Initialize font fallback when creating DWrite font manager

src/ports/SkFontMgr_win_dw.cpp

Index: src/ports/SkFontMgr_win_dw.cpp
diff --git a/src/ports/SkFontMgr_win_dw.cpp b/src/ports/SkFontMgr_win_dw.cpp
index 11afec3b53623205dad6612ab7cc0057c958181e..715bed52912c68da221ea976828aaf512c7c5308 100644
--- a/src/ports/SkFontMgr_win_dw.cpp
+++ b/src/ports/SkFontMgr_win_dw.cpp
@@ -25,6 +25,8 @@
 
 #if SK_HAS_DWRITE_2_H
 #include <dwrite_2.h>
+#else
+struct IDWriteFontFallback;
 #endif
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -264,10 +266,13 @@ class SkFontMgr_DirectWrite : public SkFontMgr {
 public:
     /** localeNameLength must include the null terminator. */
     SkFontMgr_DirectWrite(IDWriteFactory* factory, IDWriteFontCollection* fontCollection,
-                          WCHAR* localeName, int localeNameLength)
+                          WCHAR* localeName, int localeNameLength, IDWriteFontFallback* fallback)
         : fFactory(SkRefComPtr(factory))
         , fFontCollection(SkRefComPtr(fontCollection))
         , fLocaleName(localeNameLength)
+#if SK_HAS_DWRITE_2_H
+        , fFontFallback(SkSafeRefComPtr(fallback))
+#endif
     {
 #if SK_HAS_DWRITE_2_H
         if (!SUCCEEDED(fFactory->QueryInterface(&fFactory2))) {
@@ -309,6 +314,7 @@ private:
     SkTScopedComPtr<IDWriteFactory> fFactory;
 #if SK_HAS_DWRITE_2_H
     SkTScopedComPtr<IDWriteFactory2> fFactory2;
+    SkTScopedComPtr<IDWriteFontFallback> fFontFallback;
 #endif
     SkTScopedComPtr<IDWriteFontCollection> fFontCollection;
     SkSMallocWCHAR fLocaleName;
@@ -762,10 +768,7 @@ SkTypeface* SkFontMgr_DirectWrite::onMatchFamilyStyleCharacter(const char family
     }
 
 #if SK_HAS_DWRITE_2_H
-    if (fFactory2.get()) {
-        SkTScopedComPtr<IDWriteFontFallback> fontFallback;
-        HRNM(fFactory2->GetSystemFontFallback(&fontFallback), "Could not get system fallback.");
-
+    if (fFactory2.get() && fFontFallback.get()) {
         SkTScopedComPtr<IDWriteNumberSubstitution> numberSubstitution;
         HRNM(fFactory2->CreateNumberSubstitution(DWRITE_NUMBER_SUBSTITUTION_METHOD_NONE, nullptr, TRUE,
                                                  &numberSubstitution),
@@ -776,17 +779,17 @@ SkTypeface* SkFontMgr_DirectWrite::onMatchFamilyStyleCharacter(const char family
         UINT32 mappedLength;
         SkTScopedComPtr<IDWriteFont> font;
         FLOAT scale;
-        HRNM(fontFallback->MapCharacters(fontFallbackSource.get(),
-                                         0, // textPosition,
-                                         strLen,
-                                         fFontCollection.get(),
-                                         dwFamilyName,
-                                         dwStyle.fWeight,
-                                         dwStyle.fSlant,
-                                         dwStyle.fWidth,
-                                         &mappedLength,
-                                         &font,
-                                         &scale),
+        HRNM(fFontFallback->MapCharacters(fontFallbackSource.get(),
+                                          0, // textPosition,
+                                          strLen,
+                                          fFontCollection.get(),
+                                          dwFamilyName,
+                                          dwStyle.fWeight,
+                                          dwStyle.fSlant,
+                                          dwStyle.fWidth,
+                                          &mappedLength,
+                                          &font,
+                                          &scale),
              "Could not map characters");
         if (!font.get()) {
             return nullptr;
@@ -1083,6 +1086,18 @@ SK_API SkFontMgr* SkFontMgr_New_DirectWrite(IDWriteFactory* factory,
         collection = systemFontCollection.get();
     }
 
+    IDWriteFontFallback *fontFallback = nullptr;
+#if SK_HAS_DWRITE_2_H
+    SkTScopedComPtr<IDWriteFontFallback> systemFontFallback;
+    SkTScopedComPtr<IDWriteFactory2> fFactory2;
+    factory->QueryInterface(&fFactory2);
+    if (fFactory2.get()) {
+        HRNM(fFactory2->GetSystemFontFallback(&systemFontFallback),
+             "Could not get system fallback.");
+        fontFallback = systemFontFallback.get();
+    }
+#endif

[bungeman-skia, 2016/03/08 19:02:44]

This is now somewhat squirrelly, in that we're allowing the user to specify a
custom collection but not a fallback. As a result, if the collection isn't
really the system collection, the fallback won't actually be the 'right' one.
(This seems to be more of an issue with the DirectWrite API, a collection or
fontset should be able to provide its own fallback.)

That being said, I'm ok with this for now, since that's what we were doing
before anyway, but I'll need to make it possible to send in a fallback as well
at some point.

+
     WCHAR localeNameStorage[LOCALE_NAME_MAX_LENGTH];
     WCHAR* localeName = nullptr;
     int localeNameLen = 0;
@@ -1099,7 +1114,8 @@ SK_API SkFontMgr* SkFontMgr_New_DirectWrite(IDWriteFactory* factory,
         };
     }
 
-    return new SkFontMgr_DirectWrite(factory, collection, localeName, localeNameLen);
+    return new SkFontMgr_DirectWrite(
+        factory, collection, localeName, localeNameLen, fontFallback);
 }
 
 #include "SkFontMgr_indirect.h"