Will the GTK+ timeout callbacks be called in strict time order?

Question

When I add many different timeouts (with each intervall==0) in a thread, which is not the main thread (where gtk_main() resides)...

g_timeout_add(0, func, NULL);

... will then the different func() callbacks occur in the same order I called the corresponding g_timeout_add()'s?

The reason I'm asking is because GTK# is using internally timeouts to implement Application.Invoke() (see Application.cs and Timeout.cs).

EDIT: The concerning glib files are

• http://git.gnome.org/browse/glib/tree/glib/gmain.c
• http://git.gnome.org/browse/glib/tree/glib/ghook.c

Answer 1

Internally, g_timeout_add calls g_hook_insert_sorted. If g_timeout_add_full is used, the priority determines the ordering, otherwise the hook is added at the end of the list. Hooks are executed in order, so when only g_timeout_add is used, the answer is yes.

Unfortunately, there is not no explicit guarantee, and to me, it looks like an implementation detail which might change in the future.

Answer 2

How about enforcing the order of the calls by storing your callbacks explicitly in a list, then using a single g_timeout_add() to call a function that iterates over that list?

static gboolean
call_in_order (GList* callbacks)
{
  for (; callbacks != NULL; callbacks = callbacks->next)
    {
      g_assert (callbacks->data != NULL);
      GSourceFunc callback = (GSourceFunc)(callbacks->data);

      callback(NULL);
    }
}


...

 GList *callbacks = NULL;
 callbacks = g_list_append(callbacks, func1);
 callbacks = g_list_append(callbacks, func2);
 callbacks = g_list_append(callbacks, func3);
 callbacks = g_list_append(callbacks, func4);

 g_timeout_add(0, (GSourceFunc)call_in_order, callbacks);