Re: Allowing completion sources to customize completion display

[sbaugh]

Dmitry Gutov <dmitry@gutov.dev> writes:
> On 24/11/2023 19:28, Spencer Baugh wrote:
>> But basing this on the source is totally wrong.  Instead if I, as a
>> user, think inline preview is better for multi-line completion
>> candidates, then inline preview should be used for multi-line completion
>> candidates regardless of where those candidates come from.
>
> Are multi-line completions better shown inline? If I had to choose, I
> might actually choose the opposite: show the shorter ones inline, and
> the long ones in a separate buffer -- so that the current buffer's
> text doesn't jump up and down as I'm typing something.

The idea is that multi-line completions are big, so you can only really
afford to show one large completion candidate on-screen at a time.
Whereas for shorter completions you can usefully fit multiple on screen
at a time.

To be clear, I haven't mentioned any in-buffer menus like company-mode
has.  If it was done with company certainly there would be in-buffer
menus, and I think what I would want is "always show a preview frontend,
and show a tooltip frontend only if the completion candidates are
small. (not multi-line)".

> But that strongly depends on how those long completions are going to
> be presented, whether they should replace the current text or just add
> new one (multiple lines of it), whether they are allowed to vary a
> lot, etc.

The long completions in my case are ones which can both modify or add
text, both before or after point.

But that's an interesting point.  An in-buffer menu (like company-mode
has) is a lot less suitable for completions which modify the text in
complex ways.  With such completions, an in-buffer preview is nicer.

So perhaps that's another way a completion UI (such as company) could
alter its behavior based on the completions: only show completion
candidates in an in-buffer menu (a tooltip frontend) if they are
"simple" (e.g. just symbol completion which leaves point after the newly
inserted symbol).  If they are complex, do an in-buffer preview.