add g_timeout_add_seconds_once

Add a new call combing behaviors of g_timeout_add_seconds and
g_timeout_add_once.

docs/reference/glib/glib-sections.txt.in

@@ -586,6 +586,7 @@ g_timeout_add_once
 g_timeout_add_full
 g_timeout_add_seconds
 g_timeout_add_seconds_full
+g_timeout_add_seconds_once
 
 <SUBSECTION>
 g_idle_source_new

glib/gmain.c

@@ -5471,6 +5471,26 @@ g_timeout_add_seconds (guint       interval,
   return g_timeout_add_seconds_full (G_PRIORITY_DEFAULT, interval, function, data, NULL);
 }
 
+/**
+ * g_timeout_add_seconds_once:
+ * @interval: the time after which the function will be called, in seconds
+ * @function: function to call
+ * @data: data to pass to @function
+ *
+ * This function behaves like g_timeout_add_once() but with a range in seconds.
+ *
+ * Returns: the ID (greater than 0) of the event source
+ *
+ * Since: 2.78
+ */
+guint
+g_timeout_add_seconds_once (guint           interval,
+                            GSourceOnceFunc function,
+                            gpointer        data)
+{
+  return timeout_add_full (G_PRIORITY_DEFAULT, interval, TRUE, TRUE, (GSourceFunc) function, data, NULL);
+}
+
 /* Child watch functions */
 
 #ifdef G_OS_WIN32

glib/gmain.h

@@ -800,6 +800,10 @@ GLIB_AVAILABLE_IN_ALL
 guint    g_timeout_add_seconds      (guint           interval,
                                      GSourceFunc     function,
                                      gpointer        data);
+GLIB_AVAILABLE_IN_2_78
+guint    g_timeout_add_seconds_once (guint           interval,
+                                     GSourceOnceFunc function,
+                                     gpointer        data);
 GLIB_AVAILABLE_IN_ALL
 guint    g_child_watch_add_full     (gint            priority,
                                      GPid            pid,

glib/tests/timeout.c

@@ -19,6 +19,12 @@ unreachable_callback (gpointer data)
   return G_SOURCE_REMOVE;
 }
 
+static void
+unreachable_void_callback (gpointer data)
+{
+  g_assert_not_reached ();
+}
+
 static void
 test_seconds (void)
 {
@@ -51,6 +57,19 @@ test_seconds (void)
   g_source_remove (id);
 }
 
+static void
+test_seconds_once (void)
+{
+  /* Use the same principle as in test_seconds() */
+  loop = g_main_loop_new (NULL, FALSE);
+
+  g_timeout_add_once (2100, stop_waiting, NULL);
+  g_timeout_add_seconds_once (21475, unreachable_void_callback, NULL);
+
+  g_main_loop_run (loop);
+  g_main_loop_unref (loop);
+}
+
 static void
 test_weeks_overflow (void)
 {
@@ -192,6 +211,7 @@ main (int argc, char *argv[])
   g_test_init (&argc, &argv, NULL);
 
   g_test_add_func ("/timeout/seconds", test_seconds);
+  g_test_add_func ("/timeout/seconds-once", test_seconds_once);
   g_test_add_func ("/timeout/weeks-overflow", test_weeks_overflow);
   g_test_add_func ("/timeout/far-future-ready-time", test_far_future_ready_time);
   g_test_add_func ("/timeout/rounding", test_rounding);