Fixing superscript and subscript baseline for tiny fonts in SVG

third_party/WebKit/Source/platform/fonts/SimpleFontData.cpp

Index: third_party/WebKit/Source/platform/fonts/SimpleFontData.cpp
diff --git a/third_party/WebKit/Source/platform/fonts/SimpleFontData.cpp b/third_party/WebKit/Source/platform/fonts/SimpleFontData.cpp
index fbd7abc24615d9ccf030fb99fbf747c994e31ee2..2c66c022bbdf688af773a3aa029358e84ae599a8 100644
--- a/third_party/WebKit/Source/platform/fonts/SimpleFontData.cpp
+++ b/third_party/WebKit/Source/platform/fonts/SimpleFontData.cpp
@@ -130,6 +130,13 @@ void SimpleFontData::platformInit(bool subpixelAscentDescent) {
   float ascent;
   float descent;
 
+  // For tiny fonts, the rounding of fAscent and fDescent results in equal
+  // baseline for different types of text baselines (crbug.com/338908).
+  // Please see CanvasRenderingContext2D::getFontBaseline for the heuristic.
+  subpixelAscentDescent =

[eae, 2016/11/04 18:25:28]

Please use a different name here to avoid the appearance of masking the
parameter subpixelAscentDescent.

[zakerinasab, 2016/11/07 18:40:26]

Done.

+      subpixelAscentDescent &&
+      (-metrics.fAscent < 3 || -metrics.fAscent + metrics.fDescent < 2);
+
   // Beware those who step here: This code is designed to match Win32 font
   // metrics *exactly* except:
   // - the adjustment of ascent/descent on Linux/Android
@@ -138,17 +145,10 @@ void SimpleFontData::platformInit(bool subpixelAscentDescent) {
     ascent = vdmxAscent;
     descent = -vdmxDescent;
   } else {
-    // For tiny fonts, the rounding of fAscent and fDescent results in equal
-    // baseline for different types of text baselines (crbug.com/338908).
-    // Please see CanvasRenderingContext2D::getFontBaseline for the heuristic.
-    if (subpixelAscentDescent &&
-        (-metrics.fAscent < 3 || -metrics.fAscent + metrics.fDescent < 2)) {
-      ascent = -metrics.fAscent;
-      descent = metrics.fDescent;
-    } else {
-      ascent = SkScalarRoundToScalar(-metrics.fAscent);
-      descent = SkScalarRoundToScalar(metrics.fDescent);
-    }
+    ascent = subpixelAscentDescent ? -metrics.fAscent
+                                   : SkScalarRoundToScalar(-metrics.fAscent);
+    descent = subpixelAscentDescent ? metrics.fDescent
+                                    : SkScalarRoundToScalar(metrics.fDescent);
 #if OS(LINUX) || OS(ANDROID)
     // When subpixel positioning is enabled, if the descent is rounded down, the
     // descent part of the glyph may be truncated when displayed in a 'overflow:
@@ -176,8 +176,11 @@ void SimpleFontData::platformInit(bool subpixelAscentDescent) {
   DEFINE_STATIC_LOCAL(AtomicString, courierName, ("Courier"));
   String familyName = m_platformData.fontFamilyName();
   if (familyName == timesName || familyName == helveticaName ||
-      familyName == courierName)
-    ascent += floorf(((ascent + descent) * 0.15f) + 0.5f);
+      familyName == courierName) {
+    ascent += subpixelAscentDescent
+                  ? ((ascent + descent) * 0.15f)
+                  : floorf(((ascent + descent) * 0.15f) + 0.5f);
+  }
 #endif
 
   m_fontMetrics.setAscent(ascent);
@@ -348,6 +351,12 @@ PassRefPtr<SimpleFontData> SimpleFontData::emphasisMarkFontData(
   return m_derivedFontData->emphasisMark;
 }
 
+PassRefPtr<SimpleFontData> SimpleFontData::subpixelAscentDescentFontData()
+    const {
+  return SimpleFontData::create(m_platformData, m_customFontData,
+                                m_isTextOrientationFallback, true);
+}
+
 bool SimpleFontData::isTextOrientationFallbackOf(
     const SimpleFontData* fontData) const {
   if (!isTextOrientationFallback() || !fontData->m_derivedFontData)