How to open gnome-terminal in a nested mutter(wayland) window

Question

Following these instructions I succeeded in opening a new empty window and verified that a new wayland socket had appeared:

$ ls -alt /run/user/1000
...
-rw-------  1 craig craig 120 Oct 31 13:54 .mutter-Xwaylandauth.RN8CT0
srwxrwxr-x  1 craig craig   0 Oct 31 13:54 wayland-0
-rw-rw----  1 craig craig   0 Oct 31 13:54 wayland-0.lock
...
$ mutter --nested --wayland & 
(mutter:24172): mutter-WARNING **: 13:55:28.911: WL: unable to lock lockfile /run/user/1000/wayland-0.lock, maybe another compositor is running
$ ls -alt /run/user/1000
...
-rw-------  1 craig craig 120 Oct 31 13:55 .mutter-Xwaylandauth.M06TS0
srwxrwxr-x  1 craig craig   0 Oct 31 13:55 wayland-1
-rw-rw----  1 craig craig   0 Oct 31 13:55 wayland-1.lock
drwxr-xr-x  3 root  root   60 Oct 31 13:54 ..
-rw-------  1 craig craig 120 Oct 31 13:54 .mutter-Xwaylandauth.RN8CT0
srwxrwxr-x  1 craig craig   0 Oct 31 13:54 wayland-0
-rw-rw----  1 craig craig   0 Oct 31 13:54 wayland-0.lock
...

The new empty window looks like an empty canvas, I am pretty sure it is surface for wayland-1.

Now I try to open up a gnome-terminal in that wayland-1 canvas

WAYLAND_DISPLAY=wayland-1 gnome-terminal
WAYLAND_SOCKET=wayland-1 gnome-terminal

however in both cases it doesn't open up in the wayland-1 canvas, but instead opens up outside of it.

How to open gnome-terminal in a nested mutter(wayland) window?

---

EDIT: I was able to open Firefox in the nested canvas:

MOZ_DBUS_REMOTE=1 GDK_BACKEND=wayland WAYLAND_DISPLAY=wayland-1 firefox

However, replacing firefox with gnome-terminal did not work - gnome-terminal still opened outside of wayland-1.

Answer 1

The following worked for me (starting from a relatively bare-bones X11 session):

export $(dbus-launch)
mutter --nested --wayland
WAYLAND_DISPLAY=wayland-0 gnome-terminal

If you have other Wayland servers running, wayland-0 might be wayland-1 etc.

Answer 2

On some distributions gnome-terminal runs a "server" process (on Ubuntu this is done by a wrapper script which launches /usr/libexec/gnome-terminal-server - other terminals, like mate-terminal automatically launch with the --server option) which intercepts requests to open new terminal processes and launches them as as a new window within the same single server process. So when you try and launch a new terminal in your new nested session, the request is still intercepted and the gnome-terminal-server process, which is running in wayland-0, opens it as a new window within the same display it is running in, rather than the one you requested.

The best way around it is to pass a unique application ID, using the --app-id option. Like:

WAYLAND_DISPLAY=wayland-1 gnome-terminal --app-id app.x

The app.x is a "reverse DNS style indicator", so for our purposes as long as it contains two alphabetical parts, separated by a period, we are good to go. Full rules for application IDs can be found at https://developer.gnome.org/documentation/tutorials/application-id.html. If you were running two nested display servers you would need two separate app-ids, like app.x and app.y.

Some distros (such as Ubuntu) have a wrapper that runs when you run gnome-terminal, and the real gnome-terminal executable is called gnome-terminal.real. Runnning that will generate a new process, instead of a sub-window, but only if there is no gnome-terminal-server process running already (if there is it will use it and you will get the same behaviour you are trying to avoid).

There is also a --no-factory option, but that is no longer listed in the man page, and so shouldn't be expected to continue working in the future.