1 files changed, 33 insertions, 11 deletions

diff --git a/lisp/window.el b/lisp/window.el
index 9566429627d..98cdf98cda5 100644
--- a/lisp/window.el
+++ b/lisp/window.el
@@ -509,11 +509,14 @@ child if WINDOW is a horizontal combination."
       (window-left-child window)
     (window-top-child window)))
 
-(defun window-combinations (window &optional horizontal)
+(defun window-combinations (window &optional horizontal ignore-fixed)
   "Return largest number of windows vertically arranged within WINDOW.
 WINDOW must be a valid window and defaults to the selected one.
 If HORIZONTAL is non-nil, return the largest number of
-windows horizontally arranged within WINDOW."
+windows horizontally arranged within WINDOW.
+
+Optional argument IGNORE-FIXED, if non-nil, means to ignore
+fixed-size windows in the calculation."
   (setq window (window-normalize-window window))
   (cond
    ((window-live-p window)
@@ -527,9 +530,10 @@ windows horizontally arranged within WINDOW."
     (let ((child (window-child window))
           (count 0))
       (while child
-        (setq count
-              (+ (window-combinations child horizontal)
-                 count))
+        (unless (and ignore-fixed (window-size-fixed-p child horizontal))
+          (setq count
+                (+ (window-combinations child horizontal ignore-fixed)
+                   count)))
         (setq child (window-right child)))
       count))
    (t
@@ -538,9 +542,10 @@ windows horizontally arranged within WINDOW."
     (let ((child (window-child window))
           (count 1))
       (while child
-        (setq count
-              (max (window-combinations child horizontal)
-                   count))
+        (unless (and ignore-fixed (window-size-fixed-p child horizontal))
+          (setq count
+                (max (window-combinations child horizontal ignore-fixed)
+                     count)))
         (setq child (window-right child)))
       count))))
 
@@ -4905,6 +4910,24 @@ showing BUFFER-OR-NAME."
         ;; If a window doesn't show BUFFER, unrecord BUFFER in it.
         (unrecord-window-buffer window buffer)))))
 
+(defun window--combination-resizable (parent &optional horizontal)
+  "Return number of pixels recoverable from height of window PARENT.
+PARENT must be a vertical (horizontal if HORIZONTAL is non-nil)
+window combination.  The return value is the sum of the pixel
+heights of all non-fixed height child windows of PARENT divided
+by their number plus 1.  If HORIZONTAL is non-nil, return the sum
+of the pixel widths of all non-fixed width child windows of
+PARENT divided by their number plus 1."
+  (let ((sibling (window-child parent))
+        (number 0)
+        (size 0))
+    (while sibling
+      (unless (window-size-fixed-p sibling horizontal)
+        (setq number (1+ number))
+        (setq size (+ (window-size sibling horizontal t) size)))
+      (setq sibling (window-next-sibling sibling)))
+    (/ size (1+ number))))
+
 (defun split-window (&optional window size side pixelwise)
   "Make a new window adjacent to WINDOW.
 WINDOW must be a valid window and defaults to the selected one.
@@ -5042,8 +5065,7 @@ frame.  The selected window is not changed by this function."
                     ;; average size of a window in its combination.
                     (max (min (- parent-pixel-size
                                  (window-min-size parent horizontal nil t))
-                              (/ parent-pixel-size
-                                 (1+ (window-combinations parent horizontal))))
+                              (window--combination-resizable parent horizontal))
                          (window-min-pixel-size))
                   ;; Else try to give the new window half the size
                   ;; of WINDOW (plus an eventual odd pixel).
@@ -5128,7 +5150,7 @@ frame.  The selected window is not changed by this function."
                (pixel-size (/ (float new-pixel-size)
                               (if new-parent old-pixel-size parent-pixel-size)))
                (new-parent 0.5)
-               (resize (/ 1.0 (1+ (window-combinations parent horizontal))))
+               (resize (/ 1.0 (1+ (window-combinations parent horizontal t))))
                (t (/ (window-normal-size window horizontal) 2.0))))
 
         (if resize