Re: bad help + minibuffer + frame interaction

[Richard M. Stallman]

When going thru old mail I found this bug report.

    emacs -Q
    C-x 5 2   (This creates 2 frames, frame 1 and frame 2)
    [Select frame 1]
    M-x
    [Select frame 2]
    C-h f

    Select frame 1. You see the prompt "M-x" in the echo area, but if you try
    to select it, either with the mouse or with `other-window', you can't get
    there.

    Select frame 2. Go in the minibuffer and `C-g'. "M-x" now appears in the
    echo area for frame 2.

    This strange behavior is special to the help functions. Other commands
    that use the minibuffer give a "Command attempted to use minibuffer when
    active" error when the minibuffer is in use on another frame.

I can explain that.  Most commands don't allow recursive minibuffers,
but we made the help commands an exception because it is useful to be
able to type C-h f to get info about calling a function while you're
inside M-:.

Nonetheless there is a bug:

* That M-x still appears in the echo area on frame 1
once the recursive minibuffer is selected in frame 2.

The way to fix this is that some function (perhaps get_minibuffer)
should look at every frame, and for every minibuffer window, set it to
point at buffer *Minibuf-0* (which is always empty).

I think I just fixed that.

There's one other possible bug: the fact that finishing the help
command does not reselect the minibuffer.  I am not sure whether the
current behavior qualifies as a bug, but it would be nicer to reselect
the minibuffer.  Would you like to implement that?