bug#69983: Use category for display-buffer-alist

[Eli Zaretskii]

> From: Juri Linkov <juri@linkov.net>
> Cc: rudalics@gmx.at,  69983@debbugs.gnu.org
> Date: Sun, 14 Apr 2024 19:04:13 +0300
> 
> >> > If we want to enable user control of displaying warnings, we will have
> >> > to add an option for that, because currently that cannot be
> >> > controlled.  display-buffer-alist is inappropriate for such control,
> >> > since in some cases warnings are not displayed in pop-up windows.
> >>
> >> Could you show an example when warnings are not displayed in pop-up 
> >> windows.
> >
> > The two calls to 'message' there.
> 
> These calls are irrelevant.  It makes no sense to add an option
> to display text "at the bottom of 'message'".

Of course.  But what if some user would like to display the warnings
in the echo-area?  Don't we want to allow such customization?  If we
do, then display-buffer machinery is not relevant, exactly as it is
not relevant for those two calls.

> >> > Thanks, but what do you mean by "at the bottom"?  Can you describe
> >> > that place more precisely?
> >>
> >> Here is an example:
> >
> > I understand what this means in the simple cases, but not necessarily
> > what happens in more complex cases.
> 
> This case is not simple.  It demonstrates the problem
> in horizontally split windows.
> 
> > This is why I asked for a detailed definition of "at bottom".
> 
> The detailed definition is in the documentation of
> 'display-buffer-at-bottom'.

I agree that "display at bottom" is a useful feature, but why should
we decide that users could have no control of that, either?  E.g.,
another reasonable MO is to split the selected window vertically and
show the warning in the lower window.

So I think display-warning should have a variable to customize its
display, and limiting that only to what display-buffer can produce
doesn't support all the optional behaviors people could reasonably
want.  Moreover, display-buffer is IMO overly-complex for this simple
job; a simple variable with several distinct values would do.