monitor-manager: Apply privacy monitor settings on changes

When both a setting change and a monitor change happens we need to
ensure that the monitor settings are applied.
This is currently only related to privacy settings, but will in future
also handle other monitor parameters such as brightness.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1952>

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

@@ -229,6 +229,9 @@ struct _MetaMonitorManagerClass
                            unsigned short     *green,
                            unsigned short     *blue);
 
+  gboolean (* set_privacy_screen_enabled) (MetaMonitorManager *manager,
+                                           gboolean            enabled);
+
   void (* tiled_monitor_added) (MetaMonitorManager *manager,
                                 MetaMonitor        *monitor);
 

src/backends/meta-monitor-manager.c

@@ -1006,6 +1006,95 @@ experimental_features_changed (MetaSettings           *settings,
   meta_settings_update_ui_scaling_factor (settings);
 }
 
+static gboolean
+meta_monitor_manager_real_set_privacy_screen_enabled (MetaMonitorManager *manager,
+                                                      gboolean            enabled)
+{
+  GList *l;
+
+  for (l = manager->monitors; l; l = l->next)
+    {
+      g_autoptr (GError) error = NULL;
+      MetaMonitor *monitor = l->data;
+
+      if (!meta_monitor_set_privacy_screen_enabled (monitor, enabled, &error))
+        {
+          if (g_error_matches (error, G_IO_ERROR, G_IO_ERROR_NOT_SUPPORTED))
+            continue;
+
+          g_warning ("Failed to set privacy screen setting on monitor %s: %s",
+                     meta_monitor_get_display_name (monitor), error->message);
+          return FALSE;
+        }
+    }
+
+  return TRUE;
+}
+
+static gboolean
+set_privacy_screen_enabled (MetaMonitorManager *manager,
+                            gboolean            enabled)
+{
+  MetaMonitorManagerClass *manager_class =
+    META_MONITOR_MANAGER_GET_CLASS (manager);
+
+  return manager_class->set_privacy_screen_enabled (manager, enabled);
+}
+
+static gboolean
+ensure_monitors_settings (MetaMonitorManager *manager)
+{
+  MetaSettings *settings = meta_backend_get_settings (manager->backend);
+
+  return set_privacy_screen_enabled (
+    manager, meta_settings_is_privacy_screen_enabled (settings));
+}
+
+static MetaPrivacyScreenState
+get_global_privacy_screen_state (MetaMonitorManager *manager)
+{
+  MetaPrivacyScreenState global_state = META_PRIVACY_SCREEN_UNAVAILABLE;
+  GList *l;
+
+  for (l = manager->monitors; l; l = l->next)
+    {
+      MetaMonitor *monitor = l->data;
+      MetaPrivacyScreenState monitor_state;
+
+      if (!meta_monitor_is_active (monitor))
+        continue;
+
+      monitor_state = meta_monitor_get_privacy_screen_state (monitor);
+      if (monitor_state == META_PRIVACY_SCREEN_UNAVAILABLE)
+        continue;
+
+      if (monitor_state & META_PRIVACY_SCREEN_DISABLED)
+        return META_PRIVACY_SCREEN_DISABLED;
+
+      if (monitor_state & META_PRIVACY_SCREEN_ENABLED)
+        global_state = META_PRIVACY_SCREEN_ENABLED;
+    }
+
+  return global_state;
+}
+
+static void
+apply_privacy_screen_settings (MetaMonitorManager *manager)
+{
+  MetaSettings *settings = meta_backend_get_settings (manager->backend);
+  MetaPrivacyScreenState privacy_screen_state =
+    get_global_privacy_screen_state (manager);
+
+  if (privacy_screen_state == META_PRIVACY_SCREEN_UNAVAILABLE)
+    return;
+
+  if (!!(privacy_screen_state & META_PRIVACY_SCREEN_ENABLED) ==
+      meta_settings_is_privacy_screen_enabled (settings))
+    return;
+
+  ensure_monitors_settings (manager);
+}
+
 static void
 update_panel_orientation_managed (MetaMonitorManager *manager)
 {
@@ -1077,6 +1166,8 @@ meta_monitor_manager_setup (MetaMonitorManager *manager)
 
   meta_monitor_manager_ensure_initial_config (manager);
 
+  apply_privacy_screen_settings (manager);
+
   manager->in_init = FALSE;
 }
 
@@ -1094,6 +1185,11 @@ meta_monitor_manager_constructed (GObject *object)
                            G_CALLBACK (experimental_features_changed),
                            manager, 0);
 
+  g_signal_connect_object (settings,
+                           "privacy-screen-changed",
+                           G_CALLBACK (apply_privacy_screen_settings),
+                           manager, G_CONNECT_SWAPPED);
+
   monitor_manager_setup_dbus_config_handlers (manager);
 
   g_signal_connect_object (manager->display_config, "notify::power-save-mode",
@@ -1223,6 +1319,8 @@ meta_monitor_manager_class_init (MetaMonitorManagerClass *klass)
 
   klass->read_edid = meta_monitor_manager_real_read_edid;
   klass->read_current_state = meta_monitor_manager_real_read_current_state;
+  klass->set_privacy_screen_enabled =
+    meta_monitor_manager_real_set_privacy_screen_enabled;
 
   signals[MONITORS_CHANGED] =
     g_signal_new ("monitors-changed",
@@ -3356,6 +3454,8 @@ meta_monitor_manager_rebuild (MetaMonitorManager *manager,
 
   meta_monitor_manager_update_logical_state (manager, config);
 
+  ensure_monitors_settings (manager);
+
   meta_monitor_manager_notify_monitors_changed (manager);
 
   g_list_free_full (old_logical_monitors, g_object_unref);