[EditingNG] Introduce NGInluneCursor::PositionForPointInChild()

This patch introuces |NGInluneCursor::PositionForPointInChild()| as replacement
of existing verion with following differences:
 - It takes only one parameter |point_in_container|, because |child_item| is
   reduntant and as same as current cursor position.
 - It works both |NGPaintFragment| and |NGFragmentItem|.
for preparation of the CL[1].

[1] http://crrev.com/2249278 [EditingNG] Make SelectionModifier::
{Next,Previous}LinePosition() to move editable to editalbe correctly

Bug: 707656
Change-Id: If5605edd02bec664c331cecebc70c4723094ab56
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2247943
Commit-Queue: Yoshifumi Inoue <yosin@chromium.org>
Auto-Submit: Yoshifumi Inoue <yosin@chromium.org>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#779185}

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

@@ -860,14 +860,14 @@ PositionWithAffinity NGInlineCursor::PositionForPointInInlineBox(
     }
 
     if (const PositionWithAffinity child_position =
-            descendants.PositionForPointInChild(point, *child_item))
+            descendants.PositionForPointInChild(point))
       return child_position;
   }
 
   if (closest_child_after) {
     descendants.MoveTo(closest_child_after);
     if (const PositionWithAffinity child_position =
-            descendants.PositionForPointInChild(point, *closest_child_after))
+            descendants.PositionForPointInChild(point))
       return child_position;
     // TODO(yosin): we should do like "closest_child_before" once we have a
     // case.
@@ -876,7 +876,7 @@ PositionWithAffinity NGInlineCursor::PositionForPointInInlineBox(
   if (closest_child_before) {
     descendants.MoveTo(closest_child_before);
     if (const PositionWithAffinity child_position =
-            descendants.PositionForPointInChild(point, *closest_child_before))
+            descendants.PositionForPointInChild(point))
       return child_position;
     if (closest_child_before->BoxFragment()) {
       // LayoutViewHitTest.HitTestHorizontal "Top-right corner (outside) of div"
@@ -908,13 +908,18 @@ PositionWithAffinity NGInlineCursor::PositionForPointInInlineBox(
 }
 
 PositionWithAffinity NGInlineCursor::PositionForPointInChild(
-    const PhysicalOffset& point,
-    const NGFragmentItem& child_item) const {
-  DCHECK_EQ(&child_item, CurrentItem());
+    const PhysicalOffset& point_in_container) const {
+  if (auto* paint_fragment = CurrentPaintFragment()) {
+    const PhysicalOffset point_in_child =
+        point_in_container - paint_fragment->OffsetInContainerBlock();
+    return paint_fragment->PositionForPoint(point_in_child);
+  }
+  DCHECK(CurrentItem());
+  const NGFragmentItem& child_item = *CurrentItem();
   switch (child_item.Type()) {
     case NGFragmentItem::kText:
       return child_item.PositionForPointInText(
-          point - child_item.OffsetInContainerBlock(), *this);
+          point_in_container - child_item.OffsetInContainerBlock(), *this);
     case NGFragmentItem::kGeneratedText:
       break;
     case NGFragmentItem::kBox:
@@ -927,7 +932,7 @@ PositionWithAffinity NGInlineCursor::PositionForPointInChild(
         // TODO(xiaochengh): Don't fallback to legacy for NG block layout.
         if (!box_fragment->IsInlineBox()) {
           return child_item.GetLayoutObject()->PositionForPoint(
-              point - child_item.OffsetInContainerBlock());
+              point_in_container - child_item.OffsetInContainerBlock());
         }
       } else {
         // |LayoutInline| used to be culled.

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

@@ -315,6 +315,16 @@ class CORE_EXPORT NGInlineCursor {
   PositionWithAffinity PositionForPointInInlineBox(
       const PhysicalOffset& point) const;
 
+  // Returns |PositionWithAffinity| in current position at x-coordinate of
+  // |point_in_container| for horizontal writing mode, or y-coordinate of
+  // |point_in_container| for vertical writing mode.
+  // Note: Even if |point_in_container| is outside of an item of current
+  // position, this function returns boundary position of an item.
+  // Note: This function is used for locating caret at same x/y-coordinate as
+  // previous caret after line up/down.
+  PositionWithAffinity PositionForPointInChild(
+      const PhysicalOffset& point_in_container) const;
+
   // Returns first/last position of |this| line. |this| should be line box.
   PositionWithAffinity PositionForStartOfLine() const;
   PositionWithAffinity PositionForEndOfLine() const;
@@ -460,10 +470,6 @@ class CORE_EXPORT NGInlineCursor {
   wtf_size_t SpanBeginItemIndex() const;
   wtf_size_t SpanIndexFromItemIndex(unsigned index) const;
 
-  PositionWithAffinity PositionForPointInChild(
-      const PhysicalOffset& point,
-      const NGFragmentItem& child_item) const;
-
   NGInlineCursorPosition current_;
 
