From de3e97309f91fc631a1a4b5ab48cd69dd1421ed5 Mon Sep 17 00:00:00 2001 From: Marek Kasik Date: Fri, 5 Feb 2021 18:00:02 +0100 Subject: [PATCH] printing: Show all Avahi advertised printers This commit unsubscribes CUPS backend from a DBus signal in idle when listening for new items on Avahi. Since GDBus emits gathered signals in idle while checking whether the signal has been unsubscribed it could happen that a signal was not processed because it was removed from hash table of subscribed signals. This caused the situation where printers advertised on Avahi were not listed in CUPS backend sometimes. We need those signals since this happens when switching from a general subscription which listens to signals for all Avahi services to a specific one which listens to just _ipp._tcp and _ipps._tcp (chicken and egg problem). --- .../printbackends/cups/gtkprintbackendcups.c | 27 ++++++++++++++++--- 1 file changed, 24 insertions(+), 3 deletions(-) diff --git a/modules/printbackends/cups/gtkprintbackendcups.c b/modules/printbackends/cups/gtkprintbackendcups.c index b1ee0584d0..6b8c9e02ad 100644 --- a/modules/printbackends/cups/gtkprintbackendcups.c +++ b/modules/printbackends/cups/gtkprintbackendcups.c @@ -150,6 +150,7 @@ struct _GtkPrintBackendCups guint avahi_service_browser_subscription_ids[2]; char *avahi_service_browser_paths[2]; GCancellable *avahi_cancellable; + guint unsubscribe_general_subscription_id; gboolean secrets_service_available; guint secrets_service_watch_id; @@ -1009,6 +1010,12 @@ gtk_print_backend_cups_dispose (GObject *object) backend_cups->avahi_service_browser_subscription_id = 0; } + if (backend_cups->unsubscribe_general_subscription_id > 0) + { + g_source_remove (backend_cups->unsubscribe_general_subscription_id); + backend_cups->unsubscribe_general_subscription_id = 0; + } + backend_parent_class->dispose (object); } @@ -3514,6 +3521,19 @@ avahi_service_browser_signal_handler (GDBusConnection *connection, } } +static gboolean +unsubscribe_general_subscription_cb (gpointer user_data) +{ + GtkPrintBackendCups *cups_backend = user_data; + + g_dbus_connection_signal_unsubscribe (cups_backend->dbus_connection, + cups_backend->avahi_service_browser_subscription_id); + cups_backend->avahi_service_browser_subscription_id = 0; + cups_backend->unsubscribe_general_subscription_id = 0; + + return G_SOURCE_REMOVE; +} + static void avahi_service_browser_new_cb (GObject *source_object, GAsyncResult *res, @@ -3555,9 +3575,10 @@ avahi_service_browser_new_cb (GObject *source_object, cups_backend->avahi_service_browser_paths[1] && cups_backend->avahi_service_browser_subscription_id > 0) { - g_dbus_connection_signal_unsubscribe (cups_backend->dbus_connection, - cups_backend->avahi_service_browser_subscription_id); - cups_backend->avahi_service_browser_subscription_id = 0; + /* We need to unsubscribe in idle since signals in queue destined for emit + * are emitted in idle and check whether the subscriber is still subscribed. + */ + cups_backend->unsubscribe_general_subscription_id = g_idle_add (unsubscribe_general_subscription_cb, cups_backend); } g_variant_unref (output);