RenderTextHarfBuzz: Allow mid-glyph cursors in multi-grapheme clusters

base/i18n/break_iterator.cc

 // Copyright (c) 2011 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 "base/i18n/break_iterator.h"
 
 #include "base/logging.h"
 #include "third_party/icu/source/common/unicode/ubrk.h"
 #include "third_party/icu/source/common/unicode/uchar.h"
 #include "third_party/icu/source/common/unicode/ustring.h"
@@ skipping 120 matching lines @@
   if (U_FAILURE(status)) {
     NOTREACHED() << "ubrk_setText failed";
     return false;
   }
   return true;
 }
 
 bool BreakIterator::IsWord() const {
   int32_t status = ubrk_getRuleStatus(static_cast<UBreakIterator*>(iter_));
   if (break_type_ != BREAK_WORD && break_type_ != RULE_BASED)
-      return false;
+    return false;
   return status != UBRK_WORD_NONE;
 }
 
 bool BreakIterator::IsEndOfWord(size_t position) const {
   if (break_type_ != BREAK_WORD && break_type_ != RULE_BASED)
-      return false;
+    return false;
 
   UBreakIterator* iter = static_cast<UBreakIterator*>(iter_);
   UBool boundary = ubrk_isBoundary(iter, static_cast<int32_t>(position));
   int32_t status = ubrk_getRuleStatus(iter);
   return (!!boundary && status != UBRK_WORD_NONE);
 }
 
 bool BreakIterator::IsStartOfWord(size_t position) const {
   if (break_type_ != BREAK_WORD && break_type_ != RULE_BASED)
-      return false;
+    return false;
 
   UBreakIterator* iter = static_cast<UBreakIterator*>(iter_);
   UBool boundary = ubrk_isBoundary(iter, static_cast<int32_t>(position));
   ubrk_next(iter);
   int32_t next_status = ubrk_getRuleStatus(iter);
   return (!!boundary && next_status != UBRK_WORD_NONE);
 }
 
+bool BreakIterator::IsGraphemeBoundary(size_t position) const {
+  if (break_type_ != BREAK_CHARACTER)
+    return false;
+
+  UBreakIterator* iter = static_cast<UBreakIterator*>(iter_);
+  return !!ubrk_isBoundary(iter, static_cast<int32_t>(position));
+}
+
 string16 BreakIterator::GetString() const {
   DCHECK(prev_ != npos && pos_ != npos);
   return string_.substr(prev_, pos_ - prev_);
 }
 
 }  // namespace i18n
 }  // namespace base