Re: Stop frames stealing eachothers' minibuffers!

[Gregory Heytings via "Emacs development discussions." <emacs-devel@gnu.org>]

Hi Alan,

>>>>> The behaviour in Emacs 27 is chaotic.  Sometimes a minibuffer moves 
>>>>> with a frame switch, sometimes it doesn't.
>>>>
>>>> I wouldn't write it is "chaotic".  The behavior you consider 
>>>> "chaotic" is well-defined, and has been there since Emacs 21 at 
>>>> least: the minibuffer moves from frame F1 to frame F2 if and only if 
>>>> the minibuffer is active on frame F1 and a recursive minibuffer is 
>>>> entered on frame F2.
>>>
>>> I'm not sure what you mean by "is" in that sentence.
>>
>> I've reread what I wrote five times, and I don't understand the 
>> question ;-)
>
> It seems somewhat indefinite _when_ the recursive minibuffer "is" 
> entered on frame F2, relative to the other operations.
>

No it is not.  Another, perhaps more precise definition would be: in Emacs 
21 to 27, when minibuffers MB1 to MBn are active on a frame F1, and an 
operation which activates the minibuffer is used on a frame F2, the 
minibuffers MB1 to MBn are moved to frame F2, and the minibuffer MBn+1 is 
created.

>>>> There are other possible behaviors of course, but IMO the current one 
>>>> is a reasonable one.
>>>
>>> If a recursive minibuffer operation has been carried out, then the 
>>> minibuffer moves, if it hasn't it doesn't. That means Emacs has some 
>>> invisible internal state, something which doesn't seem desirable.
>>
>> What do you mean?
>
> In Emacs 27, emacs -Q, C-x 5 2, giving a two-frame setup.  In F1, C-x b. 
> C-x 5 o, moving to F2.  C-r SPACE.  Note that the open minibuffer 
> remains on F1.
>

Yes, this is normal, C-r does not use the minibuffer, but the echo area 
(you can see this because the cursor does not move leave the buffer in 
which you are).  The minibuffers and echo area are both displayed in the 
miniwindow, but they are different.

>
> Now type C-x 8 RET SPACE RET.  This sucks the open minibuffer over to 
> F2, despite the C-r operation having nothing to do with the suspended 
> operation in the minibuffer.
>

This is normal again, C-x 8 RET starts an operation which uses the 
minibuffer, and the cursor leaves the buffer in which you are and moves to 
the miniwindow.  As explained above, when an operation which activates a 
minibuffer is used on a frame while other minibuffers are active on 
another frame, they are moved to that frame.  I honestly can't see what's 
wrong with this.

IMO the only other reasonable behavior is to make sure that _all_ 
minibuffers are moved from frame F1 to frame F2 whenever one switches from 
a frame F1 to a frame F2.  This is not feasible with Emacs 21-27, and 
still not feasible with Emacs 28.