bug#42655: 27.1; iconify-frame on a Lucid build may stuck the frame

[Tino Calancha <tino.calancha@gmail.com>]

Eli Zaretskii <eliz@gnu.org> writes:

>> Set breakpoint at
>> xterm::8348
>> C-z ; frame is hidden
>> ;; I select again the hidden frame
>> ;; gdb doesn't jump to the breakpoint and the frame is 'cursed'
>> M-x
>> ;; The frame wakes up and gdb reaches the breakpoint.
>
> And if you apply your patch, do we get MapNotify immediately after
> "selecting again the hidden frame"?
No, I don't.
With the patch, I get MapNotify right after I hit `C-z'.
That seems to be OK when I start with `emacs -Q', but it doesn't help
if I start emacs loading my custom stuff.


> Btw, what does "selecting again the hidden frame" mean, exactly?  What
> gestures do you use to do that?  And what is your window manager?

[This seems to be a problem affecting only my window manager (GNOME Shell)]

- After C-z, the frame dissapear from the screen.
- Note, there is no lower/upper bar with the APP iconified.
- To get such a frame again, you can do it in several ways:
  1. use shortcut to switch between apps (in my case M-TAB)
  2. if you the current focused window is another Emacs frame, then you
    can use the shortcut to switch between windows of same app
    (in my case M-`)
  3. Click upper-left corner menu 'Activities': now you can click in the
    'iconified' frame with the mouse
  Any of those 1-3 send the MapNotify


I have tested with other window managers in several OSes (Centos 8.1,
Ubuntu 18.04/20.04).
All window managers but GNOME Shell send the MapNotify
_right after_ you land in the previously iconified frame; that is, I only
can reproduce the bug when I am using GNOME Shell.


Desktop          window-manager       bug reproduced
KDE-plasma         kWin                 No
MATE               Metacity (Marco)     No
Fluxbox            Fluxbox              No
GNOME Classic      GNOME Shell          Yes
GNOME in Wayland   GNOME Shell          Yes