bug#54038: 29.0.50; doc-view cannot show different pages in different tabs

[Juri Linkov]

> Pretty much the subject.
>
> 1. emacs -Q.
> 2. Open a pdf file.
> 3. Clone the tab using C-x t n.
> 4. Move to the next page (n).
> 5. Switch back to the original tab C-x t o.
> 6. The page is changed here too.
>
> Expected: The original and the cloned tabs should show different pages,
> just like how you can show different pages in different windows/frames.
>
> [ FWIW, the same problem also exists with pdf-tools.  ]

This is expected behavior when you use 'C-x t n' that clones
the current tab.  A new clone has exactly the same window.
You can confirm this by evaluating in each tab: 'M-: (selected-window)'.
It will show the same window number.  But doc-view can show different pages
only in different windows.