bug#71386: 29.1; Frame is auto-deleted even when it has multiple tabs

[Juri Linkov <juri@linkov.net>]

>> +(defun tab-bar-window-delete-frame (frame _kill)
>> +  "Whether FRAME should be deleted when other tabs are available for that frame.
>> +Instead of deleting the frame, close the current tab.
>
> The first and the second sentences contradict each other.  The first
> implies that this is a predicate which returns a boolean, whereas the
> second says that it closes the tab and negtlets to say anything about
> the return value.
>
>> +(defvar window-delete-frame-functions nil
>> +  "Don't delete frame when one of functions returns t.
>> +Each of functions is called with two arguments: FRAME and KILL.
>> +The function can perform an action instead of deleting the frame.")
>
> This doc string should at least explain what is the KILL argument and
> its meaning.

I tried to improve these doc strings:

diff --git a/lisp/window.el b/lisp/window.el
index 2208346ec8c..e97557b5bb2 100644
--- a/lisp/window.el
+++ b/lisp/window.el
@@ -4968,6 +4968,13 @@ frame-auto-hide-function
   :group 'frames
   :version "26.1")
 
+(defvar window-delete-frame-functions nil
+  "A list of functions to handle the frame deletion.
+Each of functions is called with two arguments: FRAME and KILL where
+KILL means the buffer shown in window will be killed.  When one of functions
+returns a non-nil value then `window--delete' will not delete the frame.
+The function can also perform own action instead of deleting the frame.")
+
 (defun window--delete (&optional window dedicated-only kill)
   "Delete WINDOW if possible.
 WINDOW must be a live window and defaults to the selected one.
@@ -4982,6 +4989,10 @@ window--delete
        ((eq deletable 'frame)
 	(let ((frame (window-frame window)))
 	  (cond
+	   ((run-hook-with-args-until-success
+	     'window-delete-frame-functions
+	     frame kill)
+	    nil)
 	   (kill
 	    (delete-frame frame))
            ((functionp (frame-parameter frame 'auto-hide-function))
diff --git a/lisp/tab-bar.el b/lisp/tab-bar.el
index 6ab6324540e..2f7578b842b 100644
--- a/lisp/tab-bar.el
+++ b/lisp/tab-bar.el
@@ -2659,6 +2659,17 @@ tab-switcher-mouse-select
   (goto-char (posn-point (event-end event)))
   (tab-switcher-select))
 
+\f
+(defun tab-bar-window-delete-frame (frame _kill)
+  "Handle frame deletion in `tab-bar-mode'.
+When there are more than one tab on the selected frame, then close
+the current tab.  In this case return t to not delete the frame
+in `window--delete'."
+  (and tab-bar-mode (> (length (funcall tab-bar-tabs-function frame)) 1)
+       (progn (tab-bar-close-tab) t)))
+
+(add-hook 'window-delete-frame-functions #'tab-bar-window-delete-frame)
+
 \f
 (defun tab-bar--reusable-frames (all-frames)
   (cond