Make hit testing after ::after content works correctly

This patch changes |NGInlineCursor::PositionForPointInInlineBox()| to
ignore pseudo element and layout generated text, e.g. ellipsis, and
style generated text, "content" in ::before/::after, to handle clicking
right of content of ::after correctly.

Before this patch, |closest_child_before| (point) holds fragment item
for value of CSS "content" in |PositionForPointInInlineBox()|, then
|PositionForPointInInlineBox()| returns null position because style
generated text is not DOM position.

After this patch, |closest_child_because| (point) holds fragment item
for last layout object having non-null |GetNode()| before pseudo
element ::after.

Bug: 1164974
Change-Id: Iaba2f0807c345b13463b956e009b730449121096
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2627242
Commit-Queue: Koji Ishii <kojii@chromium.org>
Auto-Submit: Yoshifumi Inoue <yosin@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#843942}

third_party/blink/renderer/core/layout/layout_view_test.cc

@@ -149,6 +149,15 @@ class LayoutViewHitTestTest : public testing::WithParamInterface<HitTestConfig>,
     GetFrame().GetSettings()->SetEditingBehaviorType(
         GetParam().editing_behavior);
   }
+
+  PositionWithAffinity HitTest(const PhysicalOffset offset) {
+    const HitTestRequest hit_request(HitTestRequest::kActive);
+    const HitTestLocation hit_location(offset);
+    HitTestResult hit_result(hit_request, hit_location);
+    if (!GetLayoutView().HitTest(hit_location, hit_result))
+      return PositionWithAffinity();
+    return hit_result.GetPosition();
+  }
 };
 
 INSTANTIATE_TEST_SUITE_P(
@@ -614,4 +623,53 @@ TEST_P(LayoutViewHitTestTest, HitTestVerticalRLRoot) {
       result.GetPosition());
 }
 
+// http://crbug.com/1164974
+TEST_P(LayoutViewHitTestTest, PseudoElementAfterBlock) {
+  LoadAhem();
+  InsertStyleElement(
+      "body { margin: 0px; font: 10px/15px Ahem; }"
+      "p::after { content: 'XY' }");
+  SetBodyInnerHTML("<div><p id=target>ab</p></div>");
+  const auto& text_ab = *To<Text>(GetElementById("target")->firstChild());
+  // In legacy layout, this position comes from |LayoutBlock::PositionBox()|
+  // for mac/unix, or |LayoutObject::FindPosition()| on android/windows.
+  const auto expected = PositionWithAffinity(
+      IsAndroidOrWindowsEditingBehavior() ? Position(text_ab, 2)
+                                          : Position(text_ab, 0),
+      LayoutNG() && IsAndroidOrWindowsEditingBehavior()
+          ? TextAffinity::kUpstream
+          : TextAffinity::kDownstream);
+
+  EXPECT_EQ(expected, HitTest(PhysicalOffset(20, 5))) << "after ab";
+  EXPECT_EQ(expected, HitTest(PhysicalOffset(25, 5))) << "at X";
+  EXPECT_EQ(expected, HitTest(PhysicalOffset(35, 5))) << "at Y";
+  EXPECT_EQ(expected, HitTest(PhysicalOffset(40, 5))) << "after Y";
+  EXPECT_EQ(expected, HitTest(PhysicalOffset(50, 5))) << "after XY";
+}
+
+TEST_P(LayoutViewHitTestTest, PseudoElementAfterBlockWithMargin) {
+  LoadAhem();
+  InsertStyleElement(
+      "body { margin: 0px; font: 10px/15px Ahem; }"
+      "p::after { content: 'XY'; margin-left: 10px;}");
+  SetBodyInnerHTML("<div><p id=target>ab</p></div>");
+  const auto& text_ab = *To<Text>(GetElementById("target")->firstChild());
+  // In legacy layout, this position comes from |LayoutBlock::PositionBox()|
+  // for mac/unix, or |LayoutObject::FindPosition()| on android/windows.
+  const auto expected = PositionWithAffinity(
+      IsAndroidOrWindowsEditingBehavior() ? Position(text_ab, 2)
+                                          : Position(text_ab, 0),
+      LayoutNG() && IsAndroidOrWindowsEditingBehavior()
+          ? TextAffinity::kUpstream
+          : TextAffinity::kDownstream);
+
+  EXPECT_EQ(expected, HitTest(PhysicalOffset(20, 5))) << "after ab";
+  EXPECT_EQ(expected, HitTest(PhysicalOffset(25, 5))) << "at margin-left";
+  EXPECT_EQ(expected, HitTest(PhysicalOffset(30, 5))) << "before X";
+  EXPECT_EQ(expected, HitTest(PhysicalOffset(35, 5))) << "at X";
+  EXPECT_EQ(expected, HitTest(PhysicalOffset(45, 5))) << "at Y";
+  EXPECT_EQ(expected, HitTest(PhysicalOffset(50, 5))) << "after Y";
+  EXPECT_EQ(expected, HitTest(PhysicalOffset(55, 5))) << "after XY";
+}
+
 }  // namespace blink

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

@@ -68,6 +68,31 @@ bool IsLastBRInPage(const LayoutObject& layout_object) {
   return layout_object.IsBR() && !layout_object.NextInPreOrder();
 }
 
+bool ShouldIgnoreForPositionForPoint(const NGFragmentItem& item) {
+  switch (item.Type()) {
+    case NGFragmentItem::kBox:
+      if (item.BoxFragment()) {
+        // Skip pseudo element ::before/::after
+        // All/LayoutViewHitTestTest.PseudoElementAfter* needs this.
+        return !item.GetLayoutObject()->NonPseudoNode();
+      }
+      // Skip virtually "culled" inline box, e.g. <span>foo</span>
+      // "editing/selection/shift-click.html" reaches here.
+      DCHECK(item.GetLayoutObject()->IsLayoutInline()) << item;
+      return true;
+    case NGFragmentItem::kGeneratedText:
+      return true;
+    case NGFragmentItem::kText:
+      // Returns true when |item.GetLayoutObject().IsStyleGenerated()|.
+      // All/LayoutViewHitTestTest.PseudoElementAfter* needs this.
+      return item.IsGeneratedText();
+    case NGFragmentItem::kLine:
+      NOTREACHED();
+      break;
+  }
+  return false;
+}
+
 }  // namespace
 
 inline void NGInlineCursor::MoveToItem(const ItemsSpan::iterator& iter) {
@@ -620,13 +645,8 @@ PositionWithAffinity NGInlineCursor::PositionForPointInInlineBox(
   for (; descendants; descendants.MoveToNext()) {
     const NGFragmentItem* child_item = descendants.CurrentItem();
     DCHECK(child_item);
-    if (child_item->Type() == NGFragmentItem::kBox &&
-        !child_item->BoxFragment()) {
-      // Skip virtually "culled" inline box, e.g. <span>foo</span>
-      // "editing/selection/shift-click.html" reaches here.
-      DCHECK(child_item->GetLayoutObject()->IsLayoutInline()) << child_item;
+    if (ShouldIgnoreForPositionForPoint(*child_item))
       continue;
-    }
     const LayoutUnit child_inline_offset =
         child_item->OffsetInContainerFragment()
             .ConvertToLogical(writing_direction, container_size,