Remapping global keybindings to a prefix command

Question

The following works:

(define-prefix-command 'my-map)
(global-set-key (kbd "C-@") 'my-map) ;; MacOS
(global-set-key (kbd "C-SPC") 'my-map) ;; Windows 10

The following does not:

(global-set-key [remap set-mark-command] 'my-map)

It fails with the error that my-map is not a command (commandp returns nil).

The emacs manual states that "putting a remapping in a prefix keymap like ctl-x-map typically has no effect, as such keymaps are not themselves active;" however, I am remapping a command in the active global map to a prefix map. So why does this fail?

Answer 1

Unfortunately, the use of [remap COMMMAND] syntax in a key-binding definition seems to require COMMAND to be a symbol that is a command (commandp). It doesn't seem to allow a prefix-key keymap or a prefix-key variable whose value is a keymap.

I just sent a mail to [email protected] about this. Maybe I'm missing something (probably). But it seems like (1) the doc string of define-key says that it should work, but (2) it doesn't.

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If you want, you can do almost the same thing this way:

(substitute-key-definition 'set-mark-command 'my-map global-map)

That's almost the same thing as what you tried:

(global-set-key [remap set-mark-command] 'my-map)

It does, in effect, what you ended up doing manually by binding each key individually.

The difference from remapping is that, well the command set-mark-command is not remapped. Instead, you've just rebound each of its global keys to keymap (prefix command) my-map.