Initialize font fallback when creating DWrite 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)
 
 #include "SkDWrite.h"
 #include "SkDWriteFontFileStream.h"
 #include "SkFontMgr.h"
 #include "SkHRESULT.h"
 #include "SkMutex.h"
 #include "SkStream.h"
 #include "SkTScopedComPtr.h"
 #include "SkTypeface.h"
 #include "SkTypefaceCache.h"
 #include "SkTypeface_win_dw.h"
 #include "SkTypes.h"
 #include "SkUtils.h"
 
 #include <dwrite.h>
 
 #if SK_HAS_DWRITE_2_H
 #include <dwrite_2.h>
+#else
+struct IDWriteFontFallback;
 #endif
 
 ////////////////////////////////////////////////////////////////////////////////
 
 class StreamFontFileLoader : public IDWriteFontFileLoader {
 public:
     // IUnknown methods
     virtual HRESULT STDMETHODCALLTYPE QueryInterface(REFIID iid, void** ppvObject);
     virtual ULONG STDMETHODCALLTYPE AddRef();
     virtual ULONG STDMETHODCALLTYPE Release();
@@ skipping 219 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)
+                          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))) {
             // 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());
         }
 #endif
         memcpy(fLocaleName.get(), localeName, localeNameLength * sizeof(WCHAR));
     }
@@ skipping 21 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 433 matching lines @@
         dwBcp47 = &fLocaleName;
     } 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.");
-
+    if (fFactory2.get() && fFontFallback.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;
         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;
         }
 
         SkTScopedComPtr<IDWriteFontFace> fontFace;
         HRNM(font->CreateFontFace(&fontFace), "Could not get font face from font.");
 
         SkTScopedComPtr<IDWriteFontFamily> fontFamily;
         HRNM(font->GetFontFamily(&fontFamily), "Could not get family from font.");
@@ skipping 276 matching lines @@
         }
     }
 
     SkTScopedComPtr<IDWriteFontCollection> systemFontCollection;
     if (nullptr == collection) {
         HRNM(factory->GetSystemFontCollection(&systemFontCollection, FALSE),
              "Could not get system font collection.");
         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;
 
     // Dynamically load GetUserDefaultLocaleName function, as it is not available on XP.
     SkGetUserDefaultLocaleNameProc getUserDefaultLocaleNameProc = nullptr;
     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, localeName, localeNameLen, fontFallback);
 }
 
 #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)