bug#70949: display-buffer-choose-some-window

[Juri Linkov <juri@linkov.net>]

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>>> Also, we should mention the constraints used for 'lru' and that 'mru'
>>> avoids the selected window here.
>>
>> Sorry, I don't understand what constraints.  The docstring of
>> 'display-buffer-use-some-window' doesn't mention any 'lru' constraints.
>
> For historical reasons, 'display-buffer-use-some-window' avoids windows
> that are not full-width and windows on another frame via
>
>                (append alist `((lru-frames . ,frame)
>                                (window-min-width . full-width))))
>
> The default behavior can be overridden with appropriate alist entries
> which are not mentioned in the doc-string but are described in the Elisp
> manual.  Your option should mention them because they defy a "strict"
> interpretation of 'lru'.

Thanks for explanations, now these constraints are documented.

> BTW, you could have, instead of an option, provided a 'some-window'
> alist entry with the possible values 'lru', 'mru' or a function.  Why
> did you prefer the option?

I already considered adding an alist entry, but the problem is that
it's not clear where users would put it to cover display of all buffers.
But I could reconsider such solution, if you will suggest a suitable place
for users to add such an alist like (some-window . mru) for all buffers.


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diff --git a/lisp/window.el b/lisp/window.el
index 8feeba0d83e..67af4753a70 100644
--- a/lisp/window.el
+++ b/lisp/window.el
@@ -8721,6 +8726,24 @@ display-buffer--lru-window
 	      (setq best-window window))))))
     (or best-window second-best-window)))
 
+(defcustom display-buffer-use-some-window-method 'lru
+  "Which window `display-buffer-use-some-window' should choose.
+The possible choices are `lru' (the default) to select the least
+recently used window, and `mru' to select the most recently used
+window .  When a function, it takes two arguments: a buffer and
+an alist, and should return the window where to display the buffer.
+
+When the value is `lru', it avoids selecting windows that are
+not full-width and windows on another frame.
+When the value is `mru', it avoids selecting an already selected window
+and windows on another frame."
+  :type '(choice (const :tag "Least recently used" lru)
+                 (const :tag "Most recently used" mru)
+                 (function :tag "Custom function"))
+  :group 'windows
+  :group 'frames
+  :version "30.1")
+
 (defun display-buffer-use-some-window (buffer alist)
   "Display BUFFER in an existing window.
 Search for a usable window, set that window to the buffer, and
@@ -8743,11 +8767,17 @@ display-buffer-use-some-window
 		    (window--frame-usable-p (last-nonminibuffer-frame))))
 	 (window
 	  ;; Reuse an existing window.
-	  (or (display-buffer--lru-window
-               ;; If ALIST specifies 'lru-frames' or 'window-min-width'
-               ;; let them prevail.
-               (append alist `((lru-frames . ,frame)
-                               (window-min-width . full-width))))
+	  (or (cond
+               ((eq display-buffer-use-some-window-method 'lru)
+                (display-buffer--lru-window
+                 ;; If ALIST specifies 'lru-frames' or 'window-min-width'
+                 ;; let them prevail.
+                 (append alist `((lru-frames . ,frame)
+                                 (window-min-width . full-width)))))
+               ((eq display-buffer-use-some-window-method 'mru)
+                (get-mru-window nil nil t))
+               ((functionp display-buffer-use-some-window-method)
+                (funcall display-buffer-use-some-window-method buffer alist)))
 	      (let ((window (get-buffer-window buffer 'visible)))
 		(unless (and not-this-window
 			     (eq window (selected-window)))