Bash – Real GNOME Wayland session

I have found a way to do this.

Create (if necessary) a ~/.profile file and add the following:

WAY=$(ps -aux | head -n -1 | grep "/usr/bin/gnome-shell --wayland")

if [ -z "$WAY" ]; then
    echo X11
else
    export GDK_BACKEND=wayland
    export CLUTTER_BACKEND=wayland
fi

Logout and then login in your favorite session (either X or Wayland). By using looking glass you can check if your application is actually running on Wayland. See this.

The Mutter docs specify the interface with dbus as @don_crissti has pointed out in comments:

https://gitlab.gnome.org/GNOME/mutter/blob/master/src/org.gnome.Mutter.DisplayConfig.xml

You need to find out your configuration serial and your connector:

configuration serial is the first number shown in

gdbus call \
--session \
--dest=org.gnome.Mutter.DisplayConfig \
--object-path /org/gnome/Mutter/DisplayConfig \
--method org.gnome.Mutter.DisplayConfig.GetResources

in my case that is uint32 3, so I use 3

connector: it shows in ls /sys/class/drm, in my case by trial and error I found that card0-DP-2 was the correct one so I use DP-2. You can also try to make sense of the output of DisplayConfig.GetResources and use that.

By setting the other options, the final command becomes like this:

gdbus call \
--session \
--dest=org.gnome.Mutter.DisplayConfig \
--object-path /org/gnome/Mutter/DisplayConfig \
--method org.gnome.Mutter.DisplayConfig.ApplyMonitorsConfig \
3 1 "[(0, 0, 1, 0, true, [('eDP-1', '1920x1080@60.0', [] )] )]" "[]"

Unfortunately, that does not work for me, even though I am passing the resolution (aka. "mode id") in the right format:

Error: GDBus.Error:org.freedesktop.DBus.Error.InvalidArgs: Invalid mode '1920x1080@60.0' specified
(According to introspection data, you need to pass 'uua(iiduba(ssa{sv}))a{sv}')

EDIT:

I found why, the refresh rate needs to be THE EXACT STRING that DisplayConfig.GetResources is reporting. It does not let you set what you want as refresh rate sadly! So you have to use some arbitrary string like 59.810825347900391 like so:

gdbus call \
--session \
--dest=org.gnome.Mutter.DisplayConfig \
--object-path /org/gnome/Mutter/DisplayConfig \
--method org.gnome.Mutter.DisplayConfig.ApplyMonitorsConfig \
3 1 "[(0, 0, 1, 0, true, [('eDP-1', '1920x1080@59.810825347900391', [] )] )]" "[]"

In conclusion, this is of very limited use. There should be a way of adding display modes, by generating CVT or GTF timings, but it looks like DisplayConfig does not have an interface for that :(