[SH-Blink] Add ranges to text fragment selector

Add range to text fragment selector when selection is too long is spans
across block boundaries.
Gradually add words from beginning and end of the selection until unique
match is found.

Bug: 1102382
Change-Id: I71ce2623dae410aa7f21861bf2a6de6911cfe692
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2412698
Commit-Queue: Gayane Petrosyan <gayane@chromium.org>
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Reviewed-by: David Bokan <bokan@chromium.org>
Reviewed-by: Tommy Martino <tmartino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#808404}

third_party/blink/renderer/core/page/scrolling/text_fragment_selector_generator.cc

@@ -156,6 +156,7 @@ String GetWordsFromStart(String text, int word_num) {
 constexpr int kExactTextMaxChars = 300;
 constexpr int kNoContextMinChars = 20;
 constexpr int kMaxContextWords = 10;
+constexpr int kMaxRangeWords = 10;
 
 void TextFragmentSelectorGenerator::UpdateSelection(
     LocalFrame* selection_frame,
@@ -324,8 +325,73 @@ void TextFragmentSelectorGenerator::GenerateExactSelector() {
 }
 
 void TextFragmentSelectorGenerator::ExtendRangeSelector() {
-  // TODO(gayane): Generate range selector.
+  DCHECK_EQ(kRange, step_);
+  DCHECK_EQ(kNeedsNewCandidate, state_);
+
+  // Give up if range is already too long.
+  if (num_range_start_words_ == kMaxRangeWords ||
+      num_range_end_words_ == kMaxRangeWords) {
+    step_ = kContext;
+    return;
+  }
+
+  // Initialize range start and end, if needed.
+  if (max_available_range_start_.IsEmpty() &&
+      max_available_range_end_.IsEmpty()) {
+    EphemeralRangeInFlatTree ephemeral_range(selection_range_);
+
+    Node& start_first_block_ancestor =
+        FindBuffer::GetFirstBlockLevelAncestorInclusive(
+            *ephemeral_range.StartPosition().ComputeContainerNode());
+    Node& end_first_block_ancestor =
+        FindBuffer::GetFirstBlockLevelAncestorInclusive(
+            *ephemeral_range.EndPosition().ComputeContainerNode());
+
+    // If selection starts and ends in the same block, then split selected text
+    // roughly in the middle.
+    // TODO(gayane): Should also check that there are no nested blocks.
+    if (start_first_block_ancestor.isSameNode(&end_first_block_ancestor)) {
+      String selection_text = PlainText(ephemeral_range);
+      selection_text.Ensure16Bit();
+      int selection_length = selection_text.length();
+      int mid_point =
+          FindNextWordForward(selection_text.Characters16(), selection_length,
+                              selection_length / 2);
+      max_available_range_start_ = selection_text.Left(mid_point);
+
+      // If from middle till end of selection there is no word break, then we
+      // cannot use it for range end.
+      if (mid_point == selection_length) {
         state_ = kFailure;
+        return;
+      }
+
+      max_available_range_end_ =
+          selection_text.Right(selection_text.length() - mid_point - 1);
+    } else {
+      // If not the same node, then we use first and last block of the selection
+      // range.
+      max_available_range_start_ =
+          GetNextTextBlock(selection_range_->StartPosition());
+      max_available_range_end_ =
+          GetPreviousTextBlock(selection_range_->EndPosition());
+    }
+  }
+
+  String start =
+      GetWordsFromStart(max_available_range_start_, ++num_range_start_words_);
+  String end =
+      GetWordsFromEnd(max_available_range_end_, ++num_range_end_words_);
+
+  // If the start and end didn't change, it means we exhausted the selected
+  // text and should try adding context.
+  if (selector_ && start == selector_->Start() && end == selector_->End()) {
+    step_ = kContext;
+    return;
+  }
+  selector_ = std::make_unique<TextFragmentSelector>(
+      TextFragmentSelector::SelectorType::kRange, start, end, "", "");
+  state_ = kTestCandidate;
 }
 
