bug#62029: 29.0.60; Allow users to customize eldoc buffer separator

[Yuan Fu]

> On Mar 24, 2023, at 10:44 AM, João Távora <joaotavora@gmail.com> wrote:
> 
> Yuan Fu <casouri@gmail.com> writes:
> 
>> For separator, maybe something like
>> 
>> (insert “Title" (propertize "-" 'display
>>                             '(space :align-to right)
>>                             'font-lock-face '(:strike-through t)
>>                             'face '(:strike-through t)))
>> 
>> for GUI, and use underline for terminal.
> 
> I've now pushed a commit to master introducing the user variable
> eldoc-doc-buffer-separator.  It's not a defcustom yet, as I'm not too
> familiar with those, but feel free to change it.
> 
>  (defvar eldoc-doc-buffer-separator
>    "String used to separate items in Eldoc documentation buffer."
>    (concat "\n" (propertize "\n" 'face '(:inherit separator-line :extend t)) 
> "\n"))
> 
> There is a difference between a separator and a title.  I've stopped
> short of adding titles, as I fear it would be confusing unless the
> content allows it.  To be investigated later for
> eldoc-display-in-echo-area or maybe you can try it in eldoc-box.
> 
> Also, I've been testing with these unpushed changes to elisp-mode.el,
> which render more of the docstring in emacs-lisp-mode.
> 
> The use case here is navigating around in an .el file while having a
> window open with the *eldoc* buffer.
> 
> João

Looks good to me (except for the “documentatiok” ;-) eldoc-box can also benefit 
from this (right now if you use it in emacs-lisp-mode, it just shows a thin 
strip of text, not very exciting).

I’ll experiment with the title thing in eldoc-box. Does eglot and flymake 
already pass a :source cookie? Those two displaying stuff together is the most 
possible case I can think of.

Yuan