posnp doc clarification

* lisp/subr.el (posnp): Mention that a posn object is returned
from `event-start' (bug#18211).

diff --git a/lisp/subr.el b/lisp/subr.el
index 3f5d6e427e979b7a790751921aa7a775df08a537..0f021701e9f1518e48a328a6eb75c130bb649f47 100644 (file)
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -1117,6 +1117,7 @@ The return value is a positive integer."
 
 (defun posnp (obj)
   "Return non-nil if OBJ appears to be a valid `posn' object specifying a window.
+A `posn' object is returned from functions such as `event-start'.
 If OBJ is a valid `posn' object, but specifies a frame rather
 than a window, return nil."
   ;; FIXME: Correct the behavior of this function so that all valid