 void TextFragmentSelectorGenerator::ExtendContext() {
@@ -347,9 +413,8 @@ void TextFragmentSelectorGenerator::ExtendContext() {
   // Try initiating properties necessary for calculating prefix and suffix.
   if (max_available_prefix_.IsEmpty() && max_available_suffix_.IsEmpty()) {
     max_available_prefix_ =
-        GetAvailablePrefixAsText(selection_range_->StartPosition());
-    max_available_suffix_ =
-        GetAvailableSuffixAsText(selection_range_->EndPosition());
+        GetPreviousTextBlock(selection_range_->StartPosition());
+    max_available_suffix_ = GetNextTextBlock(selection_range_->EndPosition());
   }
 
   if (max_available_prefix_.IsEmpty() && max_available_suffix_.IsEmpty()) {
@@ -371,7 +436,7 @@ void TextFragmentSelectorGenerator::ExtendContext() {
   state_ = kTestCandidate;
 }
 
-String TextFragmentSelectorGenerator::GetAvailablePrefixAsText(
+String TextFragmentSelectorGenerator::GetPreviousTextBlock(
     const Position& prefix_end_position) {
   Node* prefix_end = prefix_end_position.ComputeContainerNode();
   unsigned prefix_end_offset =
@@ -399,7 +464,7 @@ String TextFragmentSelectorGenerator::GetAvailablePrefixAsText(
   return PlainText(EphemeralRange(range_start, range_end)).StripWhiteSpace();
 }
 
-String TextFragmentSelectorGenerator::GetAvailableSuffixAsText(
+String TextFragmentSelectorGenerator::GetNextTextBlock(
     const Position& suffix_start_position) {
   Node* suffix_start = suffix_start_position.ComputeContainerNode();
   unsigned suffix_start_offset =

third_party/blink/renderer/core/page/scrolling/text_fragment_selector_generator.h

@@ -54,11 +54,11 @@ class CORE_EXPORT TextFragmentSelectorGenerator final
   void NotifySelectorReady(const TextFragmentSelector& selector);
 
   // Wrappers for tests.
-  String GetAvailablePrefixAsTextForTesting(const Position& position) {
-    return GetAvailablePrefixAsText(position);
+  String GetPreviousTextBlockForTesting(const Position& position) {
+    return GetPreviousTextBlock(position);
   }
-  String GetAvailableSuffixAsTextForTesting(const Position& position) {
-    return GetAvailableSuffixAsText(position);
+  String GetNextTextBlockForTesting(const Position& position) {
+    return GetNextTextBlock(position);
   }
 
   // Releases members if necessary.
@@ -94,11 +94,11 @@ class CORE_EXPORT TextFragmentSelectorGenerator final
 
   // Returns max text preceding given position that doesn't cross block
   // boundaries.
-  String GetAvailablePrefixAsText(const Position& position);
+  String GetPreviousTextBlock(const Position& position);
 
   // Returns max text following given position that doesn't cross block
   // boundaries.
-  String GetAvailableSuffixAsText(const Position& position);
+  String GetNextTextBlock(const Position& position);
 
   void GenerateExactSelector();
   void ExtendRangeSelector();
@@ -124,11 +124,17 @@ class CORE_EXPORT TextFragmentSelectorGenerator final
   String max_available_prefix_;
   String max_available_suffix_;
 
+  String max_available_range_start_;
+  String max_available_range_end_;
+
   // Indicates a number of words used from |max_available_prefix_| and
   // |max_available_suffix_| for the current |selector_|.
   int num_prefix_words_ = 0;
   int num_suffix_words_ = 0;
 
+  int num_range_start_words_ = 0;
+  int num_range_end_words_ = 0;
+
   DISALLOW_COPY_AND_ASSIGN(TextFragmentSelectorGenerator);
 };