Add option to specify font fallback when creating the skia font manager

src/ports/SkFontMgr_win_dw.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkTypes.h"
 #if defined(SK_BUILD_FOR_WIN32)
 
@@ skipping 246 matching lines @@
     *fontFileEnumerator = enumerator.release();
     return S_OK;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 
 class SkFontMgr_DirectWrite : public SkFontMgr {
 public:
     /** localeNameLength must include the null terminator. */
     SkFontMgr_DirectWrite(IDWriteFactory* factory, IDWriteFontCollection* fontCollection,
-                          WCHAR* localeName, int localeNameLength)
+                          IDWriteFontFallback* fallback, WCHAR* localeName, int localeNameLength)
         : fFactory(SkRefComPtr(factory))
+#if SK_HAS_DWRITE_2_H
+        , fFontFallback(SkSafeRefComPtr(fallback))
+#endif
         , fFontCollection(SkRefComPtr(fontCollection))
         , fLocaleName(localeNameLength)
     {
 #if SK_HAS_DWRITE_2_H
         if (!SUCCEEDED(fFactory->QueryInterface(&fFactory2))) {
             // IUnknown::QueryInterface states that if it fails, punk will be set to nullptr.
             // http://blogs.msdn.com/b/oldnewthing/archive/2004/03/26/96777.aspx
             SkASSERT_RELEASE(nullptr == fFactory2.get());
         }
+        if (fFontFallback.get()) {
+            // factory must be provied if fallback is non-null, else the fallback will not be used.
+            SkASSERT(fFactory2.get());
+        }
 #endif
         memcpy(fLocaleName.get(), localeName, localeNameLength * sizeof(WCHAR));
     }
 
 protected:
     int onCountFamilies() const override;
     void onGetFamilyName(int index, SkString* familyName) const override;
     SkFontStyleSet* onCreateStyleSet(int index) const override;
     SkFontStyleSet* onMatchFamily(const char familyName[]) const override;
     virtual SkTypeface* onMatchFamilyStyle(const char familyName[],
@@ skipping 14 matching lines @@
     HRESULT getDefaultFontFamily(IDWriteFontFamily** fontFamily) const;
 
     /** Creates a typeface using a typeface cache. */
     SkTypeface* createTypefaceFromDWriteFont(IDWriteFontFace* fontFace,
                                              IDWriteFont* font,
                                              IDWriteFontFamily* fontFamily) const;
 
     SkTScopedComPtr<IDWriteFactory> fFactory;
 #if SK_HAS_DWRITE_2_H
     SkTScopedComPtr<IDWriteFactory2> fFactory2;
+    SkTScopedComPtr<IDWriteFontFallback> fFontFallback;
 #endif
     SkTScopedComPtr<IDWriteFontCollection> fFontCollection;
     SkSMallocWCHAR fLocaleName;
     mutable SkMutex fTFCacheMutex;
     mutable SkTypefaceCache fTFCache;
 
     friend class SkFontStyleSet_DirectWrite;
     friend class FontFallbackRenderer;
 };
 
@@ skipping 434 matching lines @@
     } else {
         // TODO: support fallback stack.
         // TODO: DirectWrite supports 'zh-CN' or 'zh-Hans', but 'zh' misses completely
         // and may produce a Japanese font.
         HRN(sk_cstring_to_wchar(bcp47[bcp47Count - 1], &dwBcp47Local));
         dwBcp47 = &dwBcp47Local;
     }
 
 #if SK_HAS_DWRITE_2_H
     if (fFactory2.get()) {
-        SkTScopedComPtr<IDWriteFontFallback> fontFallback;
-        HRNM(fFactory2->GetSystemFontFallback(&fontFallback), "Could not get system fallback.");
+        SkTScopedComPtr<IDWriteFontFallback> systemFontFallback;
+        IDWriteFontFallback* fontFallback = fFontFallback.get();
+        if (!fontFallback) {
+            HRNM(fFactory2->GetSystemFontFallback(&systemFontFallback),
+                 "Could not get system fallback.");
+            fontFallback = systemFontFallback.get();
+        }
 
         SkTScopedComPtr<IDWriteNumberSubstitution> numberSubstitution;
         HRNM(fFactory2->CreateNumberSubstitution(DWRITE_NUMBER_SUBSTITUTION_METHOD_NONE, nullptr, TRUE,
                                                  &numberSubstitution),
              "Could not create number substitution.");
         SkTScopedComPtr<FontFallbackSource> fontFallbackSource(
             new FontFallbackSource(str, strLen, *dwBcp47, numberSubstitution.get()));
 
         UINT32 mappedLength;
         SkTScopedComPtr<IDWriteFont> font;
@@ skipping 284 matching lines @@
 
     return fFontMgr->createTypefaceFromDWriteFont(fontFace.get(), font.get(),
                                                   fFontFamily.get());
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 #include "SkTypeface_win.h"
 
 SK_API SkFontMgr* SkFontMgr_New_DirectWrite(IDWriteFactory* factory,
                                             IDWriteFontCollection* collection) {
+    return SkFontMgr_New_DirectWrite(factory, collection, nullptr);
+}
+
+SK_API SkFontMgr* SkFontMgr_New_DirectWrite(IDWriteFactory* factory,
+                                            IDWriteFontCollection* collection,
+                                            IDWriteFontFallback* fallback) {
     if (nullptr == factory) {
         factory = sk_get_dwrite_factory();
         if (nullptr == factory) {
             return nullptr;
         }
     }
 
     SkTScopedComPtr<IDWriteFontCollection> systemFontCollection;
     if (nullptr == collection) {
         HRNM(factory->GetSystemFontCollection(&systemFontCollection, FALSE),
@@ skipping 10 matching lines @@
     HRESULT hr = SkGetGetUserDefaultLocaleNameProc(&getUserDefaultLocaleNameProc);
     if (nullptr == getUserDefaultLocaleNameProc) {
         SK_TRACEHR(hr, "Could not get GetUserDefaultLocaleName.");
     } else {
         localeNameLen = getUserDefaultLocaleNameProc(localeNameStorage, LOCALE_NAME_MAX_LENGTH);
         if (localeNameLen) {
             localeName = localeNameStorage;
         };
     }
 
-    return new SkFontMgr_DirectWrite(factory, collection, localeName, localeNameLen);
+    return new SkFontMgr_DirectWrite(factory, collection, fallback, localeName, localeNameLen);
 }
 
 #include "SkFontMgr_indirect.h"
 SK_API SkFontMgr* SkFontMgr_New_DirectWriteRenderer(SkRemotableFontMgr* proxy) {
     SkAutoTUnref<SkFontMgr> impl(SkFontMgr_New_DirectWrite());
     if (impl.get() == nullptr) {
         return nullptr;
     }
     return new SkFontMgr_Indirect(impl.get(), proxy);
 }
 #endif//defined(SK_BUILD_FOR_WIN32)