(window_min_size_2): New function.

(window_min_size_1, size_window, Fdisplay_buffer)
(Fsplit_window, adjust_window_trailing_edge): Use it to avoid
windows without mode- or header-lines when window-min-height is
too small.
(size_window): Reset nodelete_p after testing it, following an
earlier note by Kim F. Storm.
(display_buffer): Do not set split_height_threshold to twice the
value of window_min_height to avoid changing the value of a
customizable variable.  Rather explicitly check whether the
height of the window that shall be splitted is at least as large
as split_height_threshold.
(Fwindow_full_width_p): New defun.
(syms_of_window): Defsubr it.
(Fdisplay_buffer): Use NILP.
(Fset_window_scroll_bars): Likewise.

1 files changed, 70 insertions, 47 deletions

diff --git a/src/window.c b/src/window.c
index e6fe32ea506..6fe78166ba1 100644
--- a/src/window.c
+++ b/src/window.c
@@ -62,6 +62,7 @@ static void window_scroll P_ ((Lisp_Object, int, int, int));
 static void window_scroll_pixel_based P_ ((Lisp_Object, int, int, int));
 static void window_scroll_line_based P_ ((Lisp_Object, int, int, int));
 static int window_min_size_1 P_ ((struct window *, int));
+static int window_min_size_2 P_ ((struct window *, int));
 static int window_min_size P_ ((struct window *, int, int, int *));
 static void size_window P_ ((Lisp_Object, int, int, int, int, int));
 static int freeze_window_start P_ ((struct window *, void *));
@@ -556,6 +557,15 @@ use  (let ((edges (window-edges))) (- (nth 2 edges) (nth 0 edges))).  */)
   return make_number (window_box_text_cols (decode_any_window (window)));
 }
 
+DEFUN ("window-full-width-p", Fwindow_full_width_p, Swindow_full_width_p, 0, 1, 0,
+       doc: /* Return t if WINDOW is as wide as its frame.
+WINDOW defaults to the selected window.  */)
+     (window)
+     Lisp_Object window;
+{
+  return WINDOW_FULL_WIDTH_P (decode_any_window (window)) ? Qt : Qnil;
+}
+
 DEFUN ("window-hscroll", Fwindow_hscroll, Swindow_hscroll, 0, 1, 0,
        doc: /* Return the number of columns by which WINDOW is scrolled from left margin.
 WINDOW defaults to the selected window.  */)
@@ -2553,7 +2563,6 @@ check_frame_size (frame, rows, cols)
     *cols = MIN_SAFE_WINDOW_WIDTH;
 }
 
-
 /* Value is non-zero if window W is fixed-size.  WIDTH_P non-zero means
    check if W's width can be changed, otherwise check W's height.
    CHECK_SIBLINGS_P non-zero means check resizablity of WINDOW's
@@ -2655,6 +2664,33 @@ window_fixed_size_p (w, width_p, check_siblings_p)
   return fixed_p;
 }
 
+/* Return the minimum size for leaf window W.  WIDTH_P non-zero means
+   take into account fringes and the scrollbar of W.  WIDTH_P zero
+   means take into account mode-line and header-line of W.  Return 1
+   for the minibuffer.  */
+
+static int
+window_min_size_2 (w, width_p)
+     struct window *w;
+     int width_p;
+{
+  int size;
+  
+  if (width_p)
+    size = max (window_min_width,
+                (MIN_SAFE_WINDOW_WIDTH
+                 + WINDOW_FRINGE_COLS (w)
+                 + WINDOW_SCROLL_BAR_COLS (w)));
+  else if (MINI_WINDOW_P (w))
+    size = 1;
+  else
+    size = max (window_min_height,
+                (MIN_SAFE_WINDOW_HEIGHT
+                 + (WINDOW_WANTS_MODELINE_P (w) ? 1 : 0)
+                 + (WINDOW_WANTS_HEADER_LINE_P (w) ? 1 : 0 )));
+
+  return size;
+}
 
 /* Return the minimum size of window W, not taking fixed-width windows
    into account.  WIDTH_P non-zero means return the minimum width,
@@ -2724,22 +2760,7 @@ window_min_size_1 (w, width_p)
         }
     }
   else
-    {
-      if (width_p)
-        size = max (window_min_width,
-                    (MIN_SAFE_WINDOW_WIDTH
-                     + WINDOW_FRINGE_COLS (w)
-                     + WINDOW_SCROLL_BAR_COLS (w)));
-      else
-        {
-          if (MINI_WINDOW_P (w)
-              || (!WINDOW_WANTS_MODELINE_P (w)
-                  && !WINDOW_WANTS_HEADER_LINE_P (w)))
-            size = 1;
-          else
-            size = window_min_height;
-        }
-    }
+    size = window_min_size_2 (w, width_p);
 
   return size;
 }
@@ -2981,11 +3002,6 @@ size_window (window, size, width_p, nodelete_p, first_only, last_only)
   Lisp_Object child, *forward, *sideward;
   int old_size, min_size, safe_min_size;
 
-  /* We test nodelete_p != 2 and nodelete_p != 1 below, so it
-     seems like it's too soon to do this here.  ++KFS.  */
-  if (nodelete_p == 2)
-    nodelete_p = 0;
-
   check_min_window_sizes ();
   size = max (0, size);
 