   ItemsSpan items_;

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

@@ -698,6 +698,152 @@ TEST_P(NGInlineCursorTest, EmptyOutOfFlow) {
   EXPECT_THAT(list, ElementsAre());
 }
 
+TEST_P(NGInlineCursorTest, PositionForPointInChildHorizontalLTR) {
+  LoadAhem();
+  InsertStyleElement(
+      "p {"
+      "direction: ltr;"
+      "font: 10px/20px Ahem;"
+      "padding: 10px;"
+      "writing-mode: horizontal-tb;"
+      "}");
+  NGInlineCursor cursor = SetupCursor("<p id=root>ab</p>");
+  const auto& text = *To<Text>(GetElementById("root")->firstChild());
+  ASSERT_TRUE(cursor.Current().IsLineBox());
+  EXPECT_EQ(PhysicalRect(PhysicalOffset(10, 10), PhysicalSize(20, 20)),
+            cursor.Current().RectInContainerBlock());
+
+  cursor.MoveTo(*text.GetLayoutObject());
+  EXPECT_EQ(PhysicalRect(PhysicalOffset(10, 15), PhysicalSize(20, 10)),
+            cursor.Current().RectInContainerBlock());
+  const PhysicalOffset left_top = cursor.Current().OffsetInContainerBlock();
+
+  EXPECT_EQ(PositionWithAffinity(Position(text, 0)),
+            cursor.PositionForPointInChild(left_top + PhysicalOffset(-5, 0)));
+  EXPECT_EQ(PositionWithAffinity(Position(text, 0)),
+            cursor.PositionForPointInChild(left_top));
+  EXPECT_EQ(PositionWithAffinity(Position(text, 0)),
+            cursor.PositionForPointInChild(left_top + PhysicalOffset(5, 0)));
+  EXPECT_EQ(PositionWithAffinity(Position(text, 1)),
+            cursor.PositionForPointInChild(left_top + PhysicalOffset(10, 0)));
+  EXPECT_EQ(PositionWithAffinity(Position(text, 1)),
+            cursor.PositionForPointInChild(left_top + PhysicalOffset(15, 0)));
+  EXPECT_EQ(PositionWithAffinity(Position(text, 2), TextAffinity::kUpstream),
+            cursor.PositionForPointInChild(left_top + PhysicalOffset(20, 0)));
+  EXPECT_EQ(PositionWithAffinity(Position(text, 2), TextAffinity::kUpstream),
+            cursor.PositionForPointInChild(left_top + PhysicalOffset(25, 0)));
+}
+
+TEST_P(NGInlineCursorTest, PositionForPointInChildHorizontalRTL) {
+  LoadAhem();
+  InsertStyleElement(
+      "p {"
+      "direction: rtl;"
+      "font: 10px/20px Ahem;"
+      "padding: 10px;"
+      "writing-mode: horizontal-tb;"
+      "}");
+  NGInlineCursor cursor = SetupCursor("<p id=root><bdo dir=rtl>AB</bdo></p>");
+  const auto& text =
+      *To<Text>(GetElementById("root")->firstChild()->firstChild());
+  ASSERT_TRUE(cursor.Current().IsLineBox());
+  EXPECT_EQ(PhysicalRect(PhysicalOffset(754, 10), PhysicalSize(20, 20)),
+            cursor.Current().RectInContainerBlock());
+
+  cursor.MoveTo(*text.GetLayoutObject());
+  EXPECT_EQ(PhysicalRect(PhysicalOffset(754, 15), PhysicalSize(20, 10)),
+            cursor.Current().RectInContainerBlock());
+  const PhysicalOffset left_top = cursor.Current().OffsetInContainerBlock();
+
+  EXPECT_EQ(PositionWithAffinity(Position(text, 2), TextAffinity::kUpstream),
+            cursor.PositionForPointInChild(left_top + PhysicalOffset(-5, 0)));
+  EXPECT_EQ(PositionWithAffinity(Position(text, 2), TextAffinity::kUpstream),
+            cursor.PositionForPointInChild(left_top));
+  EXPECT_EQ(PositionWithAffinity(Position(text, 2), TextAffinity::kUpstream),
+            cursor.PositionForPointInChild(left_top + PhysicalOffset(5, 0)));
+  EXPECT_EQ(PositionWithAffinity(Position(text, 1)),
+            cursor.PositionForPointInChild(left_top + PhysicalOffset(10, 0)));
+  EXPECT_EQ(PositionWithAffinity(Position(text, 1)),
+            cursor.PositionForPointInChild(left_top + PhysicalOffset(15, 0)));
+  EXPECT_EQ(PositionWithAffinity(Position(text, 0)),
+            cursor.PositionForPointInChild(left_top + PhysicalOffset(20, 0)));
+  EXPECT_EQ(PositionWithAffinity(Position(text, 0)),
+            cursor.PositionForPointInChild(left_top + PhysicalOffset(25, 0)));
