settings: Always use the same default values

Set the Mac key theme when creating a Quartz settings object instead of
having it the default when quartz is enabled.
This keeps compatibility with the GTK2 behavior that the Mac key theme
is not used for the X11 backend, which could now happen for a
multi-backend build.

gtk/gtksettings.c

@@ -82,12 +82,6 @@
  */
 
 
-#ifdef GDK_WINDOWING_QUARTZ
-#define DEFAULT_KEY_THEME "Mac"
-#else
-#define DEFAULT_KEY_THEME NULL
-#endif
-
 #define DEFAULT_TIMEOUT_INITIAL 200
 #define DEFAULT_TIMEOUT_REPEAT   20
 #define DEFAULT_TIMEOUT_EXPAND  500
@@ -419,7 +413,7 @@ gtk_settings_class_init (GtkSettingsClass *class)
                                              g_param_spec_string ("gtk-key-theme-name",
                                                                   P_("Key Theme Name"),
                                                                   P_("Name of key theme to load"),
-                                                                  DEFAULT_KEY_THEME,
+                                                                  NULL,
                                                                   GTK_PARAM_READWRITE),
                                              NULL);
   g_assert (result == PROP_KEY_THEME_NAME);
@@ -1454,7 +1448,12 @@ gtk_settings_get_for_screen (GdkScreen *screen)
   settings = g_object_get_data (G_OBJECT (screen), "gtk-settings");
   if (!settings)
     {
-      settings = g_object_new (GTK_TYPE_SETTINGS, NULL);
+#ifdef GDK_WINDOWING_QUARTZ
+      if (GDK_IS_QUARTZ_SCREEN (screen))
+        settings = g_object_new (GTK_TYPE_SETTINGS, "gtk-key-theme-name", "Mac", NULL);
+      else
+#endif
+        settings = g_object_new (GTK_TYPE_SETTINGS, NULL);
       settings->priv->screen = screen;
       g_object_set_data_full (G_OBJECT (screen), I_("gtk-settings"),
                               settings, g_object_unref);