csm-manager.c: Unset WAYLAND_DISPLAY during shutdown in a wayland

session.

This and others need to be cleared after a wayland session so
systemd doesn't pass them to the next session.

This is performed by others using systemd unit parameters, but we
don't currently use systemd for this.
https://gitlab.gnome.org/GNOME/gnome-shell/-/blob/main/data/[email protected]?ref_type=heads#L26

Author: mtwebster

cinnamon-session/csm-manager.c

@@ -951,6 +951,36 @@ maybe_restart_user_bus (CsmManager *manager)
         if (manager->priv->dbus_disconnected)
                 return;
 
+        if (g_strcmp0 (g_getenv ("XDG_SESSION_TYPE"), "wayland") == 0) {
+            g_debug ("CsmManager: Unsetting environment GNOME_SETUP_DISPLAY WAYLAND_DISPLAY DISPLAY XAUTHORITY");
+
+            GVariantBuilder builder;
+            g_variant_builder_init (&builder, G_VARIANT_TYPE ("as"));
+            g_variant_builder_add (&builder, "s", "GNOME_SETUP_DISPLAY");
+            g_variant_builder_add (&builder, "s", "WAYLAND_DISPLAY");
+            g_variant_builder_add (&builder, "s", "DISPLAY");
+            g_variant_builder_add (&builder, "s", "XAUTHORITY");
+
+            reply = g_dbus_connection_call_sync (manager->priv->connection,
+                                                 "org.freedesktop.systemd1",
+                                                 "/org/freedesktop/systemd1",
+                                                 "org.freedesktop.systemd1.Manager",
+                                                 "UnsetEnvironment",
+                                                 g_variant_new ("(@as)",
+                                                                g_variant_builder_end (&builder)),
+                                                 NULL,
+                                                 G_DBUS_CALL_FLAGS_NONE,
+                                                 -1, NULL, &error);
+
+            if (error != NULL) {
+                    g_debug ("CsmManager: unsetting environment failed: %s", error->message);
+                    g_clear_error (&error);
+            }
+            else {
+                g_variant_unref (reply);
+            }
+        }
+
         system = csm_get_system ();
 
         if (!csm_system_is_last_session_for_user (system))