[pango/win32-font-language] PangoWin32: Initialize DirectWrite as well

[Chun-wei Fan <fanchunwei src gnome org>]

commit b9fc0f5e65d38a984dc01d1b8e7707ee95a95a5e
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Wed Nov 11 20:15:25 2020 +0800

    PangoWin32: Initialize DirectWrite as well
    
    We want to start using DirectWrite to help us implement some features
    that are not that easily done with GDI/Uniscribe, via a GDI interop
    layer as provided by DirectWrite.

 pango/meson.build  |  1 +
 pango/pangowin32.c | 37 +++++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)
---
diff --git a/pango/meson.build b/pango/meson.build
index 91261274..21b620ec 100644
--- a/pango/meson.build
+++ b/pango/meson.build
@@ -413,6 +413,7 @@ if host_system == 'windows'
   pangowin32_deps = pango_deps + [
     libpango_dep,
     cc.find_library('gdi32'),
+    cc.find_library('dwrite'),
   ]
 
   pangowin32_rc = configure_file(
diff --git a/pango/pangowin32.c b/pango/pangowin32.c
index 213a665e..2da6473d 100644
--- a/pango/pangowin32.c
+++ b/pango/pangowin32.c
@@ -32,6 +32,9 @@
  */
 #include "config.h"
 
+#define COBJMACROS
+#include <initguid.h>
+
 #include <string.h>
 #include <stdlib.h>
 #include <glib.h>
@@ -41,6 +44,9 @@
 #include "pangowin32.h"
 #include "pangowin32-private.h"
 
+/* this is a C-compatible counterpart of the DirectWrite headers */
+#include "dwrite_c.h"
+
 #define MAX_FREED_FONTS 256
 
 gboolean _pango_win32_debug = FALSE;
@@ -134,6 +140,8 @@ _pango_win32_font_init (PangoWin32Font *win32font)
 }
 
 static GPrivate display_dc_key = G_PRIVATE_INIT ((GDestroyNotify) DeleteDC);
+static GPrivate dwrite_factory_key;
+static GPrivate dwrite_gdi_key;
 
 HDC
 _pango_win32_get_display_dc (void)
@@ -190,6 +198,34 @@ pango_win32_get_debug_flag (void)
   return _pango_win32_debug;
 }
 
+static void
+_pango_win32_setup_dwrite (void)
+{
+  IDWriteFactory *dwrite_factory = NULL;
+  IDWriteGdiInterop *dwrite_gdi = NULL;
+
+  dwrite_factory = g_private_get (&dwrite_factory_key);
+  if (dwrite_factory == NULL)
+    {
+      if (DWriteCreateFactory (DWRITE_FACTORY_TYPE_SHARED,
+                              &IID_IDWriteFactory,
+                              (IUnknown **)&dwrite_factory) != S_OK)
+        g_warning ("DWrite factory creation failed!");
+      else
+        g_private_set (&dwrite_factory_key, dwrite_factory);
+    }
+
+  dwrite_gdi = g_private_get (&dwrite_gdi_key);
+  if (dwrite_factory != NULL && dwrite_gdi == NULL)
+    {
+      if (IDWriteFactory_GetGdiInterop (dwrite_factory,
+                                       &dwrite_gdi) != S_OK)
+        g_warning ("DWrite GDI interop creation failed!");
+      else
+        g_private_set (&dwrite_gdi_key, dwrite_gdi);
+    }
+}
+
 static void
 _pango_win32_font_class_init (PangoWin32FontClass *class)
 {
@@ -212,6 +248,7 @@ _pango_win32_font_class_init (PangoWin32FontClass *class)
   class->get_metrics_factor = pango_win32_font_real_get_metrics_factor;
 
   _pango_win32_get_display_dc ();
+  _pango_win32_setup_dwrite ();
 }
 
 /**