bug#42532: 28.0.50; Can eldoc-prefer-doc-buffer be more aggressive?

[Felician Nemeth <felician.nemeth@gmail.com>]

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>> Regardless, I think it's reasonable to add a third possible value 
>> for eldoc-prefer-doc-buffer (which should really be renamed 
>> eldoc-echo-area-prefer-doc-buffer).  The value could be the symbol
>> 'aggressive or 'aggressively.  Then it would behave as you propose:
>> if the ElDoc doc buffer is showing, the echo area display code is 
>> a noop.
>>
>> What do you think?
>
> Instead of an abstract idea, here's an actual patch you can try on top
> of the current eldoc.el
> [...]

Thank you.  I've finally tried the patch out with different settings of
eldoc-echo-area-prefer-doc-buffer and eldoc-echo-area-use-multiline-p.
It works as I wished when eldoc-echo-area-prefer-doc-buffer is
'aggressively.  And it works in line with the documentation in most
cases.  However, if I understand the documentation correctly, it doesn't
work as intended with

   (setq eldoc-echo-area-use-multiline-p nil)
   (setq eldoc-echo-area-prefer-doc-buffer t)

For example, with the attached file, moving the point right after "emacs
-Q --load ./bug.el" displays the truncated documentation in the echo
area, but it shouldn't.


[-- Attachment #2: bug.el --]
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(defvar my-asdf-asdf-sdf-asdf-asdf-asdf-asdf-sdf-asdf-asdf-asdf-asdfasdf-asdf-sdf-asdf-asdf-asdf-asdfasdf-asdf 1
    "START asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf END")
(switch-to-buffer-other-window "*eldoc*")
(window-resize (get-buffer-window) (- window-min-height (window-height)))
(other-window 1)
(find-file "bug.el")
(goto-char 14)
(setq max-mini-window-height 2)
(setq eldoc-echo-area-use-multiline-p nil)
;;(setq eldoc-echo-area-use-multiline-p t)
;;(setq eldoc-echo-area-prefer-doc-buffer 'aggressively)
(setq eldoc-echo-area-prefer-doc-buffer t)
;;(setq eldoc-echo-area-prefer-doc-buffer nil)
(setq eldoc-documentation-functions '(elisp-eldoc-var-docstring elisp-eldoc-funcall  t))