Support pixel antialising in DirectWrite.

src/ports/SkTypeface_win_dw.h

Index: src/ports/SkTypeface_win_dw.h
diff --git a/src/ports/SkTypeface_win_dw.h b/src/ports/SkTypeface_win_dw.h
index 11b3fb5ffc573326acaa133f8286db7acea57cc9..944a9e48b1b021c4347c02b447049e1bd7f428d2 100644
--- a/src/ports/SkTypeface_win_dw.h
+++ b/src/ports/SkTypeface_win_dw.h
@@ -20,6 +20,9 @@
 #if SK_HAS_DWRITE_1_H
 #  include <dwrite_1.h>
 #endif
+#if SK_HAS_DWRITE_2_H
+#  include <dwrite_2.h>
+#endif
 
 class SkFontDescriptor;
 struct SkScalerContextRec;
@@ -61,10 +64,23 @@ private:
             SkASSERT_RELEASE(nullptr == fDWriteFontFace1.get());
         }
 #endif
+#if SK_HAS_DWRITE_2_H
+        if (!SUCCEEDED(fDWriteFontFace->QueryInterface(&fDWriteFontFace2))) {
+            SkASSERT_RELEASE(nullptr == fDWriteFontFace2.get());
+        }
+        if (!SUCCEEDED(fFactory->QueryInterface(&fFactory2))) {
+            SkASSERT_RELEASE(nullptr == fFactory2.get());
+        }
+#endif
     }
 
 public:
     SkTScopedComPtr<IDWriteFactory> fFactory;
+#if SK_HAS_DWRITE_2_H
+    SkTScopedComPtr<IDWriteFactory2> fFactory2;
+#else
+    void* fFactory2 = nullptr;

[bungeman-skia, 2016/06/14 14:40:52]

This makes the implementation code much easier to follow due to the nature of
the '#if' blocks. If we can require Windows 8.1 SDK or higher, we can remove
most of this ugly.

+#endif
     SkTScopedComPtr<IDWriteFontCollectionLoader> fDWriteFontCollectionLoader;
     SkTScopedComPtr<IDWriteFontFileLoader> fDWriteFontFileLoader;
     SkTScopedComPtr<IDWriteFontFamily> fDWriteFontFamily;
@@ -73,6 +89,11 @@ public:
 #if SK_HAS_DWRITE_1_H
     SkTScopedComPtr<IDWriteFontFace1> fDWriteFontFace1;
 #endif
+#if SK_HAS_DWRITE_2_H
+    SkTScopedComPtr<IDWriteFontFace2> fDWriteFontFace2;
+#else
+    void* fDWriteFontFace2 = nullptr;
+#endif
 
     static DWriteFontTypeface* Create(IDWriteFactory* factory,
                                       IDWriteFontFace* fontFace,