bug#70010: 30.0.50; completion-preview-mode behaves mode-local, but is global

[Philip Kaludercic <philipk@posteo.net>]

Eshel Yaron <me@eshelyaron.com> writes:

> Hello Philip,
>
> Philip Kaludercic <philipk@posteo.net> writes:
>
>> I tried to enable `completion-preview-mode' by adding
>>
>>   (setopt completion-preview-mode t)
>>
>> in my init, but it had not effect.
>
> Indeed, it is a minor mode, so one normally enables it by calling the
> function completion-preview-mode, perhaps interactively via M-x.

I enable all minor modes as user options, so I'd disagree that using a
function or invoking the command are the only ways to expect a minor
mode to be enabled.

>> When I check the implementation, I noticed that it modifies
>> `post-command-hook' locally.  I think it would make sense to rename
>> the current `completion-preview-mode' to
>> `completion-preview-local-mode', and then use
>> `define-globalized-minor-mode' to define `completion-preview-mode'.
>
> We can add a global variant, although IMO the natural scope for
> completion-preview-mode is per major mode: for some kinds of content you
> want to have completion preview, and for others you may want it off.
> Note that a necessary condition for completion-preview-mode to be useful
> in a certain context is that completion-at-point is useful in that
> context, since otherwise there's nothing to preview.
>
> Therefore, I recommend enabling completion-preview-mode by adding it to
> major mode hooks, such as prog-mode-hook or comint-mode-hook.
> Admittedly, if you do want to enable it for all buffers, the major mode
> hook approach would require adding it to four or five hooks, which is a
> bit less elegant than enabling a global minor mode once.
>
> So I suggest we keep completion-preview-mode local and add a global
> variant, say, completion-preview-global-mode, for enabling it globally.
> WDYT?

That seems fine as well.

-- 
	Philip Kaludercic on peregrine