context: Add 'notify_ready()' vfunc and method

This intends to replace the call to `meta_register_with_session()` that
deals with X11 session management, and is called when the user is
"ready". In thet test context, doing that makes no sense, so make it a
no-op.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1861>

src/core/meta-context-private.h

@@ -41,6 +41,8 @@ struct _MetaContextClass
 
   MetaBackend * (* create_backend) (MetaContext  *context,
                                     GError      **error);
+
+  void (* notify_ready) (MetaContext *context);
 };
 
 #endif /* META_CONTEXT_PRIVATE_H */

src/core/meta-context.c

@@ -66,6 +66,12 @@ meta_context_set_plugin_name (MetaContext *context,
   priv->plugin_name = g_strdup (plugin_name);
 }
 
+void
+meta_context_notify_ready (MetaContext *context)
+{
+  META_CONTEXT_GET_CLASS (context)->notify_ready (context);
+}
+
 static MetaCompositorType
 meta_context_get_compositor_type (MetaContext *context)
 {

src/meta/meta-context.h

@@ -51,6 +51,9 @@ META_EXPORT
 gboolean meta_context_run_main_loop (MetaContext  *context,
                                      GError      **error);
 
+META_EXPORT
+void meta_context_notify_ready (MetaContext *context);
+
 META_EXPORT
 void meta_context_terminate (MetaContext *context);
 

src/tests/meta-context-test.c

@@ -136,6 +136,11 @@ meta_context_test_create_backend (MetaContext  *context,
   g_assert_not_reached ();
 }
 
+static void
+meta_context_test_notify_ready (MetaContext *context)
+{
+}
+
 MetaContext *
 meta_create_test_context (MetaContextTestType type)
 {
@@ -158,6 +163,7 @@ meta_context_test_class_init (MetaContextTestClass *klass)
   context_class->get_compositor_type = meta_context_test_get_compositor_type;
   context_class->setup = meta_context_test_setup;
   context_class->create_backend = meta_context_test_create_backend;
+  context_class->notify_ready = meta_context_test_notify_ready;
 }
 
 static void