[gtk/wip/matthiasc/focus3: 29/32] key controller: Improve the docs

[Matthias Clasen <matthiasc src gnome org>]

commit b3f05c83ea50a10fa00fb9ebbe6f01b9c96cd35f
Author: Matthias Clasen <mclasen redhat com>
Date:   Fri Mar 8 10:19:12 2019 -0500

    key controller: Improve the docs
    
    Mention the limitations of the key forwarding api.

 gtk/gtkeventcontrollerkey.c | 7 +++++++
 1 file changed, 7 insertions(+)
---
diff --git a/gtk/gtkeventcontrollerkey.c b/gtk/gtkeventcontrollerkey.c
index b57e9df19e..2909095979 100644
--- a/gtk/gtkeventcontrollerkey.c
+++ b/gtk/gtkeventcontrollerkey.c
@@ -470,6 +470,13 @@ gtk_event_controller_key_get_im_context (GtkEventControllerKey *controller)
  *
  * Forwards the current event of this @controller to a @widget.
  *
+ * This function can only be used in handlers for the
+ * #GtkEventControllerKey::key-pressed,
+ * #GtkEventControllerKey::key-released
+ * or
+ * #GtkEventControllerKey::modifiers
+ * signals.
+ *
  * Returns: whether the @widget handled the event
  **/
 gboolean