Identifying the real display server

[Simon McVittie]

On 11/04/15 02:48, Giovanni Campagna wrote:
> Well, at this point you're essentially reinventing GDK_BACKEND, but at
> server side.

GDK_BACKEND, or a cross-toolkit generalization of it, seems like a
better model: a list of protocols, not a list of environment variables.

XDG_RUNTIME_DIR gives us the opportunity to reduce the number of
miscellaneous environment variables that need to be copied around, and I
would prefer to be aiming for a future where nobody needs to set
WAYLAND_DISPLAY or DBUS_SESSION_BUS_ADDRESS or GPG_AGENT_INFO or
SSH_AUTH_SOCK or whatever Mir's DISPLAY-equivalent is (maybe even not
DISPLAY either, on a sufficiently legacy-free system) unless they are
doing something unusual.

dbus 1.9 defaults to using $XDG_RUNTIME_DIR/bus if it exists and
DBUS_SESSION_BUS_ADDRESS is unset, and my understanding is that Wayland
does something similar. People have been talking about a similar thing
for DISPLAY for a long time, although nothing seems to have come of it.
That's a future that I'd prefer to head towards.

(tl;dr: PREFERRED_DISPLAY="wayland mir x11" would be better than
PREFERRED_DISPLAY="WAYLAND_DISPLAY MIR_DISPLAY DISPLAY".)

-- 
Simon McVittie
Collabora Ltd. <http://www.collabora.com/>