bug#69993: Wrap window buffers while cycling

[Juri Linkov <juri@linkov.net>]

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>>> So keeping the stable order of window prev/next buffers after C-x b
>>> with a hook should be implemented in tab-line.el, not in window.el?
>>
>> I don't know how you currently handle C-x <left>, C-x b or
>> 'rename-buffer' or whether a buffer is modified on the tab line so I
>> can't tell whether you would need a hook for these.  But this issue is
>> IMHO not connected to whether getting the previous or next buffer should
>> wrap or be restricted to buffers previously shown in a window.
>
> Handling 'C-x b' and 'rename-buffer' is not yet implemented.
> Probably need to add a new window parameter to keep a list
> of tab buffers and sync it with window prev/next buffers.

Now handling 'C-x b' is completely implemented here:


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diff --git a/lisp/tab-line.el b/lisp/tab-line.el
index 54e9ee16243..776d33de3e2 100644
--- a/lisp/tab-line.el
+++ b/lisp/tab-line.el
@@ -843,26 +857,9 @@ tab-line-select-tab
               (force-mode-line-update))))))))
 
 (defun tab-line-select-tab-buffer (buffer &optional window)
-  (let* ((window-buffer (window-buffer window))
-         (next-buffers (seq-remove (lambda (b) (eq b window-buffer))
-                                   (window-next-buffers window)))
-         (prev-buffers (seq-remove (lambda (b) (eq b window-buffer))
-                                   (mapcar #'car (window-prev-buffers window))))
-         ;; Remove next-buffers from prev-buffers
-         (prev-buffers (seq-difference prev-buffers next-buffers)))
-    (cond
-     ((and (eq tab-line-tabs-function #'tab-line-tabs-window-buffers)
-           (memq buffer next-buffers))
-      (dotimes (_ (1+ (seq-position next-buffers buffer)))
-        (switch-to-next-buffer window)))
-     ((and (eq tab-line-tabs-function #'tab-line-tabs-window-buffers)
-           (memq buffer prev-buffers))
-      (dotimes (_ (1+ (seq-position prev-buffers buffer)))
-        (switch-to-prev-buffer window)))
-     (t
-      (with-selected-window window
-        (let ((switch-to-buffer-obey-display-actions nil))
-          (switch-to-buffer buffer)))))))
+  (with-selected-window window
+    (let ((switch-to-buffer-obey-display-actions nil))
+      (switch-to-buffer buffer))))
 
 (defcustom tab-line-switch-cycling nil
   "Enable cycling tab switch.
@@ -919,6 +916,26 @@ tab-line-switch-to-next-tab
             (let ((switch-to-buffer-obey-display-actions nil))
               (switch-to-buffer buffer))))))))
 
+(defun tab-line-buffer-change (_window)
+  (let* ((new-buffer (window-buffer))
+         (old-buffers (window-parameter nil 'tab-line-window-buffers))
+         (prev-buffers (window-prev-buffers))
+         (next-buffers (memq new-buffer old-buffers)))
+    (when next-buffers
+      (set-window-next-buffers nil (seq-filter (lambda (b)
+                                                 (assq b prev-buffers))
+                                               (cdr next-buffers))))
+    (set-window-prev-buffers
+     nil (sort prev-buffers
+               (lambda (a b)
+                 (cond
+                  ((eq (car a) new-buffer) nil)
+                  ((eq (car b) new-buffer) t)
+                  (t (< (length (memq (car a) old-buffers))
+                        (length (memq (car b) old-buffers))))))))
+    (set-window-parameter nil 'tab-line-window-buffers
+                          (tab-line-tabs-window-buffers))))
+
 \f
 (defcustom tab-line-close-tab-function 'bury-buffer
   "What to do upon closing a tab on the tab line.
@@ -1025,13 +1042,17 @@ tab-line-mode
   "Toggle display of tab line in the windows displaying the current buffer."
   :lighter nil
   (let ((default-value '(:eval (tab-line-format))))
-    (if tab-line-mode
-        ;; Preserve the existing tab-line set outside of this mode
-        (unless tab-line-format
-          (setq tab-line-format default-value))
+    (cond
+     (tab-line-mode
+      (add-hook 'window-buffer-change-functions #'tab-line-buffer-change nil t)
+      ;; Preserve the existing tab-line set outside of this mode
+      (unless tab-line-format
+        (setq tab-line-format default-value)))
+     (t
+      (remove-hook 'window-buffer-change-functions #'tab-line-buffer-change t)
       ;; Reset only values set by this mode
       (when (equal tab-line-format default-value)
-        (setq tab-line-format nil)))))
+        (setq tab-line-format nil))))))
 
 (defcustom tab-line-exclude-modes
   '(completion-list-mode)