bug#12868: global keymap preceeds input-decode-map

[Stefan Guath]

I understand, and agree that a timeout is a bad idea. This should be reflected 
in the manual though, just as it is for local-function-key-map ("Entries in 
local-function-key-map are ignored if they conflict with bindings made in the 
minor mode, local, or global keymaps"). Maybe it should also point out the 
consequences of binding escape sequences used as prefix for common function 
keys, i.e. `ESC [' and `ESC O'. One could even consider to unable colliding 
bindings to emphasize that you have to choose, rather than 'bugging out' 
silently.

BTW, the manual states that "The intent of key-translation-map is for users to 
map one character set to another, including ordinary characters normally bound 
to self-insert-command." Does this mean that key-translation-map is the 
recommended way to implement different layouts such as Colemak/Dvorak etc at 
the lowest possible level?

If yes, in the case of remapping `o' to `y' (Colemak example), M-O would never 
get through the input-decode-map filter and therefore never pop up to 
key-translation-map in order to produce M-Y. Is that correct?

/Stefan

On 12 nov 2012, at 15:32, Stefan Monnier wrote:

>> emacs -nw -Q
>> (defun foo () (interactive) (message "foo"))
>> (global-set-key "\M-O" 'foo)
> [...]
>> Arrow keys now inserts A,B,C,D in buffer.
> [...]
>> Arrow keys sends M-O A (up), M-O B (down) etc. These should be
>> translated to function keys <up>, <down> etc in input-decode-map
>> before any key lookup.  Somehow, the binding of M-O in the global
>> keymap takes precedence.
> 
> Indeed, thanks for bringing this up.  The cause for the bug is that the
> rule for what goes first and what goes next is here ignored because we
> stop waiting for more input as soon as a real binding is found
> (i.e. right after M-O).
> 
> The predicate that decides when to stop waiting for more input would
> need to say say "don't stop if we're in the middle of a potential
> input-decode-map rewrite".  But then if you want to run `foo', you'd
> have the problem that after hitting M-O, Emacs will not actually run
> `foo' but will sit there waiting to see if the next key is one of
> [ABCD].
> 
> The only way to get our cake and eat it too would be to use some kind of
> timeout, which we have resisted so far.
> 
> 
>        Stefan