Cannot start a gnome-3.28.x wayland session with elogind

[John Frankish <john frankish outlook com>]

Hi,

Any suggestions on how to start a gnome wayland with elogind (mutter-3.28.2 is compiled against it) would be 
gratefully received.

I've compiled gnome-3.28.x and can start an X11 session by calling gnome-session from startx.

I know wayland works because I can start weston like this:

$ XDG_SESSION_TYPE=wayland XDG_RUNTIME_DIR=/run/user/1001 weston-launch

..and it reports WAYLAND_DISPLAY=wayland-0

However, when I try to start a gnome wayland session like this:

$ XDG_SESSION_TYPE=wayland XDG_RUNTIME_DIR=/run/user/1001 gnome-session

..I get:

(gnome-shell:2746): mutter: Failed to create backend: Unable to open display, DISPLAY not set
gnome-session-binary[2722]: WARNING: App 'org.gnome.Shell.desktop' exited with code 1

I've verified that elogind is running and setting $DISPLAY does not change anything (isn't it for X11?).

John