bug#38016: 27.0.50; Display issues with delay-warning and side-by-side windows in terminal

[Alan Mackenzie <acm@muc.de>]

Eli Zaretskii <eliz@gnu.org> wrote:
>> From: Tom Levy <tomlevy93@gmail.com>
>> Date: Fri, 01 Nov 2019 18:11:45 +1300

>> Maximize a terminal window to make Emacs use a side-by-side window split.
>> Run: emacs -Q -nw --eval '(delay-warning :debug "line 1\nline 2")'
>> The *scratch* and *Warnings* buffers should be displayed side by side.
>> Press M-< C-e RET DEL (in the *scratch* buffer).
>> Line 2 in the *Warnings* buffer disappears (!)

>> Variation: run Emacs as before, but press M-< C-e a RET
>> Line 2 in the *Warnings* buffer moves down (!)

>> Happens in master (27.0.50) and 24.5.1, with both gnome-terminal and
>> xterm.

> I couldn't reproduce this, neither on GNU/Linux nor on MS-Windows.
> Can anyone else reproduce this?

I see this on a Linux tty (started without the -nw argument).

> Does the "disappearing" and "moving" text really disappear and move?
> What happens if you invoke "M-x redraw-display RET" after your recipe:
> does the display return to be as expected?

Well, from the *scratch* buffer I did C-x o to move to the *warnings*
buffer, and Line 2 reappeared.

On M-x redraw-display (immediately after the DEL), Line 2 reappears
instantly after M-x.  Completing the redraw-display doesn't further
change what is displayed.

I'm running on Emacs master, though it's been a few days since I updated
it.

-- 
Alan Mackenzie (Nuremberg, Germany).