Subject: Re: bug#46299: 28.0.50; Value of tab-bar-show not respected in new frames.

From: Bastian Beranek <[email-masked]>
Date: Tue, 16 Feb 2021 11:59:14 +0100

Bastian Beranek <[email-masked]> writes:

> But how to go back? It seems that tab-bar-show should go back to "1" (in
> order to make it a real toggle, i.e. it undoes itself). However, that
> means that after the second toggle-frame-tab-bar the tab-bar will either
> be shown or not, depending on the number of tabs opened at that specific
> time. We have to consider that the user created or closed tabs in
> between, so that means that there will be situations in which
> toggle-frame-tab-bar does not really seem to do anything... For example:
>
> - 1 tab (tab bar hidden)
> - create tab -> 2 tabs (tab bar shown)
> - toggle-frame-tab-bar (tab bar hidden)
> - close tab (tab bar hidden)
> - toggle-frame-tab-bar (tab bar still hidden, because only 1 tab)

I think what we could do is:

a) always toggle the current visibility: That seems to be a must, it
   would be confusing otherwise.

b) The first time toggle-frame-tab-bar is called, add a notice to the
   frame parameters that prevents tab-bar--update-tab-bar-lines from
   changing that frames tab-bar visibility. This means that after the
   toggle the tab-bar visibility keeps its state until
   toggle-frame-tab-bar is called again.

c) When it is called a second time toggle-frame-tab-bar sets the new
   frame parameter to nil and flips the visibility again (see a).

d) Then the tab-bar--update-tab-bar-lines logic will be active again,
   but only after a new tab is created or closed on that frame.

This prevents the problem listed in my last mail, in the last step the
tab-bar will be shown after toggling (although tab-bar-show is 1 and
there is only one tab), but then once you create more tabs or close tabs
it will revert to the usual behavior.

Is this acceptable?

Proposed patch is attached.
>From 5f158962c1bc63c10ebaa49357a16e45664d5579 Mon Sep 17 00:00:00 2001
From: Bastian Beranek <[email-masked]>
Date: Tue, 16 Feb 2021 11:35:35 +0100
Subject: [PATCH] Fix behavior of toggle-frame-tab-bar (bug #46299)

* lisp/tab-bar.el (toggle-frame-tab-bar): Add frame attribute to
protect tab bar state from changing.
(tab-bar--update-tab-bar-lines): Check for new attribute
---
 lisp/tab-bar.el | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/lisp/tab-bar.el b/lisp/tab-bar.el
index 4e47ae2c10..2fa34385f1 100644
--- a/lisp/tab-bar.el
+++ b/lisp/tab-bar.el
@@ -161,7 +161,8 @@ tab-bar--update-tab-bar-lines
                          (t frames))))
     ;; Loop over all frames and update default-frame-alist
     (dolist (frame frame-lst)
-      (set-frame-parameter frame 'tab-bar-lines (tab-bar--tab-bar-lines-for-frame frame))))
+      (unless (frame-parameter frame 'tab-bar-lines-keep-state)
+        (set-frame-parameter frame 'tab-bar-lines (tab-bar--tab-bar-lines-for-frame frame)))))
   (when (eq frames t)
     (setq default-frame-alist
           (cons (cons 'tab-bar-lines (if (and tab-bar-mode (eq tab-bar-show t)) 1 0))
@@ -233,7 +234,9 @@ toggle-frame-tab-bar
   (add-hook 'after-make-frame-functions 'toggle-frame-tab-bar)"
   (interactive)
   (set-frame-parameter frame 'tab-bar-lines
-                       (if (> (frame-parameter frame 'tab-bar-lines) 0) 0 1)))
+                       (if (> (frame-parameter frame 'tab-bar-lines) 0) 0 1))
+  (set-frame-parameter frame 'tab-bar-lines-keep-state
+                       (not (frame-parameter nil 'tab-bar-lines-keep-state))))
 
 (defvar tab-bar-map (make-sparse-keymap)
   "Keymap for the tab bar.
-- 
2.30.1