bug#33870: 27.0.50; xref-goto-xref not configurable

[martin rudalics]

> Thanks, this fixed an original problem, but introduced a new problem:
> now when windows are already horizontally split, the bottom window
> is narrowed to the width of the left window.  Before this change,
> the width of Local Variables window was the same as the frame width.

The entire

        (and (not (frame-parameter nil 'unsplittable))
             (let ((split-height-threshold 0))
               (setq window (window--try-to-split-window bottom-window alist)))
             (window--display-buffer buffer window 'window alist))

is bad design.

Note that I removed this behavior in 'display-buffer-in-direction'.
There I (1) disregard 'split-window-preferred-function' and (2) only
split the argument window which would be the main window when called
from 'display-buffer-at-bottom'.

martin