RenderTextWin: Break runs at UBLOCK_MISCELLANEOUS_SYMBOLS.

ui/gfx/render_text_win.cc

 // Copyright (c) 2012 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_win.h"
 
 #include <algorithm>
 
 #include "base/i18n/break_iterator.h"
 #include "base/i18n/char_iterator.h"
@@ skipping 228 matching lines @@
           DCHECK_EQ(segment->x_range.end(), previous_segment->x_range.start());
         }
 
         previous_segment = segment;
         previous_segment_line = i;
       }
     }
   }
 }
 
+// Returns true if characters of |block_code| may trigger font fallback.
+bool IsUnusualBlockCode(const UBlockCode block_code) {
+  return block_code == UBLOCK_GEOMETRIC_SHAPES ||
+         block_code == UBLOCK_MISCELLANEOUS_SYMBOLS;
+}
+
 }  // namespace
 
 namespace internal {
 
 TextRun::TextRun()
   : font_style(0),
     strike(false),
     diagonal_strike(false),
     underline(false),
     width(0),
@@ skipping 652 matching lines @@
     run_break = std::min(script_item_break,
                          TextIndexToLayoutIndex(style.GetRange().end()));
 
     // Clamp run lengths to avoid exceeding the maximum supported glyph count.
     if ((run_break - run->range.start()) > max_run_length) {
       run_break = run->range.start() + max_run_length;
       if (!IsValidCodePointIndex(layout_text, run_break))
         --run_break;
     }
 
-    // Break runs adjacent to UBLOCK_GEOMETRIC_SHAPES character substrings.
+    // Break runs adjacent to character substrings in certain code blocks.
     // This avoids using their fallback fonts for more characters than needed,
     // in cases like "\x25B6 Media Title", etc. http://crbug.com/278913
     if (run_break > run->range.start()) {
       const size_t run_start = run->range.start();
       const int32 run_length = static_cast<int32>(run_break - run_start);
       base::i18n::UTF16CharIterator iter(layout_text.c_str() + run_start,
                                          run_length);
       const UBlockCode first_block_code = ublock_getCode(iter.get());
+      const bool first_block_unusual = IsUnusualBlockCode(first_block_code);
       while (iter.Advance() && iter.array_pos() < run_length) {
         const UBlockCode current_block_code = ublock_getCode(iter.get());
         if (current_block_code != first_block_code &&
-            (current_block_code == UBLOCK_GEOMETRIC_SHAPES ||
-             first_block_code == UBLOCK_GEOMETRIC_SHAPES)) {
+            (first_block_unusual || IsUnusualBlockCode(current_block_code))) {
           run_break = run_start + iter.array_pos();
           break;
         }
       }
     }
 
     DCHECK(IsValidCodePointIndex(layout_text, run_break));
 
     style.UpdatePosition(LayoutIndexToTextIndex(run_break));
     if (script_item_break == run_break)
@@ skipping 294 matching lines @@
   size_t position = LayoutIndexToTextIndex(run->range.end());
   position = IndexOfAdjacentGrapheme(position, CURSOR_BACKWARD);
   return SelectionModel(position, CURSOR_FORWARD);
 }
 
 RenderText* RenderText::CreateInstance() {
   return new RenderTextWin;
 }
 
 }  // namespace gfx