bug#32850: 27.0.50; window-swap-states doesn't swap window prev/next-buffers

[Juri Linkov]

>> -selected one.  If @var{window} is not live, it is replaced by a live
>> -window before putting @var{state} into it.
>> +internal window (@pxref{Windows and Frames}).  If @var{window} is not
>                                                   ^^^^^^^^^^^^^^^^^^^^^^
>> +live, it is replaced by a new live window created on the same subtree
>    ^^^^
>
> "If @var{window} is not a live window, ..."
>
>> +before putting @var{state} into it.  If @var{window} is nil, it puts
>                                                            ^^^
> "nil" is a symbol, so @code{nil}.
>
>> -specify a valid window and defaults to the selected one.  If
>> -WINDOW is not live, replace WINDOW by a live one before putting
>> -STATE into it.
>> +specify a valid window.  If WINDOW is not live, replace WINDOW
>
> Same here.

Fixed in a new patch, also taking into account Martin's suggestion
to not use the term "subtree".

diff --git a/doc/lispref/windows.texi b/doc/lispref/windows.texi
index 772bcdf9a6..9301fdfa9d 100644
--- a/doc/lispref/windows.texi
+++ b/doc/lispref/windows.texi
@@ -5706,9 +5706,10 @@ Window Configurations
 The argument @var{state} should be the state of a window returned by
 an earlier invocation of @code{window-state-get}, see above.  The
 optional argument @var{window} can be either a live window or an
-internal window (@pxref{Windows and Frames}) and defaults to the
-selected one.  If @var{window} is not live, it is replaced by a live
-window before putting @var{state} into it.
+internal window (@pxref{Windows and Frames}).  If @var{window} is not
+a live window, it is replaced by a new live window created on the same
+frame before putting @var{state} into it.  If @var{window} is @code{nil},
+it puts the window state into a new window.
 
 If the optional argument @var{ignore} is non-@code{nil}, it means to ignore
 minimum window sizes and fixed-size restrictions.  If @var{ignore}
diff --git a/lisp/window.el b/lisp/window.el
index bcd4fa2959..c0eeba7261 100644
--- a/lisp/window.el
+++ b/lisp/window.el
@@ -5889,29 +5889,34 @@ window-state-put
   "Put window state STATE into WINDOW.
 STATE should be the state of a window returned by an earlier
 invocation of `window-state-get'.  Optional argument WINDOW must
-specify a valid window and defaults to the selected one.  If
-WINDOW is not live, replace WINDOW by a live one before putting
-STATE into it.
+specify a valid window.  If WINDOW is not a live window,
+replace WINDOW by a new live window created on the same frame.
+If WINDOW is nil, create a new window before putting STATE into it.
 
 Optional argument IGNORE non-nil means ignore minimum window
 sizes and fixed size restrictions.  IGNORE equal `safe' means
 windows can get as small as `window-safe-min-height' and
 `window-safe-min-width'."
   (setq window-state-put-stale-windows nil)
-  (setq window (window-normalize-window window))
 
-  ;; When WINDOW is internal, reduce it to a live one to put STATE into,
-  ;; see Bug#16793.
+  ;; When WINDOW is internal or nil, reduce it to a live one,
+  ;; then create a new window on the same frame to put STATE into.
   (unless (window-live-p window)
     (let ((root window))
-      (setq window (catch 'live
-                     (walk-window-subtree
-                      (lambda (window)
-                        (when (and (window-live-p window)
-                                   (not (window-parameter window 
'window-side)))
-                          (throw 'live window)))
-                      root)))
-      (delete-other-windows-internal window root)))
+      (setq window (if root
+                       (catch 'live
+                         (walk-window-subtree
+                          (lambda (window)
+                            (when (and (window-live-p window)
+                                       (not (window-parameter
+                                             window 'window-side)))
+                              (throw 'live window)))
+                          root))
+                     (selected-window)))
+      (delete-other-windows-internal window root)
+      ;; Create a new window to replace the existing one.
+      (setq window (prog1 (split-window window)
+                     (delete-window window)))))
 
   (set-window-dedicated-p window nil)