bug#39649: 27.0.60; tab-line doesn't scroll

[Juri Linkov]

> 1. emacs -Q
> 2. M-x load-file tab-line-1.el
> 3. M-x global-tab-line-mode
> 4. M-: (setq tab-line-tabs-function #'tab-line-tabs-mode-buffers)
> 5. https://youtu.be/fQlrP0dlBbw

Thanks, now it's clear where the problem is:
the buffer *Messages* shows that old code is loaded,
i.e. first you load the new file tab-line-1.el
(the first line in the buffer *Messages*),
but later its functions are overridden by old file
(the third line in the buffer *Messages*).
Only the new command 'test1' remains loaded,
all other functions are overridden from old file
tab-line.el.

I believe this could be solved by changing the loading order:

1. emacs -Q
2. M-x global-tab-line-mode
   - this will load old file tab-line.el
3. M-x load-file tab-line-1.el
   - old functions will be overridden by new file tab-line-1.el

Please try this.