[LayoutNG] Add NG alternatives of LayoutText::ContainsCaretOffset

This patch adds LayoutNG alternatives of LayoutText::ContainsCaretOffset for
both "common" LayoutText and ::first-letter LayoutTextFragments, with an
extensive set of unit tests.

Bug: 771398
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_layout_ng
Change-Id: I59b17046c271bf8c5c1fb4fdf7421b37a3183073
Reviewed-on: https://chromium-review.googlesource.com/724262Reviewed-by: Koji Ishii <kojii@chromium.org>
Commit-Queue: Xiaocheng Hu <xiaochengh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#510130}

third_party/WebKit/Source/core/layout/LayoutText.cpp

@@ -1992,7 +1992,21 @@ bool LayoutText::HasNonCollapsedText() const {
 }
 
 bool LayoutText::ContainsCaretOffset(int text_offset) const {
-  // TODO(crbug.com/771398): Add LayoutNG alternative.
+  DCHECK_GE(text_offset, 0);
+  if (ShouldUseNGAlternatives()) {
+    // ::first-letter handling should be done by LayoutTextFragment override.
+    DCHECK(!IsTextFragment());
+    if (!GetNode())
+      return false;
+    const NGOffsetMappingResult& mapping = GetNGOffsetMapping();
+    if (mapping.IsNonCollapsedCharacter(*GetNode(), text_offset))
+      return true;
+    if (!mapping.IsAfterNonCollapsedCharacter(*GetNode(), text_offset))
+      return false;
+    return *mapping.GetCharacterBefore(*GetNode(), text_offset) !=
+           kNewlineCharacter;
+  }
+
   for (InlineTextBox* box : InlineTextBoxesOf(*this)) {
     if (text_offset < static_cast<int>(box->Start()) &&
         !ContainsReversedText()) {

third_party/WebKit/Source/core/layout/LayoutText.h

@@ -206,7 +206,7 @@ class CORE_EXPORT LayoutText : public LayoutObject {
   // or segment break in node with style white-space: pre/pre-line/pre-wrap).
   // TODO(editing-dev): The behavior is introduced by crrev.com/e3eb4e in
   // InlineTextBox::ContainsCaretOffset(). Try to understand it.
-  bool ContainsCaretOffset(int) const;
+  virtual bool ContainsCaretOffset(int) const;
 
   int CaretMinOffset() const override;
   int CaretMaxOffset() const override;

third_party/WebKit/Source/core/layout/LayoutTextFragment.cpp

@@ -222,4 +222,25 @@ unsigned LayoutTextFragment::ResolvedTextLength() const {
   return end - start;
 }
 
+bool LayoutTextFragment::ContainsCaretOffset(int text_offset) const {
+  if (!ShouldUseNGAlternatives())
+    return LayoutText::ContainsCaretOffset(text_offset);
+
+  DCHECK_GE(text_offset, 0);
+  if (text_offset > static_cast<int>(FragmentLength()))
+    return false;
+  const Node* node = AssociatedTextNode();
+  if (!node)
+    return false;
+  const unsigned dom_offset = text_offset + Start();
+  const NGOffsetMappingResult& mapping = GetNGOffsetMapping();
+  if (mapping.IsNonCollapsedCharacter(*node, dom_offset))
+    return true;
+  if (text_offset == 0)
+    return false;
+  if (!mapping.IsAfterNonCollapsedCharacter(*node, dom_offset))
+    return false;
+  return *mapping.GetCharacterBefore(*node, dom_offset) != kNewlineCharacter;
+}
+
 }  // namespace blink

third_party/WebKit/Source/core/layout/LayoutTextFragment.h

@@ -51,6 +51,7 @@ class CORE_EXPORT LayoutTextFragment final : public LayoutText {
 
   bool IsTextFragment() const override { return true; }
 
+  bool ContainsCaretOffset(int) const override;
   int CaretMinOffset() const override;
   int CaretMaxOffset() const override;
   unsigned ResolvedTextLength() const override;

third_party/WebKit/Source/core/layout/LayoutTextFragmentTest.cpp

@@ -41,10 +41,12 @@ TEST_F(LayoutTextFragmentTest, LegacyBasics) {
   EXPECT_EQ(0, GetFirstLetter()->CaretMinOffset());
   EXPECT_EQ(1, GetFirstLetter()->CaretMaxOffset());
   EXPECT_EQ(1u, GetFirstLetter()->ResolvedTextLength());
+  EXPECT_TRUE(GetFirstLetter()->ContainsCaretOffset(0));
 
