Code review comment for lp:~raof/mir/xserver-spawner

@Alan:
I think most non-trivial shells are going to want to support running X11 apps. It's not interesting for system-compositor usage, true.

As to why Mir should know about launching xservers - the process of tying together foreign X11 windows needs Mir support. Mir will need to include an X11 window manager in order to proxy between X11 EWMH window management and Mir - this could be in U8, but any shell that wants to support X11 apps will need identical code.

Ideally you want to start the X11 WM before any app connects to the server to avoid unexpected behaviours; the easiest way to do this is to start the X server, wait for it to come up, connect the WM proxy, and only then consider the server to be started (that's the next part of X11 integration).

I (obviously) think it makes sense to have Mir know how to start the X server.
@kdub:
This is somewhat of a circular dependency - the X server needs Mir running in order to be started (it needs the mir socket), and Mir's X11 WM needs the X server to be running. You can't easily start both from LightDM, as it would need to start Mir, it to be ready to accept connections, then start the X server.

Also, U8 wants to (a) start an X server only when an app needs it, and (b) start one-Xserver-per-app.

re: client_connection_string - Yeah, it could return a std::string (and did, at one point). I switched to char const* because I only ever wanted to consume it from things that took a char const*, but can easily switch it back.