Contextual menu ko on linux

[aligre]

Hello

First, some information about our configuration
CEF 108, built on Ubuntu 20, runned on RedHat 8.6.
multi_threaded_message_loop : 1
external_message_pump : 0
our app message loop is based on X11/Xt methods: XtAppNextEvent, XtDispatchEvent, ...

The issue: On linux, in windowed mode, the context menu (click on right mouse button) doesn't work.

Some information
. Based on traces in our main message loop and in a test web page, we've seen that
The button 3 release event is seen by CEF message loop and not by our main message loop. Seems to be the normal behavior, an event on a CEF dialog should be managed by CEF.
But the button 3 press event is seen by our main message loop and not by CEF message loop. Seems to be the cause of the issue
. This Cef issue https://bitbucket.org/chromiumembedded/cef/issues/2002/external-message-pump-on-linux-is-slow-and looks like our one but we don't have external_message_pump activated which is a prerequisite for 2002 issue.

In cefclient sample, the management of multi_threaded_message_loop mode uses uses a gtk loop with multithreading specific code to follow GTK recommandations https://www.geany.org/manual/gtk/gtk-faq/x482.html.
Maybe we have to do some similar code to manage concurrency between Xt (in our message loop) and GTK (in chromium message loop).
Does someone have any hint on that topic?

Regards, Julien