   EXPECT_EQ(0, GetRemainingText()->CaretMinOffset());
   EXPECT_EQ(2, GetRemainingText()->CaretMaxOffset());
   EXPECT_EQ(2u, GetRemainingText()->ResolvedTextLength());
+  EXPECT_TRUE(GetRemainingText()->ContainsCaretOffset(0));
 }
 
 TEST_F(LayoutTextFragmentTest, CaretMinMaxOffsetNG) {
@@ -181,4 +183,105 @@ TEST_F(LayoutTextFragmentTest, ResolvedTextLengthCollapsedRemainingTextNG) {
   EXPECT_EQ(0u, GetRemainingText()->ResolvedTextLength());
 }
 
+TEST_F(LayoutTextFragmentTest, ContainsCaretOffsetNG) {
+  ScopedLayoutNGForTest layout_ng(true);
+  ScopedLayoutNGPaintFragmentsForTest layout_ng_paint_fragments(true);
+
+  SetBasicBody("(f)oo");
+  EXPECT_TRUE(GetFirstLetter()->ContainsCaretOffset(0));     // "|(f)oo"
+  EXPECT_TRUE(GetFirstLetter()->ContainsCaretOffset(1));     // "(|f)oo"
+  EXPECT_TRUE(GetFirstLetter()->ContainsCaretOffset(2));     // "(f|)oo"
+  EXPECT_TRUE(GetFirstLetter()->ContainsCaretOffset(3));     // "(f)|oo"
+  EXPECT_FALSE(GetFirstLetter()->ContainsCaretOffset(4));    // out of range
+  EXPECT_TRUE(GetRemainingText()->ContainsCaretOffset(0));   // "(f)|oo"
+  EXPECT_TRUE(GetRemainingText()->ContainsCaretOffset(1));   // "(f)o|o"
+  EXPECT_TRUE(GetRemainingText()->ContainsCaretOffset(2));   // "(f)oo|"
+  EXPECT_FALSE(GetRemainingText()->ContainsCaretOffset(3));  // out of range
+
+  SetBasicBody("  (f)oo");
+  EXPECT_FALSE(GetFirstLetter()->ContainsCaretOffset(0));   // "|  (f)oo"
+  EXPECT_FALSE(GetFirstLetter()->ContainsCaretOffset(1));   // " | (f)oo"
+  EXPECT_TRUE(GetFirstLetter()->ContainsCaretOffset(2));    // "  |(f)oo"
+  EXPECT_TRUE(GetFirstLetter()->ContainsCaretOffset(3));    // "  (|f)oo"
+  EXPECT_TRUE(GetFirstLetter()->ContainsCaretOffset(4));    // "  (f|)oo"
+  EXPECT_TRUE(GetFirstLetter()->ContainsCaretOffset(5));    // "  (f)|oo"
+  EXPECT_TRUE(GetRemainingText()->ContainsCaretOffset(0));  // "  (f)|oo"
+  EXPECT_TRUE(GetRemainingText()->ContainsCaretOffset(1));  // "  (f)o|o"
+  EXPECT_TRUE(GetRemainingText()->ContainsCaretOffset(2));  // "  (f)oo|"
+
+  SetBasicBody("(f)oo  ");
+  EXPECT_TRUE(GetFirstLetter()->ContainsCaretOffset(0));     // "|(f)oo  "
+  EXPECT_TRUE(GetFirstLetter()->ContainsCaretOffset(1));     // "(|f)oo  "
+  EXPECT_TRUE(GetFirstLetter()->ContainsCaretOffset(2));     // "(f|)oo  "
+  EXPECT_TRUE(GetFirstLetter()->ContainsCaretOffset(3));     // "(f)|oo  "
+  EXPECT_TRUE(GetRemainingText()->ContainsCaretOffset(0));   // "(f)|oo  "
+  EXPECT_TRUE(GetRemainingText()->ContainsCaretOffset(1));   // "(f)o|o  "
+  EXPECT_TRUE(GetRemainingText()->ContainsCaretOffset(2));   // "(f)oo|  "
+  EXPECT_FALSE(GetRemainingText()->ContainsCaretOffset(3));  // "(f)oo | "
+  EXPECT_FALSE(GetRemainingText()->ContainsCaretOffset(4));  // "(f)oo  |"
+
+  SetBasicBody(" (f)oo  ");
+  EXPECT_FALSE(GetFirstLetter()->ContainsCaretOffset(0));    // "| (f)oo  "
+  EXPECT_TRUE(GetFirstLetter()->ContainsCaretOffset(1));     // " |(f)oo  "
+  EXPECT_TRUE(GetFirstLetter()->ContainsCaretOffset(2));     // " (|f)oo  "
+  EXPECT_TRUE(GetFirstLetter()->ContainsCaretOffset(3));     // " (f|)oo  "
+  EXPECT_TRUE(GetFirstLetter()->ContainsCaretOffset(4));     // " (f)|oo  "
+  EXPECT_TRUE(GetRemainingText()->ContainsCaretOffset(0));   // " (f)|oo  "
+  EXPECT_TRUE(GetRemainingText()->ContainsCaretOffset(1));   // " (f)o|o  "
