bug#17809: 24.4.50; Completions display

[Juri Linkov]

>> But then (window-height . fit-window-to-buffer) will be called
>> on the empty buffer, that will always produce a small window
>> with 3-lines height.
>
> Then don't do that.  If you want to do both - formatting and fitting -
> have QUIT-FUNCTION do that.  So in BODY put the text into the buffer and
> in QUIT-FUNCTION first format the text according to what the window size
> gives and then try to fit the window to the formatted text.

Then the users will lose the ability to override window fitting
by redefining `window-height' in `display-buffer-alist'.
Not sure how important this is.

> And note that `display-buffer-base-action' is a user variable.

Isn't `display-buffer-alist' a customizable variable intended for users?

I see no other way for a function to override `display-buffer-fallback-action',
but still allow the users to customize it in `display-buffer-alist'.
Only `display-buffer-base-action' can be used for this.