Re: `split-window-preferred-horizontally'

[martin rudalics <rudalics@gmx.at>]

 > That's how I would like it:
 >
 > If the *frame* is >= 160 chars wide
 >
 >   - if it is already (horizontally) split use the *other* window with
 >     all the `*-other-window' commands and `display-buffer'

`split-window-preferred-function' should decide if and how to split the
largest (or most recently used) window offered by `display-buffer'.  It
cannot decide which window to use when _no_ window gets split.

 >   - otherwise split it horizontally.
 >
 > If the *frame* is < 160 chars wide do above with s/horizontally/vertically/
 > (as the default behavior already is).

(defun my-spf (window)
   (if (>= (frame-width (window-frame window)) 120)
       (when (window-full-width-p window)
	(let ((split-width-threshold 120))
	  (split-window window nil t)))
     (split-window)))

seems to do what you want with a value of 120 - I can't test 160 here.

 > I suspect that emacs thinks my already (horizontally) split frame is to
 > small because the *window* is just 80 + ? chars wide.

The value of `split-width-threshold' must be set accordingly to handle
this when your frame contains more than one window.  If WINDOW is 120
columns wide, `split-width-threshold' equals 160, and you have more than
one window on your frame, `split-window' should refuse to split WINDOW.