Use pango underline metrics in RenderTextLinux.

ui/gfx/render_text_linux.cc

Index: ui/gfx/render_text_linux.cc
===================================================================
--- ui/gfx/render_text_linux.cc	(revision 140345)
+++ ui/gfx/render_text_linux.cc	(working copy)
@@ -70,6 +70,18 @@
   return subpixel_enabled;
 }
 
+// Sets underline metrics on |renderer| according to Pango font |desc|.
+void SetPangoUnderlineMetrics(PangoFontDescription *desc,
+                              internal::SkiaTextRenderer* renderer) {
+  PangoFontMetrics* metrics = GetPangoFontMetrics(desc);
+  const int underline_thickness =

[msw, 2012/06/06 01:12:51]

nit: nix "underline_" from the names to fit each on one line.

[Alexei Svitkine (slow), 2012/06/06 14:46:27]

Done.

+      pango_font_metrics_get_underline_thickness(metrics);
+  const int underline_position =
+      pango_font_metrics_get_underline_position(metrics);
+  renderer->SetUnderlineMetrics(pango_units_to_double(underline_thickness),
+                                pango_units_to_double(underline_position));
+}
+
 }  // namespace
 
 // TODO(xji): index saved in upper layer is utf16 index. Pango uses utf8 index.
@@ -445,6 +457,8 @@
         renderer.SetForegroundColor(styles[style].foreground);
         renderer.SetFontFamilyWithStyle(family_name, styles[style].font_style);
         renderer.DrawPosText(&pos[start], &glyphs[start], i - start);
+        if (styles[style].underline)
+          SetPangoUnderlineMetrics(desc.get(), &renderer);
         renderer.DrawDecorations(start_x, y, glyph_x - start_x, styles[style]);
 
         start = i;
@@ -461,6 +475,8 @@
     renderer.SetForegroundColor(styles[style].foreground);
     renderer.SetFontFamilyWithStyle(family_name, styles[style].font_style);
     renderer.DrawPosText(&pos[start], &glyphs[start], glyph_count - start);
+    if (styles[style].underline)
+      SetPangoUnderlineMetrics(desc.get(), &renderer);
     renderer.DrawDecorations(start_x, y, glyph_x - start_x, styles[style]);
     x = glyph_x;
   }