[glib] Document that pre-unmount may not be emitted

[Philip Withnall <pwithnall src gnome org>]

commit 0ef7174e74fe91183e68c81d2f5bd4a3419283ad
Author: Christian Dywan <christian twotoasts de>
Date:   Wed Dec 1 14:06:13 2010 +0100

    Document that pre-unmount may not be emitted
    
    Fixes: https://bugzilla.gnome.org/show_bug.cgi?id=636210

 gio/gmount.c         |    5 ++++-
 gio/gvolumemonitor.c |    5 ++++-
 2 files changed, 8 insertions(+), 2 deletions(-)
---
diff --git a/gio/gmount.c b/gio/gmount.c
index 3d74b85..ff50a5c 100644
--- a/gio/gmount.c
+++ b/gio/gmount.c
@@ -101,9 +101,12 @@ g_mount_default_init (GMountInterface *iface)
    * GMount::pre-unmount:
    * @mount: the object on which the signal is emitted
    *
-   * This signal is emitted when the #GMount is about to be
+   * This signal may be emitted when the #GMount is about to be
    * unmounted.
    *
+   * This signal depends on the backend and is only emitted if
+   * GIO was used to unmount.
+   *
    * Since: 2.22
    **/
   g_signal_new (I_("pre-unmount"),
diff --git a/gio/gvolumemonitor.c b/gio/gvolumemonitor.c
index cc8d917..cb22f89 100644
--- a/gio/gvolumemonitor.c
+++ b/gio/gvolumemonitor.c
@@ -159,7 +159,10 @@ g_volume_monitor_class_init (GVolumeMonitorClass *klass)
    * @volume_monitor: The volume monitor emitting the signal.
    * @mount: a #GMount that is being unmounted.
    *
-   * Emitted when a mount is about to be removed.
+   * May be emitted when a mount is about to be removed.
+   *
+   * This signal depends on the backend and is only emitted if
+   * GIO was used to unmount.
    **/ 
   signals[MOUNT_PRE_UNMOUNT] = g_signal_new (I_("mount-pre-unmount"),
                                              G_TYPE_VOLUME_MONITOR,