[gtk+] Some GdkMonitor documentation additions

[Matthias Clasen <matthiasc src gnome org>]

commit f2ad5ddbb6a1a937221331729c61763a48c196f8
Author: Matthias Clasen <mclasen redhat com>
Date:   Tue Dec 26 11:19:24 2017 -0500

    Some GdkMonitor documentation additions
    
    Document the ::invalidated signal.

 gdk/gdkmonitor.c |   14 ++++++++++++++
 1 files changed, 14 insertions(+), 0 deletions(-)
---
diff --git a/gdk/gdkmonitor.c b/gdk/gdkmonitor.c
index d36670e..536e891 100644
--- a/gdk/gdkmonitor.c
+++ b/gdk/gdkmonitor.c
@@ -37,6 +37,13 @@
  * gdk_display_get_monitor_at_window().
  */
 
+/**
+ * GdkMonitor:
+ *
+ * The GdkMonitor struct contains only private fields and should not
+ * be accessed directly.
+ */
+
 enum {
   PROP_0,
   PROP_DISPLAY,
@@ -247,6 +254,13 @@ gdk_monitor_class_init (GdkMonitorClass *class)
 
   g_object_class_install_properties (object_class, LAST_PROP, props);
 
+  /**
+   * GdkMonitor::invalidate:
+   * @monitor: the object on which this signal was emitted
+   *
+   * The ::invalidate signal gets emitted when the output represented
+   * by @monitor gets disconnected.
+   */
   signals[INVALIDATE] = g_signal_new (g_intern_static_string ("invalidate"),
                                       G_TYPE_FROM_CLASS (object_class),
                                       G_SIGNAL_RUN_FIRST,