client message with XCB_ICCCM_WM_STATE_ICONIC didn't get window minimized
https://www.x.org/releases/X11R7.6/doc/xorg-docs/specs/ICCCM/icccm.html#changing_window_state
Normal -> Iconic - The client should send a ClientMessage event as described later in this section.
In events.c, XCB_CLIENT_MESSAGE part doesn't work, and looks like an event of _NET_WM_STATE_HIDDEN for _NET_WM_STATE could work. Test with GNOME Shell in Ubuntu 18.04. events.c