Re: [PATCH] Fix display-buffer-use-some-window to honor reusable-frames

[Tom Gillespie <tgbugs@gmail.com>]

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Here is an updated patch which does not touch
'display-buffer-use-some-window' at all, and that
corrects splitting behavior and return value for
'display-buffer-use-least-recent-window'.

If a patch to 'display-buffer-use-some-window'
to honor reusable-frames is desired, let's deal with
it separately. Best!
Tom

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From 274493ccb0e15aeec88b08fcf79180616deacf6f Mon Sep 17 00:00:00 2001
From: Tom Gillespie <tgbugs@gmail.com>
Date: Thu, 26 Jan 2023 23:47:22 -0500
Subject: [PATCH] Fix display-buffer-use-least-recent-window to split, return
 window.

* lisp/window.el (display-buffer-use-least-recent-window): Return
window instead of nil, and actually split in single window case.

'display-buffer-use-least-recent-window' now returns window if one is
selected which prevents the rather nasty behavior of selecting a
window in the current frame and then also selecting a window in
another random frame as well (quite maddening).

The docs for 'display-buffer-use-least-recent-window' state that it
will pick the least recently used window or and if there is only a
single window it will split the window.

Prior to this commit that behavior was impossible to achieve because
'display-buffer-use-least-recent-window' reused the internals of
'display-buffer-use-some-window' which would attempt to find a valid
window in other frames and never split the current window.

'display-buffer-use-least-recent-window' no longer calls
'display-buffer-use-some-window' and instead directly calls
'get-lru-window' followed by 'display-buffer-pop-p-window' when
reusable-frames is not provided or nil, or 'get-buffer-window' when
reusable-frames is non-nil.  Once the window is selected it runs code
that has been duplicated from 'display-buffer-use-some-window'.
---
 lisp/window.el | 39 +++++++++++++++++++++++++++++++++++----
 1 file changed, 35 insertions(+), 4 deletions(-)

diff --git a/lisp/window.el b/lisp/window.el
index 0cd30822ff6..6dd4fed1dd3 100644
--- a/lisp/window.el
+++ b/lisp/window.el
@@ -8507,10 +8507,41 @@ display-buffer-use-least-recent-window
 This `display-buffer' action function is like
 `display-buffer-use-some-window', but will cycle through windows
 when displaying buffers repeatedly, and if there's only a single
-window, it will split the window."
-  (when-let ((window (display-buffer-use-some-window
-                      buffer (cons (cons 'inhibit-same-window t) alist))))
-    (window-bump-use-time window)))
+window, it will split the window.
+
+If `reusable-frames' is provided in the alist then
+`display-buffer-use-least-recent-window' will attempt to find a
+window in other frames accordingly. By default it only searches
+the current frame."
+  (let* ((not-this-window t)
+         (reusable-frames (assq 'reusable-frames alist))
+         (frame (or (window--frame-usable-p (selected-frame))
+                    (window--frame-usable-p (last-nonminibuffer-frame))))
+         (window (or (get-lru-window frame nil not-this-window)
+                     (if (not reusable-frames)
+                         (display-buffer-pop-up-window buffer alist)
+                       (window (get-buffer-window buffer reusable-frames)))))
+         (quit-restore (and (window-live-p window)
+			    (window-parameter window 'quit-restore)))
+         (quad (nth 1 quit-restore)))
+    (unless (eq window (selected-window))
+      (when (window-live-p window)
+        ;; If the window was used by `display-buffer' before, try to
+        ;; resize it to its old height but don't signal an error.
+        (when (and (listp quad)
+                   (integerp (nth 3 quad))
+                   (> (nth 3 quad) (window-total-height window)))
+          (condition-case nil
+              (window-resize window (- (nth 3 quad) (window-total-height window)))
+            (error nil)))
+        (prog1
+            (window--display-buffer buffer window 'reuse alist)
+          (window--even-window-sizes window)
+          (unless (cdr (assq 'inhibit-switch-frame alist))
+            (window--maybe-raise-frame (window-frame window))))))
+    (when window
+      (window-bump-use-time window)
+      window)))
 
 (defun display-buffer-use-some-window (buffer alist)
   "Display BUFFER in an existing window.
-- 
2.39.1