Function: get-lru-window

Return the least recently used window on frames specified by ALL-FRAMES.
Return a full-width window if possible. A minibuffer window is
never a candidate. A dedicated window is never a candidate
unless DEDICATED is non-nil, so if all windows are dedicated, the
value is nil. Avoid returning the selected window if possible.
Optional argument NOT-SELECTED non-nil means never return the
selected window.

The following non-nil values of the optional argument ALL-FRAMES
have special meanings:

- t means consider all windows on all existing frames.

- `visible' means consider all windows on all visible frames on
the current terminal.

- 0 (the number zero) means consider all windows on all visible
and iconified frames on the current terminal.

- A frame means consider all windows on that frame only.

Any other value of ALL-FRAMES means consider all windows on the selected frame and no others.