Make NGInlineItemsBuilder construct whitespace-collapsed offset mapping

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

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/layout/ng/inline/ng_inline_items_builder.h"
 
 #include "core/layout/LayoutObject.h"
 #include "core/layout/ng/inline/ng_inline_node.h"
 #include "core/style/ComputedStyle.h"
 
 namespace blink {
 
+NGInlineItemsBuilder::NGInlineItemsBuilder(
+    Vector<NGInlineItem>* items,
+    Vector<Vector<unsigned>>* removed_indexes)
+    : items_(items),
+      removed_indexes_(removed_indexes),
+      input_strings_lengths_(Vector<unsigned>()) {
+  DCHECK(removed_indexes);
+}
+
 NGInlineItemsBuilder::~NGInlineItemsBuilder() {
   DCHECK_EQ(0u, exits_.size());
   DCHECK_EQ(text_.length(), items_->IsEmpty() ? 0 : items_->back().EndOffset());
 }
 
 String NGInlineItemsBuilder::ToString() {
   // Segment Break Transformation Rules[1] defines to keep trailing new lines,
   // but it will be removed in Phase II[2]. We prefer not to add trailing new
   // lines and collapsible spaces in Phase I.
   // [1] https://drafts.csswg.org/css-text-3/#line-break-transform
   // [2] https://drafts.csswg.org/css-text-3/#white-space-phase-2
   unsigned next_start_offset = text_.length();
-  RemoveTrailingCollapsibleSpaceIfExists(&next_start_offset);
+  bool trailing_space_removed =
+      RemoveTrailingCollapsibleSpaceIfExists(&next_start_offset);
+  if (trailing_space_removed && removed_indexes_) {
+    DCHECK(input_strings_lengths_);
+    AddLastTrailingSpaceToRemovedIndexes(input_strings_lengths_->back());
+  }
 
   return text_.ToString();
 }
 
 // Determine "Ambiguous" East Asian Width is Wide or Narrow.
 // Unicode East Asian Width
 // http://unicode.org/reports/tr11/
 static bool IsAmbiguosEastAsianWidthWide(const ComputedStyle* style) {
   UScriptCode script = style->GetFontDescription().GetScript();
   return script == USCRIPT_KATAKANA_OR_HIRAGANA ||
@@ skipping 81 matching lines @@
   return c == kSpaceCharacter || c == kTabulationCharacter ||
          c == kNewlineCharacter;
 }
 
 // Characters needing a separate control item than other text items.
 // It makes the line breaker easier to handle.
 static inline bool IsControlItemCharacter(UChar c) {
   return c == kTabulationCharacter || c == kNewlineCharacter;
 }
 
+// Returns the largest integer in [0, |max|) that is absent in |integers|, or
+// kNotFound if such an integer does not exist.
+static size_t GetLargestAbsentInteger(const Vector<unsigned>& integers,
+                                      unsigned max) {
+  DCHECK(integers.IsEmpty() || integers.back() < max);
+  if (!max || integers.size() == max)
+    return kNotFound;
+  if (integers.IsEmpty() || integers.back() + 1 < max)
+    return max - 1;
+  for (unsigned i = integers.size() - 1; i;) {
+    DCHECK_LT(integers[i - 1], integers[i]);
+    if (integers[i - 1] + 1 < integers[i] - 1)
+      return integers[i] - 1;
+    --i;
+  }
+  DCHECK_GT(integers[0], 0u);
+  return integers[0] - 1;
+}
+
 void NGInlineItemsBuilder::Append(const String& string,
                                   const ComputedStyle* style,
                                   LayoutObject* layout_object) {
+  if (removed_indexes_) {
+    DCHECK(input_strings_lengths_);
+    input_strings_lengths_->push_back(string.length());
+    removed_indexes_->emplace_back();
+  }
+
   if (string.IsEmpty())
     return;
   text_.ReserveCapacity(string.length());
 
   EWhiteSpace whitespace = style->WhiteSpace();
   if (!ComputedStyle::CollapseWhiteSpace(whitespace))
     return AppendWithoutWhiteSpaceCollapsing(string, style, layout_object);
   if (ComputedStyle::PreserveNewline(whitespace) && !is_svgtext_)
     return AppendWithPreservingNewlines(string, style, layout_object);
 
   AppendWithWhiteSpaceCollapsing(string, 0, string.length(), style,
                                  layout_object);
 }
 
 void NGInlineItemsBuilder::AppendWithWhiteSpaceCollapsing(
     const String& string,
     unsigned start,
     unsigned end,
     const ComputedStyle* style,
     LayoutObject* layout_object) {
   unsigned start_offset = text_.length();
   for (unsigned i = start; i < end;) {
     UChar c = string[i];
     if (c == kNewlineCharacter) {
       // LayoutBR does not set preserve_newline, but should be preserved.
       if (!i && end == 1 && layout_object && layout_object->IsBR()) {
-        AppendForcedBreak(style, layout_object);
+        bool trailing_space_removed = AppendForcedBreak(style, layout_object);
+        if (trailing_space_removed && removed_indexes_)
+          AddLastTrailingSpaceToRemovedIndexes(i);

[kojii, 2017/06/19 05:56:33]

Why don't we add to removed_indexes in RemoveTrailingCollapsibleSpaceIfExists()
but let it return the result and do here?

