutObject());
+  Vector<String> list;
+  while (cursor) {
+    list.push_back(ToDebugString(cursor));
+    cursor.MoveToNextInlineLeafOnLine();
+  }
+  EXPECT_THAT(list, ElementsAre("abc", "def", ""))
+      << "We don't have items from second line.";
+}
+
 TEST_P(NGInlineCursorTest, NextInlineLeafWithEllipsis) {
   LoadAhem();
   InsertStyleElement(
@@ -658,6 +695,42 @@ TEST_P(NGInlineCursorTest, PreviousInlineLeafIgnoringLineBreak) {
   EXPECT_THAT(list, ElementsAre("xyz", "DEF", "abc"));
 }
 
+TEST_P(NGInlineCursorTest, PreviousInlineLeafOnLineFromLayoutInline) {
+  // TDOO(yosin): Remove <style> once NGFragmentItem don't do culled inline.
+  InsertStyleElement("b { background: gray; }");
+  NGInlineCursor cursor = SetupCursor(
+      "<div id=root>"
+      "<b>abc</b> def<br>"
+      "<b>ABC</b> <b id=start>DEF</b><br>"
+      "</div>");
+  cursor.MoveTo(*GetElementById("start")->GetLayoutObject());
+  Vector<String> list;
+  while (cursor) {
+    list.push_back(ToDebugString(cursor));
+    cursor.MoveToPreviousInlineLeafOnLine();
+  }
+  EXPECT_THAT(list, ElementsAre("#start", "ABC"))
+      << "We don't have 'DEF' and items in first line.";
+}
+
+TEST_P(NGInlineCursorTest, PreviousInlineLeafOnLineFromLayoutText) {
+  // TDOO(yosin): Remove <style> once NGFragmentItem don't do culled inline.
+  InsertStyleElement("b { background: gray; }");
+  NGInlineCursor cursor = SetupCursor(
+      "<div id=root>"
+      "<b>abc</b> def<br>"
+      "<b>ABC</b> <b id=start>DEF</b><br>"
+      "</div>");
+  cursor.MoveTo(*GetElementById("start")->firstChild()->GetLayoutObject());
+  Vector<String> list;
+  while (cursor) {
+    list.push_back(ToDebugString(cursor));
+    cursor.MoveToPreviousInlineLeafOnLine();
+  }
+  EXPECT_THAT(list, ElementsAre("DEF", "", "ABC"))
+      << "We don't have items in first line.";
+}
+
 TEST_P(NGInlineCursorTest, PreviousLine) {
   NGInlineCursor cursor = SetupCursor("<div id=root>abc<br>xyz</div>");
   NGInlineCursor line1(cursor);

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

@@ -76,13 +76,12 @@
 #include "third_party/blink/renderer/core/layout/layout_text_control.h"
 #include "third_party/blink/renderer/core/layout/layout_text_fragment.h"
 #include "third_party/blink/renderer/core/layout/layout_view.h"
+#include "third_party/blink/renderer/core/layout/ng/inline/ng_inline_cursor.h"
 #include "third_party/blink/renderer/core/layout/ng/inline/ng_inline_node.h"
 #include "third_party/blink/renderer/core/layout/ng/list/layout_ng_list_item.h"
 #include "third_party/blink/renderer/core/layout/ng/list/layout_ng_list_marker.h"
 #include "third_party/blink/renderer/core/loader/progress_tracker.h"
 #include "third_party/blink/renderer/core/page/page.h"
-#include "third_party/blink/renderer/core/paint/ng/ng_paint_fragment.h"
-#include "third_party/blink/renderer/core/paint/ng/ng_paint_fragment_traversal.h"
 #include "third_party/blink/renderer/core/paint/paint_layer.h"
 #include "third_party/blink/renderer/core/paint/paint_layer_scrollable_area.h"
 #include "third_party/blink/renderer/core/style/computed_style_constants.h"
@@ -1265,17 +1264,18 @@ static AXObject* NextOnLineInternalNG(const AXObject& ax_object) {
   DCHECK(!ax_object.IsDetached());
   const LayoutObject& layout_object = *ax_object.GetLayoutObject();
   DCHECK(ShouldUseLayoutNG(layout_object)) << layout_object;
-  if (layout_object.IsListMarkerIncludingNG())
+  if (layout_object.IsListMarkerIncludingNG() ||
+      !layout_object.IsInLayoutNGInlineFormattingContext())
     return nullptr;
-
-  const auto fragments = NGPaintFragment::InlineFragmentsFor(&layout_object);
-  if (fragments.IsEmpty() || !fragments.IsInLayoutNGInlineFormattingContext())
+  NGInlineCursor cursor;
+  cursor.MoveTo(layout_object);
+  if (!cursor)
     return nullptr;
-  NGPaintFragmentTraversal runner(*fragments.back().ContainerLineBox(),
-                                  fragments.back());
-  for (runner.MoveToNextInlineLeaf(); !runner.IsAtEnd();
-       runner.MoveToNextInlineLeaf()) {
-    LayoutObject* runner_layout_object = runner->GetMutableLayoutObject();
+  for (;;) {
+    cursor.MoveToNextInlineLeafOnLine();
+    if (!cursor)
+      break;
+    LayoutObject* runner_layout_object = cursor.CurrentMutableLayoutObject();
     if (AXObject* result =
             ax_object.AXObjectCache().GetOrCreate(runner_layout_object))
       return result;
@@ -1345,17 +1345,18 @@ static AXObject* PreviousOnLineInlineNG(const AXObject& ax_object) {
   DCHECK(!ax_object.IsDetached());
   const LayoutObject& layout_object = *ax_object.GetLayoutObject();
   DCHECK(ShouldUseLayoutNG(layout_object)) << layout_object;
-  if (layout_object.IsListMarkerIncludingNG())
+  if (layout_object.IsListMarkerIncludingNG() ||
+      !layout_object.IsInLayoutNGInlineFormattingContext())
     return nullptr;
-
-  const auto fragments = NGPaintFragment::InlineFragmentsFor(&layout_object);
-  if (fragments.IsEmpty() || !fragments.IsInLayoutNGInlineFormattingContext())
+  NGInlineCursor cursor;
+  cursor.MoveTo(layout_object);
+  if (!cursor)
     return nullptr;
-  NGPaintFragmentTraversal runner(*fragments.front().ContainerLineBox(),
-                                  fragments.front());
-  for (runner.MoveToPreviousInlineLeaf(); !runner.IsAtEnd();
-       runner.MoveToPreviousInlineLeaf()) {
-    LayoutObject* earlier_layout_object = runner->GetMutableLayoutObject();
+  for (;;) {
+    cursor.MoveToPreviousInlineLeafOnLine();
+    if (!cursor)
+      break;
+    LayoutObject* earlier_layout_object = cursor.CurrentMutableLayoutObject();
     if (AXObject* result =
             ax_object.AXObjectCache().GetOrCreate(earlier_layout_object))
       return result;