+  EXPECT_TRUE(GetRemainingText()->ContainsCaretOffset(2));   // " (f)oo|  "
+  EXPECT_FALSE(GetRemainingText()->ContainsCaretOffset(3));  // " (f)oo | "
+  EXPECT_FALSE(GetRemainingText()->ContainsCaretOffset(4));  // " (f)oo  |"
+}
+
+TEST_F(LayoutTextFragmentTest, ContainsCaretOffsetSpacesInBetweenNG) {
+  ScopedLayoutNGForTest layout_ng(true);
+  ScopedLayoutNGPaintFragmentsForTest layout_ng_paint_fragments(true);
+
+  SetBasicBody("(f)   oo");
+  EXPECT_TRUE(GetFirstLetter()->ContainsCaretOffset(0));     // "|(f)   oo"
+  EXPECT_TRUE(GetFirstLetter()->ContainsCaretOffset(1));     // "(|f)   oo"
+  EXPECT_TRUE(GetFirstLetter()->ContainsCaretOffset(2));     // "(f|)   oo"
+  EXPECT_TRUE(GetFirstLetter()->ContainsCaretOffset(3));     // "(f)|   oo"
+  EXPECT_TRUE(GetRemainingText()->ContainsCaretOffset(0));   // "(f)|   oo"
+  EXPECT_TRUE(GetRemainingText()->ContainsCaretOffset(1));   // "(f) |  oo"
+  EXPECT_FALSE(GetRemainingText()->ContainsCaretOffset(2));  // "(f)  | oo"
+  EXPECT_TRUE(GetRemainingText()->ContainsCaretOffset(3));   // "(f)   |oo"
+  EXPECT_TRUE(GetRemainingText()->ContainsCaretOffset(4));   // "(f)   o|o"
+  EXPECT_TRUE(GetRemainingText()->ContainsCaretOffset(5));   // "(f)   oo|"
+}
+
+TEST_F(LayoutTextFragmentTest, ContainsCaretOffsetPreNG) {
+  ScopedLayoutNGForTest layout_ng(true);
+  ScopedLayoutNGPaintFragmentsForTest layout_ng_paint_fragments(true);
+
+  SetBodyInnerHTML("<pre id='target'>(f)   oo\n</pre>");
+  EXPECT_TRUE(GetFirstLetter()->ContainsCaretOffset(0));     // "|(f)   oo\n"
+  EXPECT_TRUE(GetFirstLetter()->ContainsCaretOffset(1));     // "(|f)   oo\n"
+  EXPECT_TRUE(GetFirstLetter()->ContainsCaretOffset(2));     // "(f|)   oo\n"
+  EXPECT_TRUE(GetFirstLetter()->ContainsCaretOffset(3));     // "(f)|   oo\n"
+  EXPECT_TRUE(GetRemainingText()->ContainsCaretOffset(0));   // "(f)|   oo\n"
+  EXPECT_TRUE(GetRemainingText()->ContainsCaretOffset(1));   // "(f) |  oo\n"
+  EXPECT_TRUE(GetRemainingText()->ContainsCaretOffset(2));   // "(f)  | oo\n"
+  EXPECT_TRUE(GetRemainingText()->ContainsCaretOffset(3));   // "(f)   |oo\n"
+  EXPECT_TRUE(GetRemainingText()->ContainsCaretOffset(4));   // "(f)   o|o\n"
+  EXPECT_TRUE(GetRemainingText()->ContainsCaretOffset(5));   // "(f)   oo|\n"
+  EXPECT_FALSE(GetRemainingText()->ContainsCaretOffset(6));  // "(f)   oo\n|"
+}
+
+TEST_F(LayoutTextFragmentTest, ContainsCaretOffsetPreLineNG) {
+  ScopedLayoutNGForTest layout_ng(true);
+  ScopedLayoutNGPaintFragmentsForTest layout_ng_paint_fragments(true);
+
+  SetBodyInnerHTML("<div id='target' style='white-space: pre-line'>F \n \noo");
+  EXPECT_TRUE(GetFirstLetter()->ContainsCaretOffset(0));     // "|F \n \noo"
+  EXPECT_TRUE(GetFirstLetter()->ContainsCaretOffset(1));     // "F| \n \noo"
+  EXPECT_FALSE(GetRemainingText()->ContainsCaretOffset(0));  // "F| \n \noo"
+  EXPECT_TRUE(GetRemainingText()->ContainsCaretOffset(1));   // "F |\n \noo"
+  EXPECT_FALSE(GetRemainingText()->ContainsCaretOffset(2));  // "F \n| \noo"
+  EXPECT_TRUE(GetRemainingText()->ContainsCaretOffset(3));   // "F \n |\noo"
+  EXPECT_TRUE(GetRemainingText()->ContainsCaretOffset(4));   // "F \n \n|oo"
+  EXPECT_TRUE(GetRemainingText()->ContainsCaretOffset(5));   // "F \n \no|o"
+  EXPECT_TRUE(GetRemainingText()->ContainsCaretOffset(6));   // "F \n \noo|"
+}
+
 }  // namespace blink