[Xiaocheng, 2017/06/19 17:53:01]

Updating |removed_indexes_| needs the number of characters in the current string
that have been processed (i.e., |i|).

Let me try passing in this parameter instead, and hope that the performance
impact is negligible.

         return;
       }
 
       if (last_collapsible_space_ == CollapsibleSpace::kNone)
         text_.Append(kSpaceCharacter);
+      else if (removed_indexes_)
+        removed_indexes_->back().push_back(i);
       last_collapsible_space_ = CollapsibleSpace::kNewline;
       i++;
       continue;
     }
 
     if (c == kSpaceCharacter || c == kTabulationCharacter) {
       if (last_collapsible_space_ == CollapsibleSpace::kNone) {
         text_.Append(kSpaceCharacter);
         last_collapsible_space_ = CollapsibleSpace::kSpace;
+      } else if (removed_indexes_) {
+        removed_indexes_->back().push_back(i);
       }
       i++;
       continue;
     }
 
     if (last_collapsible_space_ == CollapsibleSpace::kNewline) {
-      RemoveTrailingCollapsibleNewlineIfNeeded(&start_offset, string, i, style);
+      bool trailing_newline_removed = RemoveTrailingCollapsibleNewlineIfNeeded(
+          &start_offset, string, i, style);
+      if (trailing_newline_removed && removed_indexes_)
+        AddLastTrailingSpaceToRemovedIndexes(i);
     }
 
     size_t end_of_non_space = string.Find(IsCollapsibleSpace, i + 1);
     if (end_of_non_space == kNotFound)
       end_of_non_space = string.length();
     text_.Append(string, i, end_of_non_space - i);
     i = end_of_non_space;
     last_collapsible_space_ = CollapsibleSpace::kNone;
   }
 
@@ skipping 29 matching lines @@
 
   last_collapsible_space_ = CollapsibleSpace::kNone;
 }
 
 void NGInlineItemsBuilder::AppendWithPreservingNewlines(
     const String& string,
     const ComputedStyle* style,
     LayoutObject* layout_object) {
   for (unsigned start = 0; start < string.length();) {
     if (string[start] == kNewlineCharacter) {
-      AppendForcedBreak(style, layout_object);
+      bool trailing_space_removed = AppendForcedBreak(style, layout_object);
+      if (trailing_space_removed && removed_indexes_)
+        AddLastTrailingSpaceToRemovedIndexes(start);
       start++;
       continue;
     }
 
     size_t end = string.find(kNewlineCharacter, start + 1);
     if (end == kNotFound)
       end = string.length();
     AppendWithWhiteSpaceCollapsing(string, start, end, style, layout_object);
     start = end;
   }
 }
 
-void NGInlineItemsBuilder::AppendForcedBreak(const ComputedStyle* style,
+bool NGInlineItemsBuilder::AppendForcedBreak(const ComputedStyle* style,
                                              LayoutObject* layout_object) {
   // Remove collapsible spaces immediately before a preserved newline.
   unsigned start_offset = text_.length();
-  RemoveTrailingCollapsibleSpaceIfExists(&start_offset);
+  bool trailing_space_removed =
+      RemoveTrailingCollapsibleSpaceIfExists(&start_offset);
 
   Append(NGInlineItem::kControl, kNewlineCharacter, style, layout_object);
 
   // Remove collapsible spaces immediately after a preserved newline.
   last_collapsible_space_ = CollapsibleSpace::kSpace;
+  return trailing_space_removed;
 }
 
 void NGInlineItemsBuilder::Append(NGInlineItem::NGInlineItemType type,
                                   UChar character,
                                   const ComputedStyle* style,
                                   LayoutObject* layout_object) {
   DCHECK_NE(character, kSpaceCharacter);
   DCHECK_NE(character, kZeroWidthSpaceCharacter);
 
   text_.Append(character);
   unsigned end_offset = text_.length();
   AppendItem(items_, type, end_offset - 1, end_offset, style, layout_object);
   last_collapsible_space_ = CollapsibleSpace::kNone;
 }
 
 void NGInlineItemsBuilder::Append(NGInlineItem::NGInlineItemType type,
                                   const ComputedStyle* style,
                                   LayoutObject* layout_object) {
   unsigned end_offset = text_.length();
   AppendItem(items_, type, end_offset, end_offset, style, layout_object);
 }
 
