Implement Pango RenderText for Linux.

ui/gfx/render_text.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 "ui/gfx/render_text.h"
 
 #include <algorithm>
 
 #include "base/i18n/break_iterator.h"
 #include "base/logging.h"
@@ skipping 181 matching lines @@
   sel.set_caret_placement(SelectionModel::TRAILING);
   SetSelectionModel(sel);
 }
 
 void RenderText::MoveCursorLeft(BreakType break_type, bool select) {
   SelectionModel position(selection_model());
   position.set_selection_start(GetCursorPosition());
   // Cancelling a selection moves to the edge of the selection.
   if (break_type != LINE_BREAK && !EmptySelection() && !select) {
     // Use the selection start if it is left of the selection end.
-    SelectionModel selection_start(GetSelectionStart(), GetSelectionStart(),
-                                   SelectionModel::LEADING);
+    SelectionModel selection_start =  GetSelectionModelForSelectionStart();
     if (GetCursorBounds(selection_start, false).x() <
         GetCursorBounds(position, false).x())
       position = selection_start;
     // For word breaks, use the nearest word boundary left of the selection.
     if (break_type == WORD_BREAK)
       position = GetLeftSelectionModel(position, break_type);
   } else {
     position = GetLeftSelectionModel(position, break_type);
   }
   if (select)
     position.set_selection_start(GetSelectionStart());
   MoveCursorTo(position);
 }
 
 void RenderText::MoveCursorRight(BreakType break_type, bool select) {
   SelectionModel position(selection_model());
   position.set_selection_start(GetCursorPosition());
   // Cancelling a selection moves to the edge of the selection.
   if (break_type != LINE_BREAK && !EmptySelection() && !select) {
     // Use the selection start if it is right of the selection end.
-    SelectionModel selection_start(GetSelectionStart(), GetSelectionStart(),
-                                   SelectionModel::LEADING);
+    SelectionModel selection_start = GetSelectionModelForSelectionStart();
     if (GetCursorBounds(selection_start, false).x() >
         GetCursorBounds(position, false).x())
       position = selection_start;
     // For word breaks, use the nearest word boundary right of the selection.
     if (break_type == WORD_BREAK)
       position = GetRightSelectionModel(position, break_type);
   } else {
     position = GetRightSelectionModel(position, break_type);
   }
   if (select)
@@ skipping 365 matching lines @@
     // Pan to show the cursor when it overflows to the right,
     delta_offset = display_rect_.right() - cursor_bounds_.right();
   } else if (cursor_bounds_.x() < display_rect_.x()) {
     // Pan to show the cursor when it overflows to the left.
     delta_offset = display_rect_.x() - cursor_bounds_.x();
   }
   display_offset_.Offset(delta_offset, 0);
   cursor_bounds_.Offset(delta_offset, 0);
 }
 
+SelectionModel RenderText::GetSelectionModelForSelectionStart() {
+  if (GetSelectionStart() < GetCursorPosition()) {
+    return SelectionModel(GetSelectionStart(),
+                          GetSelectionStart(),
+                          SelectionModel::LEADING);
+  } else {
+    return SelectionModel(GetSelectionStart(),
+                          GetIndexOfPreviousGrapheme(GetSelectionStart()),
+                          SelectionModel::TRAILING);
+  }
+}
+
 }  // namespace gfx