[gtk+] Document ::snapshot vfunc

[Matthias Clasen <matthiasc src gnome org>]

commit 3dc53dab697b76fc3ec414ad21f6f5ee51fef529
Author: Matthias Clasen <mclasen redhat com>
Date:   Sat Nov 19 12:37:19 2016 -0500

    Document ::snapshot vfunc

 gtk/gtkwidget.h |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/gtk/gtkwidget.h b/gtk/gtkwidget.h
index 7a3f061..911f3ba 100644
--- a/gtk/gtkwidget.h
+++ b/gtk/gtkwidget.h
@@ -315,6 +315,8 @@ struct _GtkWidget
  *   region.
  * @queue_draw_child: Child wants to be redrawn. The region given is in
  *   the child's coordinate system.
+ * @snapshot: Signal emitted when a widget is supposed to create a snapshot
+ *   of itself.
  */
 struct _GtkWidgetClass
 {