-void NGInlineItemsBuilder::RemoveTrailingCollapsibleNewlineIfNeeded(
+bool NGInlineItemsBuilder::RemoveTrailingCollapsibleNewlineIfNeeded(
     unsigned* next_start_offset,
     const String& after,
     unsigned after_index,
     const ComputedStyle* after_style) {
   DCHECK_EQ(last_collapsible_space_, CollapsibleSpace::kNewline);
 
   if (text_.IsEmpty() || text_[text_.length() - 1] != kSpaceCharacter)
-    return;
+    return false;
 
   const ComputedStyle* before_style = after_style;
   if (!items_->IsEmpty()) {
     NGInlineItem& item = items_->back();
     if (text_.length() < item.EndOffset() + 2)
       before_style = item.Style();
   }
 
-  if (ShouldRemoveNewline(text_, before_style, after, after_index, after_style))
-    RemoveTrailingCollapsibleSpace(next_start_offset);
+  if (!ShouldRemoveNewline(text_, before_style, after, after_index,
+                           after_style))
+    return false;
+  RemoveTrailingCollapsibleSpace(next_start_offset);
+  return true;
 }
 
-void NGInlineItemsBuilder::RemoveTrailingCollapsibleSpaceIfExists(
+bool NGInlineItemsBuilder::RemoveTrailingCollapsibleSpaceIfExists(
     unsigned* next_start_offset) {
-  if (last_collapsible_space_ != CollapsibleSpace::kNone && !text_.IsEmpty() &&
-      text_[text_.length() - 1] == kSpaceCharacter)
-    RemoveTrailingCollapsibleSpace(next_start_offset);
+  if (last_collapsible_space_ == CollapsibleSpace::kNone || text_.IsEmpty() ||
+      text_[text_.length() - 1] != kSpaceCharacter)
+    return false;
+  RemoveTrailingCollapsibleSpace(next_start_offset);
+  return true;
 }
 
 void NGInlineItemsBuilder::RemoveTrailingCollapsibleSpace(
     unsigned* next_start_offset) {
   DCHECK_NE(last_collapsible_space_, CollapsibleSpace::kNone);
   DCHECK(!text_.IsEmpty());
   DCHECK_EQ(text_[text_.length() - 1], kSpaceCharacter);
 
   unsigned new_size = text_.length() - 1;
   text_.Resize(new_size);
@@ skipping 18 matching lines @@
     if (!item.Length()) {
       // Trailing spaces can be removed across non-character items.
       item.SetOffset(new_size, new_size);
       continue;
     }
     NOTREACHED();
     break;
   }
 }
 
+void NGInlineItemsBuilder::AddLastTrailingSpaceToRemovedIndexes(
+    unsigned last_string_end) {
+  DCHECK(removed_indexes_);
+  DCHECK(input_strings_lengths_);
+  DCHECK_EQ(removed_indexes_->size(), input_strings_lengths_->size());
+  for (unsigned i = removed_indexes_->size(); i;) {
+    Vector<unsigned>& indexes = (*removed_indexes_)[--i];
+    size_t last_unremoved =
+        GetLargestAbsentInteger(indexes, (i + 1) == removed_indexes_->size()
+                                             ? last_string_end
+                                             : (*input_strings_lengths_)[i]);
+    if (last_unremoved == kNotFound)
+      continue;
+
+    indexes.insert(
+        std::lower_bound(indexes.begin(), indexes.end(), last_unremoved) -
+            indexes.begin(),
+        last_unremoved);
+    return;
+  }
+  NOTREACHED();
+}
+
 void NGInlineItemsBuilder::AppendBidiControl(const ComputedStyle* style,
                                              UChar ltr,
                                              UChar rtl) {
   Append(NGInlineItem::kBidiControl,
          style->Direction() == TextDirection::kRtl ? rtl : ltr);
 }
 
 void NGInlineItemsBuilder::EnterBlock(const ComputedStyle* style) {
   // Handle bidi-override on the block itself.
   switch (style->GetUnicodeBidi()) {
@@ skipping 76 matching lines @@
 }
 
 void NGInlineItemsBuilder::Exit(LayoutObject* node) {
   while (!exits_.IsEmpty() && exits_.back().node == node) {
     Append(NGInlineItem::kBidiControl, exits_.back().character);
     exits_.pop_back();
   }
 }
 
 }  // namespace blink