[gtk/portal-session-state] application: Add a query-end signal

[Matthias Clasen <matthiasc src gnome org>]

commit 87a05b3257d661f46525b45aa66befbfbe68eb96
Author: Matthias Clasen <mclasen redhat com>
Date:   Mon Jan 21 20:45:15 2019 -0500

    application: Add a query-end signal
    
    This lets us take just-in-time inhibitors, and makes
    the session support a little more real.

 gtk/gtkapplication-dbus.c |  2 ++
 gtk/gtkapplication.c      | 19 +++++++++++++++++++
 2 files changed, 21 insertions(+)
---
diff --git a/gtk/gtkapplication-dbus.c b/gtk/gtkapplication-dbus.c
index 07fd2ed6bd..eec78dfef8 100644
--- a/gtk/gtkapplication-dbus.c
+++ b/gtk/gtkapplication-dbus.c
@@ -234,6 +234,8 @@ screensaver_signal_portal (GDBusConnection *connection,
         }
       else if (session_state == QUERY_END)
         {
+          g_signal_emit_by_name (dbus->impl.application, "query-end");
+
           g_dbus_proxy_call (dbus->inhibit_proxy,
                              "QueryEndResponse",
                              g_variant_new ("(o)", dbus->session_id),
diff --git a/gtk/gtkapplication.c b/gtk/gtkapplication.c
index 5d26f07088..aff5749136 100644
--- a/gtk/gtkapplication.c
+++ b/gtk/gtkapplication.c
@@ -129,6 +129,7 @@
 enum {
   WINDOW_ADDED,
   WINDOW_REMOVED,
+  QUERY_END,
   LAST_SIGNAL
 };
 
@@ -644,6 +645,24 @@ gtk_application_class_init (GtkApplicationClass *class)
                   g_cclosure_marshal_VOID__OBJECT,
                   G_TYPE_NONE, 1, GTK_TYPE_WINDOW);
 
+  /**
+   * GtkApplication::query-end:
+   * @application: the #GtkApplication which emitted the signal
+   *
+   * Emitted when the session manager is about to end the session, only
+   * if #GtkApplication::register-session is %TRUE. Applications can
+   * connect to this signal and call gtk_application_inhibit() with
+   * %GTK_APPLICATION_INHIBIT_LOGOUT to delay the end of the session
+   * until state has been saved.
+   *
+   * Since: 3.24.5
+   */
+  gtk_application_signals[QUERY_END] =
+    g_signal_new (I_("query-end"), GTK_TYPE_APPLICATION, G_SIGNAL_RUN_FIRST,
+                  0,
+                  NULL, NULL,
+                  NULL,
+                  G_TYPE_NONE, 0);
   /**
    * GtkApplication:register-session:
    *