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

base/i18n/break_iterator.cc

Index: base/i18n/break_iterator.cc
diff --git a/base/i18n/break_iterator.cc b/base/i18n/break_iterator.cc
index fe26a03a0b89fa85ba7501d4aaf9dd59464369f3..4d72a9f8e84665ee27c178beb3163dc06cba22ed 100644
--- a/base/i18n/break_iterator.cc
+++ b/base/i18n/break_iterator.cc
@@ -138,13 +138,13 @@ bool BreakIterator::SetText(const base::char16* text, const size_t length) {
 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));
@@ -154,7 +154,7 @@ bool BreakIterator::IsEndOfWord(size_t position) const {
 
 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));
@@ -163,6 +163,14 @@ bool BreakIterator::IsStartOfWord(size_t position) const {
   return (!!boundary && next_status != UBRK_WORD_NONE);
 }
 
+bool BreakIterator::IsGraphemeBoundary(size_t position) const {
+  if (break_type_ != BREAK_CHARACTER)

[msw, 2014/06/29 22:29:09]

q: Wouldn't any other break type work, except perhaps RULE_BASED?
(ex. wouldn't any line/word break also be a character break?)

[ckocagil, 2014/07/24 21:46:55]

Makes sense, but I'm not sure. We can ask the BreakIterator owner after your
review.

[msw, 2014/07/25 00:36:59]

+jshin for thoughts here and general BreakIterator review.

+    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_);