Calculate Underline thickness from Font

Source/platform/fonts/mac/SimpleFontDataMac.mm

 /*
  * Copyright (C) 2005, 2006, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Alexey Proskuryakov
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 137 matching lines @@
 
         // Special case hack to use "Times New Roman" in place of "Times".
         // "Times RO" is a common font whose family name is "Times".
         // It overrides the normal "Times" family font.
         // It also appears to have a corrupt regular variant.
         NSString *fallbackFontFamily;
         if ([[m_platformData.font() familyName] isEqual:@"Times"])
             fallbackFontFamily = @"Times New Roman";
         else
             fallbackFontFamily = webFallbackFontFamily();
-        
+
         // Try setting up the alternate font.
         // This is a last ditch effort to use a substitute font when something has gone wrong.
 #if !ERROR_DISABLED
         RetainPtr<NSFont> initialFont = m_platformData.font();
 #endif
         if (m_platformData.font())
             m_platformData.setFont([[NSFontManager sharedFontManager] convertFont:m_platformData.font() toFamily:fallbackFontFamily]);
         else
             m_platformData.setFont([NSFont fontWithName:fallbackFontFamily size:m_platformData.size()]);
 
@@ skipping 19 matching lines @@
             [m_platformData.font() familyName], [initialFont.get() familyName]);
     }
 
     // If all else fails, try to set up using the system font.
     // This is probably because Times and Times New Roman are both unavailable.
     if (failedSetup) {
         m_platformData.setFont([NSFont systemFontOfSize:[m_platformData.font() pointSize]]);
         WTF_LOG_ERROR("failed to set up font, using system font %s", m_platformData.font());
         initFontData(this);
     }
-    
+
     int iAscent;
     int iDescent;
     int iLineGap;
     unsigned unitsPerEm;
+
     iAscent = CGFontGetAscent(m_platformData.cgFont());
     // Some fonts erroneously specify a positive descender value. We follow Core Text in assuming that
     // such fonts meant the same distance, but in the reverse direction.
     iDescent = -abs(CGFontGetDescent(m_platformData.cgFont()));
     iLineGap = CGFontGetLeading(m_platformData.cgFont());
     unitsPerEm = CGFontGetUnitsPerEm(m_platformData.cgFont());
 
     float pointSize = m_platformData.m_size;
     float ascent = scaleEmToUnits(iAscent, unitsPerEm) * pointSize;
     float descent = -scaleEmToUnits(iDescent, unitsPerEm) * pointSize;
     float lineGap = scaleEmToUnits(iLineGap, unitsPerEm) * pointSize;
+    float underlineThickness = CTFontGetUnderlineThickness(m_platformData.ctFont());
 
     // We need to adjust Times, Helvetica, and Courier to closely match the
     // vertical metrics of their Microsoft counterparts that are the de facto
     // web standard. The AppKit adjustment of 20% is too big and is
     // incorrectly added to line spacing, so we use a 15% adjustment instead
     // and add it to the ascent.
     NSString *familyName = [m_platformData.font() familyName];
     if ([familyName isEqualToString:@"Times"] || [familyName isEqualToString:@"Helvetica"] || [familyName isEqualToString:@"Courier"])
         ascent += floorf(((ascent + descent) * 0.15f) + 0.5f);
 
     // Compute and store line spacing, before the line metrics hacks are applied.
     m_fontMetrics.setLineSpacing(lroundf(ascent) + lroundf(descent) + lroundf(lineGap));
 
     // Hack Hiragino line metrics to allow room for marked text underlines.
     // <rdar://problem/5386183>
     if (descent < 3 && lineGap >= 3 && [familyName hasPrefix:@"Hiragino"]) {
         lineGap -= 3 - descent;
         descent = 3;
     }
-    
+
     if (platformData().orientation() == Vertical && !isTextOrientationFallback())
         m_hasVerticalGlyphs = fontHasVerticalGlyphs(m_platformData.ctFont());
 
     float xHeight;
 
     if (platformData().orientation() == Horizontal) {
         // Measure the actual character "x", since it's possible for it to extend below the baseline, and we need the
         // reported x-height to only include the portion of the glyph that is above the baseline.
         GlyphPage* glyphPageZero = GlyphPageTreeNode::getRootChild(this, 0)->page();
         NSGlyph xGlyph = glyphPageZero ? glyphPageZero->glyphForCharacter('x') : 0;
         if (xGlyph)
             xHeight = -CGRectGetMinY(platformBoundsForGlyph(xGlyph));
         else
             xHeight = scaleEmToUnits(CGFontGetXHeight(m_platformData.cgFont()), unitsPerEm) * pointSize;
     } else
         xHeight = verticalRightOrientationFontData()->fontMetrics().xHeight();
 
     m_fontMetrics.setUnitsPerEm(unitsPerEm);
     m_fontMetrics.setAscent(ascent);
     m_fontMetrics.setDescent(descent);
     m_fontMetrics.setLineGap(lineGap);
     m_fontMetrics.setXHeight(xHeight);
+    m_fontMetrics.setUnderlineThickness(underlineThickness);
 }
 
 static CFDataRef copyFontTableForTag(FontPlatformData& platformData, FourCharCode tableName)
 {
     return CGFontCopyTableForTag(platformData.cgFont(), tableName);
 }
 
 void SimpleFontData::platformCharWidthInit()
 {
     m_avgCharWidth = 0;
     m_maxCharWidth = 0;
-    
+
     RetainPtr<CFDataRef> os2Table(AdoptCF, copyFontTableForTag(m_platformData, 'OS/2'));
     if (os2Table && CFDataGetLength(os2Table.get()) >= 4) {
         const UInt8* os2 = CFDataGetBytePtr(os2Table.get());
         SInt16 os2AvgCharWidth = os2[2] * 256 + os2[3];
         m_avgCharWidth = scaleEmToUnits(os2AvgCharWidth, m_fontMetrics.unitsPerEm()) * m_platformData.m_size;
     }
 
     RetainPtr<CFDataRef> headTable(AdoptCF, copyFontTableForTag(m_platformData, 'head'));
     if (headTable && CFDataGetLength(headTable.get()) >= 42) {
         const UInt8* head = CFDataGetBytePtr(headTable.get());
@@ skipping 165 matching lines @@
         RetainPtr<CGFontRef> runCGFont(AdoptCF, CTFontCopyGraphicsFont(runFont, 0));
         if (!CFEqual(runCGFont.get(), cgFont.get()))
             return false;
     }
 
     addResult.iterator->value = true;
     return true;
 }
 
 } // namespace WebCore