Re: Prefer to split along the longest edge

[Eli Zaretskii <eliz@gnu.org>]

> Date: Wed, 18 Dec 2024 11:05:55 +0100
> Cc: nicolas.despres@gmail.com, juri@linkov.net, emacs-devel@gnu.org
> From: martin rudalics <rudalics@gmx.at>
> 
>  > It could be both.  But I firmly object to make this be customizable
>  > _only_ through display-buffer action alists, because that is even less
>  > user-friendly than function values of defcustoms.
> 
> If we make this and other display buffer options a defcustom too, we'd
> have to specify the semantics of that defcustom.  In particular:

To clarify: I was talking only about this particular toggle, not about
"other display-buffer options".  The difference is that those other
options already exist, so removing or redesigning them is not easy at
best, and thus probably isn't worth our while.

> - Should the defcustom hold for any buffer to be displayed?
> 
> - Should it override what the calling program specifies in the ALIST
>    argument.
> 
> - Would a 'display-buffer-alist' entry override it?
> 
> Once these have been resolved, we can easily add defcustoms for most
> options that are currently only available via 'display-buffer-alist'.

I don't necessarily see how the above questions are relevant to the
issue at hand.  AFAIU, the OP asked for a capability to tell Emacs to
split horizontally first instead of vertically.  My interpretation of
that is that this desire is global, for all the use cases.  So a
single global option seems appropriate, and my personal answer to the
above questions would be YES to the first one at least.  As for the
other two: can display-buffer-alist specify the splitting behavior
this today?  If not, I don't see why we should forcibly introduce such
a possibility, which will then require us to consider who can override
whom.  If display-buffer-alist cannot specify splitting, then the
problem with overriding doesn't exist.