@@ -2996,22 +3012,23 @@ size_window (window, size, width_p, nodelete_p, first_only, last_only)
     {
       old_size = WINDOW_TOTAL_COLS (w);
       min_size = window_min_width;
-      /* Ensure that there is room for the scroll bar and fringes!
-         We may reduce display margins though.  */
-      safe_min_size = (MIN_SAFE_WINDOW_WIDTH
-                       + WINDOW_FRINGE_COLS (w)
-                       + WINDOW_SCROLL_BAR_COLS (w));
+      safe_min_size = window_min_size_2 (w, 1);
     }
   else
     {
       old_size = XINT (w->total_lines);
       min_size = window_min_height;
-      safe_min_size = MIN_SAFE_WINDOW_HEIGHT;
+      safe_min_size = window_min_size_2 (w, 0);
     }
 
   if (old_size < min_size && nodelete_p != 2)
     w->too_small_ok = Qt;
 
+  /* Move the following test here since otherwise the
+     preceding test doesn't make sense.  martin. */
+  if (nodelete_p == 2)
+    nodelete_p = 0;
+
   /* Maybe delete WINDOW if it's too small.  */
   if (nodelete_p != 1 && !NILP (w->parent))
     {
@@ -3708,9 +3725,6 @@ displayed.  */)
       frames = Qnil;
       if (FRAME_MINIBUF_ONLY_P (f))
         XSETFRAME (frames, last_nonminibuf_frame);
-      /* Don't try to create a window if we would get an error.  */
-      if (split_height_threshold < window_min_height << 1)
-        split_height_threshold = window_min_height << 1;
 
       /* Note that both Fget_largest_window and Fget_lru_window
          ignore minibuffers and dedicated windows.
@@ -3733,25 +3747,30 @@ displayed.  */)
       else
         window = Fget_largest_window (frames, Qt);
 
-      /* If we got a tall enough full-width window that can be split,
-         split it.  */
+      /* If the largest window is tall enough, full-width, and either eligible
+         for splitting or the only window, split it.  */
       if (!NILP (window)
           && ! FRAME_NO_SPLIT_P (XFRAME (XWINDOW (window)->frame))
-          && window_height (window) >= split_height_threshold
-          && WINDOW_FULL_WIDTH_P (XWINDOW (window)))
+          && 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 = Fsplit_window (window, Qnil, Qnil);
       else
         {
           Lisp_Object upper, lower, other;
 
           window = Fget_lru_window (frames, Qt);
-          /* If the LRU window is selected, and big enough,
-             and can be split, 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)
-                  || EQ (XWINDOW (window)->parent, Qnil))
-              && window_height (window) >= window_min_height << 1)
+              && ((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);
@@ -4000,9 +4019,11 @@ See Info node `(elisp)Splitting Windows' for more details and examples.*/)
 
   if (NILP (horflag))
     {
-      if (size_int < window_min_height)
+      int window_safe_height = window_min_size_2 (o, 0);
+      
+      if (size_int < window_safe_height)
         error ("Window height %d too small (after splitting)", size_int);
-      if (size_int + window_min_height > XFASTINT (o->total_lines))
+      if (size_int + window_safe_height > XFASTINT (o->total_lines))
         error ("Window height %d too small (after splitting)",
                XFASTINT (o->total_lines) - size_int);
       if (NILP (o->parent)
@@ -4015,10 +4036,11 @@ See Info node `(elisp)Splitting Windows' for more details and examples.*/)
     }
   else
     {
-      if (size_int < window_min_width)
+      int window_safe_width = window_min_size_2 (o, 1);
+      
+      if (size_int < window_safe_width)
         error ("Window width %d too small (after splitting)", size_int);
-
-      if (size_int + window_min_width > XFASTINT (o->total_cols))
+      if (size_int + window_safe_width > XFASTINT (o->total_cols))
         error ("Window width %d too small (after splitting)",
                XFASTINT (o->total_cols) - size_int);
       if (NILP (o->parent)
@@ -4499,7 +4521,7 @@ adjust_window_trailing_edge (window, delta, horiz_flag)
 
       /* Don't make this window too small.  */
       if (XINT (CURSIZE (window)) + delta
-          < (horiz_flag ? window_min_width : window_min_height))
+          < window_min_size_2 (XWINDOW (window), horiz_flag))
         {
           Fset_window_configuration (old_config);
           error ("Cannot adjust window size as specified");
@@ -6897,7 +6919,7 @@ Fourth parameter HORIZONTAL-TYPE is currently unused.  */)
         vertical_type = Qnil;
     }
 
-  if (!(EQ (vertical_type, Qnil)
+  if (!(NILP (vertical_type)
         || EQ (vertical_type, Qleft)
         || EQ (vertical_type, Qright)
         || EQ (vertical_type, Qt)))
@@ -7502,6 +7524,7 @@ The selected frame is the one whose configuration has changed.  */);
   defsubr (&Swindow_buffer);
   defsubr (&Swindow_height);
   defsubr (&Swindow_width);
+  defsubr (&Swindow_full_width_p);
   defsubr (&Swindow_hscroll);
   defsubr (&Sset_window_hscroll);
   defsubr (&Swindow_redisplay_end_trigger);