Adjust GetLeft/RightSelectionModel return, cursor on edit.

ui/gfx/render_text.h

 // 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.
 
 #ifndef UI_GFX_RENDER_TEXT_H_
 #define UI_GFX_RENDER_TEXT_H_
 #pragma once
 
 #include <algorithm>
 #include <vector>
@@ skipping 31 matching lines @@
 
   Font font;
   SkColor foreground;
   bool strike;
   bool underline;
   ui::Range range;
 };
 
 typedef std::vector<StyleRange> StyleRanges;
 
-// TODO(msw): Distinguish between logical character and glyph?
+// TODO(msw): Distinguish between logical character stops and glyph stops?
+// CHARACTER_BREAK cursor movements should stop at neighboring characters.
+// WORD_BREAK cursor movements should stop at the nearest word boundaries.
+// LINE_BREAK cursor movements should stop at the text ends as shown on screen.
 enum BreakType {
   CHARACTER_BREAK,
   WORD_BREAK,
   LINE_BREAK,
 };
 
 // TODO(xji): publish bidi-editing guide line and replace the place holder.
 // SelectionModel is used to represent the logical selection and visual
 // position of cursor.
 //
@@ skipping 116 matching lines @@
   size_t GetCursorPosition() const;
   void SetCursorPosition(const size_t position);
 
   void SetCaretPlacement(SelectionModel::CaretPlacement placement) {
       selection_model_.set_caret_placement(placement);
   }
 
   // Moves the cursor left or right. Cursor movement is visual, meaning that
   // left and right are relative to screen, not the directionality of the text.
   // If |select| is false, the selection range is emptied at the new position.
-  // If |break_type| is CHARACTER_BREAK, move to the neighboring character.
-  // If |break_type| is WORD_BREAK, move to the nearest word boundary.
-  // If |break_type| is LINE_BREAK, move to text edge as shown on screen.
   void MoveCursorLeft(BreakType break_type, bool select);
   void MoveCursorRight(BreakType break_type, bool select);
 
   // Set the selection_model_ to the value of |selection|.
   // Returns true if the cursor position or selection range changed.
   bool MoveCursorTo(const SelectionModel& selection);
 
   // Move the cursor to the position associated with the clicked point.
   // If |select| is false, the selection range is emptied at the new position.
   bool MoveCursorTo(const Point& point, bool select);
@@ skipping 54 matching lines @@
   // the values for later use and return cursor_bounds_.
   const Rect& CursorBounds();
 
  protected:
   RenderText();
 
   void set_cursor_bounds_valid(bool valid) { cursor_bounds_valid_ = valid; }
 
   const StyleRanges& style_ranges() const { return style_ranges_; }
 
-  // Get the cursor position that visually neighbors |position|.
-  // If |move_by_word| is true, return the neighboring word delimiter position.
-  virtual SelectionModel GetLeftCursorPosition(const SelectionModel& current,
-                                               bool move_by_word);
-  virtual SelectionModel GetRightCursorPosition(const SelectionModel& current,
-                                                bool move_by_word);
+  // Get the selection model that visually neighbors |position| by |break_type|.
+  // The returned value represents a cursor/caret position without a selection.
+  virtual SelectionModel GetLeftSelectionModel(const SelectionModel& current,
+                                               BreakType break_type);
+  virtual SelectionModel GetRightSelectionModel(const SelectionModel& current,
+                                                BreakType break_type);
+
+  // Get the logical index of the grapheme preceeding the argument |position|.
+  virtual size_t GetIndexOfPreviousGrapheme(size_t position) const;
 
   // Apply composition style (underline) to composition range and selection
   // style (foreground) to selection range.
   void ApplyCompositionAndSelectionStyles(StyleRanges* style_ranges) const;
 
  private:
   friend class RenderTextTest;
 
   FRIEND_TEST_ALL_PREFIXES(RenderTextTest, DefaultStyle);
   FRIEND_TEST_ALL_PREFIXES(RenderTextTest, CustomDefaultStyle);
@@ skipping 39 matching lines @@
   Rect display_rect_;
   // The offset for the text to be drawn, relative to the display area.
   Point display_offset_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderText);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_RENDER_TEXT_H_