third_party/WebKit/Source/core/layout/LayoutTextTest.cpp

@@ -184,4 +184,61 @@ TEST_F(LayoutTextTest, ContainsCaretOffsetInPre) {
   EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(7));  // "foo\nbar|"
 }
 
+TEST_F(LayoutTextTest, ContainsCaretOffsetNG) {
+  ScopedLayoutNGForTest layout_ng(true);
+  ScopedLayoutNGPaintFragmentsForTest layout_ng_paint_fragments(true);
+
+  // This test records the behavior introduced in crrev.com/e3eb4e
+  SetBasicBody(" foo   bar ");
+  EXPECT_FALSE(GetBasicText()->ContainsCaretOffset(0));   // "| foo   bar "
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(1));    // " |foo   bar "
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(2));    // " f|oo   bar "
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(3));    // " fo|o   bar "
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(4));    // " foo|   bar "
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(5));    // " foo |  bar "
+  EXPECT_FALSE(GetBasicText()->ContainsCaretOffset(6));   // " foo  | bar "
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(7));    // " foo   |bar "
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(8));    // " foo   b|ar "
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(9));    // " foo   ba|r "
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(10));   // " foo   bar| "
+  EXPECT_FALSE(GetBasicText()->ContainsCaretOffset(11));  // " foo   bar |"
+  EXPECT_FALSE(GetBasicText()->ContainsCaretOffset(12));  // out of range
+}
+
+TEST_F(LayoutTextTest, ContainsCaretOffsetNGInPre) {
+  ScopedLayoutNGForTest layout_ng(true);
+  ScopedLayoutNGPaintFragmentsForTest layout_ng_paint_fragments(true);
+
+  // These tests record the behavior introduced in crrev.com/e3eb4e
+
+  SetBodyInnerHTML("<pre id='target'>foo   bar</pre>");
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(0));  // "|foo   bar"
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(1));  // "f|oo   bar"
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(2));  // "fo|o   bar"
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(3));  // "foo|   bar"
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(4));  // "foo |  bar"
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(5));  // "foo  | bar"
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(6));  // "foo   |bar"
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(7));  // "foo   b|ar"
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(8));  // "foo   ba|r"
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(9));  // "foo   bar|"
+
+  SetBodyInnerHTML("<pre id='target'>foo\n</pre>");
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(0));   // "|foo\n"
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(1));   // "f|oo\n"
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(2));   // "fo|o\n"
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(3));   // "foo|\n"
+  EXPECT_FALSE(GetBasicText()->ContainsCaretOffset(4));  // "foo\n|"
+
+  SetBodyInnerHTML("<pre id='target'>foo\nbar</pre>");
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(0));  // "|foo\nbar"
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(1));  // "f|oo\nbar"
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(2));  // "fo|o\nbar"
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(3));  // "foo|\nbar"
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(4));  // "foo\n|bar"
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(5));  // "foo\nb|ar"
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(6));  // "foo\nba|r"
+  EXPECT_TRUE(GetBasicText()->ContainsCaretOffset(7));  // "foo\nbar|"
+}
+
 }  // namespace blink