+}
+
+TEST_P(NGInlineCursorTest, PositionForPointInChildVerticalLTR) {
+  LoadAhem();
+  InsertStyleElement(
+      "p {"
+      "direction: ltr;"
+      "font: 10px/20px Ahem;"
+      "padding: 10px;"
+      "writing-mode: vertical-lr;"
+      "}");
+  NGInlineCursor cursor = SetupCursor("<p id=root>ab</p>");
+  const auto& text = *To<Text>(GetElementById("root")->firstChild());
+  ASSERT_TRUE(cursor.Current().IsLineBox());
+  EXPECT_EQ(PhysicalRect(PhysicalOffset(10, 10), PhysicalSize(20, 20)),
+            cursor.Current().RectInContainerBlock());
+
+  cursor.MoveTo(*text.GetLayoutObject());
+  EXPECT_EQ(PhysicalRect(PhysicalOffset(15, 10), PhysicalSize(10, 20)),
+            cursor.Current().RectInContainerBlock());
+  const PhysicalOffset left_top = cursor.Current().OffsetInContainerBlock();
+
+  EXPECT_EQ(PositionWithAffinity(Position(text, 0)),
+            cursor.PositionForPointInChild(left_top + PhysicalOffset(0, -5)));
+  EXPECT_EQ(PositionWithAffinity(Position(text, 0)),
+            cursor.PositionForPointInChild(left_top));
+  EXPECT_EQ(PositionWithAffinity(Position(text, 0)),
+            cursor.PositionForPointInChild(left_top + PhysicalOffset(0, 5)));
+  EXPECT_EQ(PositionWithAffinity(Position(text, 1)),
+            cursor.PositionForPointInChild(left_top + PhysicalOffset(0, 10)));
+  EXPECT_EQ(PositionWithAffinity(Position(text, 1)),
+            cursor.PositionForPointInChild(left_top + PhysicalOffset(0, 15)));
+  EXPECT_EQ(PositionWithAffinity(Position(text, 2), TextAffinity::kUpstream),
+            cursor.PositionForPointInChild(left_top + PhysicalOffset(0, 20)));
+  EXPECT_EQ(PositionWithAffinity(Position(text, 2), TextAffinity::kUpstream),
+            cursor.PositionForPointInChild(left_top + PhysicalOffset(0, 25)));
+}
+
+TEST_P(NGInlineCursorTest, PositionForPointInChildVerticalRTL) {
+  LoadAhem();
+  InsertStyleElement(
+      "p {"
+      "direction: rtl;"
+      "font: 10px/20px Ahem;"
+      "padding: 10px;"
+      "writing-mode: vertical-rl;"
+      "}");
+  NGInlineCursor cursor = SetupCursor("<p id=root><bdo dir=rtl>AB</bdo></p>");
+  const auto& text =
+      *To<Text>(GetElementById("root")->firstChild()->firstChild());
+  ASSERT_TRUE(cursor.Current().IsLineBox());
+  EXPECT_EQ(PhysicalRect(PhysicalOffset(10, 10), PhysicalSize(20, 20)),
+            cursor.Current().RectInContainerBlock());
+
+  cursor.MoveTo(*text.GetLayoutObject());
+  EXPECT_EQ(PhysicalRect(PhysicalOffset(15, 10), PhysicalSize(10, 20)),
+            cursor.Current().RectInContainerBlock());
+  const PhysicalOffset left_top = cursor.Current().OffsetInContainerBlock();
+
+  EXPECT_EQ(PositionWithAffinity(Position(text, 2), TextAffinity::kUpstream),
+            cursor.PositionForPointInChild(left_top + PhysicalOffset(0, -5)));
+  EXPECT_EQ(PositionWithAffinity(Position(text, 2), TextAffinity::kUpstream),
+            cursor.PositionForPointInChild(left_top));
+  EXPECT_EQ(PositionWithAffinity(Position(text, 2), TextAffinity::kUpstream),
+            cursor.PositionForPointInChild(left_top + PhysicalOffset(0, 5)));
+  EXPECT_EQ(PositionWithAffinity(Position(text, 1)),
+            cursor.PositionForPointInChild(left_top + PhysicalOffset(0, 10)));
+  EXPECT_EQ(PositionWithAffinity(Position(text, 1)),
+            cursor.PositionForPointInChild(left_top + PhysicalOffset(0, 15)));
+  EXPECT_EQ(PositionWithAffinity(Position(text, 0)),
+            cursor.PositionForPointInChild(left_top + PhysicalOffset(0, 20)));
+  EXPECT_EQ(PositionWithAffinity(Position(text, 0)),
+            cursor.PositionForPointInChild(left_top + PhysicalOffset(0, 25)));
+}
+
 TEST_P(NGInlineCursorTest, Previous) {
   // TDOO(yosin): Remove <style> once NGFragmentItem don't do culled inline.
   InsertStyleElement("b { background: gray; }");