Re: split-window-preferred-function

[martin rudalics]

> Maybe a function in `split-window-preferred-function' should take care
> of all these conditions to decide how to split within a given
> window configuration?

Writing such a function is not entirely trivial.  Who's supposed to
write `split-window-preferred-function' in the first place?  Wasn't the
original motivation of this to simply allow horizontal splitting?

> The following patch implements this (note that checking for non-nil
> Vsplit_window_preferred_function is not necessary in the else-branch
> because when Vsplit_window_preferred_function is called unconditionally
> it never reaches this else-branch with the second place where
> Fsplit_window is called).

Looks good.  But as Stefan remarked the function should return nil and
have `disply-buffer' continue the standard processing of this when it
was not able to split the window for whatever reason.