[introspection] Work around g-i limitation with hb_language_t

src/hb-gobject-structs.cc

@@ -94,10 +94,6 @@ static hb_glyph_position_t *glyph_position_reference (hb_glyph_position_t *g)
 static void glyph_position_destroy (hb_glyph_position_t *g) { free (g); }
 HB_DEFINE_BOXED_TYPE (glyph_position, glyph_position_reference, glyph_position_destroy)
 
-static hb_language_t language_reference (hb_language_t l) { return l; }
-static void language_destroy (hb_language_t l) { }
-HB_DEFINE_BOXED_TYPE (language, language_reference, language_destroy)
-
 static hb_segment_properties_t *segment_properties_reference (hb_segment_properties_t *g)
 {
   hb_segment_properties_t *c = (hb_segment_properties_t *) calloc (1, sizeof (hb_segment_properties_t));
@@ -111,3 +107,14 @@ HB_DEFINE_BOXED_TYPE (segment_properties, segment_properties_reference, segment_
 static hb_user_data_key_t user_data_key_reference (hb_user_data_key_t l) { return l; }
 static void user_data_key_destroy (hb_user_data_key_t l) { }
 HB_DEFINE_BOXED_TYPE (user_data_key, user_data_key_reference, user_data_key_destroy)
+
+
+static hb_language_t *language_reference (hb_language_t *l)
+{
+  hb_language_t *c = (hb_language_t *) calloc (1, sizeof (hb_language_t));
+  if (unlikely (!c)) return NULL;
+  *c = *l;
+  return c;
+}
+static void language_destroy (hb_language_t *l) { free (l); }
+HB_DEFINE_BOXED_TYPE (language, language_reference, language_destroy)

src/hb-gobject-structs.h

@@ -81,6 +81,14 @@ GType hb_gobject_segment_properties_get_type (void);
 GType hb_gobject_user_data_key_get_type (void);
 #define HB_GOBJECT_TYPE_USER_DATA_KEY (hb_gobject_user_data_key_get_type ())
 
+/* Currently gobject-introspection doesn't understand that hb_language_t
+ * can be passed by-value.  As such we box it up.  May remove in the
+ * future.
+ *
+ *   https://bugzilla.gnome.org/show_bug.cgi?id=707656
+ */
+GType hb_gobject_language_get_type (void);
+#define HB_GOBJECT_TYPE_LANGUAGE (hb_gobject_language_get_type ())
 
 HB_END_DECLS