Re: Access to readline completions without line editing

[Chet Ramey]

On 9/26/23 9:54 PM, sbaugh@catern.com wrote:
> Hi,
>
> GNU Emacs wraps many readline-using programs, but disables readline in
> favor of its own line-editing commands.  However, it would be great for
> Emacs to still be able to access readline completions on demand; then
> Emacs would display those completions to the user in Emacs-y ways.

What do you mean by `readline completions'? Readline has builtin support
for only a few things: filename and directory name completion, username
completion for tilde expansion, and very little else.

Readline primarily offers support for determining the word to be completed,
calling an application-specific completion function if one is set, and
inserting or displaying the results. All of this requires that readline
be used to perform line editing and is part of the readline API.

> Right now there's no support in Emacs for accessing these completions,
> so completion in such programs is usually reimplemented inside Emacs in
> ad-hoc ways, or isn't supported at all.

Again, it's not clear what you mean by `these completions'. Do you mean
something like bash-completion? If you do, then any access to application-
specific completion functions has to be provided by the application.

> How should we access these completions if we want to disable
> line-editing? 

If you want to disable readline, then readline won't have any access to
the line editing data, and can't really do anything.

> What do you recommend?  Is there an existing mechanism
> which would be suitable for this? 

There are application-specific mechanisms like bash's `compgen' builtin.

> Or could a new feature for this be
> added to readline?

How would that work? Readline's not in the picture here.

Chet
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/