[mutter/wayland] mutter-launch: fix for more systemd API changes

[Giovanni Campagna <gcampagna src gnome org>]

commit 24074a81d0a10261a99c2cc9167809cc27253573
Author: Giovanni Campagna <gcampagn redhat com>
Date:   Mon Sep 16 17:21:34 2013 +0200

    mutter-launch: fix for more systemd API changes
    
    Modern systemd changed the semantics of sd_session_get_tty() to
    return the full path, rather than just the tty name.
    
    Reviewed by Ray Strode in IRC.

 src/wayland/weston-launch.c |   13 ++++++++++++-
 1 files changed, 12 insertions(+), 1 deletions(-)
---
diff --git a/src/wayland/weston-launch.c b/src/wayland/weston-launch.c
index 52019d4..3cb4226 100644
--- a/src/wayland/weston-launch.c
+++ b/src/wayland/weston-launch.c
@@ -566,7 +566,18 @@ setup_tty(struct weston_launch *wl)
 
        ok = sd_session_get_tty(session, &tty);
        if (ok == 0) {
-               snprintf(path, PATH_MAX, "/dev/%s", tty);
+               /* Old systemd only has the tty name in the TTY
+                  field, new one has the full char device path.
+
+                  Check what we have and fix it properly.
+               */
+               if (strncmp(tty, "/dev", strlen("/dev")) == 0) {
+                       strncpy(path, tty, PATH_MAX);
+                       path[PATH_MAX-1] = 0;
+               } else {
+                       snprintf(path, PATH_MAX, "/dev/%s", tty);
+               }
+
                wl->tty = open(path, O_RDWR | O_NOCTTY | O_CLOEXEC);
                free(tty);
 #ifdef HAVE_SD_SESSION_GET_VT