Keymap priorities - how do define a global, low-priority binding from a minor mode?

Keymap priorities - how do define a global, low-priority binding from a minor mode?

[David Reitter]

I have defined a global minor mode which gives me a bunch of key  
bindings, among them bindings for `up' and `down'.

Turns out that the global minor mode overrides local key maps, at  
least minibuffer-local-map, which defines its own bindings for these  
keys (which I would prefer).

How do I specify priorities for key bindings? Can I define a minor  
mode key map that does not override the minibuffer map? Is using the  
global key map from a global minor mode a clean solution??

In this particular case, defining a key for [remap 'next-line] does  
the job, but is semantically different - it doesn't allow me to  
distinguish between C-n and `down', so I'm trying to get rid of it.

Thanks,
David

Re: Keymap priorities - how do define a global, low-priority binding from a minor mode?

[Stefan Monnier]

> I have defined a global minor mode which gives me a bunch of key  bindings,
> among them bindings for `up' and `down'.

> Turns out that the global minor mode overrides local key maps, at  least
> minibuffer-local-map, which defines its own bindings for these keys (which
> I would prefer).

> How do I specify priorities for key bindings? Can I define a minor mode key
> map that does not override the minibuffer map?

No.  Please report it as a feature request.  I think a good change would be
for minor-mode-map-alist entries to have higher or lower priority depending
on whether the minor mode's variable is buffer-local or global.  This way,
global minor mode would get lower priority than buffer-local maps (there's
still emulation-mode-map-alist if you want something or higher priority),
which seem like The Right Thing.

> Is using the global key map from a global minor mode a clean solution??

It's not great, but it's the best we have.


        Stefan

Re: Keymap priorities - how do define a global, low-priority binding from a minor mode?

[david.reitter]

Stefan,
Thanks, I'll put together a suggestion at some point - but probably
after the release.

>> Is using the global key map from a global minor mode a clean solution??
>It's not great, but it's the best we have.

For the record, here's an alternative, certainly somewhat ugly. The
`down' key is bound to the below function, which then looks up what the
binding would be if the global minor mode was switched off.
This stops short of advising `next-line' (which would affect a lot of
code). Modifying the global map would have been the alternative, but I
didn't do it because people using my mode like to override its key map
in their .emacs, and they couldn't do that if I hardcoded additional
bindings to be set when the mode is switched on and off.

(defun osxkeys-visual-line-down-in-buffers ()
"Moves the cursor down one (visual) line.
If the `down' key would normally be bound to something else than
`next-line' (as it is the case in minibuffers), the other binding
is called."
  (interactive)
  (let* (osx-key-mode  ;; turn off mode temporarily
	 (binding (key-binding [down])))
    (if (eq binding 'next-line)
	(call-interactively (function visual-line-down))
      (call-interactively binding))))

;; mark functions for CUA
(dolist (cmd
	 '( beginning-of-visual-line
	    end-of-visual-line
	    visual-line-down visual-line-up
	    osxkeys-visual-line-up-in-buffers
	    osxkeys-visual-line-down-in-buffers))
  (put cmd 'CUA 'move))