Allow custom font collection for DirectWrite 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 585d809406a765454dbc85f3850b303c8ba05561..1bb5d996f9256e42653037e9d54efe56fdaf8832 100644
--- a/src/ports/SkFontMgr_win_dw.cpp
+++ b/src/ports/SkFontMgr_win_dw.cpp
@@ -1067,7 +1067,8 @@ SkTypeface* SkFontStyleSet_DirectWrite::matchStyle(const SkFontStyle& pattern) {
 ////////////////////////////////////////////////////////////////////////////////
 #include "SkTypeface_win.h"
 
-SK_API SkFontMgr* SkFontMgr_New_DirectWrite(IDWriteFactory* factory) {
+SK_API SkFontMgr* SkFontMgr_New_DirectWrite(IDWriteFactory* factory,
+                                            IDWriteFontCollection* collection) {
     if (nullptr == factory) {
         factory = sk_get_dwrite_factory();
         if (nullptr == factory) {
@@ -1075,9 +1076,14 @@ SK_API SkFontMgr* SkFontMgr_New_DirectWrite(IDWriteFactory* factory) {
         }
     }
 
-    SkTScopedComPtr<IDWriteFontCollection> sysFontCollection;
-    HRNM(factory->GetSystemFontCollection(&sysFontCollection, FALSE),
-         "Could not get system font collection.");
+    SkTScopedComPtr<IDWriteFontCollection> fontCollection;
+    if (collection != nullptr) {
+      fontCollection.swap(SkTScopedComPtr<IDWriteFontCollection>(collection));
+    }
+    else {
+      HRNM(factory->GetSystemFontCollection(&fontCollection, FALSE),
+        "Could not get system font collection.");
+    }

[bungeman-skia, 2016/01/29 20:12:29]

I would write this whole block as

SkTScopedComPtr<IDWriteFontCollection> fontCollection(collection);
if (!fontCollection.get()) {
    HRNM(factory->GetSystemFontCollection(&fontCollection, FALSE),
         "Could not get system font collection.");
}

which avoids a branch and a long line with an unclear swap.

[Ilya Kulshin, 2016/01/29 22:10:15]

Done. While looking at it I also noticed that SkTScopedComPtr unexpectedly does
not AddRef, so I added an AddRef too.

Aside: does anyone know why SkTScopedComPtr does not AddRef when constructed
from a raw pointer? That is rather counterintuitive behavior.

 
     WCHAR localeNameStorage[LOCALE_NAME_MAX_LENGTH];
     WCHAR* localeName = nullptr;
@@ -1095,7 +1101,7 @@ SK_API SkFontMgr* SkFontMgr_New_DirectWrite(IDWriteFactory* factory) {
         };
     }
 
-    return new SkFontMgr_DirectWrite(factory, sysFontCollection.get(), localeName, localeNameLen);
+    return new SkFontMgr_DirectWrite(factory, fontCollection.get(), localeName, localeNameLen);
 }
 
 #include "SkFontMgr_indirect.h"