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

[Juri Linkov <juri@linkov.net>]

>> >> > 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.

This proves that a new option is not needed.  QED.

>> >> > 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.

This is easy to customize with a category in display-buffer-alist.

> 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.

Adding dozens of new variables that replace display-buffer-alist
makes no sense.