Rewrite RenderText::IndexOfAdjacentGrapheme() in terms of IsCursorablePosition().

This moves the implementation of IndexOfAdjacentGrapheme() entirely into the base class, removing the need for platform-specific implementations.

This rewrite exposed a couple of problems in RenderTextLinux::IsCursorablePosition() that caused some tests to fail. The fixes are also included.

Also includes additional test coverage for UTF16 surrogate pairs, which was only caught by a Linux-specific password censorship test.

BUG=125664
TEST=Existing unit tests.

Review URL: https://chromiumcodereview.appspot.com/10389148

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@137320 0039d316-1c4b-4281-b951-d872f2087c98

7 files changed, 46 insertions, 83 deletions

diff --git a/ui/gfx/render_text.cc b/ui/gfx/render_text.cc
index 79ded6f..46b1d00 100644
--- a/ui/gfx/render_text.cc
+++ b/ui/gfx/render_text.cc
@@ -653,6 +653,30 @@ const Rect& RenderText::GetUpdatedCursorBounds() {
   return cursor_bounds_;
 }
 
+size_t RenderText::IndexOfAdjacentGrapheme(size_t index,
+    LogicalCursorDirection direction) {
+  if (index > text().length())
+    return text().length();
+
+  EnsureLayout();
+
+  if (direction == CURSOR_FORWARD) {
+    while (index < text().length()) {
+      index++;
+      if (IsCursorablePosition(index))
+        return index;
+    }
+    return text().length();
+  }
+
+  while (index > 0) {
+    index--;
+    if (IsCursorablePosition(index))
+      return index;
+  }
+  return 0;
+}
+
 SelectionModel RenderText::GetSelectionModelForSelectionStart() {
   const ui::Range& sel = selection();
   if (sel.is_empty())
diff --git a/ui/gfx/render_text.h b/ui/gfx/render_text.h
index 4398366..f50c1d1 100644
--- a/ui/gfx/render_text.h
+++ b/ui/gfx/render_text.h
@@ -269,8 +269,8 @@ class UI_EXPORT RenderText {
   // range 0 to text().length() inclusive (the input is clamped if it is out of
   // that range). Always moves by at least one character index unless the
   // supplied index is already at the boundary of the string.
-  virtual size_t IndexOfAdjacentGrapheme(size_t index,
-                                         LogicalCursorDirection direction) = 0;
+  size_t IndexOfAdjacentGrapheme(size_t index,
+                                 LogicalCursorDirection direction);
 
   // Return a SelectionModel with the cursor at the current selection's start.
   // The returned value represents a cursor/caret position without a selection.
diff --git a/ui/gfx/render_text_linux.cc b/ui/gfx/render_text_linux.cc
index d24f8be..f22342e 100644
--- a/ui/gfx/render_text_linux.cc
+++ b/ui/gfx/render_text_linux.cc
@@ -138,30 +138,6 @@ SelectionModel RenderTextLinux::FindCursorPosition(const Point& point) {
                         (trailing > 0) ? CURSOR_BACKWARD : CURSOR_FORWARD);
 }
 
-size_t RenderTextLinux::IndexOfAdjacentGrapheme(
-    size_t index,
-    LogicalCursorDirection direction) {
-  if (index > text().length())
-    return text().length();
-  EnsureLayout();
-  ptrdiff_t char_offset = ui::UTF16IndexToOffset(text(), 0, index);
-  if (direction == CURSOR_BACKWARD) {
-    if (char_offset > 0) {
-      do {
-        --char_offset;
-      } while (char_offset > 0 && !log_attrs_[char_offset].is_cursor_position);
-    }
-  } else {  // direction == CURSOR_FORWARD
-    if (char_offset < num_log_attrs_ - 1) {
-      do {
-        ++char_offset;
-      } while (char_offset < num_log_attrs_ - 1 &&
-               !log_attrs_[char_offset].is_cursor_position);
-    }
-  }
-  return ui::UTF16OffsetToIndex(text(), 0, char_offset);
-}
-
 std::vector<RenderText::FontSpan> RenderTextLinux::GetFontSpansForTesting() {
   EnsureLayout();
 
@@ -281,6 +257,10 @@ std::vector<Rect> RenderTextLinux::GetSubstringBounds(ui::Range range) {
 bool RenderTextLinux::IsCursorablePosition(size_t position) {
   if (position == 0 && text().empty())
     return true;
+  if (position >= text().length())
+    return position == text().length();
+  if (!ui::IsValidCodePointIndex(text(), position))
+    return false;
 
