When weston-launch is run under X, it uses the DRM backend (and when I just tried it, I ended up needing to reboot). It would be useful if weston-launch worked with the X backend because without root permissions, weston --xserver will fail to spawn an X server with "Unable to retrieve master".
weston-launch is not meant to work under X. Or rather, under X, the expected behaviour is to switch to a new vt and launch weston on kms. weston --xserver should work with the weston X backend without needing root priviledges. If it doesn't, it's a bug.
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