bug#62427: tab-bar-new-tab-to now handles cases with multiple side-windows

["Benson Chu" <bensonchu457@fastmail.com>]

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Oops, I only replied to Eli. I'll send my explanation, and new patch. 

> When the variable tab-bar-new-tab-choice is set to t, the intended
> behavior is to create a new tab with a single window, and that single
> window displaying the current buffer of the currently selected window,
> and the new window should have a fresh set of window parameters.

> Typically, this is done by first calling delete-other-windows, so the
> currently selected window is the only window. The call to
> delete-other-windows also ignores window-parameters, so even windows
> that have the no-delete-other-windows parameter still get deleted. Then,
> the current window is split, to create a fresh new window with fresh
> window parameters, and then delete-window is called to delete the
> currently selected window.

> This strategy doesn't work when the current window is a side-window,
> because delete-other-windows has a check which says that a side-window
> cannot be the only window in a frame. So, to work around this, we just
> remove the window-side parameter beforehand, so the above strategy still
> works.

> Another way we could do this was to get the current-buffer, then delete
> all side-windows. After deleting all side-windows, we know the current
> selected window is NOT a side-window, and then we can call
> delete-other-windows, split-window, and delete-window.

On Mon, Mar 27, 2023, at 12:06 PM, Eli Zaretskii wrote:
>> From: Juri Linkov <juri@linkov.net>
>> Cc: bensonchu457@fastmail.com,  62427@debbugs.gnu.org
>> Date: Mon, 27 Mar 2023 19:39:25 +0300
>> 
>> > Maybe I'll agree, but I still don't understand the problem well
>> > enough.  Would you please explain the original problem that led
>> > tab-bar.el to care about these window parameters?
>> 
>> Sorry, I can't explain.  I just did that Martin said to do
>> in bug#53662.
>
> That's okay, Benson Chu explained it.
>
> Let me think about this.

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From 9596fe47f899c77567f4051990add7a31c8718aa Mon Sep 17 00:00:00 2001
From: Benson Chu <bensonchu457@gmail.com>
Date: Fri, 24 Mar 2023 15:38:03 -0500
Subject: [PATCH] ; tab-bar-new-tab now handles multiple side-windows

; Previously, calling tab-bar-new-tab-to only removes the 'window-side
; property on the currently selected window, and then a call to
; delete-other-windows was made to ensure that the selected window was
; the only window.

; However, if there are other side-windows (with the same side)
; present, the call to delete-other-windows will fail on the
; window--sides-check. This is because according to the check, all
; windows on the same side should have the same 'window-side, and
; because we only removed the 'window-side parameters on one of the
; windows, there will be inconsistencies with that window and its
; parent and siblings. Because of this, the call to
; delete-other-windows to fail.

; This patch makes sure that all windows on a given side will have
; 'window-side set to nil, so that the call to delete-other-windows
; will not fail.

* lisp/tab-bar.el (tab-bar-new-tab-to): remove 'window-side
from selected window, window's parent, and all window's
siblings.

Copyright-paperwork-exempt: yes
---
 lisp/tab-bar.el | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/lisp/tab-bar.el b/lisp/tab-bar.el
index dce6fa735fc..f05abffbcdb 100644
--- a/lisp/tab-bar.el
+++ b/lisp/tab-bar.el
@@ -1556,7 +1556,13 @@ tab-bar-new-tab-to
       ;; with `delete-other-windows' and `split-window'.
       (unless (eq tab-bar-new-tab-choice 'clone)
         (set-window-parameter nil 'window-atom nil)
-        (set-window-parameter nil 'window-side nil))
+        (let ((side (window-parameter nil 'window-side)))
+          (when side
+            (walk-window-tree
+             (lambda (window)
+               (when (eq side (window-parameter window 'window-side))
+                 (set-window-parameter window 'window-side nil)))
+             nil t))))
       (let ((ignore-window-parameters t))
         (if (eq tab-bar-new-tab-choice 'clone)
             ;; Create new unique windows with the same layout
-- 
2.40.0