Re: completing-read (and M-x) with pop-up-frames non-nil changes framefocus

[Richard M. Stallman]

    On Windows, you have to manually select original the frame (e.g. click the
    title bar).

    In any case, you should not need to move the mouse or click the original
    frame. *Completions* should only be displayed, not selected, whether or not
    it is in another frame.

When focus follows the mouse, it is difficult to avoid selecting it
if it shows up under the mouse.

When the window manager is using click-to-focus, it would be good if
this frame appeared without being selected.  Emacs once tried to
implement this, around 10 years ago, but I think it did not work
right, so it was taken out.