Upstream custom freetype embolding strength from Android

src/ports/SkFontHost_FreeType.cpp

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkAdvancedTypefaceMetrics.h"
 #include "SkBitmap.h"
 #include "SkCanvas.h"
@@ skipping 1385 matching lines @@
     metrics->fLeading = leading * scale;
     metrics->fAvgCharWidth = avgCharWidth * scale;
     metrics->fXMin = xmin * scale;
     metrics->fXMax = xmax * scale;
     metrics->fXHeight = x_height;
     metrics->fCapHeight = cap_height;
     metrics->fUnderlineThickness = underlineThickness * scale;
     metrics->fUnderlinePosition = underlinePosition * scale;
 }
 
+///////////////////////////////////////////////////////////////////////////////
+
+// hand-tuned value to reduce outline embolden strength
+#ifndef SK_OUTLINE_EMBOLDEN_DIVISOR
+    #ifdef SK_BUILD_FOR_ANDROID_FRAMEWORK
+        #define SK_OUTLINE_EMBOLDEN_DIVISOR   34

[bungeman-skia, 2015/01/09 16:07:38]

It would be nice if Android specified this in their SkUserConfig.h, and then
this block just becomes

#ifndef SK_OUTLINE_EMBOLDEN_DIVISOR
#    define SK_OUTLINE_EMBOLDEN_DIVISOR 24
#endif

On the other hand this name is less than entirely good for global visibility, if
it gets moved out to SkUserConfig.h it should probably be
SK_FREETYPE_OUTLINE_EMBOLDEN_DIVISOR

+    #else
+        #define SK_OUTLINE_EMBOLDEN_DIVISOR   24
+    #endif
+#endif
+
+///////////////////////////////////////////////////////////////////////////////
+
 void SkScalerContext_FreeType::emboldenIfNeeded(FT_Face face, FT_GlyphSlot glyph)
 {
     // check to see if the embolden bit is set
     if (0 == (fRec.fFlags & SkScalerContext::kEmbolden_Flag)) {
         return;
     }
 
     switch (glyph->format) {
         case FT_GLYPH_FORMAT_OUTLINE:
             FT_Pos strength;
-            strength = FT_MulFix(face->units_per_EM, face->size->metrics.y_scale) / 24;
+            strength = FT_MulFix(face->units_per_EM, face->size->metrics.y_scale)
+                       / SK_OUTLINE_EMBOLDEN_DIVISOR;
             FT_Outline_Embolden(&glyph->outline, strength);
             break;
         case FT_GLYPH_FORMAT_BITMAP:
             FT_GlyphSlot_Own_Bitmap(glyph);
             FT_Bitmap_Embolden(glyph->library, &glyph->bitmap, kBitmapEmboldenStrength, 0);
             break;
         default:
             SkDEBUGFAIL("unknown glyph format");
     }
 }
@@ skipping 276 matching lines @@
     if (style) {
         *style = SkFontStyle(weight, width, slant);
     }
     if (isFixedPitch) {
         *isFixedPitch = FT_IS_FIXED_WIDTH(face);
     }
 
     FT_Done_Face(face);
     return true;
 }