(prefer_window_split_horizontally): New variable.

(display_buffer): Consider splitting window horizontally depending on
prefer_window_split_horizontally.

1 files changed, 57 insertions, 13 deletions

diff --git a/src/window.c b/src/window.c
index ae4c419cccd..a34c4200b7f 100644
--- a/src/window.c
+++ b/src/window.c
@@ -163,6 +163,13 @@ Lisp_Object Vdisplay_buffer_function;
 
 Lisp_Object Veven_window_heights;
 
+/* Non-nil means that windows are split horizontally, i.e. side-by-side,
+   instead of vertically by `display-buffer'.  An integer value means that
+   windows may only be split horizontally if the newly created window is at
+   least as wide as that value.  */
+
+Lisp_Object Vprefer_window_split_horizontally;
+
 /* List of buffer *names* for buffers that should have their own frames.  */
 
 Lisp_Object Vspecial_display_buffer_names;
@@ -3653,7 +3660,12 @@ the buffer, it may be split, subject to the value of the variable
 
 If `even-window-heights' is non-nil, window heights will be evened out
 if displaying the buffer causes two vertically adjacent windows to be
-displayed.  */)
+displayed.  
+
+If `prefer-window-split-horizontally' is non-nil, windows are split
+horizontally, i.e. side-by-side, instead of vertically if possible. If the
+variable has an integer value, windows may only be split horizontally if the
+newly created window is at least as wide as that value.  */)
      (buffer, not_this_window, frame)
      Lisp_Object buffer, not_this_window, frame;
 {
@@ -3755,13 +3767,26 @@ displayed.  */)
       else
         window = Fget_largest_window (frames, Qt);
 
-      /* If the largest window is tall enough, full-width, and either eligible
-         for splitting or the only window, split it.  */
+      /* If we prefer to split horizontally and the window is wide
+         enough, split it horizontally.  */
       if (!NILP (window)
           && ! FRAME_NO_SPLIT_P (XFRAME (XWINDOW (window)->frame))
           && WINDOW_FULL_WIDTH_P (XWINDOW (window))
-          && (window_height (window) >= split_height_threshold
-              || (NILP (XWINDOW (window)->parent)))
+          && !NILP (Vprefer_window_split_horizontally)
+          && (!NUMBERP (Vprefer_window_split_horizontally) ||
+              (window_width(window) >=
+               2 * XINT (Vprefer_window_split_horizontally)))
+          && (window_width(window)) >= (2 * window_min_width))
+        {
+          window = Fsplit_window (window, Qnil, Qt);
+        }
+      /* Else, if the largest window is tall enough, full-width, and either
+         eligible for splitting or the only window, split it. */
+      else if (!NILP (window)
+               && ! FRAME_NO_SPLIT_P (XFRAME (XWINDOW (window)->frame))
+               && WINDOW_FULL_WIDTH_P (XWINDOW (window))
+               && (window_height (window) >= split_height_threshold
+                   || (NILP (XWINDOW (window)->parent)))
           && (window_height (window)
               >= (2 * window_min_size_2 (XWINDOW (window), 0))))
         window = call1 (Vsplit_window_preferred_function, window);
@@ -3770,16 +3795,27 @@ displayed.  */)
           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 we prefer to split horizontally and the LRU window is
+             wide enough, split it horizontally. */
           if (!NILP (window)
               && ! FRAME_NO_SPLIT_P (XFRAME (XWINDOW (window)->frame))
-              && ((EQ (window, selected_window)
-                   && window_height (window) >= split_height_threshold)
-                  || (NILP (XWINDOW (window)->parent)))
-              && (window_height (window)
-                  >= (2 * window_min_size_2 (XWINDOW (window), 0))))
-            window = call1 (Vsplit_window_preferred_function, window);
+              && !NILP (Vprefer_window_split_horizontally)
+              && window_width(window) >= (2 * window_min_width)
+              && (!NUMBERP (Vprefer_window_split_horizontally) ||
+                  window_width(window) >=
+                  (2 * XINT (Vprefer_window_split_horizontally))))
+            window = Fsplit_window (window, Qnil, Qt);
+          /* Else if the LRU window is tall enough, and either
+             eligible for splitting and selected, or the only window,
+             split it.  */
+          else if (!NILP (window)
+                   && ! FRAME_NO_SPLIT_P (XFRAME (XWINDOW (window)->frame))
+                   && ((EQ (window, selected_window)
+                        && window_height (window) >= split_height_threshold)
+                       || (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.  */
@@ -7354,6 +7390,14 @@ work using this function.  */);
 If nil, `display-buffer' will leave the window configuration alone.  */);
   Veven_window_heights = Qt;
 
+  DEFVAR_LISP ("prefer-window-split-horizontally", &Vprefer_window_split_horizontally,
+               doc: /* *Non-nil means that windows are split horizontally, i.e. 
+side-by-side, instead
+of vertically by `display-buffer'.
+An integer value means that windows may only be split horizontally if the newly
+created window is at least as wide as that value.  */);
+  Vprefer_window_split_horizontally = Qnil;
+
   DEFVAR_LISP ("minibuffer-scroll-window", &Vminibuf_scroll_window,
                doc: /* Non-nil means it is the window that C-M-v in minibuffer should scroll.  */);
   Vminibuf_scroll_window = Qnil;