(Vsplit_window_preferred_function): New var.

(Fdisplay_buffer): Use it.
(syms_of_window): Export, and initialize it.

2 files changed, 26 insertions, 4 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 86d84bb780c..7fc05c40994 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,9 @@
+2007-09-07  Stefan Monnier  <monnier@iro.umontreal.ca>
+
+        * window.c (Vsplit_window_preferred_function): New var.
+        (Fdisplay_buffer): Use it.
+        (syms_of_window): Export, and initialize it.
+
 2007-09-06  Pixel  <pixel@mandriva.com>  (tiny change)
 
         * image.c (gif_load): Fix bug: Handle nonexistent colormap.
diff --git a/src/window.c b/src/window.c
index 3db1802a861..2b33bf5803d 100644
--- a/src/window.c
+++ b/src/window.c
@@ -192,6 +192,10 @@ Lisp_Object Qtemp_buffer_show_hook;
 
 EMACS_INT split_height_threshold;
 
+/* How to split windows (horizontally/vertically/hybrid).  */
+
+Lisp_Object Vsplit_window_preferred_function;
+
 /* Number of lines of continuity in scrolling by screenfuls.  */
 
 EMACS_INT next_screen_context_lines;
@@ -3723,6 +3727,8 @@ displayed.  */)
       || !NILP (XWINDOW (FRAME_ROOT_WINDOW (f))->dedicated))
     {
       Lisp_Object frames;
+      struct gcpro gcpro1;
+      GCPRO1 (buffer);
 
       frames = Qnil;
       if (FRAME_MINIBUF_ONLY_P (f))
@@ -3758,14 +3764,14 @@ displayed.  */)
               || (NILP (XWINDOW (window)->parent)))
           && (window_height (window)
               >= (2 * window_min_size_2 (XWINDOW (window), 0))))
-        window = Fsplit_window (window, Qnil, Qnil);
+        window = call1 (Vsplit_window_preferred_function, window);
       else
         {
           Lisp_Object upper, lower, other;
 
           window = Fget_lru_window (frames, Qt);
-          /* If the LRU window is tall enough, and either eligible for splitting
-          and selected or the only window, split it.  */
+          /* If the LRU window is tall enough, and either eligible for
+             splitting and selected or the only window, split it.  */
           if (!NILP (window)
               && ! FRAME_NO_SPLIT_P (XFRAME (XWINDOW (window)->frame))
               && ((EQ (window, selected_window)
@@ -3773,7 +3779,7 @@ displayed.  */)
                   || (NILP (XWINDOW (window)->parent)))
               && (window_height (window)
                   >= (2 * window_min_size_2 (XWINDOW (window), 0))))
-            window = Fsplit_window (window, Qnil, Qnil);
+            window = call1 (Vsplit_window_preferred_function, window);
           else
             window = Fget_lru_window (frames, Qnil);
           /* If Fget_lru_window returned nil, try other approaches.  */
@@ -3819,6 +3825,7 @@ displayed.  */)
                               0);
             }
         }
+      UNGCPRO;
     }
   else
     window = Fget_lru_window (Qnil, Qnil);
@@ -7490,6 +7497,15 @@ by `display-buffer'.  The value is in line units.
 If there is only one window, it is split regardless of this value.  */);
   split_height_threshold = 500;
 
+  DEFVAR_LISP ("split-window-preferred-function",
+               &Vsplit_window_preferred_function,
+               doc: /* Function to use to split a window.
+This is used by `display-buffer' to allow the user to choose whether
+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).
 The value is in line units. */);