* src/keymap.c (Fmake_composed_keymap): Move to subr.el.

* lisp/subr.el (make-composed-keymap): Move from C.  Change calling
convention, and improve docstring to bring attention to a subtle point.
* lisp/minibuffer.el (completing-read-default): Adjust accordingly.

1 files changed, 14 insertions, 0 deletions

diff --git a/lisp/subr.el b/lisp/subr.el
index ef19797012a..d57c507a548 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -526,6 +526,20 @@ but optional second arg NODIGITS non-nil treats them like other chars."
 	  (define-key map (char-to-string loop) 'digit-argument)
 	  (setq loop (1+ loop))))))
 
+(defun make-composed-keymap (maps &optional parent)
+  "Construct a new keymap composed of MAPS and inheriting from PARENT.
+When looking up a key in the returned map, the key is looked in each
+keymap of MAPS in turn until a binding is found.
+If no binding is found in MAPS, the lookup continues in PARENT, if non-nil.
+As always with keymap inheritance, a nil binding in MAPS overrides
+any corresponding binding in PARENT, but it does not override corresponding
+bindings in other keymaps of MAPS.
+MAPS can be a list of keymaps or a single keymap.
+PARENT if non-nil should be a keymap."
+  `(keymap
+    ,@(if (keymapp maps) (list maps) maps)
+    ,@parent))
+
 (defun define-key-after (keymap key definition &optional after)
   "Add binding in KEYMAP for KEY => DEFINITION, right after AFTER's binding.
 This is like `define-key' except that the binding for KEY is placed