backends: Split monitor manager creation into create and setup

The monitor manager instance was created and setup in one step; at
construction. This is problematic if, in the future, the monitor manager
creation can fail, as the monitor manager is created quite late.

To make it possible to in the future fail creating a monitor manager,
create the instance very early when initiating the backend, then on
post init backend setup, "setup" the monitor manager state, i.e. read
the current state and setup the stage.

https://bugzilla.gnome.org/show_bug.cgi?id=785381

src/backends/meta-backend.c

@@ -355,15 +355,6 @@ on_device_removed (ClutterDeviceManager *device_manager,
     }
 }
 
-static MetaMonitorManager *
-create_monitor_manager (MetaBackend *backend)
-{
-  if (g_getenv ("META_DUMMY_MONITORS"))
-    return g_object_new (META_TYPE_MONITOR_MANAGER_DUMMY, NULL);
-
-  return META_BACKEND_GET_CLASS (backend)->create_monitor_manager (backend);
-}
-
 static void
 create_device_monitors (MetaBackend          *backend,
                         ClutterDeviceManager *device_manager)
@@ -441,7 +432,7 @@ meta_backend_real_post_init (MetaBackend *backend)
   clutter_actor_realize (priv->stage);
   META_BACKEND_GET_CLASS (backend)->select_stage_events (backend);
 
-  priv->monitor_manager = create_monitor_manager (backend);
+  meta_monitor_manager_setup (priv->monitor_manager);
 
   meta_backend_sync_screen_size (backend);
 
@@ -579,6 +570,15 @@ experimental_features_changed (MetaSettings            *settings,
 #endif /* HAVE_REMOTE_DESKTOP */
 }
 
+static MetaMonitorManager *
+meta_backend_create_monitor_manager (MetaBackend *backend)
+{
+  if (g_getenv ("META_DUMMY_MONITORS"))
+    return g_object_new (META_TYPE_MONITOR_MANAGER_DUMMY, NULL);
+
+  return META_BACKEND_GET_CLASS (backend)->create_monitor_manager (backend);
+}
+
 static MetaRenderer *
 meta_backend_create_renderer (MetaBackend *backend,
                               GError     **error)
@@ -601,16 +601,18 @@ meta_backend_initable_init (GInitable     *initable,
 
   priv->egl = g_object_new (META_TYPE_EGL, NULL);
 
+  priv->orientation_manager = g_object_new (META_TYPE_ORIENTATION_MANAGER, NULL);
+
   priv->renderer = meta_backend_create_renderer (backend, error);
   if (!priv->renderer)
     return FALSE;
 
+  priv->monitor_manager = meta_backend_create_monitor_manager (backend);
+
   priv->cursor_tracker = g_object_new (META_TYPE_CURSOR_TRACKER, NULL);
 
   priv->dnd = g_object_new (META_TYPE_DND, NULL);
 
-  priv->orientation_manager = g_object_new (META_TYPE_ORIENTATION_MANAGER, NULL);
-
   return TRUE;
 }
 

src/backends/meta-monitor-manager-private.h

@@ -259,6 +259,8 @@ struct _MetaMonitorManagerClass
   MetaLogicalMonitorLayoutMode (*get_default_layout_mode) (MetaMonitorManager *);
 };
 
+void                meta_monitor_manager_setup (MetaMonitorManager *manager);
+
 void                meta_monitor_manager_rebuild (MetaMonitorManager *manager,
                                                   MetaMonitorsConfig *config);
 void                meta_monitor_manager_rebuild_derived (MetaMonitorManager *manager,

src/backends/meta-monitor-manager.c

@@ -676,6 +676,20 @@ experimental_features_changed (MetaSettings           *settings,
   meta_settings_update_ui_scaling_factor (settings);
 }
 
