x-popup-* blocking?

Hello,

I'm working on a Wayland Window Manager in Elisp using ewc.el presented by Michael Bauer at EmacsConf 2022. It uses River for the heavy lifting.

https://github.com/thkoch2001/rau

It was all fine until I accidentally right clicked on a tab and everything came to a hold.


```
(easy-menu-define words-menu global-map
       "Menu for word navigation commands."
       '("Words"
          ["Forward word" forward-word]
          ["Backward word" backward-word]))

(x-popup-menu t words-menu)
```

This will call create_and_show_popup_menu in Emacs' pgtkmenu.c. I believe that it blocks somewhere in there.

At the same time there is a network connection process in ewc.el:

```
(make-network-process :filter (ewc-filter client)
```

As long as I don't click on the popup everything is fine. I can also close it with ESC. But when I click on the popup, everything freezes, even the Mouse cursor.

River debug log:

> debug(input): entering cursor mode down
> debug(wm): manage sequence start

Emacs debug output:

> Gdk-Message: 18:37:26.260: button 1 press, seat 0x56b2f8a9dbc0 state 0

Nothing gets logged in the *Messages* buffer.

Note that the emacs process has two wayland protocol connections to River open here: First the pgtk connection where emacs is a regular client displaying its windows and then the connection implemented in ewc.el where emacs acts as a window manager.

I assume the next step is to compile Emacs with debug symbols and attach a gdb to it when it freezes. But maybe somebody already has some useful thoughts before that.

This probably all works as intended and I have to accept that Emacs is single-threaded.

Thank you, Thomas