tests/clutter: Always use stage from backend

This removes all occurrences of creating a custom stage from the tests,
making them always use the one from MetaBackend. This will allow for
further cleanups.

https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1364

src/tests/clutter-test-utils.c

@@ -4,6 +4,8 @@
 #include <glib-object.h>
 #include <clutter/clutter.h>
 
+#include "compositor/meta-plugin-manager.h"
+
 typedef struct {
   gpointer dummy_field;
 } ClutterTestEnvironment;
@@ -26,25 +28,30 @@ log_func (const gchar    *log_domain,
   return TRUE;
 }
 
-/*
- * clutter_test_init:
- * @argc: (inout): number of arguments in @argv
- * @argv: (inout) (array length=argc) (nullable): array of arguments
- *
- * Initializes the Clutter test environment.
- *
- * Since: 1.18
- */
-void
-clutter_test_init (int    *argc,
-                   char ***argv)
+static const char *
+test_get_plugin_name (void)
 {
-  const char *display = g_getenv ("DISPLAY");
+  const char *name;
+
+  name = g_getenv ("MUTTER_TEST_PLUGIN_PATH");
+  if (name)
+    return name;
+  else
+    return "libdefault";
+}
+
+static void
+init_common_pre (void)
+{
+  const char *display;
 
   if (G_UNLIKELY (test_environ != NULL))
     g_error ("Attempting to initialize the test suite more than once, "
              "aborting...\n");
 
+  meta_plugin_manager_load (test_get_plugin_name ());
+  meta_test_init ();
+
   display = g_getenv ("DISPLAY");
   if (!display || *display == '\0')
     {
@@ -57,15 +64,53 @@ clutter_test_init (int    *argc,
    * rate, and run the master clock using a 60 fps timer instead.
    */
   _clutter_set_sync_to_vblank (FALSE);
+}
 
-  /* perform the actual initialization */
-  g_assert (clutter_init (NULL, NULL) == CLUTTER_INIT_SUCCESS);
-
+static void
+init_common_post (int    *argc,
+                  char ***argv)
+{
   g_test_init (argc, argv, NULL);
   g_test_bug_base ("https://bugzilla.gnome.org/show_bug.cgi?id=%s");
 
   /* our global state, accessible from each test unit */
   test_environ = g_new0 (ClutterTestEnvironment, 1);
+
+  meta_start ();
+}
+
+/*
+ * clutter_test_init:
+ * @argc: (inout): number of arguments in @argv
+ * @argv: (inout) (array length=argc) (nullable): array of arguments
+ *
+ * Initializes the Clutter test environment.
+ *
+ * Since: 1.18
+ */
+void
+clutter_test_init (int    *argc,
+                   char ***argv)
+{
+  init_common_pre ();
+  g_assert (clutter_init (NULL, NULL) == CLUTTER_INIT_SUCCESS);
+  init_common_post (argc, argv);
+}
+
+void
+clutter_test_init_with_args (int            *argc,
+                             char         ***argv,
+                             const char     *parameter_string,
+                             GOptionEntry   *entries,
+                             const char     *translation_domain)
+{
+  init_common_pre ();
+  g_assert (clutter_init_with_args (argc, argv,
+                                    parameter_string,
+                                    entries,
+                                    translation_domain,
+                                    NULL) == CLUTTER_INIT_SUCCESS);
+  init_common_post (argc, argv);
 }
 
 /**
@@ -91,17 +136,39 @@ typedef struct {
   GDestroyNotify test_notify;
 } ClutterTestData;
 
+static gboolean
+list_equal_unsorted (GList *list_a,
+                     GList *list_b)
+{
+  GList *l_a;
+  GList *l_b;
+
+  for (l_a = list_a, l_b = list_b;
+       l_a && l_b;
+       l_a = l_a->next, l_b = l_b->next)
+    {
+      if (l_a->data != l_b->data)
+        return FALSE;
+    }
+
+  return !l_a && !l_b;
+}
+
 static void
 clutter_test_func_wrapper (gconstpointer data_)
 {
   const ClutterTestData *data = data_;
   ClutterActor *stage;
+  GList *pre_stage_children;
+  GList *post_stage_children;
 
   g_test_log_set_fatal_handler (log_func, NULL);
 
   /* ensure that the previous test state has been cleaned up */
   stage = clutter_test_get_stage ();
-  g_assert_false (clutter_actor_is_mapped (stage));
+  clutter_actor_hide (stage);
+
+  pre_stage_children = clutter_actor_get_children (stage);
 
   if (data->test_data != NULL)
     {
@@ -119,7 +186,13 @@ clutter_test_func_wrapper (gconstpointer data_)
   if (data->test_notify != NULL)
     data->test_notify (data->test_data);
 
-  clutter_actor_remove_all_children (stage);
+  post_stage_children = clutter_actor_get_children (stage);
+
+  g_assert_true (list_equal_unsorted (pre_stage_children, post_stage_children));
+
+  g_list_free (pre_stage_children);
+  g_list_free (post_stage_children);
+
   clutter_actor_hide (stage);
 }
 
@@ -244,6 +317,18 @@ clutter_test_run (void)
   return res;
 }
 
+void
+clutter_test_main (void)
+{
+  meta_run_main_loop ();
+}
+
+void
+clutter_test_quit (void)
+{
+  meta_quit (META_EXIT_SUCCESS);
+}
+
 typedef struct {
   ClutterActor *stage;