third_party/WebKit/Source/core/layout/ng/inline/ng_offset_mapping_result.cc

@@ -185,4 +185,13 @@ bool NGOffsetMappingResult::IsAfterNonCollapsedCharacter(
          unit->GetType() != NGOffsetMappingUnitType::kCollapsed;
 }
 
+Optional<UChar> NGOffsetMappingResult::GetCharacterBefore(
+    const Node& node,
+    unsigned offset) const {
+  const size_t text_content_offset = GetTextContentOffset(node, offset);
+  if (text_content_offset == kNotFound || !text_content_offset)
+    return {};
+  return text_[text_content_offset - 1];
+}
+
 }  // namespace blink

third_party/WebKit/Source/core/layout/ng/inline/ng_offset_mapping_result.h

@@ -9,6 +9,7 @@
 #include "platform/heap/Handle.h"
 #include "platform/wtf/Allocator.h"
 #include "platform/wtf/HashMap.h"
+#include "platform/wtf/Optional.h"
 #include "platform/wtf/Vector.h"
 #include "platform/wtf/text/WTFString.h"
 
@@ -110,16 +111,19 @@ class CORE_EXPORT NGOffsetMappingResult {
                                                       unsigned) const;
 
   // Returns the text content offset corresponding to the given DOM offset.
+  // TODO(xiaochengh): Use Optional<> return type to indicate inexistent result.
   size_t GetTextContentOffset(const Node&, unsigned) const;
 
   // Starting from the given DOM offset in the node, finds the first
   // non-collapsed character and returns its offset; Or returns the last offset
   // in the node if such a character does not exist.
+  // TODO(xiaochengh): Use Optional<> return type to indicate inexistent result.
   unsigned StartOfNextNonCollapsedCharacter(const Node&, unsigned offset) const;
 
   // Starting from the given DOM offset in the node, reversely finds the first
   // non-collapsed character and returns 1 + its offset; Or returns 0 if such a
   // character does not exist.
+  // TODO(xiaochengh): Use Optional<> return type to indicate inexistent result.
   unsigned EndOfLastNonCollapsedCharacter(const Node&, unsigned offset) const;
 
   // Returns true if the character at the position is non-collapsed. If the
@@ -131,6 +135,10 @@ class CORE_EXPORT NGOffsetMappingResult {
   // offset is at the beginning of the node, returns false.
   bool IsAfterNonCollapsedCharacter(const Node&, unsigned offset) const;
 
+  // Maps the given DOM offset to text content, and then returns the text
+  // content character before the offset. Returns nullopt if it does not exist.
+  Optional<UChar> GetCharacterBefore(const Node&, unsigned offset) const;
+
   // TODO(xiaochengh): Add APIs for reverse mapping.
 
  private: