monitor-manager: Make the config manager an 'experimental feature'

Instead of using a environment variable, add a new 'experimental
feature' gsetting keyword "monitor-config-manager" that enables the use
of the new MetaMonitorConfigManager. This commit also makes it possible
to switch between the two systems without restarting mutter.

The D-Bus API is disabled when the experimental feature is not enabled,
and clients trying to access it will get a access-denied error in
response. A new property 'IsExperimentalApiEnabled' is added to let the
D-Bus client know whether it is possible to use the experimental API or
not.

https://bugzilla.gnome.org/show_bug.cgi?id=777732

src/backends/meta-backend-private.h

@@ -100,7 +100,8 @@ struct _MetaBackendClass
 typedef enum _MetaExperimentalFeature
 {
   META_EXPERIMENTAL_FEATURE_NONE = 0,
-  META_EXPERIMENTAL_FEATURE_SCALE_MONITOR_FRAMEBUFFER = (1 << 0)
+  META_EXPERIMENTAL_FEATURE_SCALE_MONITOR_FRAMEBUFFER = (1 << 0),
+  META_EXPERIMENTAL_FEATURE_MONITOR_CONFIG_MANAGER = (1 << 1)
 } MetaExperimentalFeature;
 
 void meta_init_backend (GType backend_gtype);

src/backends/meta-backend.c

@@ -430,6 +430,8 @@ experimental_features_handler (GVariant *features_variant,
       /* So far no experimental features defined. */
       if (g_str_equal (feature, "scale-monitor-framebuffer"))
         features |= META_EXPERIMENTAL_FEATURE_SCALE_MONITOR_FRAMEBUFFER;
+      else if (g_str_equal (feature, "monitor-config-manager"))
+        features |= META_EXPERIMENTAL_FEATURE_MONITOR_CONFIG_MANAGER;
       else
         g_info ("Unknown experimental feature '%s'\n", feature);
     }

src/backends/meta-monitor-manager-dummy.c

@@ -356,7 +356,7 @@ meta_monitor_manager_dummy_ensure_initial_config (MetaMonitorManager *manager)
 
   config = meta_monitor_manager_ensure_configured (manager);
 
-  if (manager->config_manager)
+  if (meta_is_monitor_config_manager_enabled ())
     meta_monitor_manager_update_logical_state (manager, config);
   else
     meta_monitor_manager_update_logical_state_derived (manager);

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

@@ -315,6 +315,8 @@ struct _MetaMonitorManager
 
   GnomePnpIds *pnp_ids;
   UpClient *up_client;
+
+  gulong experimental_features_changed_handler_id;
 };
 
 struct _MetaMonitorManagerClass
@@ -390,6 +392,8 @@ struct _MetaMonitorManagerClass
   MetaLogicalMonitorLayoutMode (*get_default_layout_mode) (MetaMonitorManager *);
 };
 
+gboolean            meta_is_monitor_config_manager_enabled (void);
+
 void                meta_monitor_manager_rebuild (MetaMonitorManager *manager,
                                                   MetaMonitorsConfig *config);
 void                meta_monitor_manager_rebuild_derived   (MetaMonitorManager *manager);

src/backends/meta-monitor-manager.c

@@ -74,6 +74,14 @@ meta_monitor_manager_init (MetaMonitorManager *manager)
 {
 }
 
+gboolean
+meta_is_monitor_config_manager_enabled (void)
+{
+  return meta_backend_is_experimental_feature_enabled (
+    meta_get_backend (),
+    META_EXPERIMENTAL_FEATURE_MONITOR_CONFIG_MANAGER);
+}
+
 static void
 meta_monitor_manager_set_primary_logical_monitor (MetaMonitorManager *manager,
                                                   MetaLogicalMonitor *logical_monitor)
@@ -240,7 +248,7 @@ power_save_mode_changed (MetaMonitorManager *manager,
 void
 meta_monitor_manager_lid_is_closed_changed (MetaMonitorManager *manager)
 {
-  if (manager->config_manager)
+  if (meta_is_monitor_config_manager_enabled ())
     meta_monitor_manager_ensure_configured (manager);
   else
     meta_monitor_config_lid_is_closed_changed (manager->legacy_config, manager);
@@ -390,7 +398,7 @@ meta_monitor_manager_ensure_configured (MetaMonitorManager *manager)
   MetaMonitorsConfigMethod fallback_method =
     META_MONITORS_CONFIG_METHOD_TEMPORARY;
 
-  if (!manager->config_manager)
+  if (!meta_is_monitor_config_manager_enabled ())
     {
       legacy_ensure_configured (manager);
       return NULL;
@@ -497,13 +505,41 @@ done:
   return config;
 }
 
+static void
+experimental_features_changed (MetaBackend        *backend,
+                               MetaMonitorManager *manager)
+{
+  MetaDBusDisplayConfig *skeleton = META_DBUS_DISPLAY_CONFIG (manager);
+  gboolean was_config_manager_enabled;
+  gboolean is_config_manager_enabled;
+
+  is_config_manager_enabled = meta_is_monitor_config_manager_enabled ();
+  was_config_manager_enabled =
+    meta_dbus_display_config_get_is_experimental_api_enabled (skeleton);
+
+  if (was_config_manager_enabled != is_config_manager_enabled)
+    {
+      meta_dbus_display_config_set_is_experimental_api_enabled (
+        skeleton, is_config_manager_enabled);
+
+      meta_monitor_manager_on_hotplug (manager);
+    }
+}
+
 static void
 meta_monitor_manager_constructed (GObject *object)
 {
   MetaMonitorManager *manager = META_MONITOR_MANAGER (object);
+  MetaDBusDisplayConfig *skeleton = META_DBUS_DISPLAY_CONFIG (manager);
   MetaMonitorManagerClass *manager_class =
     META_MONITOR_MANAGER_GET_CLASS (manager);
 
+  manager->experimental_features_changed_handler_id =
+    g_signal_connect (meta_get_backend (),
+                      "experimental-features-changed",
+                      G_CALLBACK (experimental_features_changed),
+                      manager);
+
   if (manager_class->is_lid_closed == meta_monitor_manager_real_is_lid_closed)
     {
       manager->up_client = up_client_new ();
@@ -514,12 +550,18 @@ meta_monitor_manager_constructed (GObject *object)
   g_signal_connect_object (manager, "notify::power-save-mode",
                            G_CALLBACK (power_save_mode_changed), manager, 0);
 
+  meta_dbus_display_config_set_is_experimental_api_enabled (
+    skeleton,
+    meta_is_monitor_config_manager_enabled ());
+
   manager->in_init = TRUE;
 
-  if (g_strcmp0 (g_getenv ("MUTTER_USE_CONFIG_MANAGER"), "1") == 0)
-    manager->config_manager = meta_monitor_config_manager_new (manager);
-  else
-    manager->legacy_config = meta_monitor_config_new (manager);
+  /*
+   * MetaMonitorConfigManager will only be used if the corresponding
+   * experimental feature is enabled.
+   */
+  manager->config_manager = meta_monitor_config_manager_new (manager);
+  manager->legacy_config = meta_monitor_config_new (manager);
 
   meta_monitor_manager_read_current_state (manager);
 
@@ -613,6 +655,9 @@ meta_monitor_manager_finalize (GObject *object)
   meta_monitor_manager_free_crtc_array (manager->crtcs, manager->n_crtcs);
   g_list_free_full (manager->logical_monitors, g_object_unref);
 
+  g_signal_handler_disconnect (meta_get_backend (),
+                               manager->experimental_features_changed_handler_id);
+
   G_OBJECT_CLASS (meta_monitor_manager_parent_class)->finalize (object);
 }
 
@@ -993,10 +1038,7 @@ save_config_timeout (gpointer user_data)
 {
   MetaMonitorManager *manager = user_data;
 
-  if (manager->config_manager)
-    g_assert (!"missing implementation");
-  else
-    legacy_restore_previous_config (manager);
+  legacy_restore_previous_config (manager);
 
   manager->persistent_timeout_id = 0;
   return G_SOURCE_REMOVE;
@@ -1020,13 +1062,8 @@ meta_monitor_manager_legacy_handle_apply_configuration  (MetaDBusDisplayConfig *
   guint output_index;
   GPtrArray *crtc_infos, *output_infos;
 
-  if (manager->config_manager)
-    {
-      g_dbus_method_invocation_return_error (invocation, G_DBUS_ERROR,
-                                             G_DBUS_ERROR_NOT_SUPPORTED,
-                                             "Used old configuration API with new configuration system");
-      return TRUE;
-    }
+  if (meta_monitor_config_manager_get_current (manager->config_manager))
+    meta_monitor_config_manager_set_current (manager->config_manager, NULL);
 
   if (serial != manager->serial)
     {
@@ -1286,6 +1323,14 @@ meta_monitor_manager_handle_get_current_state (MetaDBusDisplayConfig *skeleton,
   MetaMonitorManagerCapability capabilities;
   int max_screen_width, max_screen_height;
 
