[glib] Document g_timeout_add_seconds first call latency

[Emilio Pozuelo Monfort <epm src gnome org>]

commit 89ca0f729665f812b142b9a107515c945237082a
Author: Emilio Pozuelo Monfort <pochu27 gmail com>
Date:   Sat Mar 12 10:08:52 2011 +0000

    Document g_timeout_add_seconds first call latency
    
    And fix /timeout/rounding to not fail if the first call
    happens after 2 seconds.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=644552

 glib/gmain.c         |    6 +++++-
 glib/tests/timeout.c |    8 +++++++-
 2 files changed, 12 insertions(+), 2 deletions(-)
---
diff --git a/glib/gmain.c b/glib/gmain.c
index 3a480f3..d4f393e 100644
--- a/glib/gmain.c
+++ b/glib/gmain.c
@@ -4118,7 +4118,11 @@ g_timeout_add_seconds_full (gint           priority,
  * g_timeout_source_new_seconds() and attaches it to the main loop context 
  * using g_source_attach(). You can do these steps manually if you need 
  * greater control. Also see g_timout_add_seconds_full().
- * 
+ *
+ * Note that the first call of the timer may not be precise for timeouts
+ * of one second. If you need finer precision and have such a timeout,
+ * you may want to use g_timeout_add() instead.
+ *
  * Return value: the ID (greater than 0) of the event source.
  *
  * Since: 2.14
diff --git a/glib/tests/timeout.c b/glib/tests/timeout.c
index 824afc0..bae2b4f 100644
--- a/glib/tests/timeout.c
+++ b/glib/tests/timeout.c
@@ -53,7 +53,13 @@ test_func (gpointer data)
 
   current_time = g_get_monotonic_time ();
 
-  g_assert (current_time / 1000000 - last_time / 1000000 == 1);
+  /* We accept 2 on the first iteration because _add_seconds() can
+   * have an initial latency of 1 second, see its documentation.
+   */
+  if (count == 0)
+    g_assert (current_time / 1000000 - last_time / 1000000 <= 2);
+  else
+    g_assert (current_time / 1000000 - last_time / 1000000 == 1);
 
   last_time = current_time;
   count++;