Hi Felician,

Sorry for the late reply. I'm working, and am very close to publishing,
the promised introduction of eldoc-display-functions to help users (and
third-party devs) better control the display of eldoc documentation.

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?

João

On Sat, Jul 25, 2020 at 7:18 PM Felician Nemeth <felician.nemeth@gmail.com>
wrote:

> With the attached file, start emacs as:
>
>   emacs -Q --load bug.el
>
> and then move the point left or right.  Originally I started to write
> this file as demonstration to bug#42421, but you fixed the bug faster
> than I could find time to finish it.  Now, I think everything works as
> documented, but with the help of this recipe, I'd like to argue that
> eldoc-prefer-doc-buffer is a bit annoying in this case.  Its
> documentation says:
>
>    Prefer ElDoc’s documentation buffer if it is showing in some frame.
>    If this variable’s value is t and a piece of documentation needs to
>    be truncated to fit in the echo area, do so if ElDoc’s documentation
>    buffer is not already showing, since the buffer always holds the full
>    documentation.
>
> I think it would be better to show the documentation only in the *eldoc*
> buffer and not in the echo area even if the documentation doesn't need
> to be truncated but the echo are needs to be resized to display the full
> documentation.
>
> (bug.el changes eldoc-documentation-function to circumvent bug#42531,
> which I reported few minutes ago, but changing the order of the hooks in
> eldoc--eval-expression-setup, doesn't seem to fix bug#42531)
>
> Thank you, João, for your work on eldoc.
>
>

-- 
João Távora