+  if (!meta_is_monitor_config_manager_enabled ())
+    {
+      g_dbus_method_invocation_return_error (invocation, G_DBUS_ERROR,
+                                             G_DBUS_ERROR_ACCESS_DENIED,
+                                             "This experimental API is currently not enabled");
+      return TRUE;
+    }
+
   g_variant_builder_init (&monitors_builder,
                           G_VARIANT_TYPE (MONITORS_FORMAT));
   g_variant_builder_init (&logical_monitors_builder,
@@ -1741,11 +1786,11 @@ meta_monitor_manager_handle_apply_monitors_config (MetaDBusDisplayConfig *skelet
   GList *logical_monitor_configs = NULL;
   GError *error = NULL;
 
-  if (!manager->config_manager)
+  if (!meta_is_monitor_config_manager_enabled ())
     {
       g_dbus_method_invocation_return_error (invocation, G_DBUS_ERROR,
-                                             G_DBUS_ERROR_NOT_SUPPORTED,
-                                             "Used new configuration API with old configuration system");
+                                             G_DBUS_ERROR_ACCESS_DENIED,
+                                             "This experimental API is currently not enabled");
       return TRUE;
     }
 
@@ -1888,10 +1933,7 @@ meta_monitor_manager_confirm_configuration (MetaMonitorManager *manager,
   g_source_remove (manager->persistent_timeout_id);
   manager->persistent_timeout_id = 0;
 
-  if (manager->config_manager)
-    g_assert (!"not implemented");
-  else
-    legacy_confirm_configuration (manager, ok);
+  legacy_confirm_configuration (manager, ok);
 }
 
 static gboolean
@@ -2643,7 +2685,7 @@ legacy_on_hotplug (MetaMonitorManager *manager)
 void
 meta_monitor_manager_on_hotplug (MetaMonitorManager *manager)
 {
-  if (manager->legacy_config)
+  if (!meta_is_monitor_config_manager_enabled ())
     {
       legacy_on_hotplug (manager);
       return;

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

@@ -1260,7 +1260,7 @@ meta_monitor_manager_kms_ensure_initial_config (MetaMonitorManager *manager)
 
   config = meta_monitor_manager_ensure_configured (manager);
 
-  if (manager->config_manager)
+  if (meta_is_monitor_config_manager_enabled ())
     meta_monitor_manager_update_logical_state (manager, config);
   else
     meta_monitor_manager_update_logical_state_derived (manager);

src/org.gnome.Mutter.DisplayConfig.xml

@@ -291,6 +291,17 @@
     -->
     <signal name="MonitorsChanged" />
 
+    <!--
+	IsExperimentalApiEnabled:
+
+	True if the experimental APIs are enabled, false if not. The
+	experimental APIs consists of the following methods:
+
+	  GetCurrentState()
+	  ApplyMonitorsConfig()
+    -->
+    <property name="IsExperimentalApiEnabled" type="b" access="read" />
+
     <!--
 	GetCurrentState:
 	@serial: configuration serial

src/tests/meta-monitor-manager-test.c

@@ -112,7 +112,7 @@ meta_monitor_manager_test_ensure_initial_config (MetaMonitorManager *manager)
 
   config = meta_monitor_manager_ensure_configured (manager);
 
-  if (manager->config_manager)
+  if (meta_is_monitor_config_manager_enabled ())
     meta_monitor_manager_update_logical_state (manager, config);
   else
     meta_monitor_manager_update_logical_state_derived (manager);

src/tests/monitor-test-utils.c

@@ -28,11 +28,7 @@
 gboolean
 is_using_monitor_config_manager (void)
 {
-  MetaBackend *backend = meta_get_backend ();
-  MetaMonitorManager *monitor_manager =
-    meta_backend_get_monitor_manager (backend);
-
-  return !!monitor_manager->config_manager;
+  return meta_is_monitor_config_manager_enabled ();
 }
 
 void

src/tests/unit-tests.c

@@ -219,9 +219,15 @@ run_tests (gpointer data)
 
   meta_backend_override_experimental_features (backend);
 
-  meta_backend_enable_experimental_feature (
-    backend,
-    META_EXPERIMENTAL_FEATURE_SCALE_MONITOR_FRAMEBUFFER);
+  if (g_strcmp0 (g_getenv ("MUTTER_USE_CONFIG_MANAGER"), "1") == 0)
+    {
+      meta_backend_enable_experimental_feature (
+        backend,
+        META_EXPERIMENTAL_FEATURE_MONITOR_CONFIG_MANAGER);
+      meta_backend_enable_experimental_feature (
+        backend,
+        META_EXPERIMENTAL_FEATURE_SCALE_MONITOR_FRAMEBUFFER);
+    }
 
   ret = g_test_run ();