RE: put input focus on active minibuffer

[Drew Adams]

> > No, please do not do this.  A user should be able to select
> > different buffers and windows, including by clicking the mouse
> > or using keyboard keys, while the minibuffer is active.  A user
> > should be able to do all kinds of things while the minibuffer is
> > active - including come back to the minibuffer to continue
> > inputting text there etc.
> 
> Agreed.
> 
> But, if using GNU Emacs 24.4 or later, perhaps make use of
> `focus-in-hook`? For example, something along the lines of:
> 
>     (defun focus-to-active-minibuffer ()
>       (if (minibuffer-window-active-p (minibuffer-window))
>           (select-window (minibuffer-window))))
> 
>     (add-hook 'focus-in-hook #'focus-to-active-minibuffer)

If you do that then whenever a frame receives the focus so
will its (active) minibuffer window.  That precludes the user
interactions I described above, and about which you "Agreed".

A user needs to be able to interact with other windows directly,
whatever frame they are in.  This interaction needs to be able
to include inserting text etc. - actions that require that
window to have the focus.

Users need to be able to change the focus to anywhere they
like when the minibuffer is active.  Just because it is active
and the user will want to interact with it, does not mean that
the user should not be able to interact with other window as
well.

What you suggest could be useful for a particular command
that wants/needs, for some reason, to preclude the user from
focussing other windows while the minibuffer is active.  But
it is not applicable to the general case of using a minibuffer.