Improve RenderTextWin font fallback.

ui/gfx/render_text.cc

Index: ui/gfx/render_text.cc
===================================================================
--- ui/gfx/render_text.cc	(revision 111944)
+++ ui/gfx/render_text.cc	(working copy)
@@ -67,8 +67,9 @@
     } else if (i->range.end() > new_range.end()) {
       i->range.set_start(new_range.end());
       break;
-    } else
+    } else {
       NOTREACHED();
+    }
   }
   // Add the new range in its sorted location.
   style_ranges->insert(i, style_range);
@@ -186,8 +187,8 @@
   MoveCursorTo(position);
 }
 
-bool RenderText::MoveCursorTo(const SelectionModel& selection_model) {
-  SelectionModel sel(selection_model);
+bool RenderText::MoveCursorTo(const SelectionModel& model) {
+  SelectionModel sel(model);
   size_t text_length = text().length();
   // Enforce valid selection model components.
   if (sel.selection_start() > text_length)
@@ -205,10 +206,12 @@
     sel.set_caret_placement(end.caret_placement());
   }
 
-  if (!IsCursorablePosition(sel.selection_start()) ||
-      !IsCursorablePosition(sel.selection_end()) ||
-      !IsCursorablePosition(sel.caret_pos()))
+  if (!IsCursorablePosition(sel.selection_start(), false) ||
+      !IsCursorablePosition(sel.selection_end(), false) ||
+      !IsCursorablePosition(sel.caret_pos(),
+          (sel.caret_placement() == SelectionModel::TRAILING))) {

[xji, 2011/11/29 21:15:48]

I did not quite get the reason of introducing "bool is_trailing" to
IsCursorablePosition.

As to this call site, it originally means caret_pos() itself should also be a
cursorable position regardless whether it is the leading edge or trailing edge.

For example:
ABC,  "BC" belongs to one grapheme, 
cursorable positions are |ABC, A|BC, and ABC|.
If selection model is (2, trailing, 3), which means caret_pos is 2, it is the
trailing edge of 2nd character, and the logical index is 3, it is not a correct
selection_model because 2nd character is not the start of a grapheme.

After this change, if caret_placement() is trailing, does 
IsCursorPosition(sel.caret_pos(), true)
check the same position as
IsCursorPosition(sel.selection_end(), false)?

will it be treated as a valid selection model in Win?

     return false;
+  }
 
   bool changed = !sel.Equals(selection_model_);
   SetSelectionModel(sel);
@@ -227,7 +230,7 @@
   size_t start = std::min(range.start(), text_length);
   size_t end = std::min(range.end(), text_length);
 
-  if (!IsCursorablePosition(start) || !IsCursorablePosition(end))
+  if (!IsCursorablePosition(start, false) || !IsCursorablePosition(end, false))
     return false;
 
   size_t pos = end;
@@ -410,7 +413,7 @@
   // binary searching the cursor position.
   // TODO(oshima): use the center of character instead of edge.
   // Binary search may not work for language like Arabic.
-  while (std::abs(static_cast<long>(right_pos - left_pos)) > 1) {
+  while (std::abs(right_pos - left_pos) > 1) {
     int pivot_pos = left_pos + (right_pos - left_pos) / 2;
     int pivot = font.GetStringWidth(text().substr(0, pivot_pos));
     if (pivot < x) {
@@ -479,8 +482,7 @@
                                                  BreakType break_type) {
   if (break_type == LINE_BREAK)
     return LeftEndSelectionModel();
-  size_t pos = std::max(static_cast<long>(current.selection_end() - 1),
-                        static_cast<long>(0));
+  size_t pos = std::max<int>(current.selection_end() - 1, 0);
   if (break_type == CHARACTER_BREAK)
     return SelectionModel(pos, pos, SelectionModel::LEADING);
 
@@ -610,8 +612,7 @@
   selection_model_.set_selection_start(selection_model.selection_start());
   DCHECK_LE(selection_model.selection_end(), text().length());
   selection_model_.set_selection_end(selection_model.selection_end());
-  DCHECK_LT(selection_model.caret_pos(),
-            std::max(text().length(), static_cast<size_t>(1)));
+  DCHECK_LT(selection_model.caret_pos(), std::max<size_t>(text().length(), 1));
   selection_model_.set_caret_pos(selection_model.caret_pos());
   selection_model_.set_caret_placement(selection_model.caret_placement());
 
@@ -625,7 +626,7 @@
   SelectionModel::CaretPlacement placement = (caret_pos == cursor) ?
       SelectionModel::LEADING : SelectionModel::TRAILING;
   size_t selection_start = select ? GetSelectionStart() : cursor;
-  if (IsCursorablePosition(cursor)) {
+  if (IsCursorablePosition(cursor, false)) {
     SelectionModel sel(selection_start, cursor, caret_pos, placement);
     SetSelectionModel(sel);
   }