Improve minibuffer-inactive-mode documentation

* lisp/minibuffer.el (minibuffer-inactive-mode): Clarify when it's
used (bug#13641).

diff --git a/lisp/minibuffer.el b/lisp/minibuffer.el
index 9f327df28f5e0b120216a057548063c37b17b4b0..f193c420376003c9aada34e5a50f538d743e31f5 100644 (file)
--- a/lisp/minibuffer.el
+++ b/lisp/minibuffer.el
@@ -2706,7 +2706,14 @@ not active.")
   :abbrev-table nil          ;abbrev.el is not loaded yet during dump.
   ;; Note: this major mode is called from minibuf.c.
   "Major mode to use in the minibuffer when it is not active.
-This is only used when the minibuffer area has no active minibuffer.")
+This is only used when the minibuffer area has no active minibuffer.
+
+Note that the minibuffer may change to this mode more often than
+you might expect.  For instance, typing `M-x' may change the
+buffer to this mode, then to a different mode, and then back
+again to this mode upon exit.  Code running from
+`minibuffer-inactive-mode-hook' has to be prepared to run
+multiple times per minibuffer invocation.")
 
 (defvaralias 'minibuffer-mode-map 'minibuffer-local-map)