Shows Japanese and English mixed queries correctly.

ui/gfx/font_list.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 <stdlib.h>
 
 #include "base/logging.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
@@ skipping 128 matching lines @@
   int font_style = 0;
   ParseFontDescriptionString(font_description_string_, &font_names,
                              &font_style, &old_size);
 
   if (old_size == size)
     return FontList(font_description_string_);
 
   return FontList(BuildFontDescription(font_names, font_style, size));
 }
 
+int FontList::GetHeight() const {
+  int ascent = 0;
+  int descent = 0;
+
+  const std::vector<Font>& fonts = GetFonts();
+  for (std::vector<Font>::const_iterator i = fonts.begin();
+       i != fonts.end(); ++i) {
+    ascent = std::max(ascent, i->GetBaseline());
+    descent = std::max(descent, i->GetHeight() - i->GetBaseline());
+  }
+  return ascent + descent;

[msw, 2013/07/11 22:47:29]

Does this meaningfully differ from max(i->GetHeight())? Why is this better?
i.e. does max(h) =?= max(b) + max(h-b) in this case?

[Yuki, 2013/07/12 08:25:53]

I supposed there could be two fonts.
  Spec of Font A: ascent = 5, descent = 0, height = 5
  Spec of Font B: ascent = 0, descent = 5, height = 5
In this case, we need 5 pixels for ascent and another 5 pixels for descent to
draw text on the same baseline.  So font height must be 5 + 5 = 10 pixels, and
baseline must be 5 pixels.

In order to respect the baseline, we should take care ascent and descent
separately.

[msw, 2013/07/12 09:36:04]

Perfect example and explanation, thanks! But text may still jarringly vertically
re-align when input yields new, e.g. taller font. Should FontList or some user
anticipate fonts by locale or past/system languages? Do you think that's worth
filing a bug or adding a TODO?

[Yuki, 2013/07/12 10:29:24]

I'm optimistic for that case.  Most of Latin fonts have enough space above and
below the baseline.  I don't remember any character needs extra space.

If a FontList has only a Japanese font (smaller), and the text includes Latin
characters (taller), the problem occurs.  However, I think it's better to add
your favorite Latin font to the FontList rather than anticipating some default
fonts.  For better UX, we should choose the best Latin font for Japanese text. 
At least, Serif or Sans Serif matters.

Summary
1. Most users type/read Latin characters in addition to their native language.
2. We should specify Latin font in addition to their native language's font.
3. Latin font should have enough space.

I don't think it's worth to file a bug or add a TODO.

[msw, 2013/07/12 10:41:58]

sgtm, we can just followup if any actual defects are observed.

+}
+
+int FontList::GetBaseline() const {
+  int baseline = 0;
+

[msw, 2013/07/11 22:47:29]

nit: remove blank line.

[Yuki, 2013/07/12 08:25:53]

Done.

+  const std::vector<Font>& fonts = GetFonts();
+  for (std::vector<Font>::const_iterator i = fonts.begin();
+       i != fonts.end(); ++i) {
+    baseline = std::max(baseline, i->GetBaseline());
+  }
+  return baseline;
+}
+
 int FontList::GetFontStyle() const {
   if (!fonts_.empty())
     return fonts_[0].GetStyle();
 
   std::vector<std::string> font_names;
   int font_style;
   int font_size;
   ParseFontDescriptionString(font_description_string_, &font_names,
                              &font_style, &font_size);
   return font_style;
@@ skipping 30 matching lines @@
       if (font_style == Font::NORMAL)
         fonts_.push_back(font);
       else
         fonts_.push_back(font.DeriveFont(0, font_style));
     }
   }
   return fonts_;
 }
 
 }  // namespace gfx