bug#32825: 27.0.50; Deterministic window management

[martin rudalics]

> With emacs -Q and without additional customizations, every error
> (e.g. evaluating a non-existent variable) is shown in a different window
> (first in 1, then in 2, then again in 1):
>
> +---------------------+
> | 1.                  |
> |                     |
> +---------------------+
> | 2.                  |
> |                     |
> +---------------------+
> | low selected window |
> +---------------------+
>

I see.  The window at the bottom must be made small enough here so it
can't be split.  I suppose the behavior you observe is caused by the
already familiar

            ;; Forget debugger window, it won't be back (Bug#17882).
            (setq debugger-previous-window nil))

because 'debugger-previous-window' is nil here when it happens.

> This bug can be avoided by adding display-buffer-at-bottom
> after display-buffer-below-selected, i.e. by using such actions:
>
> display-buffer-reuse-window
> display-buffer-in-previous-window
> display-buffer-below-selected
> display-buffer-at-bottom
>
> This provides a nicer behavior because display-buffer-at-bottom tries
> to resize other windows to accommodate the *Backtrace*.

I think we should first investigate the 'debugger-previous-window'
resettings.  Maybe Michael can help.

martin