Detect missing glyphs as returned by Vista in RenderTextWin.

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/logging.h"
@@ skipping 635 matching lines @@
         glyphs_missing = true;
       } else if (hr == S_OK) {
         // If |hr| is S_OK, there could still be missing glyphs in the output,
         // see: http://msdn.microsoft.com/en-us/library/windows/desktop/dd368564.aspx
         ScriptGetFontProperties(cached_hdc_, &run->script_cache, &properties);
         for (int i = 0; i < run->glyph_count; ++i) {
           if (run->glyphs[i] == properties.wgDefault) {
             glyphs_missing = true;
             break;
           }
+
+          // On Vista, when trying to draw Simplified Chinese via font linking,

[msw, 2012/05/02 22:19:09]

Perhaps generalize this comment if there may be other plaform/font triggers.
Consider mentioning the bug.

[Alexei Svitkine (slow), 2012/05/03 14:37:20]

Done.

+          // missing glyphs in the Meiryo font are returned as wgBlank instead
+          // of wgDefault, with fZeroWidth set.
+          if (run->glyphs[i] == properties.wgBlank &&
+              run->visible_attributes[i].fZeroWidth) {
+            // Check whether this glyph corresponds entirely to whitespace. If
+            // it doesn't, assume there are missing glyphs.
+            const ui::Range range = GetTextRangeForRunGlyph(run, i);
+            DCHECK_NE(0U, range.length());

[msw, 2012/05/02 22:19:09]

Use DCHECK_GT? Also DCHECK_LT/LE(range.end(), run->range.end()))?

+
+            const string16 glyph_text(&run_text[range.start()], range.length());
+            if (!ContainsOnlyWhitespace(glyph_text)) {
+               glyphs_missing = true;
+               break;
+            }
+          }
         }
       }
 
       // Skip font substitution if there are no missing glyphs.
       if (!glyphs_missing)
         break;
 
       // If there are missing glyphs, first try finding a fallback font using a
       // meta file, if it hasn't yet been attempted for this run.
       // TODO(msw|asvitkine): Support RenderText's font_list()?
@@ skipping 131 matching lines @@
   // Find the text run containing the argument point (assumed already offset).
   size_t run = 0;
   for (; run < runs_.size(); ++run)
     if (runs_[run]->preceding_run_widths <= point.x() &&
         runs_[run]->preceding_run_widths + runs_[run]->width > point.x())
       break;
   return run;
 }
 
 SelectionModel RenderTextWin::FirstSelectionModelInsideRun(
-    internal::TextRun* run) {
+    const internal::TextRun* run) {
   size_t cursor = IndexOfAdjacentGrapheme(run->range.start(), CURSOR_FORWARD);
   return SelectionModel(cursor, CURSOR_BACKWARD);
 }
 
 SelectionModel RenderTextWin::LastSelectionModelInsideRun(
-    internal::TextRun* run) {
+    const internal::TextRun* run) {
   size_t caret = IndexOfAdjacentGrapheme(run->range.end(), CURSOR_BACKWARD);
   return SelectionModel(caret, CURSOR_FORWARD);
 }
 
+ui::Range RenderTextWin::GetTextRangeForRunGlyph(const internal::TextRun* run,
+                                                 size_t glyph_index) const {
+  int first_seen = -1;
+  int last_seen = -1;
+  for (size_t char_index = 0; char_index < run->range.length(); ++char_index) {
+    if (run->logical_clusters[char_index] == glyph_index) {
+      last_seen = char_index;
+      if (first_seen == -1)
+        first_seen = char_index;
+    }
+  }
+  DCHECK_NE(first_seen, -1);
+  return ui::Range(first_seen, last_seen + 1);
+}
+
 RenderText* RenderText::CreateRenderText() {
   return new RenderTextWin;
 }
 
 }  // namespace gfx