Revert "Revert "Revert "[hb-directwrite] Don't load dwrit.dll dynamically"""

This reverts commit 361a438658.

src/hb-directwrite.cc

@@ -43,6 +43,14 @@
  * Functions for using HarfBuzz with DirectWrite fonts.
  **/
 
+/* Declare object creator for dynamic support of DWRITE */
+typedef HRESULT (* WINAPI t_DWriteCreateFactory)(
+  DWRITE_FACTORY_TYPE factoryType,
+  REFIID              iid,
+  IUnknown            **factory
+);
+
+
 /*
  * DirectWrite font stream helpers
  */
@@ -137,6 +145,7 @@ public:
 
 struct hb_directwrite_face_data_t
 {
+  HMODULE dwrite_dll;
   IDWriteFactory *dwriteFactory;
   IDWriteFontFile *fontFile;
   DWriteFontFileStream *fontFileStream;
@@ -158,12 +167,33 @@ _hb_directwrite_shaper_face_data_create (hb_face_t *face)
     return nullptr; \
   } HB_STMT_END
 
+  data->dwrite_dll = LoadLibrary (TEXT ("DWRITE"));
+  if (unlikely (!data->dwrite_dll))
+    FAIL ("Cannot find DWrite.DLL");
+
+  t_DWriteCreateFactory p_DWriteCreateFactory;
+
+#if defined(__GNUC__)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wcast-function-type"
+#endif
+
+  p_DWriteCreateFactory = (t_DWriteCreateFactory)
+			  GetProcAddress (data->dwrite_dll, "DWriteCreateFactory");
+
+#if defined(__GNUC__)
+#pragma GCC diagnostic pop
+#endif
+
+  if (unlikely (!p_DWriteCreateFactory))
+    FAIL ("Cannot find DWriteCreateFactory().");
+
   HRESULT hr;
 
   // TODO: factory and fontFileLoader should be cached separately
   IDWriteFactory* dwriteFactory;
-  hr = DWriteCreateFactory (DWRITE_FACTORY_TYPE_SHARED, __uuidof (IDWriteFactory),
-			    (IUnknown**) &dwriteFactory);
+  hr = p_DWriteCreateFactory (DWRITE_FACTORY_TYPE_SHARED, __uuidof (IDWriteFactory),
+			      (IUnknown**) &dwriteFactory);
 
   if (unlikely (hr != S_OK))
     FAIL ("Failed to run DWriteCreateFactory().");
@@ -227,6 +257,8 @@ _hb_directwrite_shaper_face_data_destroy (hb_directwrite_face_data_t *data)
     delete data->fontFileStream;
   if (data->faceBlob)
     hb_blob_destroy (data->faceBlob);
+  if (data->dwrite_dll)
+    FreeLibrary (data->dwrite_dll);
   if (data)
     delete data;
 }