bug#9751: 23.3; Alternative Keyboard Feature/Bug

[Stefan Monnier]

>> Oh, yes, it wasn't complete.  Here is a more complete one which seems to
>> work to remap 3 to 4 with 3 globally bound to `undefined'.
> It still does nothing.  I guess for testing it, a Greek keyboard layout
> is not necessary.  It's enough to evaluate:
> (define-key function-key-map [?*] [?b])
> and typing `*' is expected to run `beginning-of-buffer' in Info.

Oh, right because * is not bound to `undefined', instead it's bound to
self-insert-command which is remapped to `undefined'.  Damn!
The patch below at least works for this test case,


        Stefan


=== modified file 'src/keyboard.c'
--- src/keyboard.c      2011-10-03 20:50:54 +0000
+++ src/keyboard.c      2011-10-24 20:15:14 +0000
@@ -8902,6 +8902,14 @@
   return 0;
 }
 
+static int
+test_undefined (Lisp_Object binding)
+{
+  return (EQ (binding, Qundefined)
+         || (!NILP (binding) && SYMBOLP (binding)
+             && EQ (Fcommand_remapping (binding, Qnil, Qnil), Qundefined)));
+}
+
 /* Read a sequence of keys that ends with a non prefix character,
    storing it in KEYBUF, a buffer of size BUFSIZE.
    Prompt with PROMPT.
@@ -9852,7 +9860,9 @@
            }
        }
 
-      if (first_binding < nmaps && NILP (submaps[first_binding])
+      if (first_binding < nmaps
+         && NILP (submaps[first_binding])
+         && !test_undefined (defs[first_binding])
          && indec.start >= t)
        /* There is a binding and it's not a prefix.
           (and it doesn't have any input-decode-map translation pending).
@@ -9879,7 +9889,9 @@
                                  /* If there's a binding (i.e.
                                     first_binding >= nmaps) we don't want
                                     to apply this function-key-mapping.  */
-                                 fkey.end + 1 == t && first_binding >= nmaps,
+                                 fkey.end + 1 == t
+                                 && (first_binding >= nmaps
+                                     || test_undefined (defs[first_binding])),
                                  &diff, prompt);
            UNGCPRO;
            if (done)