[glib: 1/2] giochannel: Clarify type of GSource callback in documentation

[Sebastian Dröge <sdroege src gnome org>]

commit f02c6eb5145304f0a73370993b1e95da92758f6e
Author: Philip Withnall <withnall endlessm com>
Date:   Fri Sep 6 10:49:39 2019 +0100

    giochannel: Clarify type of GSource callback in documentation
    
    This should clarify questions like
    https://stackoverflow.com/q/57807738/2931197.
    
    Signed-off-by: Philip Withnall <withnall endlessm com>

 glib/giochannel.c | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/glib/giochannel.c b/glib/giochannel.c
index 1956e9dc6..ed8546331 100644
--- a/glib/giochannel.c
+++ b/glib/giochannel.c
@@ -596,6 +596,9 @@ g_io_channel_purge (GIOChannel *channel)
  * given @channel. For example, if condition is #G_IO_IN, the source will 
  * be dispatched when there's data available for reading.
  *
+ * The callback function invoked by the #GSource should be added with
+ * g_source_set_callback(), but it has type #GIOFunc (not #GSourceFunc).
+ *
  * g_io_add_watch() is a simpler interface to this same functionality, for 
  * the case where you want to add the source to the default main loop context 
  * at the default priority.