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

[martin rudalics]

> 'window-live-p' doesn't check windows saved in window-configurations in tabs.
>
> Maybe it should check tab window-configurations on all frames
> by a new function 'window-configuration-windows'
> (something like used in 'tab-bar-get-buffer-tab').
>
> But then what about windows saved by 'window-configuration-to-register'?
> Should they be checked by 'window-live-p' too?
>
> Or maybe better to change 'image-mode-winprops-alist' to the hash
> 'image-mode-winprops-hash' where window keys are garbage-collected?
> So when a window is deleted from all window-configurations,
> it will be garbage-collected?

GC tries to remove dead buffers window configurations stored in their
list of previous or next buffers.  But checking for whether a dead
window has disappeared from all stored configurations is more demanding
- maybe we could reserve a bit in each window the collector resets for
all dead windows at the beginning of each cycle and at the end reclaim
the space of all windows that did not have that bit set when the window
was found in a stored window configuration.

martin