bug#44180: 28.0.50; Emacs frames won't redisplay unless resized

[Eric Abrahamsen <eric@ericabrahamsen.net>]

On 10/23/20 21:25 PM, Eli Zaretskii wrote:
>> From: Eric Abrahamsen <eric@ericabrahamsen.net>
>> Date: Fri, 23 Oct 2020 11:17:16 -0700
>> 
>> I rebuilt Emacs on one of my machines yesterday, and am seeing odd
>> behavior (with emacs -Q): I use a tiling window manager, which
>> fullscreens frames by default, and when I open multiple Emacs frames,
>> only one of them redisplays correctly, the others stay "frozen" and do
>> not update the display until I manually resize the frame.
>> 
>> I start Emacs, use "C-x 5 2" a couple of times to get my usual three
>> frames. Only the last-created frame has "live" redisplay: I can switch
>> focus between the frames, but the others won't update. If I switch to a
>> frozen frame and do something like `find-file', I see the window title
>> change to "minibuffer", and commands are accepted correctly, but the
>> frame contents aren't updated.
>
> Sounds like Emacs thinks those other frames are invisible or
> iconified.  Emacs never redisplays such frames, for obvious reasons.

Thanks for the clue. I get:

(mapcar (lambda (f) (frame-parameter f 'visibility)) (frame-list))
=> (icon icon t)df

Whichever frame I've forced to be "live" always gets t, and the others
become icons.

If I split the screen to show two frames side-by-side, they both become
visible.

I haven't changed anything in my window manager config, and the i3
package hasn't been updated since August. The only recent commit that
looks like it could be at all relevant is 2c0cd90083.

Hope this points the way further...