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

[martin rudalics]

>> We might be able to provide such a function but can you tell me why you
>> would need it and how you would use it?
>
> It could be used in 'image-mode-winprops':
>
>    (when cleanup
>      (setq image-mode-winprops-alist
>              (delq nil (mapcar (lambda (winprop)
>                          (let ((w (car-safe winprop)))
>                            (if (or (not (windowp w))
>                                          (window-live-p w)
>             new function =>              
(window-live-in-all-window-configurations w))
>                                winprop)))
>                                image-mode-winprops-alist))))

I can't tell from here what 'window-live-in-all-window-configurations'
is supposed to return.  Its name appears misleading - do we care if 'w'
is live in a configuration of another frame but w's?  So please tell me
the doc-string of ‘window-live-in-all-window-configurations’ first.

And please always keep in mind: The only agent that has access to _all_
window configurations is the garbage collector.  If we wanted to change
that, we'd have to make window configurations explicitly deletable like
buffers or windows with functions like 'make-window-configuration',
'delete-window-configuration' and 'window-configurations-list'.  While
this might not pose great problems for read_minibuf, it certainly will
for configurations in plain Lisp code which all of a sudden would become
noncollectable after the last reference to them has gone ...

martin