[pango/pango1-dwrite: 4/6] PangoCairo: Create cairo_font_face_t using DirectWrite

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

commit 545f164f3bc56bccf2e3ac371f56e35307ed1701
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Mon Aug 15 17:35:09 2022 +0800

    PangoCairo: Create cairo_font_face_t using DirectWrite
    
    ...if Cairo is built with DirectWrite support.  With this, we can
    support colored Emoji, a long-standing issue, on Windows without needing
    to use FontConfig, on Windows 8.1 or later, since DirectWrite added support
    for colored Emoji starting with Windows 8.1.
    
    This will really fix issue !302 completely, regarding the Emoji not
    shown in color!

 pango/pangocairo-win32font.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)
---
diff --git a/pango/pangocairo-win32font.c b/pango/pangocairo-win32font.c
index 5b860bab8..0141c4149 100644
--- a/pango/pangocairo-win32font.c
+++ b/pango/pangocairo-win32font.c
@@ -75,6 +75,32 @@ pango_cairo_win32_font_create_font_face (PangoCairoFont *font)
 {
   PangoCairoWin32Font *cwfont = PANGO_CAIRO_WIN32_FONT (font);
   PangoWin32Font *win32font =  &cwfont->font;
+  void *dwrite_font_face = NULL;
+  gpointer dwrite_font = NULL;
+
+#ifdef HAVE_CAIRO_WIN32_DIRECTWRITE
+  dwrite_font_face = pango_win32_font_get_dwrite_font_face (win32font);
+  if (dwrite_font_face != NULL)
+    {
+      cairo_font_face_t *cairo_face = cairo_dwrite_font_face_create_for_dwrite_fontface (dwrite_font_face);
+
+      if (cairo_face != NULL)
+        {
+          static const cairo_user_data_key_t key;
+
+          cairo_font_face_set_user_data (cairo_face, &key,
+                                         dwrite_font_face,
+                                         (cairo_destroy_func_t) pango_win32_dwrite_font_face_release);
+
+          return cairo_face;
+        }
+      else
+        {
+          g_warning ("cairo_font_face creation failed with DirectWrite, fallback to GDI");
+          pango_win32_dwrite_font_face_release (dwrite_font_face);
+        }
+    }
+#endif
 
   return cairo_win32_font_face_create_for_logfontw (&win32font->logfontw);
 }