Mac: Fix PlatformFontMac::DeriveFont.

ui/gfx/platform_font_mac_unittest.mm

 // 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 <Cocoa/Cocoa.h>
 #include <stddef.h>
 
 #include "base/macros.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/gfx/font.h"
@@ skipping 18 matching lines @@
 
   // Bold italic
   gfx::Font bold_italic_font(
       base_font.Derive(0, gfx::Font::ITALIC, gfx::Font::Weight::BOLD));
   traits = [[NSFontManager sharedFontManager]
       traitsOfFont:bold_italic_font.GetNativeFont()];
   EXPECT_EQ(static_cast<NSFontTraitMask>(NSBoldFontMask | NSItalicFontMask),
             traits);
 }
 
+TEST(PlatformFontMacTest, DeriveFontUnderline) {
+  // Create a default font.
+  gfx::Font base_font;
+
+  // Make the font underlined.
+  gfx::Font derived_font(base_font.Derive(
+      0, base_font.GetStyle() | gfx::Font::UNDERLINE, base_font.GetWeight()));
+
+  // Validate the derived font properties against its native font instance.
+  NSFontTraitMask traits = [[NSFontManager sharedFontManager]
+      traitsOfFont:derived_font.GetNativeFont()];
+  gfx::Font::Weight actual_weight = (traits & NSFontBoldTrait)
+                                        ? gfx::Font::Weight::BOLD
+                                        : gfx::Font::Weight::NORMAL;
+
+  int actual_style = gfx::Font::UNDERLINE;
+  if (traits & NSFontItalicTrait)
+    actual_style |= gfx::Font::ITALIC;
+
+  EXPECT_TRUE(derived_font.GetStyle() & gfx::Font::UNDERLINE);
+  EXPECT_EQ(derived_font.GetStyle(), actual_style);
+  EXPECT_EQ(derived_font.GetWeight(), actual_weight);
+}
+
 TEST(PlatformFontMacTest, ConstructFromNativeFont) {
   gfx::Font normal_font([NSFont fontWithName:@"Helvetica" size:12]);
   EXPECT_EQ(12, normal_font.GetFontSize());
   EXPECT_EQ("Helvetica", normal_font.GetFontName());
   EXPECT_EQ(gfx::Font::NORMAL, normal_font.GetStyle());
 
   gfx::Font bold_font([NSFont fontWithName:@"Helvetica-Bold" size:14]);
   EXPECT_EQ(14, bold_font.GetFontSize());
   EXPECT_EQ("Helvetica", bold_font.GetFontName());
   EXPECT_EQ(gfx::Font::Weight::BOLD, bold_font.GetWeight());
@@ skipping 46 matching lines @@
       // (plus baseline). So the height depends on the rounding of the ascender,
       // and can be as much as 1 greater than the simple sum of floats.
       EXPECT_LE(sum, font.GetHeight());
       EXPECT_GE(sum + 1, font.GetHeight());
 
       // Recreate the rounding performed for GetBaseLine().
       EXPECT_EQ(ceil(ceil(ascender) - descender + leading), font.GetHeight());
     }
   }
 }