Re: split-window-preferred-function

[Juri Linkov]

> I think we need to allow the function to return nil and in this case
> continue with the rest of the code.  I.e. it should be possible to
> reproduce in Elisp what happens when split-window-preferred-function
> is nil.  A good way to make sure that's true is to write the code in
> Elisp in the first place.

If I understand you correctly, this patch implements what you meant:

Index: src/window.c
===================================================================
RCS file: /sources/emacs/emacs/src/window.c,v
retrieving revision 1.604
diff -c -w -b -r1.604 window.c
*** src/window.c        19 Mar 2008 15:18:29 -0000      1.604
--- src/window.c        22 Mar 2008 01:07:04 -0000
***************
*** 3848,3853 ****
--- 3848,3859 ----
        else
        window = Fget_largest_window (frames, Qt);
  
+       if (!NILP (Vsplit_window_preferred_function))
+       tem = call1 (Vsplit_window_preferred_function, window);
+ 
+       if (!NILP (tem))
+       window = tem;
+       else
        /* If the largest window is tall enough, full-width, and either eligible
           for splitting or the only window, split it.  */
        if (!NILP (window)
***************
*** 3857,3863 ****
                   || (NILP (XWINDOW (window)->parent)))
          && (window_height (window)
              >= (2 * window_min_size_2 (XWINDOW (window), 0))))
!       window = call1 (Vsplit_window_preferred_function, window);
        else
        {
          Lisp_Object upper, other;
--- 3863,3869 ----
                || (NILP (XWINDOW (window)->parent)))
            && (window_height (window)
                >= (2 * window_min_size_2 (XWINDOW (window), 0))))
!         window = Fsplit_window (window, Qnil, Qnil);
        else
        {
          Lisp_Object upper, other;
***************
*** 3872,3878 ****
                       || (NILP (XWINDOW (window)->parent)))
                   && (window_height (window)
                       >= (2 * window_min_size_2 (XWINDOW (window), 0))))
!           window = call1 (Vsplit_window_preferred_function, window);
          else
            window = Fget_lru_window (frames, Qnil);
          /* If Fget_lru_window returned nil, try other approaches.  */
--- 3878,3884 ----
                  || (NILP (XWINDOW (window)->parent)))
              && (window_height (window)
                  >= (2 * window_min_size_2 (XWINDOW (window), 0))))
!           window = Fsplit_window (window, Qnil, Qnil);
          else
            window = Fget_lru_window (frames, Qnil);
          /* If Fget_lru_window returned nil, try other approaches.  */
***************
*** 7598,7604 ****
  to split windows horizontally or vertically or some mix of the two.
  It is called with a window as single argument and should split it in two
  and return the new window.  */);
!   Vsplit_window_preferred_function = intern ("split-window");
  
    DEFVAR_INT ("window-min-height", &window_min_height,
              doc: /* *Delete any window less than this tall (including its 
mode line).
--- 7604,7610 ----
  to split windows horizontally or vertically or some mix of the two.
  It is called with a window as single argument and should split it in two
  and return the new window.  */);
!   Vsplit_window_preferred_function = Qnil;
  
    DEFVAR_INT ("window-min-height", &window_min_height,
              doc: /* *Delete any window less than this tall (including its 
mode line).

-- 
Juri Linkov
http://www.jurta.org/emacs/