bug#23124: Two minibuffer resize related bugs

[martin rudalics]

>> (1) Save the attached foo.el file somewhere and make its first line match
>>       the location where you stored it.
>>
>> (2) Start Emacs with the options -Q and -l to load foo.el.
>>
>> (3) Type C-x 5 2.
>>
>> (4) Go back to the initial frame, move to the end of the last non-empty
>>       line after ";; (bar)" and type C-x C-e.
>>
>> At this moment "nothing" happens here (Bug#1).  When I now switch (via
>> Alt TAB) to the new frame (the one created via C-x 5 2), the message
>> appears there.  When I now type C-p in the new frame, the minibuffer
>> window shrinks back but the space previously occupied by the modeline of
>> the window above is not redrawn, hence I get two modelines above each
>> other (Bug#2).

I've now traced this behavior back to this

commit 9d6ec23f7d4f8fbbfdcea353c4b58e47f76a7342
Author: Eli Zaretskii <eliz@gnu.org>
Date:   Sat Oct 24 18:54:15 2015 +0300

    Update frame title when redisplay scrolls selected window

    * src/xdisp.c (redisplay_window): Reconsider the frame's title
    when the mode-line of the frame's selected window needs to be
    updated.

In fact, removing the

      x_consider_frame_title (w->frame);

call from redisplay_window fixes both bugs here.

> Let's start with a much simpler reproducer:
>
>    . emacs -Q
>    . Type "C-x" and wait until you see "C-x-" in the echo area
>    . Type "5 2"
>
> Result: a new frame is displayed, with both frames showing the
> "C-x 5 2" echo, which already sounds like a bug (only one frame should
> show it).
>
> Now type "C-p" -- only one of the two echo messages will disappear,
> the one in the non-selected window stays put.
>
> This didn't happen in Emacs 24.5, where the "C-x 5 2" echo is first
> cleared, and then redisplayed after the new frame is created.
>
> According to my testing, this problem appeared between Aug 31 and Sep
> 30 last year.

This a different problem preceding the one I described.

martin