   EnsureLayout();
   ptrdiff_t offset = ui::UTF16IndexToOffset(text(), 0, position);
diff --git a/ui/gfx/render_text_linux.h b/ui/gfx/render_text_linux.h
index cd3bf9a..4bc665c 100644
--- a/ui/gfx/render_text_linux.h
+++ b/ui/gfx/render_text_linux.h
@@ -23,9 +23,6 @@ class RenderTextLinux : public RenderText {
   virtual base::i18n::TextDirection GetTextDirection() OVERRIDE;
   virtual Size GetStringSize() OVERRIDE;
   virtual SelectionModel FindCursorPosition(const Point& point) OVERRIDE;
-  virtual size_t IndexOfAdjacentGrapheme(
-      size_t index,
-      LogicalCursorDirection direction) OVERRIDE;
   virtual std::vector<FontSpan> GetFontSpansForTesting() OVERRIDE;
 
  protected:
diff --git a/ui/gfx/render_text_unittest.cc b/ui/gfx/render_text_unittest.cc
index f0802410..bc79dc7 100644
--- a/ui/gfx/render_text_unittest.cc
+++ b/ui/gfx/render_text_unittest.cc
@@ -617,6 +617,13 @@ TEST_F(RenderTextTest, GraphemePositions) {
   // LTR ab, LTR 2-character grapheme, LTR cd.
   const string16 kText2 = WideToUTF16(L"ab"L"\x0915\x093f"L"cd");
 
+  // The below is 'MUSICAL SYMBOL G CLEF', which is represented in UTF-16 as
+  // two characters forming the surrogate pair 0x0001D11E.
+  const std::string kSurrogate = "\xF0\x9D\x84\x9E";
+
+  // LTR ab, UTF16 surrogate pair, LTR cd.
+  const string16 kText3 = UTF8ToUTF16("ab" + kSurrogate + "cd");
+
   struct {
     string16 text;
     size_t index;
@@ -645,6 +652,15 @@ TEST_F(RenderTextTest, GraphemePositions) {
     { kText2, 6, 5, 6 },
     { kText2, 7, 6, 6 },
     { kText2, 50, 6, 6 },
+    { kText3, 0, 0, 1 },
+    { kText3, 1, 0, 2 },
+    { kText3, 2, 1, 4 },
+    { kText3, 3, 2, 4 },
+    { kText3, 4, 2, 5 },
+    { kText3, 5, 4, 6 },
+    { kText3, 6, 5, 6 },
+    { kText3, 7, 6, 6 },
+    { kText3, 50, 6, 6 },
   };
 
   // TODO(asvitkine): Disable tests that fail on XP bots due to lack of complete
diff --git a/ui/gfx/render_text_win.cc b/ui/gfx/render_text_win.cc
index b5cfec3..6705cb6 100644
--- a/ui/gfx/render_text_win.cc
+++ b/ui/gfx/render_text_win.cc
@@ -251,57 +251,6 @@ SelectionModel RenderTextWin::FindCursorPosition(const Point& point) {
   return SelectionModel(cursor, trailing ? CURSOR_BACKWARD : CURSOR_FORWARD);
 }
 
-size_t RenderTextWin::IndexOfAdjacentGrapheme(
-    size_t index,
-    LogicalCursorDirection direction) {
-  EnsureLayout();
-
-  if (text().empty())
-    return 0;
-
-  if (index >= text().length()) {
-    if (direction == CURSOR_FORWARD || index > text().length()) {
-      return text().length();
-    } else {
-      // The requested |index| is at the end of the text. Use the index of the
-      // last character to find the grapheme.
-      index = text().length() - 1;
-      if (IsCursorablePosition(index))
-        return index;
-    }
-  }
-
-  size_t run_index =
-      GetRunContainingCaret(SelectionModel(index, CURSOR_FORWARD));
-  DCHECK(run_index < runs_.size());
-  internal::TextRun* run = runs_[run_index];
-  size_t start = run->range.start();
-  size_t ch = index - start;
-
-  if (direction == CURSOR_BACKWARD) {
-    // If |ch| is the start of the run, use the preceding run, if any.
-    if (ch == 0) {
-      if (run_index == 0)
-        return 0;
-      run = runs_[run_index - 1];
-      start = run->range.start();
-      ch = run->range.length();
-    }
-
-    // Loop to find the start of the grapheme.
-    WORD cluster = run->logical_clusters[ch - 1];
-    do {
-      ch--;
-    } while (ch > 0 && run->logical_clusters[ch - 1] == cluster);
-  } else {  // direction == CURSOR_FORWARD
-    WORD cluster = run->logical_clusters[ch];
-    while (ch < run->range.length() && run->logical_clusters[ch] == cluster)
-      ch++;
-  }
-
-  return start + ch;
-}
-
 std::vector<RenderText::FontSpan> RenderTextWin::GetFontSpansForTesting() {
   EnsureLayout();
 
diff --git a/ui/gfx/render_text_win.h b/ui/gfx/render_text_win.h
index 9a5ff65..02fc0a0 100644
--- a/ui/gfx/render_text_win.h
+++ b/ui/gfx/render_text_win.h
@@ -69,9 +69,6 @@ class RenderTextWin : public RenderText {
   virtual base::i18n::TextDirection GetTextDirection() OVERRIDE;
   virtual Size GetStringSize() OVERRIDE;
   virtual SelectionModel FindCursorPosition(const Point& point) OVERRIDE;
-  virtual size_t IndexOfAdjacentGrapheme(
-      size_t index,
-      LogicalCursorDirection direction) OVERRIDE;
   virtual std::vector<FontSpan> GetFontSpansForTesting() OVERRIDE;
 
  protected: