RE: [External] : general "toggle" command? general "toggle" prefix?

[Drew Adams]

> There are many kinds of settings in Emacs, and for quite a few
> we have implemented or considered commands to toggle
> between recent settings.
> 
> Might it be useful to have a prefix for toggling a setting?
> Might it be possible to write a general command that can
> toggle various kinds of settings?

I have a command for toggling a variable value,
`icicle-toggle-option', which is bound to
`M-i M-i' during completion in Icicle minor mode.
Description:

 Toggle option's value.

 This makes sense for binary (toggle) options.
 By default, completion candidates are limited to
 user options that have `boolean' custom types.
 However, there are many "binary" options
 that allow other non-nil values than t.

 You can use a prefix argument to change the set
 of completion candidates, as follows:

  - With a non-negative prefix arg, all user
    options are candidates.
  - With a negative prefix arg, all variables
    are candidates.

(More generally, during completion prefix key
`M-i' is bound to `icicle-toggle-map', which
has lots of toggle keys.)