+void
+meta_monitor_manager_setup (MetaMonitorManager *manager)
+{
+  manager->in_init = TRUE;
+
+  manager->config_manager = meta_monitor_config_manager_new (manager);
+
+  meta_monitor_manager_read_current_state (manager);
+
+  meta_monitor_manager_ensure_initial_config (manager);
+
+  manager->in_init = FALSE;
+}
+
 static void
 meta_monitor_manager_constructed (GObject *object)
 {
@@ -707,17 +721,8 @@ meta_monitor_manager_constructed (GObject *object)
                            manager, 0);
 
   manager->current_switch_config = META_MONITOR_SWITCH_CONFIG_UNKNOWN;
-  manager->in_init = TRUE;
-
-  manager->config_manager = meta_monitor_config_manager_new (manager);
-
-  meta_monitor_manager_read_current_state (manager);
-
-  meta_monitor_manager_ensure_initial_config (manager);
 
   initialize_dbus_interface (manager);
-
-  manager->in_init = FALSE;
 }
 
 static void

src/backends/native/meta-monitor-manager-kms.c

@@ -798,31 +798,6 @@ meta_monitor_manager_kms_resume (MetaMonitorManagerKms *manager_kms)
   handle_hotplug_event (manager);
 }
 
-static void
-meta_monitor_manager_kms_init (MetaMonitorManagerKms *manager_kms)
-{
-  MetaBackend *backend = meta_get_backend ();
-  MetaRenderer *renderer = meta_backend_get_renderer (backend);
-  MetaRendererNative *renderer_native = META_RENDERER_NATIVE (renderer);
-  GSource *source;
-
-  manager_kms->fd = meta_renderer_native_get_kms_fd (renderer_native);
-
-  drmSetClientCap (manager_kms->fd, DRM_CLIENT_CAP_UNIVERSAL_PLANES, 1);
-
-  const char *subsystems[2] = { "drm", NULL };
-  manager_kms->udev = g_udev_client_new (subsystems);
-  meta_monitor_manager_kms_connect_uevent_handler (manager_kms);
-
-  source = g_source_new (&kms_event_funcs, sizeof (MetaKmsSource));
-  manager_kms->source = (MetaKmsSource *) source;
-  manager_kms->source->fd_tag = g_source_add_unix_fd (source,
-                                                      manager_kms->fd,
-                                                      G_IO_IN | G_IO_ERR);
-  manager_kms->source->manager_kms = manager_kms;
-  g_source_attach (source, NULL);
-}
-
 static void
 get_crtc_connectors (MetaMonitorManager *manager,
                      MetaCrtc           *crtc,
@@ -1122,6 +1097,31 @@ meta_monitor_manager_kms_finalize (GObject *object)
   G_OBJECT_CLASS (meta_monitor_manager_kms_parent_class)->finalize (object);
 }
 
+static void
+meta_monitor_manager_kms_init (MetaMonitorManagerKms *manager_kms)
+{
+  MetaBackend *backend = meta_get_backend ();
+  MetaRenderer *renderer = meta_backend_get_renderer (backend);
+  MetaRendererNative *renderer_native = META_RENDERER_NATIVE (renderer);
+  GSource *source;
+
+  manager_kms->fd = meta_renderer_native_get_kms_fd (renderer_native);
+
+  drmSetClientCap (manager_kms->fd, DRM_CLIENT_CAP_UNIVERSAL_PLANES, 1);
+
+  const char *subsystems[2] = { "drm", NULL };
+  manager_kms->udev = g_udev_client_new (subsystems);
+  meta_monitor_manager_kms_connect_uevent_handler (manager_kms);
+
+  source = g_source_new (&kms_event_funcs, sizeof (MetaKmsSource));
+  manager_kms->source = (MetaKmsSource *) source;
+  manager_kms->source->fd_tag = g_source_add_unix_fd (source,
+                                                      manager_kms->fd,
+                                                      G_IO_IN | G_IO_ERR);
+  manager_kms->source->manager_kms = manager_kms;
+  g_source_attach (source, NULL);
+}
+
 static void
 meta_monitor_manager_kms_class_init (MetaMonitorManagerKmsClass *klass)
 {