Screen sharing in wayland (XDG_CURRENT_DESKTOP)

/etc/xdg/xfce4/xinitrc contains a line setting XDG_CURRENT_DESKTOP=XFCE. But in order for screen sharing to work with wayland i have to set the value to XDG_CURRENT_DESKTOP=XFCE:labwc:wlroots before running startxfce4 --wayland.

added 5. Wayland label

With systemd it is enough to override systemd unit environment variable e.g xdg-desktop-portal-wlr :

[Service]
Environment="XDG_CURRENT_DESKTOP=wlroots"

The reason why there are checks for this is becouse it could lead to unstable behaviour.

I don't know if we should change anything here, it would only apply to labwc, it's hard to guess what we should do for other compositors apparently. Since user override works fine, it looks more like an enhancement request.

added 2. Enhancement label